May 13, 2007
The Atmosphere…
We live at the bottom of a ‘sea of air’ known as the atmosphere. The outermost part of this ‘sea of air’ reaches more than 500 miles above the surface of the Earth. Early attempts at studying the nature of the atmosphere used clues from the weather, the beautiful multi-colored sunsets and sunrises, and the twinkling of stars. Now with the use of sensitive instruments from space, we are able to get a better view of the functioning of our atmosphere.
The atmosphere, solar energy, and our planet’s magnetic fields combine to support life on Earth. The atmosphere absorbs the energy from the Sun, recycles water and other chemicals, and works with the electrical and magnetic forces to provide a moderate climate. The atmosphere also protects us from high-energy radiation and the frigid vacuum of space.
The envelope of gas surrounding the Earth changes from the ground up. Four distinct layers have been identified using thermal characteristics (temperature changes), chemical composition, movement, and density.
The troposphere starts at the Earth's surface and extends 5 to 9 miles up. Since the troposphere is located at the bottom of the atmosphere, it is the densest part. Temperatures drop rapidly as you climb through the troposphere at an average rate of about 10 degrees Celsius per kilometer. Almost all weather occurs in this part of the atmosphere. The tropopause, a strong temperature inversion, separates the troposphere from the next layer.
The stratosphere starts just above the troposphere and extends to roughly 30 miles high. Compared to the troposphere, this part of the atmosphere is dry and less dense. The temperature in this region increases gradually due to the absorption of ultraviolet radiation. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer. Ninety-nine percent of "air" is located in the troposphere and stratosphere. The stratopause separates the stratosphere from the next layer.
The mesosphere starts just above the stratosphere and extends to more than 50 miles high. In this region, the temperatures again fall rapidly with height and can reach nearly 100 degrees Celsius below zero. Chemicals in this layer are in an excited state, as they absorb unfiltered energy from the Sun. The mesopause separates the mesophere from the highest layer in the atmosphere.
The thermosphere starts just above the mesosphere and extends to an astonishing 500 plus miles above the surface of the Earth. Here temperatures go up as you increase in altitude due to the Sun's energy. Temperatures in this region can go as high as 1,700 degrees Celsius! Although the air is extremely thin here, chemical reactions occur much faster than on the surface of the Earth. Finally, at roughly 500 miles up, you begin to run out of gas and into the realm of space.
Posted by jeremy.kappell at 10:38 PM | Comments (0)
April 15, 2007
Severe Thunderstorm Ingredients
Here in Kentuckiana, we’ve learned to live with the threat of severe weather, especially during the spring months. However, it must be noted that severe thunderstorms do not strike out of chance. Certain ingredients must come together to create conditions that are favorable for the development of those big boomers. These ingredients include; instability, vertical wind shear, lift and moisture…
A word of caution, the following might be little heavy on scientific detail for some people. However, for those fascinated by the extreme forces of nature, please read on.
Instability: Instability is a condition in which air will rise freely on its own due to positive buoyancy. As an example, imagine a beach ball at the bottom of a swimming pool. Once the beach ball is released, it accelerates upward to the top of the pool. The beach ball rises because it is less dense than the water surrounding it. A similar process occurs when instability is released in the atmosphere. Air in the lower part of the atmosphere is lifted until it becomes less dense than surrounding air. Once it is less dense, it rises on its own. The speed that is rises depends on the density difference between the air rising and the surrounding air. In a thunderstorm, this rising air is called an updraft. It is the updraft of a storm that allows it to grow and sustain itself as it feeds on low-level moisture.
Vertical Wind Shear: First, it is important to note that there are two types of vertical wind shear. The first is called “vertical speed shear” and is a significant increase in wind speed with height. The second is called “vertical direction shear” and is a significant change of wind direction with height. Both of these are important in the development of severe storms for several reasons. A significant increase of wind speed with height will tilt a storm's updraft. This allows the updraft and downdraft to occur in separate regions of the storm allowing the storm to have a longer life span. Strong upper atmospheric winds, associated with the jet stream, allow the updraft of the storm to sustain itself while keeping the storm fed with low-level moisture. Directional shear in the lower part of the atmosphere helps initiate the development of a rotating updraft. This is one of the most important factors in determining whether a storm will be capable of producing a tornado or not.
Lift: While instability release is like a beach ball rising from the bottom of a swimming pool, lift occurs when air is forced to rise. Newton’s first law states that an object at rest will remain at rest unless acted upon by an outside force. The same is true when referring to lift in the atmosphere. Often times the air near the surface will not rise unless acted upon by an outside force. This outside force is called a lifting mechanism. A lifting mechanism is needed to force air near the surface to initially rise. Without a lifting mechanism, parcels of air will not reach the point in the atmosphere where they can rise on their own due to positive buoyancy. Therefore, despite having sufficient instability in the atmosphere, it will not be released without a lifting mechanism. Some lifting mechanisms include; Frontal Boundaries (like cold fronts or warm fronts), Upper Level Disturbances, Orographic Lifting (upslope flow associated with higher elevations), Low Level Warm Air or Moisture Advection (the transport of warmer temps or higher amounts of moisture by the wind), and Low Pressure Systems.
Moisture: Low-level moisture is the fuel to which a thunderstorm feeds off of. While dew point temperature is a measure of how much moisture is in the air, severe thunderstorms are more likely when the surface dew point is generally 55 F or higher. Low dew point values inhibit sufficient energy release in the atmosphere and significantly reduce the threat of severe storms. The depth of moisture in the lower troposphere and the rate of moisture advection are also important. While a lack of moisture in the lower atmosphere reduces the severe storm threat, a lack of moisture in the middle of the atmosphere can actually increase the threat of severe weather. Dry air in the middle layers of the atmosphere can act as a lid helping to increase amounts of heat and moisture at the lower levels. This low level heat and moisture is often released suddenly with the help of a lifting mechanism creating explosive thunderstorm development. The advection of low-level moisture brought by the wind can aid in a thunderstorm’s growth by increasing the amount of fuel available for the storm to feed off of.
Posted by jeremy.kappell at 09:37 PM | Comments (0)
April 03, 2007
Outbreak of severe weather leads to the return of winter…
Unfortunately, our spell of unseasonably warm weather has departed with the storms from last night. The severe weather was a classic result of the clash of seasons and now we are left to deal with the cold once again.
Until today, temperatures had been above normal for the better part of the last five weeks. Temperatures averaged more than 8 degrees above normal for the month of March and were closer to about 15 to 20 degrees above normal over the last two weeks. The recent warmth included 14 straight days at or above 70 degrees starting on April 21st. It also included five 80-degree days including an 85 degree temperature set on April 25th, a record high of 84 degrees set on the 26th, and an 84 degree high temperature set yesterday before the storms arrived.
Now that we have become accustomed to the warm weather, it looks like we will become reacquainted with the cold. While we were sitting back and enjoying the early summer-like weather, cold air was being bottled up across a large section of Canada. Now that bottle has been opened and cold air will continue to pour into the region for much of the next week to come. In fact, today’s afternoon temperatures should be some 30 to 35 degrees colder than what we saw yesterday. Ouch!
It looks like the coldest of the weather should occur during the early morning hours on Friday, Saturday and Easter Sunday. Be prepared for temperatures to dip well into the 20s. Be sure to protect those daffodils.
Posted by jeremy.kappell at 08:57 PM | Comments (0)
March 20, 2007
What Causes The Seasons?
Now that spring has arrived and warmer temperatures are returning to Kentuckiana, it leaves one to wonder what causes the seasons that we experience here in the middle latitudes?
Despite a popular belief, the seasons have nothing to do with how far the Earth is from the Sun. If this were the case, it would be warmer here during January as opposed to July. Instead, the seasons are caused by tilt of the Earth on its axis, by as much as 23.5 degrees.
The Earth has an elliptical orbit around the Sun. The Earth is at its closest distance to the Sun in January (called Perihelion) and the furthest in July (the Aphelion). But this distance change is not great enough to cause a substantial difference in our climate. This is why the Earth’s 23.5 degree tilt is all important in changing our seasons. Near June 21st, the summer solstice, the Earth is tilted such that the Sun is positioned directly over the Tropic of Cancer at 23.5 degrees north latitude. It is this time of the year the northern hemisphere “leans” toward and receives the most direct rays from the Sun. Since the Sun’s rays enter the atmosphere at a higher angle, they don’t have to travel as far before reaching the Earth’s surface. This translates to less light being scattered by the atmosphere and more reaching the surface causing warmer temperatures. In addition, the high sun angle produces longer days.
