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Meghan's WEATHER CORNER |
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October 2009
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"I live in the Star Ranch subdivision near Hutto. Last night the storm was short, but severe. Hail and very strong twister like winds blew down my fence on both sides along with my neighbor's play house and patio furniture. It also picked up their big trampoline and it landed three houses away. My garage doors seemed to suck in and out." - Lynn Bryan We know severe wind gusts over 65 mph tore up homes and businesses in Hutto and Taylor a couple of nights ago, but were those wind gusts the result of a microburst or a tornado? What happened in Hutto was a severe downburst wind event. They often happen very quickly and without much warning. Below you will see a couple of images I found to help explain a microburst. This is the same type of an event that brought down the Cowboys practice bubble up in Irving back in May.
It is the same event that brought down Delta Flight 191 as it attempted to land at DFW International Airport on August 2, 1985. Sadly, 8 crew and 126 passengers lost their lives in that crash, but it was essential in the development of windshear detection equipment that keeps airplanes in safer environments today.
A downburst (or microburst) is a different process than a tornado, but severe wind damage is easily seen in both situations. Heavy rain-cooled air rushes down out of the base of the thunderstorm. Research has shown that melting of hail can play an important role in downburst formation. The rainshaft and winds in a microburst smash into the surface of the earth and spread outward from the point of impact. Hutto and Taylor were likely at that point of impact where winds were upwards of 65 mph.
In these pictures from the National Oceanic and Atmospheric Administration below, notice the surface curl soon after a microburst impacted the area. It is a real world example of the schematic above.
One of the things the meteorologists at our local National Weather Service offices are trained to do is observe damage patterns after severe wind events. The patterns can help determine and support what processes might have been occurring at the time the damage was sustained. The swirling and chaotic winds in a tornado will leave strikingly different damage patterns than straight-line wind or microburst events. Since the wind spreads outwards in all directions, the wind regime in a microburst is opposite to that of a tornado. The environment prior to thunderstorm development is also very important. Our atmosphere this time of year is not as favorable for tornado development, due to the lack of upper level wind support.
We need strong upper level winds moving from southwest to northeast and low level winds out of the southeast to create a rotating thunderstorm updraft. As that rotating updraft grows taller and turns faster, a tornado can spin up at the surface. We most often see this along strong cold fronts in the spring.
Scattered thunderstorms that we see over the next couple of days, will be in a favorable environment for severe downburst or microburst winds. As in the case of Hutto and Taylor, no severe thunderstorm warning was in effect at the time of the microburst. They can happen suddenly and with very little warning, so keep an eye to the sky the next couple of days. 3 CommentsLeave a comment |
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Meghan Danahey
Meghan Danahey can be seen Monday-Friday on KVUE News Daybreak and Midday. |
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I'm a month late reading this, but I am glad I found it. This was a clear, straight forward explanation of the difference between a tornado and a downburst that was easy for anyone to understand. My only expreience with a strong wind, hurricanes excluded, was several years ago. That wind lifted a roof off my mobile home. It was an aluminum roof that allowed the addition of extra insulation. I never did understand how it managed to rip the roof off and throw it into the next door neighbor's yard.
Howdy Meghan,
I enjoy your morning weather report. You are energetic, bright, and charming, and
provide an accurate forecast.
That said, regarding the George Strait concert at the Cedar Park Center, and your "not a bad seat" statement, I must say that my floor seat was really bad...screens were directly overhead, could hardly see George and folks stood up straight from the beginning of the concert. Certainly not worth over $160 each...certainly not.
Dominick
Howdy Dominick... That stinks about your George Strait experience! I have to admit that I will not likely buy concert tickets at the new Cowboys stadium in the future. I just went to U2 and the sound was so bad you couldn't tell what song was playing! People were leaving their $100 seats only three or four songs into the show. A man quoted in the Fort Worth Star Telegram said, "it sounded like Charlie Brown's teacher." Good for football. Bad for live music!