Mark Murray: April 2009 Archives

Rob writes:

"Recently there was a storm rolling in from the West. I mean...this thing had been a big yellow, orange, red and maroon ball for well over an hour barreling towards Austin. Then...as so often happens...somewhere between 620 and 360, the storm broke into a million weak little pieces. Just like someone hit it with a sledge hammer. I cannot tell you how OFTEN this same thing happens. So...here is my question:

Why does this seem to be so? Am I just crazy or is there something about the terrain of the city (the hill country or the higher "city" temps) that help it to repel some storms? Is it just an illusion and once a storm is upon the city, the radar "sees" the storm more accurately?

Thanks man...love yer work!"

Hello Rob,

That's a great question, and one that I get often! There are a couple of things going on that could explain why storms always seem to break up as they approach your house. First, remember that a typical thunderstorm has an average life cycle of around 30 minutes. So if you see a thunderstorm on radar that's about 30 minutes away, chances are that it may fizzle before reaching you.

The other reason has to do with the radar, itself. Of course we have access to several radars that cover Central Texas, but the ones we use most often are the National Weather Service Doppler Radars located in New Braunfels (close to I-35) and near Granger in Williamson County. When the radar signal leaves the radar dish, it is a very tightly focused beam of energy. Say we have thunderstorms moving in from the western Hill Country. By the time the radar beam reaches those storms, it is a much wider beam. It may be too wide to detect breaks in a line of storms. But, by the time the storms reach the I-35 corridor, the beam is narrowly focused and is able to detect breaks in the line of storms that have been there all along. So, depending on the radar location, a radar time lapse can give the false impression that a solid line of storms is "breaking up" as it gets closer to the radar site.

Thanks for writing!

Mark Murray

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Thanks for making our first KVUE Storm Spotter training in Round Rock such a big success!! Because of your calls and email, we're likely to have more training sessions in the near future. Watch this space! I'll post details in the next few days!

-Mark

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