Jul 21, 2023 - