National Weather Service United States Department of Commerce

Severe Thunderstorms in the Southeast U.S; Flash Flooding Threat for the Northern Gulf Coast

Severe thunderstorms are expected across portions of the Southeast and Carolinas today where a Slight Risk (Level 2 of 5) has been issued. A Slight Risk Excessive Rainfall Outlook (Level 2 of 4) has been issued for part of the northern Gulf Coast today due to the threat of flash, urban, and riverine flooding. Read More >

Automatically generated image showing areas of storm relative helicity.

 

Thumbnail of an automatically generated image showing areas of storm relative helicity. Thumbnail of an automatically generated image showing areas of storm relative helicity. Thumbnail of an automatically generated image showing areas of storm relative helicity.
Hour - 1 Hour - 2 Hour -3

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Helicity (0-1 Km) 

This is the 0-1 km (approximately 0-3,000 Ft. AGL) storm relative helicity which is a measure of the amount of low level wind shear available for tornadogenesis. This is not a good indicator of supercell potential which is related more strongly to 0-6 KM vertical shear. Values greater than 100 m**2/s**2, do suggest an increased threat of tornadoes provided a supercell is present.  Larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.

The arrows indicate the approximate right supercell storm motion using the Bunkers technique.

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