The opposite is true in the southern hemisphere on June 21st, where a low sun angle produces more scattering of light, shorter days and colder temperatures. Therefore, near June 21st, the southern hemisphere is having its winter solstice because it “leans” away from the Sun.
On or near September 21st, the Earth reaches the autumnal equinox. As the Earth revolves around the Sun, it gets positioned such that the Sun is directly over the equator. Basically, the Sun’s energy is in balance between the northern and southern hemispheres. The same holds true this time of the year on the spring equinox, as the sun is once again directly over the equator.
Lastly, on the winter solstice, near December 21st, the Sun is positioned directly over the Tropic of Capricorn at 23.5 degrees south latitude. It is this time of the year that the southern hemisphere receives the more direct sunlight, producing higher sun angles, longer days and thus warmer temperatures. The northern hemisphere “leans” away from the sun on December 21st producing low sun angles and the short days of early winter.
Posted by jeremy.kappell at 02:14 PM | Comments (0)
February 21, 2007
Severe Storm Prediction; NWS, WHAS11 and You
With the winter season beginning to wind down across Kentuckiana, we now focus our attention on springtime and the severe weather that often accompanies it. The following is a look at the three organizations that will help to keep you ahead of the storms as they arrive this spring.
Storm Prediction Center (SPC)
Norman, OK
The Storm Prediction Center (SPC) is part of the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP). The main focus of SPC is to monitor the development of severe storms and issue forecasts for the contiguous United States up to three days in advance. The following are a list of the three primary forecast products issued by SPC.
Convective Outlooks
Convective Outlooks are a categorical and probability forecast that describe the general threat of severe convective storms. These outlooks are issued for the next 6 to 72 hours and are updated as often as five times a day.
Mesoscale Discussion
Mesoscale Discussions are designed to give local forecasters a heads up on a region that is becoming a severe weather threat and give an indication of whether a watch is likely. MDs usually precede a severe thunderstorm or tornado watch by 1 to 3 hours. MDs are also issued to update information on watches that have already been issued.
Weather Watches
Severe Weather Watches are issued when conditions are expected to become favorable for the development of severe thunderstorms or tornadoes within a defined region, generally less than 50,000 square miles. Watches are intended to be issued 1 to 6 hours in advance of the arrival of severe weather.
National Weather Service (NWS)
Louisville, KY
Your local National Weather Service office in Louisville is a part of a network of 122 Weather Forecast Offices (WFOs) across the United States. Although the NWS is responsible for a wide array of forecast products to support a variety of users, their main purpose is to issue forecast products that help protect life and property of the general public. The most critical forecast products are advisories and warnings.
Weather Advisories
An advisory is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. Advisories are for less serious conditions than warnings, that cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property.
Weather Warnings
A warning is issued when a hazardous weather or hydrologic event is occurring, imminent or likely. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action. Severe Thunderstorm Warnings are issued for thunderstorms capable of producing three quarter (3/4) inch hail and or winds of 58 mph (50 knots) or greater. A tornado warning is issued whenever the public has reported a tornado or developing tornado and or Doppler Radar indicates the possibility of a tornado or developing tornado, Tornadic Vortex Signature (TVS).
Local Media (WHAS11)
Louisville, KY
Among the many responsibilities of WHAS11 (and other local media), is the vital role of collaboration between their weather staff (First Alert StormTeam) and the National Weather Service. A strong, collaborative relationship between the two organizations is imperative in order to provide timely, detailed and accurate weather information to the public when a weather emergency occurs. Through timely relaying of NWS and official emergency management information as well as by providing supplementary observations, interpretation, discussion, integration and tailoring to an audience, local media communicates essential information about potential dangerous weather to the public.
Through education and communication, the media have significantly reduced the number of deaths and injuries due to severe weather events over the past 50 years. Although many attributes of a local media station play a role in keeping the public safe, below is a list of the top five.
Immediacy
All official advisories, watches and warnings, and Emergency Alert System (EAS) messages for the area of concern should be broadcast in a timely and prudent manner, with all essential information, and with the issuing authority clearly identified.
Accuracy
Presentation of a warning or a forecast should include attribution and an estimate of the confidence or uncertainty to be associated with it. To assist in conveying the limitations of predictions, media are encouraged to utilize and educate the public about products that display uncertainty. It is important that there be no embellishment or exaggeration of facts as these may make a situation appear better or worse than it is.
Collaboration
Cooperation, coordination, and two-way communication between the NWS and local media is imperative for the delivery of timely, detailed and accurate weather information to the public. The broadcast media and other private sector meteorologists, while retaining autonomy and independence, have much to contribute to the weather tandem. It is important that the NWS and the media listen to one another, share plans and information, and seek one another’s input on emergency plans and operations.
Balance
"Being first" and "being the best" are important motivators and highly desirable in the media business. Indeed, fair and open competition based on quality of service is in the public's best interest. However, in balancing market forces with the public good during periods of severe weather, the broadcast meteorologist and higher management should always place the interests of the public first. Every effort should be made to restrain unwarranted claims and to avoid exploiting an emergency situation for competitive advantage.
Professionalism
A high level of professional expertise is required to perform properly during a weather emergency. While professionalism begins with meteorological education and training, it also includes experience, understanding, and the ability to remain calm under pressure. In addition to technical skills, professionalism in providing weather information to the public includes ability to balance public interest with competitive forces and adherence to the highest standards of journalism, with its constant striving for accuracy.
Posted by jeremy.kappell at 06:04 PM | Comments (0)
February 06, 2007
February brings balance to mild winter…
I’ve always said that nature tends to works in cycles. So far this winter, there has been two; a warm one, and now a cold one. So how much longer will the cold last and what is the outlook for an early spring?
It wasn’t long ago that many residents were asking what happened to winter. We don’t have to ask that question any more. After starting out the winter with temperatures that averaged some 10 to 15 degrees above normal, things have cooled down in a big way in recent weeks across Kentuckiana.
Despite a chilly start to December, high temperatures averaged out to roughly 52 degrees for the month, a full 10 degrees above normal. January started off even warmer as temperatures reached the 60’s on six different occasions including a record high of 68 degrees set on the 5th. The first 15 days of January brought high temperatures that averaged nearly 55 degrees. That is 15 degrees above normal for what is supposed to be the coldest part of the year!
My how things have changed… We haven’t seen a single 60 degree temperature in the three plus weeks since January 15th. In fact, we’ve only seen 50 once since the extraordinarily mild start to the winter, a 53 degree high set on January 27th. In total, as of this writing, high temperatures have average 35.9 degrees since the mid way point of January.
As cold as January ended, February has started off even colder. Including an 18 degree high temperature set on February 5th, high temperatures have averaged out to a very chilly 27.5 degrees since the start of the month. That is about 17 degrees below normal for this time of the year! Low temperatures have been even colder. Including a 5 degree reading on the morning of the 5th, low temps have averaged out to a bone chilling 13.8 degrees!
So how much longer will we have to deal with the cold weather? We’ll despite the recent warm prognostications of a famous groundhog, it looks like we will be dealing with the chilly conditions for a while longer. Current long range computer models still indicate quite a bit of cold air coming our way over the next week or two. Along with the cold conditions, we are also currently tracking a couple systems that could bring some measurable snow to the area next week. On a warmer note, the climatologically coldest part of the winter season is behind us and May is only a few months away!
Posted by jeremy.kappell at 06:22 PM | Comments (1)
January 15, 2007
Where is all the snow?
That is a really dumb question. Anyone with a television set knows that the snow is in Colorado. However, there certainly hasn’t been much around here so far this winter. Following the warmest year on record for the United States, January has started off like a summer monsoon across Kentuckiana with a ton of rain and some very warm temperatures.
On the heals of a December where temperatures averaged about five degrees above normal and where only two tenths of an inch of snow fell, January has started off even warmer and with even less snow. The first 15 days of the month produced high temperatures that averaged more than 15 degrees above average! In addition to the warm temps, January has already brought more than 3 inches of rain and no measurable snowfall.
Officially, the measly two tenths of an inch (0.2”) of snow that we picked up in December is the total so far for this winter season. Considering that Louisville averages about 15 inches a season and that the season is already half over, we are way below normal in this category. If we don’t get some snow soon, we are in danger of breaking the all-time record for least snowfall in a season. That mark was set during the very warm 1988-1989 winter season when Louisville only saw 9 tenths of an inch (0.9”) of snow. Heck, that’s almost five times the amount we’ve seen so far this winter!
Now before you snow lovers get caught up in a tizzy, understand that a lot can happen between now and May. In fact, the greatest snowfall on record occurred during the month of February. Between the dates of February 4th and the 6th in 1998, Louisville saw nearly two feet of the white stuff! 22.4 inches to be exact, which is exactly 112 times more than we have seen so far this season!
Should we escape the rest of January and February without a significant snow there is still some hope as we head into the last month or two of the cold season. On March 23rd 1968, 11 inches of snow fell on the city which was good for the most snow ever from a storm during the month of March. More recently, on March 31st of 1987, the Louisville area picked up between 6 and 9 inches of some heavy, wet snow.
Now the end of March is certainly late the season for significant snow. However, believe it or not, but way back in 1898, 10 inches of snow fell in Louisville on May 6th. That’s right, just two days after Plaudit won the 23rd Kentucky Derby, 10 inches of snow fell on Kentuckiana!
Now I’m not predicting a May snow this year, but there is still plenty of winter left. Climatologically, this is the coldest part of the year and the recent cold snap is a result of a large scale weather pattern change that is now occurring across the United States. The upper level ridge that was responsible for the near record temperatures recently over the Eastern U.S. has dissipated and a persistent trough appears to be taking its place. This will translate to more cold weather over the next couple of weeks. And where there is cold, there will be at least a chance of snow. Stay tuned.
Posted by jeremy.kappell at 11:06 PM | Comments (3)
January 02, 2007
2006: Weather Year in Review
2006 turned out to be a very warm and wet year across Kentuckiana. From severe storms and tornadoes to record heat and torrential rainfall, we saw everything last year except for the cold and snow.
The tone was set just 24 hours into the New Year. On January 2nd of 2006, the mercury soared to a record high of 72 degrees just hours before severe weather raked through the region. Powerful thunderstorms rolled across central Kentucky and south central Indiana on that unusually warm and humid early January producing six tornadoes! It was the largest wintertime tornado outbreak on record for the area. Elizabethtown was the hardest hit with F-2 damage a few miles north of downtown along US 31W. Other F-2 tornadoes struck parts of Adair and Lincoln Counties of Kentucky on that day.
Severe storms also struck parts of Kentuckiana on March 9th, April 2nd and 7th, May 25th, July 14th and on August 10th. The May 25th outbreak brought widespread wind damage to much of the Ohio Valley. Winds to 70 mph were reported at Big Clifty in central Kentucky along with two inch diameter hail. A storm produced a gust of 64 mph at the Louisville International Airport.
In addition to several rounds of severe weather, 2006 also brought a few notable flooding events to the area. On January 23rd, one to as much as three inches of rain combined with melting snow to produce flash flooding across much of Southern Indiana and parts of Kentucky. On July 14th, a series of thunderstorms with very heavy rain moved from Floyd and Clark Counties in Indiana and into parts of Jefferson, Shelby, Scott and Woodford Counties in Kentucky. As much as four inches of rain was reported near Sellersburg, IN.
The worst flooding of the year occurred on September 22nd and 23rd. A slow moving storm system brought torrential rainfall for much of southern Indiana and north central Kentucky. The heaviest rain fell along the I-64 corridor where more than 7 inches of the wet stuff was recorded in many areas over the two day period. Louisville picked up 4.28 inches on the 22nd to set a daily rainfall record and was only two one hundredths away from the September record as well. Unfortunately, six people lost their lives in the flood waters produced by the tremendous rainfall. It was the worst flooding in Louisville since March of 1997.
In addition to the abundant rainfall for the year, several record temperatures were set. As already mentioned, Louisville hit 72 degrees on January 2nd, smashing the old record of 66 degrees set all the way back in 1897. On April 15th Louisville reached 86 degrees which broke the previous record of 85 set in 1912. Another record high fell on November 30th with a temp of 74 degrees, shattering the old mark of 70 set in 1991. The final record was broke on December 17th with a high of 70 which eclipsed the old record high for the date set in 1984. No record low temperatures were set during 2006.
The coldest it got during 2006 was 9 degrees above zero on the morning of February 19th. The hottest temperature recorded was 95 degrees set on three different days, August 2nd, 7th and 10th. Overall, Louisville had an average temperature of 58.5 degrees for the year, which is about 1.7 degrees above average and was good for the 4th warmest year on record. Precipitation was more than 12 inches above average with a total of 56.85 inches (good for 7th wettest on record). Nearly all of this fell in liquid form as Louisville only officially picked up five inches of snow at the airport, which is about 10 inches below average.
Posted by jeremy.kappell at 01:29 PM | Comments (0)
December 17, 2006
Will it be a White Christmas in 2006?
Despite the recent record warm temperatures across Kentuckiana, many folks are asking about our chances for a White Christmas this year. Here, we’ll take a statistical look at the odds of a White Christmas in Louisville as well as a brief look at those weather models we are always talking about…
By definition, an official White Christmas is defined as having an inch or more of snow on the ground on Christmas day. Looking back at Louisville records, we’ve only seen nine “official” White Christmas’s in the past 120 years. That’s an average of only one White Christmas every 14 years! The last one occurred in 2004, so going by averages, were not do again until 2018!
The good news for snow lovers is that there have been a lot more “quasi” White Christmas’s here in Louisville. By “quasi”, I mean a Christmas when we’ve had some snow, just not quite a full inch. In fact even though we’ve only had nine “official” White Christmas’s dating back to 1884, we’ve picked up at least a trace of snow 47 times during that same period. That’s an average of one about every three years!
As far as the greatest snow on Christmas Day in Louisville, look no further than 2004. Following the Holiday Storm of 2004, where parts of Kentuckiana was buried under more than 30 inches of the white stuff, six inches was left on the ground in Louisville on Christmas morning. Before that, you have to go way back to 1890 when we picked up an estimated 5 inches for the second snowiest Christmas on record for Louisville. Another interesting statistic to note is the fact that we’ve picked up at least a trace of snow for the past seven Christmas’s, including 6 inches in 2004, 3 inches in 1999, 1 inch in 2000 and a trace in ’01, ’02, ’03 as well as ’05.
So can we keep this string going? That is a tough question, since we are still a week away from the big day. As of this writing, December 17th, current weather models are indicating the arrival of colder conditions as we head into the Christmas weekend. That bodes well for the possibility of frozen precipitation. However, we still need a storm system to work with in order for snow to form. At this time, we are tracking a possible system that could bring us either rain or snow just in time for Christmas. The big question will be how strong this storm becomes and exactly what track it takes. These two factors will make all the difference as to whether Christmas ’06 is a white one or not. Stay tuned…
Posted by jeremy.kappell at 11:48 PM | Comments (0)
December 06, 2006
Decreasing Daylight
You always know that winter has arrived across Kentuckiana when it turns dark by 5:30 in the afternoon. It is this time of the year when our daylight has decreased to the point where you have to go to work late and come home early in order to commute without your headlights on. It is also this time of the year that usually precedes the coldest part of winter...
There is an obvious correlation between the amount of sunlight we receive and the amount of heat that is available. Unfortunately, we are nearing the shortest days of the year and you know that will translate into many more cold days ahead.
As of this writing, December 5th, the sun officially rises at 7:45am and sets at 5:22 pm here in Louisville, KY, which happens to be located near 38 degrees N latitude. That translates to only 9 hours and 37 minutes of sunlight. It’s no wonder why our average high temperature, this time of the year, is only in the upper 40’s. By December 22nd, the shortest day of the year and the winter solstice, our total daylight decreases to 9 hours and 30 minutes and helps to produce an average high temperature of only 44 degrees.
The good news is that we are not alone in our plight against dwindling daylight. In fact, many folks across this great country have it much worse than we do. Take Chicago for instance. Located at about 42 degrees N latitude, Chicago will only receive about 9 hours and 7 minutes of daylight on the solstice. They will also average only about 32 degrees for a high temperature on that day.
Although Chicago is certainly a dark and dismal place to spend the winter, a far worse place to spend your time during the chilly months is Minneapolis-St. Paul, MN. The Twin Cities are located at roughly 45 degrees N latitude (that’s more than two-thirds the distance from the equator to the Artic Circle). It’s no wonder that they only receive about 8 hours and 45 minutes of sunlight and have an average high temperature in the mid 20’s this time of the year.
The folks in Minnesota actually have it pretty good compared to those who live in the northern most US territory. Fairbanks, Alaska, for example, is located at approximately 65 degrees N latitude (which is only about two degrees away from the Artic Circle!) and receives only about 3 hours and 41 minutes of daylight on the shortest day of the year. That converts into 20 hours and 19 minutes of darkness in Fairbanks! It also translates into some frigid temperatures… how about an average high of only 2 degrees F!
At least the people of Fairbanks get to see the sun this time of the year. That is not the case for Barrow, AK. This northern most city of the US is located at more than 71 degrees N latitude and is positioned nearly 5 degrees latitude north of the Artic Circle. The folks in Barrow have not seen the sun since it set on November 19th and won’t see it again until January 23rd, giving them more than two months of darkness this time each year. All that darkness doesn’t allow for much warmth. Average high temperatures in Barrow remain well below zero during the winter months, yikes!
With all that being said, we really don’t have it too bad here in the lower Ohio Valley. It’s all about perspective you see. When the sun finally rises again in Barrow we will be in the heart of our winter season experiencing high temperatures that average near 40 degrees. That seems rather balmy considering the folks in Barrow won’t see 40 degrees again until June!
Posted by jeremy.kappell at 07:38 PM | Comments (1)
November 14, 2006
What is Indian Summer?
These questions were recently posed by a viewer... Would the unusually warm weather we saw last week be considered “Indiana Summer”? And is Global Warming responsible for this? Keep reading for the answers...
Yes, last Thursday and Friday’s 70+ degree weather would be considered "Indian Summer". Anytime you get 70 or 80 degree weather around these parts following the first heavy frost or freeze of the season, it is considered to be an "Indian Summer". This, however, does not have anything to do with Global Warming. 70 degree weather frequently occurs this time of the year. It usually doesn't last long though, like this time, but can occur in almost any winter month (it is rarer in December and January, however). People are often quick to blame Global Warming for any warmer than "normal" weather. The thing is, though, it's not often that our weather stays in the normal range for very long. It is natural for weather to cycle through warm and cold spells this time of the year. If it didn't, then that wouldn't be "normal." It looks like the rest of this week will be colder than normal. That doesn’t mean that we’re going into a new ice age though.
Posted by jeremy.kappell at 05:39 PM | Comments (1)
October 27, 2006
What is the difference between a frost and a hard freeze?
Ever wonder why frost occurs while temperatures remain above freezing? Or how about, what is the difference between a frost and a freeze? If you answered yes to one of these questions, then keep reading...
The proverbial frost on a pumpkin refers to ice crystals forming on a surface once temperatures drop below the freezing mark, 32 degrees F. However, the air temperature does not necessarily need to “officially” drop below the freezing mark for frost to form. The National Weather Service, NWS, keeps its “official” temperatures in a sheltered area some five feet above the ground at the airport. However, because cold air is denser than warm air, the coldest air is found in the lowest couple of feet above the surface. On a clear and calm night, the temperature difference between the surface and five feet up can be 5 degrees or more. In addition to the coldest temps being found right near the earths surface, some surfaces radiate heat more effectively than others. For example metal, glass and vegetation are very efficient at emitting long-wave energy back into that atmosphere. This allows coldest temperatures to be achieved on these surfaces first. That is why frost can many times be found here first when air temperatures are marginal.
So far this season, our “official” lowest temperature was 33 degrees set on the morning of October 25th. Despite the fact that the “official” temperature never reached the freezing mark, many areas reported temps as low as the upper 20’s. The second half of this month has turned out to be very cold. In fact, morning temperatures at the airport have dipped into the 30’s seven times since October the 12th. Patchy frost was reported on most of those cold mornings.
A hard freeze refers to when the actual air temperature falls below the freezing mark for several hours at a time. For this to occur, typically the “official” low temperature will reach the freezing mark if not lower. Although Louisville has not had a hard freeze so far this season, but many locations across Kentuckiana have experienced subfreezing temperatures during the recent cold spell.
Posted by jeremy.kappell at 08:19 AM | Comments (2)
October 01, 2006
September Soaks Kentuckiana…
On the heels of a wet summer across Kentuckiana, the flood gates opened up in September and left many residents fleeing for higher grounds.
Climatologically speaking, September is one of the driest months of the year for Louisville averaging only about 3 inches of rainfall. Not so this time around. Despite a dry start to the month, it ended up being the second wettest on record for the city dating back to the 1870’s with a whopping 9.60 inches of rain!
After picking up only 0.03 inches of rainfall during the first nine days of the month, the rains began to fall on the 10th. In fact, strong thunderstorms dumped about 2 and 1/3 inches between the 10th and the 12th in Louisville as a slow moving cold front moved through the region. Following this first real rain event of the month, Kentuckiana saw a lull in activity over the next week and a half that would prove to be the calm before the storm.
On Friday September 22nd a powerful storm system began to move out of the plains and into the Ohio Valley bringing with it a surge of rainfall. Although steady rains moved into the area early during the day, it was Friday night that the heavens opened up on Kentuckiana. A strong complex of slow moving thunderstorms dumped an incredible amount of rain across the area creating a rash of flash flooding.
By the time the rain finally stopped on the 23rd, it was apparent that the Louisville area had been hit by its worst flooding since 1997. Unfortunately, six people lost their lives in the deluge across north-central Kentucky as six to nine inches of rain fell across much of the metro area mainly along the east to west I-64 corridor. Louisville set a rainfall record on the 22nd with 4.28 inches of rain, just 0.02 inches shy of the all-time September record.
Fortunately, unlike the 1997 flood, most small streams and rivers across the region were back in their banks within a few days after the storm.
An additional inch and a half of rain fell over the last four days of September. In total, Louisville saw rain on 13 of the 30 days of the month and the 9.60 inches recorded at the airport was second only to the 10.49 inches that fell in 1979. At this point, Louisville has picked up almost 46 and ½ inches of rain on the year which is about 12 inches above average. Considering the fact that Louisville only averages about 44 and ½ inches of rain per year, 2006 will end of wetter than average even if it doesn’t rain again for the rest of the year.
Not that we’re expecting to go another three months without rainfall, the near future, however, does look drier. Current weather models are pointing towards warmer and drier weather for the first half of October.
Posted by jeremy.kappell at 11:05 PM | Comments (0)
September 19, 2006
2006 Summer in Review
Although the summer season doesn’t officially end until Saturday (September 23rd), the winds of change have arrived across Kentuckiana and for all practical purposes the cool season has already begun. Looking back, it turned out to be both a wet and hot summer here in 2006…
The unofficial start to the summer started off on a very wet note as Louisville picked up nearly two and a half inches of rain during the first two days of June. In total, June brought more than six inches of rain and temperatures that averaged about a half degree below average. June also delivered four 90-degree days including a 92 degree temperature recorded on the 22nd.
After seeing only four 90-degree days during the entire month of June, July started out with a hot streak of four straight 90-degree days including a 94 degree temperature recorded on July 2nd. After a cool stretch of 80-degree weather from the 5th through the 13th which included nearly 3 inches of rain, the heat was on once again. Louisville saw six 90-degree days in a row between the 14th and the 19th including another 94 degree temperature set on the 16th. In total, July brought about four and a half inches of rain and temperatures that averaged about a degree above average and included thirteen 90-degree days.
August started out even hotter than July recording six 90-degree temperatures during the first seven days of the month and included the hottest temperature of the summer at 95 degrees, which was recorded on three occasions; August 2nd, 7th and 10th. In total, Louisville saw eleven 90-degree days in August as temperatures averaged almost two and a half degrees above normal for the month. Louisville also received more than five inches of rain during August.
Including three 90-degree temperatures recorded in May, the summer of 2006 totaled thirty-one 90-degree days. Comparatively, Louisville averages about thirty 90-degree days per summer. However, the average temperature during the months of June, July and August ran about two and a half degrees above normal as rainfall totaled about fifteen and a half inches, which is also above normal by more than four inches.
Since the beginning of September, Louisville has not seen a 90 degree mark as temperatures have averaged nearly three degrees below normal. No complaints here though. I say bring on the cool days of autumn and we’ll quit counting 90-degree days again until next summer.
Posted by jeremy.kappell at 09:20 PM | Comments (0)
September 05, 2006
Global Warming: A Real Hot Topic!
Global warming has been a controversial issue that dates back several decades, but at no point has this issue been more heated than now. A recent documentary on the subject hosted by Tom Brokaw on the Discovery Channel has sparked more debate on this hot topic than ever before. But what exactly is global warming and is it really as imminent as the media has portrayed it to be?
Energy from the sun drives the Earth’s weather and climate. Energy from the sun heats the Earth’s surface and in turn, the Earth radiates energy back into space. Naturally occurring greenhouse gasses (such as water vapor, carbon dioxide and methane) trap some of the outgoing energy (or radiation). These gasses serve an important role in sustaining life on Earth by retaining heat somewhat like the glass panels of a greenhouse. Without this natural “greenhouse effect,” temperatures would be much lower than they are now and life as we know it today would not be possible. Instead, thanks to greenhouse gasses, the Earth’s average temperature is a very hospitable 60 degrees F.
As mentioned, carbon dioxide is a naturally occurring greenhouse gas and like water, is constantly cycled. Life on earth is carbon-based, and the source of that carbon is atmospheric carbon dioxide. Carbon dioxide is naturally produced by the respiration of animals, by the decomposition of plants, and by forest fires as well as volcanic eruptions. All the while, the oceans absorb carbon dioxide from the atmosphere and plants consume carbon dioxide in the process of photosynthesis.
Despite the natural occurrence of carbon dioxide and other greenhouse gasses, it is clear that certain human activities have added to the concentration of greenhouse gasses in our atmosphere. Increasing levels of carbon dioxide and methane in the atmosphere have been well documented in recent years. According to the EPA (the Environmental Protection Agency), since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have gone up nearly 30% while methane concentrations have more than doubled. These increases are magnifying Earth’s natural greenhouse effect, but to what extent?
A warming trend of about 1 degree F has been recorded since the late 19th century. Warming has been noted in both the northern and southern hemispheres. Melting glaciers and a decreased snow pack in many areas are feeding speculation that global warming is real and accelerating. In fact, scientists believe that sea level has risen by about 6 inches over the past century globally. However, is this just a part of a natural cycle or are we actually seeing the start of a large scale, human induced climate change?
Figuring out to what extent human activities have altered the chemical composition of the atmosphere is not easy. This is because many factors, both natural and human, affect our planet’s temperature such as changing amounts of incoming solar radiation and natural climatic variation. Current scientific understanding of these other factors remains incomplete. In short, scientists think rising levels of greenhouse gasses are contributing to global warming, as would be expected. But to what extent is difficult to determine at the present time. As atmospheric levels of greenhouse gasses continue to rise, scientists estimate average global temperatures will continue to rise as a result, but by how much and how fast?
As already mentioned, many greenhouse gasses are naturally occurring. One major reason for these naturally occurring greenhouse gasses are volcanoes. There are currently 70 active volcanoes in the United States alone. These quaking mountains constantly emit large levels of water vapor, carbon dioxide and methane into the atmosphere. However, looking back through history you will find that following large volcanic eruptions, notable world wide cooling has taken place. For instance, the eruption of Mt. Pinatubo (Philippines) in 1991 produced an average drop in world temperature by nearly 2 degrees F in the subsequent two years. The reason for the drop in temperature was not because of the vast amounts of greenhouse gasses that were emitted during the eruption, but because of the sulfates and particulate matter (ash) that were also ejected into the atmosphere. Sulfates and other particulate matter act to reflect incoming solar radiation leading to less heating at the Earth’s surface.
The eruption of Mt. Tambora (Indonesia) in 1815 resulted in an extremely cold spring and summer in 1816, which became known as the year without a summer. The Tambora eruption is believed to be the largest volcanic eruption in the last ten thousand years producing massive amounts of both greenhouse gasses as well as particulate matter. North America and Europe were hit exceptionally hard. Snow occurred in New England and the Great Lakes during the months of June, July and August. Sea ice migrated across Atlantic shipping lanes and alpine glaciers advanced down mountain slope to exceptionally low elevations.
Although volcanic eruptions don’t produce as much greenhouse gas as man does on an annual basis, it has been shown that sulfates and particulate matter may have a larger impact on planetary temperature. In addition to the constant release of greenhouse gasses, humans are also releasing large amounts of atmospheric particles, such as sulfates, into the atmosphere. Since these pollutants are also increasing in time, scientists expect sulfates to at least partially offset the global warming due to greenhouse gasses.
If atmospheric levels of greenhouse gasses continue to rise at the current rate, scientists estimate that average global temperatures will continue to rise as a result. The Intergovernmental Panel on Climate Change (IPCC) projects further global warming of anywhere between 2 and 10 degrees F will be possible by the year 2100. The very large range is a result of the many uncertainties such as; greenhouse gas emissions, solar irradiance, the possible cooling effects of atmospheric particles such as sulfates and the climate’s response to changes in the atmosphere. The IPCC states that even the low end of this warming projection “would probably be greater than any seen in the last 10,000 years but the actual annual to decadal changes would include considerable natural variability.”
Although many scientist are fairly confident about there projections on global temperature and precipitation change, they are less confident about the ones for small-scale areas like local temperatures and precipitation patterns. This is largely due to the fact that current computer models used to forecast global climate change are not finite enough to accurately simulate how things may change at smaller scales.
The IPCC cautions, “Complex systems, such as the climate, can respond in non-linear ways and produce surprises.” One common belief is that a warmer Earth will produce more frequent and intense storms including hurricanes. Recent history will certainly support this claim as 2005 provided an unprecedented number of Atlantic hurricanes as well as some of the strongest hurricanes recorded this century. Although we appear to be going into a new era of heightened hurricane activity, this cannot be attributed to global warming alone.
Scientists believe that the recent increase in hurricane activity is largely a result of naturally occurring long-term fluctuations in sea surface temperature in the Atlantic, known as the Atlantic multidecadal oscillation (AMO). The AMO can cause warmer than average sea surface temperatures in the Atlantic over long periods of time. Scientists believe the last time this occurred was in the 1950’s and 60’s. It was also during that period that the Atlantic was experiencing frequent and powerful hurricanes such as Beulah in 1967 and Camille in 1969. The 1970’s and 80’s brought a dramatic decrease in hurricane activity in the Atlantic which corresponded to cooler than average water temperatures.
Since 1995, however, the Atlantic has warmed once again resulting in the recent active hurricane seasons. Many scientists argue, however, that global warming may be increasing the effect of the AMO causing the rash of hurricane activity over the past decade. Unfortunately, the current warm phase of the AMO is expected to last at least another decade and could very well produce even stronger storms as sea surface temperatures continue to rise.
The current state of global warming research can’t provide definitive answers to all of our questions. It is a certainty that human activities are adding greenhouse gasses to our atmosphere and that these gasses tend to warm our planet. The big questions such as: How much warming will occur? How fast will this warming occur? And how will the climate respond to this warming? Remain unanswered and will likely remain that way for several more decades.
Posted by jeremy.kappell at 02:04 PM | Comments (2)
August 09, 2006
Questions concerning humidity...
Ever wonder what's the difference between humidity and dew point? Or how about, why does high humidity make us feel so uncomfortable? If so, read on...
What’s the difference between humidity and dew point? (Beau Wolf, Corydon)
Humidity and dew point are closely related and the two can be very confusing to the layman. Humidity is a percentage that is given to describe how “saturated” or “unsaturated” the air is with respect to moisture. At 100% humidity, the air cannot hold any more moisture and at which time condensation will occur. The lower the humidity value, the drier the air is and the more moisture it is capable of holding. The dew point can be described as the temperature to which a parcel of air would have to be cooled to before condensation will occur. The higher the dew point, the more moisture there is in the air. Note that the dew point will never exceed the temperature and that when temperature and dew point are the same, humidity is 100%. Also notice how humidity fluctuates wildly throughout the day while the dew point stays relatively constant. For instance, in the morning you may have a temperature of 70 degrees and a dew point also of 70 degrees giving you 100% humidity. By afternoon, your temperature may reach 90 while the dew point remains at 70. This produces a humidity value of only 55%.
