Why this heat won’t go away

Thanks to joeyd on Click2pins for this morning's sunrise pic

We’re all exhausted by this relentless heat and a viewer asked:

Is this related to the El Nino, La Nina effect? Do we expect a shift anytime this year?



Absolutely. I want to explain how La Nina and a warming Arctic are both contributing to this heat wave. So let’s start with what is called a heat dome:

High-pressure circulation in the atmosphere acts like a dome or cap, trapping heat at the surface and favoring the formation of a heat wave. Courtesy NOAA

A heat dome is high pressure trapping heat, but HOW do these form? Thank the Pacific Ocean. Cool La Nina waters to the south meet warmer waters to the north. I’ve illustrated this below:

Warm Water north and Cool Water south help create the Heat Dome. Courtesy Tropicaltidbits.com

According to the National Oceanic and Atmospheric Association, a team of scientists investigated what triggers heat domes and found the main cause was a strong change in ocean temperatures from west to east in the tropical Pacific Ocean during the preceding winter. You can see the warm/cold difference above that persists today and has been in place since last winter. Accordingly, this causes more warm air, heated by the ocean surface, to rise over the western Pacific. Wind moves that hot air east toward the United States where it sinks, resulting in heat waves. You can read more here.

That’s La Nina’s role. And now to the Arctic, which is warmer than it has ever been, so there is no strong plunge of cool air south. Consequently, the jet stream this summer is weak and staying north, unable to move any cold air into the heat dome to break it down or move it out. Not that there is a lot of cold air TO move our way. Here is today’s jet stream:

Courtesy Weather Underground and The Weather Company

And the first two weeks of August? Climatologist Judah Cohen pointed out this week that the American and European ensemble models both show strong heat domes moving across the Northern Hemisphere, the strongest of them settling by mid-August right over the central United States. If you don’t already, you should absolutely be following Cohen on Twitter @judah47.

Here’s a look at the European and the thing to notice is the BROWN color -- those are the heat domes and while they may shift a bit, they don’t go anywhere:

The European model through August 12 showing heat domes continue. Courtesy Tropicaltidbits.com

Bottom line, the heat continues. I responded to Greg and he wrote: “Thanks for clarifying the La Nina information. Maybe next spring it will shift and we will have more rain and cooler temperatures. You might say something about these long-term trends in your forecasts. People might find it interesting. You would probably be the only person on local TV speaking about it. Thanks again, Greg”

You’re welcome and thanks for the question! I hope everyone found it interesting! And I hope La Nina will shift by spring as models keep it around at least through winter.

Have a great weekend and stay cool! More dust arrives tomorrow.


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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.