National Weather Service United States Department of Commerce

Heavy Rain in the Ohio and Tennessee Valleys; Watching for Tropical Cyclone Development in the Atlantic

Heavy to excessive rainfall may bring areas of flash and urban flooding over portions of the Ohio and Tennessee Valleys. Two tropical waves in the Atlantic are being monitored for tropical cyclone formation within the next few days. One tropical wave will bring periods of heavy rain, thunderstorms, flood risk, and landslides to Puerto Rico and the US Virgin Islands through Friday morning. 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

4 Panel Display | Animated Loop

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.

Back to Convective Parameters Home