Why does high humidity make us feel so uncomfortable? (Joe Arnold, Louisville)
The reason your body sweats during the heat of the day is to help you stay cool. As the sweat on your skin evaporates, it takes heat away from your body producing an affect known as evaporational cooling. Evaporational cooling is critical in keeping your body temperature at normal levels. Unfortunately, this process doesn't work nearly as efficiently when the humidity is high and can cause your body to overheat. The higher the humidity is, the less evaporation that can take place and the less cooling your body receives. When high humidity combines with high temperatures, as it often times does here in Kentuckiana, it can make it very difficult for people to function normally. At its worst, the combination of the two can lead to a heat exhaustion or even a heat stroke. So take it easy out there this summer, drink plenty of fluids and stay inside away from the heat when you can.
Posted by jeremy.kappell at 06:21 PM | Comments (0)
June 28, 2006
Air Quality & Summer Pollution
We often times here meteorologists refer to the things like Air Quality Index and Air Quality Alert during the summer time, but what do they mean and how do they effect us? Below is a list of definitions that will help you determine just exactly what the weatherman is talking about.
Air Quality Index - A way to measure the amount of the six major pollutants in the air. These pollutants are particulates, sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), lead (Pb), and ozone (O3). A measurement of 0 to 100 is considered acceptable, but from 100 to 150 is unhealthy for old people, young children, and people with asthma. Above 150 is unhealthy for everyone.
Although any of the above mentioned pollutants can affect our weather, the most common in Kentuckiana are ozone and particulates. Particulates or particulate matter are fine particles of foreign matter that float around in the air we breathe. PM10 describes the fraction of airborne particulate matter that is less than 10 microns in size. Fine particles are of the greatest concern since they are capable of being easily transported over long distances on currents of air. Also, fine particles may be drawn into the respiratory airways where they may adversely affect health. Recently, the attention of scientists has been drawn towards studying the PM2.5 fraction and even smaller particles, which can penetrate the very deepest parts of the lung. PM10 and other particulate matter may vary considerably in chemical and physical composition. The principal sources of these particles are combustion processes, including traffic and industry.
Ground Level Ozone – Sometimes referred to as smog, ground level ozone is formed by a chemical reaction between volatile organic pollutants (VOCs) and oxides of nitrogen (NOx) in the presence of sunlight. Ozone concentrations can reach unhealthy levels when the weather is hot and sunny with little or no wind. Ozone at the ground level causes adverse effects on lung function and other unhealthy respiratory effects. Also known as tropospheric ozone, ground level ozone occurs near the earth's surface in the lowest layer of the atmosphere, also known as the troposphere. In the troposphere, ozone is a natural constituent of the air we breathe. However, at critical increased concentrations, it becomes a harmful pollutant. In natural (unpolluted) conditions, ozone is formed in the troposphere when UV radiation that reaches the Earth’s surface converts nitrogen dioxide to nitric oxide and an oxygen radical. The oxygen radical may subsequently react with diatomic oxygen, 02, to form ozone. Ozone is then broken down when it reacts with nitric oxide, forming diatomic oxygen and nitrogen dioxide.
Air Quality Alert - A message issued by the Department of Natural Resources (DNR) through the National Weather Service when the AQI is expected to reach above 100. This message encourages you to prevent air pollution by postponing the use of lawn mowing, motor vehicles, boats, as well as filling their vehicle gas tanks.
Jeremy Kappell
WHAS11 First Alert StormTeam Meteorologist
7/03/05
Posted by at 05:41 PM | Comments (2)
June 05, 2006
Summertime Thunderstorms: Nature’s Air Filter
It’s not a coincidence that most Air Quality Alert Days occur during the hot and dry days of summer. It is during these stretches that pollutants can build up to dangerous levels in the lower portions of our atmosphere. However, thanks to the miracle of water, we have a lot less ozone and particulate matter to worry about.
In the wintertime, we see frequent cold fronts here in Kentuckiana that sweep away the unclean air and thanks to strong jet stream winds, we also get a lot of mixing between the lower and upper levels of the atmosphere to readily disperse pollution. However, these are luxuries that we don’t get to enjoy very often here during the summertime.
A major reason for the build up of pollution in the lower part of the atmosphere during the summer months is stagnant high pressure. High pressure is characterized by fair skies and light winds. Both of these characteristics promote the build up of pollutants near the surface where we live and breath. Fair skies promote the formation of ground level ozone under strong daytime heating and light winds don’t allow for polluted air near the surface to mix with cleaner air at higher altitudes.
These high-pressure systems tend to hang around during the summer months because of the location of the jet stream. The jet stream, the river of high velocity air aloft that steers weather systems across the globe, is normally located well to the north of Kentuckiana during the summer months. Without a push from those upper level winds, high-pressure systems often stagnate for long periods during the summertime. It is during these hot and dry stretches that we need to be extra cautious about the amount of pollution that we are helping to create.
So how does air pollution get removed during the summertime? The answer is water. Ever notice the residue that is left on your car windshield after a rain? That residue is pollution that has been removed from the air by the rainfall. Water is a very efficient recycler. Water constantly renews its purity by cycling itself from liquid into vapor and back again. It’s the constant recycling of water that also helps to restore purity to the air that we breath. You see with every raindrop that falls from the sky, pollutants are collected and carried back to the Earth.
Unfortunately, a few sprinkles of rain or a passing shower will not produce enough water to sufficiently clean the volume of polluted air that we have to deal with during the summer months. A thunderstorm, however, is a different story. Thanks to the intensity of rainfall during a typical summertime thunderstorm, the air under the storm undergoes a vigorous cleaning process. As an added bonus, evaporational cooling produced by the rainfall, also helps to reduce the temperature of the air making it both clean and comfortable. Think of it kind of like a gigantic outdoor air conditioning unit.
So the next time a thunderstorm passes over your house, go out side, take a deep breath and enjoy the clean air!
Posted by at 01:20 PM | Comments (1)
April 30, 2006
Derby Day Weather History…
The first Saturday day in May has produced a Kentucky Derby winner at Churchill Downs for more than 130 years now. These champions of the horse track have fought their way to victory against some of the toughest competition the world has to offer. They have also had to fight their way to victory again some of the worst that Mother Nature has to offer.
Smarty Jones weathered the storm in 2004 and ran away with the 130th Run For The Roses after a thunderstorm had muddied the track with nearly a half-inch of rain. Although last years race was certainly wet, Exterminator endured the wettest race in 1918, struggling to victory after more than an inch of rain fell. According to climatology, there is a 40% of rain falling on Derby Day. However, there is only a 25% of rain falling between the hours of 1 and 7PM.
Last year’s race brought afternoon temperatures that reached a very comfortable 80 degrees with lots of sunshine. Not all Derbies are that temperate though. In 1959, temperatures rose to a record 94 degrees as Tommy Lee nosed out a sweaty victory under a scorching late afternoon sun! Some 40 years after the 1959 Derby heat wave, winter returned to the Kentucky Derby. The passage of a powerful cold front on the eve of the 1989 Derby, was followed by temperatures that tumbled through the 40’s on race day. As Sunday Silence entered the starting gates for the start of the 115th running of the Kentucky Derby, the temperature had reached a bone chilling 43 degrees… the coldest post time temperature on record! Cloudy skies, light rain and a stiff northwest wind helped to produce wind chill readings near the freezing mark! A few wet snowflakes were even reported around the city late that afternoon!
The average race time temperature is a very pleasant 72 degrees. The very first Kentucky Derby was held in 1875 as Aristides rode to victory with temps in the mid 60’s under partly sunny skies. In 1973, a 65-degree day at Churchill Downs brought the fastest Derby on record as Secretariat recorded a winning time of 1:59:40. It is uncertain whether this year’s “run for the roses” will yield a record time, but at least it looks dry this time around.
Posted by at 11:22 PM | Comments (2)
April 17, 2006
Tornado, Fact or Myth?
With severe weather season in full swing across Kentuckiana, now is a good time to brush up on some tornado safety. Here is a list of common myths as well as facts about these deadly forces of nature...
Myth: "Opening windows will equalize air pressure and prevent an explosion"
Fact: Most experts agree that tornado-force winds will take care of opening the windows for you. Forget this old advice, and use your time to take cover immediately!
Myth: "Go to the Southwest Corner of your Basement"
Fact: Some studies suggest this might actually be the most dangerous place in your basement. If a tornado hits from the southwest, it could push debris into that area. The absolute best place to go is under the stairway that leads to your basement. The stairs will protect you from any debris that may fall into the basement. If you don’t have a basement, go to an interior bathroom or closet on the lowest floor of your home. Remember to always protect your neck and head.
