By KSN Chief Meteorologist Dave Freeman

March 2005 -- You may not realize it, but there is a revolution in the air this spring! For the first time in more than 50 years, the National Weather Service is taking another look at just what is a "severe thunderstorm?" And, it is a change that the KSN WeatherLab Team is very glad to see--and I bet most of you will be glad to see it too.

Regular readers of this column know that I have been asking the NWS for a long time to reconsider the size of hail that determines a "severe" thunderstorm. (See August, 2002 column and November 2004 column) Back in the 1950s, the NWS set 3/4" diameter hail (the size of a penny) as "severe." This has always bothered me because penny sized hail by itself does not pose a danger that would, for example, require people to go to shelter, etc. And, over the years, as weather radars and the skill of meteorologists have improved, this has resulted in a large number of severe thunderstorm warnings being issued for storms that really do not pose any significant threat to people. On top of that, in this day and age, severe thunderstorm warnings are broadcast by the media, NOAA Weather Alert Radio, pagers, cell phones, email--you get the idea. Back in the 1950s, no one would have ever dreamed of our "connected" world!

So, many meteorologists have been asking that quarter sized hail (approximately 1" in diameter) be set as the threshold for "severe" hail. The KSN WeatherLab Team believes this is a sound decision. Some property damage can occur and windows can be broken. This is a much more significant size of hail that really does warrant folks taking action at home.

This storm season, the National Weather Service offices in Kansas and in Hastings, NE, are conducting a field experiment using the 1" hail criteria for severe thunderstorm warnings. Here in the KSN WeatherLab, we believe this will reduce the number of severe thunderstorm warnings, and focus attention on those storms that really do pose a threat to the public. We will do all we can to support the Weather Service in this experiment, which we believe will be successful.

It is important to note that while the hail criteria for a warning will change, the wind speed for severe thunderstorms will remain the same. Winds of 58mph or greater are considered "severe." Here in the KSN WeatherLab we believe this is the right thing to do, as 58mph winds are strong enough to cause some property damage, including breaking windows, roof damage, broken tree limbs and even some trees being uprooted.

You should also remember that, of course, tornadoes will continue to be warned on as usual.

Of course, here in the KSN WeatherLab, we will work just as hard as ever to track storms in Kansas to make sure that you and your family have all the time you need to take shelter from storms that are dangerous. And, we'll be working with our colleagues at the National Weather Service to follow this important experiment to determine its benefits.

Dave Freeman
KSN Chief Meteorologist
weatherlab@ksn.com