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Storm Watch

These charts are sometimes unavailable due to problems at COLA.

Forecast, Day 1 of Totals Totals Index and Precipitable Water.
Forecast, Day 2
Forecast, Day 3
Forecast, Day 4
Forecast, Day 5
Forecast, Day 6

The panels below are prepared daily from the US GFS model. They are produced by COLA, and come online about 5am and 5pm EST. They show forecasts of two important measures of the likelihood of thunderstorms -- CAPE (Convective Available Potential Energy ) and Precipitable Water (PW).

The yellow-brown shading indicates the amount of CAPE in the atmosphere, which is a good indicator of the potential for strong thunderstorms and severe weather. High values of CAPE indicate that most (but not necessarily all) conditions exist for strong thunderstorms. The scale is given in the top right corner of the map. CAPE measures the amount of energy available for convection throughout the depth of the atmosphere up to the limit of convection. It is also directly related to the maximum potential vertical speed within an updraft. While there are no hard-and-fast rules, readings over 1000 joules per kilogram (J/kg) would suggest the likelihood of thunderstorms, and over 2500 the possibility of severe storms.

The Precipitable Water lines on the maps show how much rain you would theoretically get at any particular point if you could squeeze the whole atmosphere like a sponge. Obviously, you need something to trigger the "squeezing", such as uplift caused by mountains, or instability in the atmosphere. That is why these two measures are overlaid on the map -- the tot-tots to tell you the forecast level of instability, and the PW to indicate how much moisture is available.

The boxes at right show the layout of the weatherwall. Be sure to check that the maps have been updated.