Myth: “Tornadoes never strike big cities"
Fact: In the past several years, tornadoes have roared through several major cities including; Miami Florida, Nashville Tennessee and Fort Worth Texas. Of course Louisville was hit by a particularly large and powerful tornado on April 3, 1974. Despite folklore, no city or town has "Natural Protection" from a tornado.
Myth: “The low pressure a tornado creates will cause buildings to explode.”
Fact: Scientific evidence shows this is not true. In fact, in particularly strong tornadoes, violent winds and debris slamming into buildings will cause them to be destroyed well before the center of the storm, where the lowest pressure is, reaches it.
Myth: “Tornados only occur in the spring months.”
Fact: Most tornados do occur during the months from March to June and from 3 to 9 PM. However, tornados have been recorded in every month and at all times of the day and night.
Myth: “Areas near rivers, lakes and mountains are safe from tornadoes.”
Fact: No place is safe from tornadoes. In the late 1980s, a tornado swept through Yellowstone National Park, leaving a path of destruction up a 10,000 ft. mountain.
Two places you don’t want to be during a tornado are mobile homes and automobiles. Mobile homes offer no protection from the ferocious winds of a tornado. In fact nearly 40% of all tornado deaths occur in mobile homes. If you live in a mobile home, be sure to have a designated safe place to go to before the tornado warning is issued. If you're caught outdoors during a tornado, don't try to outrun it in your car. A tornado can change directions quickly. You should seek shelter indoors. If that isn't possible, get out of your car and duck down in the lowest spot you can find, such as a ditch or gully. Because a tornado doesn't suck objects up, but rather blows them around at speeds, which can easily exceed 300mph, a highway underpass is not safe since it leaves you exposed to flying debris. During these devastating storms, even the smallest items caught in its furry such as roof shingle parts, glass fragments, wood splinters and the like are bullets in the wind causing serious or even fatal injuries. Staying low to avoid this debris is the key to survival if caught outdoors.
Posted by at 12:11 AM | Comments (0)
April 05, 2006
What causes a thunderstorm?
With all of the severe weather we've seen lately here in Kentuckiana, it leaves one to wonder what causes the atmospheric phenomenon known as a thunderstorm?
In a nutshell, warm, moist, high velocity rising air in a sufficiently large volume creates a thunderstorm. The fuel for all storms is warm, moist air present near the Earth’s surface. If the atmosphere around the cloud is unstable, meaning it cools faster with increasing height than the ascending cloud, then the parcel of air containing the cloud is said to be buoyant. Just like an inflated beach ball that has been submerged under water, it will rise quickly to the top. As the cloud parcel rises, latent heat is released from the condensation of water vapor. The latent heat releases more energy into the parcel helping to increase its upward velocity. This process creates a column of rapidly rising air known as an updraft. Ultimately, it is this updraft that feeds a thunderstorm. A thunderstorm will last as long as a supply of warm and moist air is available.
Thunderstorms don’t always develop despite having an abundance of warm and moist air though. That is because a trigger is necessary to get the air rising in the first place. This trigger can be a large thermal created by lots of sunshine during the heat of the day, or the upward motion produced by fronts pushing air together.
A thunderstorm can extend several miles above the surface of the Earth. Because temperatures drop as you move up in the atmosphere, the tops of thunderstorms are made of ice. It is this complex mixture of water, ice and high velocity air currents that create the electric field in a storm. Strong electric charges build up between different parts of the thunderstorm as well as the ground below. This results in the phenomenon we know as lightning.
The energy in even a modest thunderstorm can be impressive. A 20-minute thunderstorm is said to produce about 100,000,000,000 watts of energy. That is more energy than was released from the atomic bomb dropped on Hiroshima.
Posted by at 12:50 PM | Comments (0)
March 14, 2006
Severe Storms “March” Into Kentuckiana…
A day after state tornado drills were administered for both Indiana & Kentucky, severe weather struck both states almost as if on cue. From high winds to flooding rains to large hail, we saw it all last week…
As the large upper level wind pattern began to change by midweek last week, so did our weather. A deep trough developed over much of the west, resulting in a south flow across the Ohio Valley and much of the Eastern US. Moisture was quick to return to the region and as several ripples traveled along the jet stream, a series of storm systems began to impact our weather.
The first in this series of storms arrived early Wednesday the 8th day of March. This first wave was in the form of a warm front that resulted in some heavy rains across much of southern Indiana. Anywhere between about a half inch to an inch of rain was recorded across most Indiana counties. Not a blockbuster of a storm, but it was enough to start moistening up the previously dry grounds.
The next day, Thursday the 9th, featured a vigorous shortwave trough in the upper levels and an accompanied surface cold front that dealt us some rain, some lightning and a whole lot of wind. Wind damage reports started pouring in by mid-afternoon from all across Kentuckiana as a prefrontal squall line of thunderstorms started sweeping across the area. A funnel cloud was reported in Dubois County, IN shortly before a barn was destroyed and a house was damaged by high thunderstorm winds. Although, numerous trees and power lines were downed by the afternoon storms, a second, more powerful, line of storms would rake through the area just hours later marking the arrival of the cold front. The second storm raced through the area delivering wide spread 60mph winds from Harrison & Floyd Counties in Indiana to Hardin & Nelson Counties in Kentucky. These winds blew a roof off a home in E-town, downed hundreds of trees and left tens of thousands of people without power.
In the wake of the powerful system on Thursday, Mother Nature gave us a break on Friday the 10th as high pressure briefly made a return to the area. The pleasant weather did not last long though. As another ripple developed in the jet stream, a warm front began surging moisture back into the area early on Saturday the 11th, just in time for the start of the first leg of the Triple Crown of Running – The Anthem 5K held in downtown Louisville. The storm resulted in a few severe thunderstorm warnings, some very heavy rain and about 6,500 soaked runners. The rain was so heavy, in fact, a large portion of southern Indiana picked up between 3 and 4 inches of rainfall causing lots of flash flooding.
Sunday the 12th turned out to be almost as wet as the 11th. As a weak cool front made its way south across the viewing area, a large area of heavy rain and severe thunderstorms made a north to south migration across Kentuckiana during the morning hours. The heavy rains only exacerbated the already swollen creeks and rivers especially in southern Indiana where so much rain had already fallen just the day before. To add insult to injury, after the front had made its plight through the viewing area, it backed back up as a warm front during the afternoon hours resulting in pockets of more heavy rain and a few more severe thunderstorms. By the end of the day, evacuations had been ordered for several small communities including Milltown, IN, which was engulfed by the usually tame Blue River, and several counties declared a state of emergency as many state roads and highways became impassable due to the rampant flood waters.
The last of the storms arrived on Monday, March 13th. As a powerful cold front approached from the west, another line of thunderstorms raced through the region during the late morning and into the afternoon hours. These storms intensified once again during the afternoon and produced high winds and some very large hail. Three quarter inch hail was very common across much of the southeastern viewing area. Hail to the size of quarters was reported near the town of Buffalo in Larue County, KY while the town of Upton in Hardin County, KY reported hail to the size of half dollars! These hail reports actually paled in comparison to the baseball sized hail that was reported just to the south in Warren County, KY.
When all was said and done, some places received as much as 8 inches of rainfall, saw winds up to 60mph and hail to the size of baseballs… Wow, what a week for weather! It leaves one to wonder what the months of April, May & June will bring?
Posted by at 01:37 PM | Comments (5)
March 06, 2006
Severe Storm Season Approaching...
It's getting to be that time of the year again. As warmer temperatures begin their cyclical return to the region, the threat for severe storms also returns. As a way to prepare for this upcoming severe weather season, both Indiana & Kentucky will be conducting practice drills this week...
Both Indiana and Kentucky will run statewide tornado drills this week. The week of March 5th-12th is "Severe Weather Preparedness Week" for Indiana and March has been designated "Severe Storm Preparedness Month" in Kentucky. On March 7 at 10:07 a.m. EST, Kentucky Division of Emergency Management, in conjunction with The National Weather Service, will originate an EAS message encouraging all Kentuckians to be aware of and to prepare for severe storms. Government agengies, businesses, schools, and residents throughout Kentucky are invited to participate in this drill. Take a moment to consider what you would do if a tornado threatened your area. It is imperative to have a plan in place BEFORE the warning is issued!
