National Weather Service United States Department of Commerce

Severe Weather Threats Across the Plains; Dangerous Heat and Wildfire Concerns for the West; Watching the Tropics

Severe thunderstorms are expected across the Central Plains accompanied by damaging wind gusts and large hail. In addition, heavy rainfall may lead to instances of flash flooding from the Plains and mid-Atlantic regions. The heavy rainfall threat continues across Florida and across the northern Gulf as we monitor a tropical disturbance tracking westward. Critical fire weather for the Great Basin. Read More >

Automatically generated image showing areas of 0-3 km storm relative helicity.

 

Thumbnail of an automatically generated image showing areas of 0-3 km storm relative helicity. Thumbnail of an automatically generated image showing areas of 0-3 km storm relative helicity. Thumbnail of an automatically generated image showing areas of 0-3 km storm relative helicity.
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4 Panel Display | Animated Loop

Helicity (0-3 Km) 

This is the 0-3 km (0-10,000 Ft. AGL) storm relative helicity which is a measure of the amount of wind shear available from the ground to roughly 700 MB.   Values greater than 250 m**2/s**2 suggest an increased threat of tornadoes, but high values with this index do not necessarily suggest that the environment is supportive of supercell structures (look at 0-6 km shear).  Larger values are generally better, but there are no clear "boundaries" between non-tornadic and significant tornadic supercells.  Negative values suggest that anti-cylonic (left moving) supercells will dominate.

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