What is the 'heat dome'?

By  | 

By: Charles Roop | WCTV Pinpoint Weather
July 19, 2019

Cooling shelters have begun opening up throughout the Quad Cities area due to extreme heat. (MGN Image)

TALLAHASSEE, Fla. (WCTV) – Many have been hearing about this thing called the “heat dome.” It’s not really a dome, and it shouldn’t be confused with
the Thunderdome. So, what is it? And why were many people baking cookies and biscuits in their cars?

This hot and humid pattern has to do with not just one, but two high pressure systems at different levels of the troposphere (the layer of the atmosphere where life and weather exists).

The first one is sitting in the upper levels, and sprawls across the eastern and central United States. The higher pressure is a signal of higher heights. For instance, the 250-millibar level is higher above the ground. These higher heights mean, in a nutshell, a warmer column of air. This higher pressure aloft also keeps storm systems and cold fronts away, maintaining the heat from the Midwest to New England.

The second high is in the lower levels, but over the Atlantic Ocean. Because of a high pressure’s clockwise flow (in the Northern Hemisphere), it’s pulling the muggy air from the tropics into the region.

And that leads to another topic about the heat and the human body: Humidity. We sweat to cool our bodies down, since evaporation is a cooling process. But when there is so much water vapor in the air, it just stays one’s skin. It keeps the person from cooling off, and they stay hot. Prolonged exposure to the heat can be dangerous.

With a warming planet, the heat waves will likely become more frequent. Heat-trapping greenhouse gas emissions will likely shift the bell curve in many locations in the globe, making heat extremes more common.

This pattern will begin to break down, leaving cooler-than-normal temperatures as soon as late next week for much of the country. There is a 40% to 50% chance of below-average temperatures for the Big Bend and South Georgia, according to the Climate Prediction Center.