Mark Johnson explains difference between thunderstorm and thundershower

CLEVELAND - I rarely use the term thundershower. But I did last week during one of my broadcasts.

It caught the attention of one thoughtful viewer who fired off this e-mail:

"What Meteorology school did Mark Johnson go to? The one in the bottom of a Cracker Jacks Box???? WHAT in the world is a THUNDERSHOWER??? I have lived in many large cities (Chicago, Orlando, Phoenix, Las Vegas and Boise) and NOT ONCE has a weatherman used such a silly term as "thundershower" ! Is He insane, because he certainly is not funny. Annoying would be a more fitting description. You can consider this household as EX-WEWS WEATHER REPORT VIEWERS. Time to teach the ole man some new, technically-correct terminology or just replace him altogether with someone who knows how to speak properly. Thank you."

Technically, a shower is defined as: "Rain from convective clouds characterized by the suddenness with which they start and stop, & by the rapid changes of intensity (AMS Glossary of Meteorology)." In aviation weather observations , rain showers are encoded as RW. R = rain. W= shower.

A thunderstorm is defined as: "In general, a local storm , invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder , usually with strong gusts of wind , heavy rain , and sometimes with hail . (AMS Glossary of Meteorology)" The aviation weather code for a thunderstorm is TRW. T=thunder. R=rain. W=shower.

Technically, every rumble of thunder is logged at a TRW, a thunderstorm. But, who am I forecasting for? Other scientists or the general public? Is a light rain shower with a brief rumble of thunder really a storm to you? Probably not. 

Broadcast meteorology is about taking information that can be very technical, and changing it into language and images that viewers can more readily understand and, more importantly, use to plan their daily lives.

To viewers and listeners, the word "storm" promotes images of heavy rain, high winds or worse. That's why many meteorologists across the country, on TV, Radio and at the National Weather Service use the term "thundershower" to denote weather that is less threatening to the public. 

Here's a meteorologist from the National Weather Service commenting on the use of the word "thundershower" in his forecasts: "I still use it, and there are others that use it too. There's nothing wrong with it. It's a perfectly good term to describe non-severe, garden variety summertime convection. Many media outlets, including The Weather Channel, CNN, and others, still occasionally use it to delineate between days when strong/severe thunderstorms are expected versus very little risk of such."

Other meteorologists use phrases like "showers, some with a few rumbles of thunder" in their forecasts where the person wishes to de-emphasize the thunder and lightning threat. This is just a longer way of saying "thundershowers." The word "shower" is perceived as being less threatening than the word "storm."

So, to respond to the viewer's email, the term "thundershower" does not exist when recording official weather data. But, in the world of weather communication, it is often used to describe a day when rain showers of varying intensity will contain a brief rumble or two of thunder. It implies strong to severe thunderstorms will not be a factor in planning your important daily events.

Thanks for the e-mail...I think.

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