Daily Archives: June 15, 2008

The Thunderscale

The “Thunderscale”


Kenneth Burchfiel


For earthquakes, there’s the Richter scale. Tornadoes, the Fujita scale. Hurricanes? Saffir and Simpson took care of that. To this day, though, there remains no universally accepted scale for measuring the output of thunderstorms. Though the following certainly isn’t scientifically developed, nor is it detailed and researched enough to become a standard, it is one option that weather aficionados like myself can use.


Thunderscale: a means for categorizing thunderstorms by intensity

Note: all but one point of criteria for each level (TS1-Ts6) must be met over a given location for a storm to fall into the level for that spot. This means that a thunderstorm can have different TS levels depending on the location of the observer, an important thing to note. What might be a TS2 storm for one viewer might be a TS5 storm just 20 miles away.

For observers, thus, this system becomes personalized. (Example: “I experienced TS3 conditions yesterday.”) However, for newscasters and storm overviews, it’s best to use what one might call Max Thunderscale, or MTS, in reference to the storm’s center. (Example: “The storm reached a MTS of 6 yesterday before dissipating.”)


TS1: Light

    –Drizzle or no rainfall

    –Generally calm winds

    –Widespread breaks in cloud cover

    –Thunder is faint or imperceptible


TS2: Moderate

    –Rain is light, but steady

    –Noticeable winds (3+ mph)

    –Some breaks in cloud cover

    –Thunder and lightning are noticeable, but distant


TS3: Heavy

    –Moderate rainfall with some heavy bursts

    –Winds gusting to 10 mph or more

–Sky is mainly overcast, except for one or two breaks

    –Consistent perceptible thunder


TS4: Severe

    –Rainfall thick enough to blur out distant locations

    –Winds gusting to 15 mph or more

    –Sky is both overcast and noticeably dark

    –Lightning is visible and persistent; thunder jarring at times


TS5: Dangerous

    –Downpours of rain

    –Winds gusting over 30 mph

    –Sky nearly black

    –Thunder in immediate vicinity; less than three seconds in between lightning and thunder

    –Hail at times


TS6: Life-threatening

    –Rain and hail fall in visible sheets; nearly impossible to see over 50 meters

    –Winds gusting at 50 mph or more

    –Sky is all but black; green tint possible

    –Constant, immediate lightning with booming thunder

    –Hail larger than a centimeter

    –Tornadoes reported in the area


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