National Weather Service United States Department of Commerce

Erin Strengthens to a Hurricane; Heavy Rainfall Possible in Puerto Rico and the Virgin Islands, the Upper Midwest, South Texas

Hurricane Erin may bring isolated flash and urban flooding, landslides or mudslides, and possible tropical storm conditions to Puerto Rico and the U.S. Virgin Islands this weekend. Scattered thunderstorms and heavy rainfall may bring areas of flooding this weekend over the Upper Midwest. A tropical disturbance will bring locally heavy rain and mainly urban flash flooding to far southern Texas. Read More >

Automatically generated image showing areas of convective available potential energy.

 

Thumbnail of an automatically generated image showing areas of convective available potential energy. Thumbnail of an automatically generated image showing areas of convective available potential energy. Thumbnail of an automatically generated image showing areas of convective available potential energy.
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CAPE 

This is a surface based Convective Available Potential Energy (CAPE) measurement only.  In the cool season, elevated instability may be much higher than surface based cape.

On average, CAPE of 1000 J/Kg is usually sufficient for strong to severe storms. CAPE of 3,000 to 4,000 J/Kg or higher is usually a signal of a very volatile atmosphere that could produce severe storms if other environmental parameters are in place.

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