National Weather Service United States Department of Commerce

Regional Outbreaks of Severe Weather Through Early Next Week; Early Season Heat Wave across the South

Active spring pattern across the center of our nation with several episodes of severe weather and heavy rainfall expected into next week. The potential for very large hail, long track tornadoes, severe wind gusts, frequent cloud to ground lightning strikes and flash flooding are in the outlook. Furthermore, dangerous early season heat wave continues for the Gulf Coast states into early next week. Read More >

Automatically generated image showing areas of energy helicity index.

 

Thumbnail of an automatically generated image showing areas of energy helicity index. Thumbnail of an automatically generated image showing areas of energy helicity index. Thumbnail of an 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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