In addition to the drills, mother nature may give us a little practice of her own. Spring-like thunderstorms will be possible by later this week. Stay tuned...
Posted by at 12:02 AM | Comments (2)
February 15, 2006
A brighter and lighter outlook
It's true, winter has some pluses. It's time for hot chocolate and sledding. Also, families are brought closer together if for no other reason than to stay warm because we can't afford to pay for the heat. But now that we're well past the holidays, it's time to get serious about getting lighter and I don't mean shedding some pounds.
You've noticed it already. You probably have mentioned it to at least one other person and just the thought has brought a smile to your face. What is it? It's staying lighter later. No earthshaking revelation here but this trend will continue into the third week of June.
We were in the dark the longest at the end of December when we received about 9 and a half hours of daylight. Now we are receiving about 11 hours of daylight and gaining at a rate of 2 minutes a day. By the end of June we will bask in nearly 15 hours of daylight. Of course with all this additional sunshine, it does mean that we are increasing our daily temperatures. We are about 4 degrees warmer now then we were just a month ago.
Have you ever thought about the fact that our warmest weather in summer does not come on the day with the longest period of daylight? And conversely the coldest weather in winter does not fall on the day with the least number of daylight hours? Think about it, July is our hottest month but June 21st is our "longest" day. The same in winter, January is the coldest month but December 21st is out "shortest" day. What's with that?
The answer is....because of the oceans. With the Earth's surface covered mostly by water, water temperatures plays a big role in the Earth's temperature. It takes some time for all that water to warm up or cool down. In fact, there is about a month difference between the shortest day and coldest ocean water temperature and between the longest day and the warmest ocean water temperature. That's why January is the coldest month and July is the warmest. Is that cool with you?
Posted by ken.schulz at 08:54 PM | Comments (0)
February 08, 2006
What's up now with our weather?
What's up now with our weather? First, we get thinking that it's going to be a cold winter. Cold air started to settle into the area right after Thanksgiving reaching it's peak (or perhaps I should say it's depth) on December 9 when the high was only 23 after starting off the day at 12 degrees.
Temperatures remained seasonably cold through Christmas. Then on December 27 we hit 56 degrees and it got into the low 60's the next day. That was nothing. On January 2 the temperature hit and unbelievably balmy 72 degrees! Severe storms broke the back of that warm spell but just 6 days later on the 8th of January we were back in the upper 60’s. When Januray was over it went into the books as the 4th warmest on record. Then we got believeing that we wouldn't have any more winetr weather. However, winter returned the first weekend in February with highs in the 20’s and blowing snow. Now we may be looking at a stretch of weather with more cold than warm. So, what’s going on?
Weather tends to be the study of the law of averages. When we experience unusually warm weather, somebody else is having unusually cold weather. Large-scale weather pattern tend to shift but very slowly. Once a weather pattern that gets set up over us it may be over us for a period of 6 weeks before it is replaced. When it does so then the cold air that was someone else’s problem becomes our problem while those folks who were dealing with the cold get a chance to warm-up.
If this is the case we may be dealing with wintry weather up through the first weeks of March. Hey, the groundhog may be right after all!
Posted by ken.schulz at 08:22 PM | Comments (0)
February 07, 2006
It’s cold and getting colder…
It’s been said that weather runs in cycles. After a prolonged period of mild weather that started just before the New Year and ran through the month of January, winter has returned to Kentuckiana and it looks to stick around for a while…
The upper air pattern that brought us all the mild weather for much of this winter season has now reversed. Now the large ridge of high pressure that was responsible for the recent warmth has been replaced by a rather large trough of low pressure for much of the Eastern US. What does this mean to the layman? Well, basically that the cold air that has returned to the region will remain with us for at least another week, maybe longer. Current weather models are hinting at a formidable shot of cold air due to arrive here over the weekend. Should this scenario play out, we could be looking at the coldest temperatures we’ve seen so far this winter season as highs struggle to reach the middle and upper 20’s while lows dip back into the teens. In addition to the cold, we can look forward to lots of clouds, strong northerly winds and snow showers. Stay tuned…
Posted by at 05:50 PM | Comments (0)
February 01, 2006
Normal?
Last year was tied for the warmest year ever on record globally. We just went through the 4th warmest January on record here in the Louisville area and February started 20 degrees warmer than normal. So what’s normal?
Well, a rare event in weather is a “normal” day. When meteorologists talk about a normal or average temperature for a day, you would think that we’re referring to a temperature that occurs quite often on that date but…that is not the case. In fact we should probably never refer to a temperature as normal or average but call it the median temperature instead. So what does that mean? A median temperature is one where 50% of the days will be colder than that temperature and 50% of the days will be warmer. Now, that’s sounds about normal!
Posted by ken.schulz at 07:53 PM | Comments (0)
January 31, 2006
January Warmth...
If you were thinking that this was an unusually warm January for Kentuckiana, then you were correct. Only now that January has officially ended, we can prove it.
The average temperature for the month turned out to be 44.2 degrees. (Average monthly temperatures are determined by adding up all the highs and all the lows for the month then dividing the total by the number of days in the month, ie... 31 for January) The average monthly temperature of 44.2 degrees turned out to be the 4th warmest on record for Louisville dating back to 1870! In fact, the last time Louisville saw a January as warm as January 2006 was way back in 1950 when the temperature averaged out to be 44.6 degrees. On eight occasions the high temperature exceeded 60 degrees, including a daily record high of 72 degrees set on January 2nd. The coldest temperature recorded during the month was only 24 degrees on the morning of the 26th. Ironically, 24 degrees is about what the low temperature should be for this time of the year.
Posted by at 06:20 PM | Comments (1)
Weekend Snow??
Some of the computer models are finally pointing to a real snow producer for the area by this weekend.
Of course, Mother Nature will pick her own storm track but if the low travels just right, we could be seeing some significant snow totals. Odds are that the heaviest will stay just north of us but we need to watch this one carefully. We are 5 inches behind in snowfall for the season. It has been a very warm January which begs the question.....just how crazy will our weather get in February? We'll keep updating the First Alert StormTeam Forecast to pinpoint what you can expect for your weekend.
Posted by jamie.martin at 01:05 PM | Comments (0)
January 03, 2006
2006: A Stormy Start
Our New Year's Holiday was anything but normal.
First, the holiday was not on the First. It was on the Second.
It always brightens my New Year's Day to see the Rose Parade in sparkling sunlight from California.
Not this year.
There was Jack Hannah of the Columbus Zoo on a float called "the rain forest."
And it really was raining, raining hard. Jack was covered in clear plastic.
Water covered the camera lense and the tubas in the marching bands.
But that was just the beginning.
I settled in to watch the Gator Bowl and the Louisville Cardinals played a great first half.
New Year's Day in Louisville felt like we were in Jacksonville.
It was partly sunny and uncommonly warm. But, the Cards were hot.
Then the weather intervened again.
The game was interrupted by tornado warnings.
Then my wife, with some urging from Ken Schulz, ordered us all to the basement as the wind roared outside.
Virginia Tech scored the winning touchdown, while I watched the storm from a basement window.
By the time the storm cleared, I was relegated to watching the Sugar Bowl
The Sugar Bowl? Yes, the same Bowl game that was moved to Atlanta because of hurricane damage at the Superdome. It was a difficult day to escape the weather.
But at least West Virginia preserved a little dignity for the Big East Conference by downing Georgia 38-35. The Georgia Dome was full of hang dawg looks as the Mountaineers proved that the Big East belongs in the BCS final eight.
And speaking of bowls, allow me just one mention of the New Year's Eve Meineke Car Care Bowl in Charlotte. Instead of Car Care, .it should have been Who Cares. But, it gave North Carolina State a platform to shut out, yes shut out South Florida. These are the mighty Bulls, who scored 45 points on Louisville in September. Can anybody tell me, how these guys beat a 9-3 Louisville team.? At least the weather was calm for this game.
I wound up my holiday seeing the tornado damage in Hardin county. There was also the news of wildfires in Oklahoma, where it refuses to rain, and a torrent in California, where it almost never rains. And whatever happened to snow in January? It was a holiday slightly out of kilter.
Here's hoping for a 2006 where we return to normal weather patterns and a very short hurricane season.
Happy New Year.
Posted by gary.roedemeier at 11:31 AM | Comments (0)
