Why so hot?

courtesy pixabay.com

We did it “officially” yesterday -- 100° for the first time since Aug. 29, 2020 and the forecast for the week ahead has a LOT of triple digits in it:

10 DAY forecast

And while that 102° looks daunting, the American Model predicts that Saturday’s temperatures in our area will reach 105°! Here’s a look across the state:

American model forecast courtesy tropicaltidbits.com

The reason is what is called a warm core high. People don’t think of it often, but air has weight -- you know this because your car tires are inflated to a certain air pressure and when that air isn’t there those tires go flat! The weight of air, or its pressure, decreases as we go up and perhaps you’ve felt the pressure difference in your ears going up in an airplane.

The bottom line here is that we measure the weight of the air (that’s what a barometer is for) and when it’s heavy it’s considered high pressure. When the air is lighter it’s considered low pressure.

What we have now is a warm core high, meaning that the warm air goes way up there. Here’s a simple way to look at warm high pressure when it dominates the atmosphere -- those levels of 700 mb, 500 mb and 300 mb are right at 10,000 feet, 18,000 feet and 30,000 feet:

courtesy Jeff Haby theweatherprediction.com

Notice the downward arrows in the above graphic indicating heavy, sinking air. When air sinks to the surface it compresses and that heats it up even more. In addition, without much rising air we don’t get clouds or rain -- just a lot of hot, blue sky!

That warm core high is forecast to be right over our region Saturday and when it’s right over you, it’s even hotter, thus the forecast to 105°:

A huge High Pressure dome will be right over us Saturday. Graphic courtesy tropicaltidbits.com

Of course, the big question is how do we get rid of it? Not easily, I’m afraid. Cooler air from the north will chip away at it and humid air from the Gulf will chip away at it, so we might see it ease next week, or at least relocate to the west. But it’s forecast to build back our way to produce a firecracker of a July 4th:

courtesy tropicaltidbits.com

In addition, the July climate forecast has us in a 50-60% chance for above normal temperatures:

courtesy NOAA

If there is any upside, it’s that highs like this one keep tropical storms away. In fact, sometimes it takes such a storm to break down the high and get us back to more average temps. You can read more about high and low pressure systems from Professor Jeff Haby right here.

Frank

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About the Authors:

KPRC 2's chief meteorologist with three decades of experience forecasting Houston's weather.

Amanda Cochran is an Edward R. Murrow award-winning journalist. She specializes in Texas features, consumer and business news and local crime coverage.