Thunderstorms and Heavy Rainfall in the Mid-Atlantic; Fire Weather Concerns in the West

Thunderstorms are expected to bring heavy rain and potential significant flash and urban flooding to the Mid-Atlantic on Thursday, especially along the I-95 urban corridor. Dry conditions, gusty winds, and isolated dry thunderstorms will continue to bring a critical fire weather threat to the northwestern Great Basin into the interior Northwest through Thursday. Read More >

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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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Thunderstorms and Heavy Rainfall in the Mid-Atlantic; Fire Weather Concerns in the West

Convective Parameters - EHI