Severe Thunderstorms in the High Plains; Heavy Rainfall in the Mid-Atlantic

An Enhanced Risk (level 3 of 5) of severe thunderstorms is forecast across portions of the Central High Plains this afternoon. Severe wind gusts up to 70 mph and large hail will be possible. While PTC Eight has dissipated, additional heavy to excessive rainfall will be possible today across the Mid-Atlantic, especially in southeastern Virginia. Read More >

Automatically generated image showing areas of energy helicity index.


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EHI

The Energy Helicity Index (EHI) is a number which represents the combination of instability and storm relative helicity. Our calculation uses mixed layer CAPE (surface to 3000ft average parcel) and 0-3 km storm relative helicity. Values greater than 2 or 3 have been correlated to cyclonic supercells with increased tornadic potential. Negative values are indicative of an environment favorable for anti-cyclonic (left moving) supercells, but tornadoes associated with anti-cyclonic supercells are extremely rare.

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Severe Thunderstorms in the High Plains; Heavy Rainfall in the Mid-Atlantic

Convective Parameters - EHI