Severe Weather Risk More than Slight
The D.C. area is under a "slight risk" for severe thunderstorms tomorrow, and I don't like it one bit.
It's not that I'm averse to heavy downpours, loud claps of thunder, gusty winds, large hail and the potential for tornadoes. In fact, as a meteorologist, I think all these are pretty exciting. My beef is with the the word "slight," and the misleading message it may send to the public at large.
Keep reading for more on my problem with "slight," and see our full forecast for the latest on tomorrow's potential for severe storms and what kind of weather will follow into next week.
The "slight risk" designation comes from the National Weather Service's Storm Prediction Center (SPC) , which routinely issues forecasts for severe weather across the country, and indicates a 15-30% chance that a severe thunderstorm will happen within roughly 25 miles of any given point inside the area circled in the graphic above, according to SPC. A severe thunderstorm is defined as "a thunderstorm producing hail that is at least penny size, 0.75 inches in diameter or larger, and/or wind gusts to 58 mph or greater, and/or a tornado."
Technically speaking, I'd say "slight" is a fair translation of a 15-30 percent chance. The truth of the matter, however, is that the potential for severe weather tomorrow in the D.C. area and throughout the mid-Atlantic is real and significant, and often is on days the region is classified under the "slight risk" category. Yet, my hunch is that many people interpret "slight" along the lines of its dictionary definition -- "of little importance ... trivial" -- which is a dangerous assumption considering the damage to life and property a severe thunderstorm or tornado can cause.
In gambling terms, if Big Brown was given only a slight chance of winning the Triple Crown in next Saturday's Belmont Stakes, I'd probably bet against him. (For the record, oddsmakers are giving the horse a much better chance than that.)
Furthermore, while I don't have any hard stats on this, my recollection is that most of the severe thunderstorms and tornadoes that occur in the mid-Atlantic occur on "slight risk" days. This is mainly because, unlike the central United States and Southeast, the mid-Atlantic rarely sees the atmospheric conditions needed to be categorized under a "moderate" or "high" risk.
A skilled weather forecaster and communicator, if he or she even reports the risk assigned by SPC, will put that information into context by providing a more in-depth explanation of the potential for severe storms (see our latest forecast, for example). Problem is, people don't always get their weather information straight from the source. Often, it's filtered by a radio DJ or broadcast in the form of an Internet headline, both of which may mention a "slight risk" with little or no elaboration.
What "slight risk" fails to communicate, at least in my mind, is that the risk of severe storms is quite real compared to a day on which there's a chance of merely garden-variety thunderstorms. Tomorrow, for example, several ingredients that would support the formation of severe storms -- including an unstable atmosphere, changing wind speed and direction with height, and the jet stream swinging over our region -- are expected to be in place.
Even so, it's entirely possible that few or no severe storms will materialize. But that doesn't change the fact that the atmosphere will be much more ripe for the development of severe weather than it normally is -- a situation not well-portrayed by the term "slight risk," in my opinion.
Considering I started this complaining, I should probably step up to the plate and suggest an alternative label to "slight." Instead, I'll let you take the first crack using the comments link below.
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