Tuesday, November 19, 2013

Is It Time To Drop The "Thunder" In Severe Thunderstorm Warnings?

Our region tends to get a few events each year, most often in autumn and winter, that I typically classify as a fall (or winter) squall. Cold season squall lines in this part of the world don't carry thunder, often are short in duration, and can produce heavy rains and gusty winds.

Sometimes those winds are of severe criteria, sometimes not.

Severe criteria is greater than 58 miles per hour. While Monday's squall line did not produce severe criteria winds, it did produce 50+ wind gusts for a time and I think warnings were warranted.

The problem is that the warnings in place for such an event aren't the right kind of warning.

As of now, because squall lines are "convective", meaning that the development of the line is because of a temperature difference or some sort of atmospheric boundary, this places squall lines into the same class of warning as severe thunderstorms.

In the summer, makes total sense. In the autumn or winter, when lightning is minimal or nonexistent...it's a different story.

So, the result is a severe (thunder)storm warning that really isn't producing thunder but produces gusty winds.

This leads to the following results on twitter. By the way, I'm not blasting the messengers here...because the headline from the NWS reads "Severe Thunderstorm Warning".

I also don't blame the local National Weather Service guys. They do mention in the text of the warning that these were generally lightning-less lines of wind and rain moving in.  That said, they're stuck in the "box" that the national NWS has put them in regarding warnings.

I don't think issuing the warnings yesterday was a bad idea. It was the right call given the limits on what they can and can't issue. They could issue a blanket high wind warning but the atmospheric criteria for a high wind warning is non-convective, which yesterday morning isn't. That leaves severe thunderstorms or no warning at all...and if the line drops 60-70 mile per hour winds, God helped the forecaster who didn't issue that warning...

Should the NWS take a longer look at simply calling anything with a high wind and/or hail element "severe storms", simply removing the thunder part of the equation?  From a public communication end game standpoint, it might make sense to do so. For the Mid Atlantic and Northeast, where thunderless squalls happen a few times each year, it definitely makes it easier to communicate the end impact to the user. 

Most people associate storms in the summer with the potential for lightning, hail, wind so using the "severe storm warning" term would be universal and cover both the autumn events that carry no thunder and lightning as well as their summertime brethren.

It is a bit of a nit pick on my end but I do think if the NWS is going to be accurate in its description of warnings and impacts, a thunderless line of storms should probably not be in a severe thunderstorm warning.  Short of creating a new warning, the simpler solution is to just remove the word "thunder" from the existing severe thunderstorm warning going forward and just call them severe storms.

I know such a suggestion probably doesn't get acted upon anytime soon -- but I do think it will improve communication to the public and would more accurately define the incoming threat, regardless of time of year or whether it really does have thunder and lightning with it or not.