Should forecasters rank thunderstorm intensity?

AccuWeather’s Margusity develops scale

Imagine watching the radar as a line of thunderstorms approaches and as you mouse over the various storms, instantly seeing how intense they are on a scale from 1-5? That’s AccuWeather senior meteorologist Henry Margusity’s vision for his “T Scale” which ranks thunderstorms based on a set of six criteria

The criteria all fit into to the overall the impact a storm might have on a given area and include: rainfall rate, maximum wind gusts, hail size, peak tornado possibility, lightning frequency and darkness factor.

The lowest end of the scale, T1, signifies a relatively “weak” thunderstorm which produces no damage, whereas an “extreme” T5 thunderstorm at the upper end would produce severe and widespread damage.

“I’m trying to communicate to the public what these thunderstorms are going to do whether it’s heavy rain, winds to 70 mph, tornadoes,” Margusity said. “Every thunderstorm has its own identity, its own characteristics.”

A key application of the scale is communicating relative risk. Whereas the storm that spawned a tornado demolishing parts of an entire town in Iowa Saturday was a T5, Margusity says today’s storms predicted for the Tennessee and Ohio Valleys probably wouldn’t exceed a T4 (or “intense”).

“The scale tells you today’s storms are not going to be as extreme, but are still going to be intense so you better be ready for it,” Margusity said.

(Margusity is projecting up to T3 intensity storms for the D.C. area late tonight and Tuesday morning)

Margusity, who has beta-tested the scale on his blog and Facebook page says the response so far has been “favorable.” He now plans to develop a technical manuscript to submit to a peer reviewed journal. He thinks the proposed scale will “stir up” the meteorological community, which has yet to embrace such a tool. He also hopes to develop digital applications using the scale.

“My goal is to get this on every cell phone,” he said. “I’m all about getting the public to understand what’s about to happen.”

Separate from the T scale, the Weather Channel’s severe weather expert Dr. Greg Forbes has developed the Tornado Condition Index (TORCON) which provides a percententage risk of tornado development within 50 miles of a location in a specified area of severe thunderstorm activity. It does not provide information on other thunderstorm impacts.

Capital Weather Gang’s (CWG) Thundercast Scale

In a number of ways, Margusity’s “T scale” is analagous to the “Thundercast Scale” independently developed by CWG. The number of lightning bolts in CWG’s scale is pretty similar to Margusity’s T1-T4 levels. As Margusity’s scale is more detailed and fleshed out than our scale, we are considering adopting it. Margusity says he welcomes partners. What do you think?

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.

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