Upper Highs and Summer Dry Spells

Stagnant summer weather is the norm from June to August, punctuated by the occasional tropical wave or high-plains storm which drifts down from Colorado. Of course, there’s a heat-driven shower or thunderstorm now and then as well, but rainfall in each of the summer months averages less than half of what we see in either May or September.

The reason summer is such a dry season here (compared to say, Florida where it rains many summer afternoons) is due to a persistent high aloft this time of year.

Clouds and storms require rising air which can get high enough to cool, condense, and precipitate the moisture out. The upper high places an invisible thermodynamic “cap” on this action, so skies are often clear to partly cloudy on summer afternoons.

You’ll notice when the high aloft is strong or nearly overhead the clouds will be very stunted vertically; when we get toward the edge of the high lifting from daytime heating may overcome the “cap” and allow heat-driven storms to form.

Upper level highs can develop “weak spots” due to air cooling aloft, and sometimes mid-level lows will form right in the middle of one. Thus, a high aloft does not mean rain potential is zero, but when we speak of a moderate to strong high controlling Texoma weather, then you’d better rely on the garden hose to keep the yard green, and the carwash to keep your vehicle clean.

Take Care,

Steve LaNore

Chief Meteorologist

KXII-TV

 

 

 

 

 

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