Convective Available Potential Energy (CAPE) Forecast: Severe Storms Texas Tuesday

Another Excessive Rain Event in 10+ Days
03/29/2018, 8:40 am EDT
Dr. Klotzbach at Colorado State University 2018 Tropical Outlook
04/05/2018, 11:30 am EDT
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We've already seen plenty of severe thunderstorms during early spring but now that April is here severe storms become more prevalent and stronger. One way to forecast severe storms intensity is using oe of many severe weather indices. Convective available potential energy (CAPE) index is one of the best and indicates hostile weather across eastern Texas Tuesday afternoon.

Discussion: Warm and moist air is invited northward across Texas from the Gulf of Mexico ahead of an approaching cold front on Monday.  Interestingly, models indicate limited sunshine possibly related to excessive low level moisture caused by recent heavy rains across eastern Texas. Therefore wile dew points climb to 65-70F afternoon temperatures struggle to pass 80F.

Monday night is breezy from the south, mild and humid with lows generally near the dew point, around 70. A strong cold front moves into northwest Texas Tuesday morning surging south and east reaching the Texas coast prior to dawn Wednesday.

The front moves through eastern Texas at the right time to cause severe thunderstorms and possible isolated tornadoes Tuesday afternoon and into early evening. The convective available potential energy (CAPE) forecast is for values in the 2000-3000 j/kg range mid-to-late Tuesday afternoon across eastern Texas. CAPE values in that range support severe thunderstorms (Table 1). Values exceeding 3000 j/kg can trigger tornadoes.

CAPE Range




All Clear


Marginal Instability

Showery, some heavy


Moderately Unstable


2000-3000Very Unstable

Severe thunderstorms

>3000Extremely Unstable


Table 1: Approximate (can vary slightly regionally and seasonally) implications of CAPE index.

Expect severe thunderstorms with possible isolated tornadoes across south-central and eastern Texas Tuesday afternoon. Severe weather watch boxes issued by the Storm Prediction Center are certain.