EPIC HEAT WAVE LOOMING?

There isn’t much stirring over the tropical Atlantic Basin yet, that is, there are no storms or hurricanes lurking in the foreseeable future. No Eyewall Janets. But that’s not unexpected in July.

Meanwhile, what’s really catching meteorologists’ attention is the steroidal upper-level high pressure area forecast to burgeon over the center of the nation.

That means a heat wave, perhaps one of epic proportions, looms for areas from Texas and Louisiana northward into the Upper Midwest. Expect the atmospheric oven to be turned on “broil” beginning this weekend.

My friend and former colleague at The Weather Channel, Stu Ostro, sent me some images of reconstructed upper-level weather maps from the 1930s. (They are “reconstructed” from surface data since upper air observations were few and far between 75 years ago.)

The 1930s, if you recall, were the Dust Bowl days. They were also years of legendary hot spells, especially in 1934 and 1936. One map Stu forwarded to me from late July 1934 bears an uncanny (scary?) resemblance to the pattern expected to develop this weekend.

That blistering period in 1934 saw state records set in Iowa (118F) and Ohio (113F)! Will it get that hot this year? Probably not. Iowa and Ohio haven’t exactly been dealing with Dust Bowl conditions of late. Still, be prepared for searing heat on the Plains and in parts of the Midwest. Certainly thermometer readings of 110F or so seem within reach.

Why so hot underneath big high pressure ridges? Such ridges are essentially huge atmospheric mountains. Air slides down the slopes of the “mountain,” heating and drying under its own compression. The result is a minimum of cloudiness, virtually no rain, and scorching sunshine. Heat wave!

Ironically, the humidity near the surface may be extremely high as low-level air imported from the Gulf of Mexico barges northward. That means heat indices, the combination of heat and humidity, will reach dangerous levels. No, let me be blunter: Killer levels.

I hope that forewarned is forearmed. As the old police sergeant on “Hill Street Blues” used to say, “Be careful out there.”

July 13, 2011

UPDATE, JULY 14: Several of the numerical models are now suggesting that the huge, hot upper-air high will migrate into the mid-South and Southeast by the middle of next week. If that happens–and I wouldn’t bet against it–well, if you live in Atlanta, can you say one-hundred degrees?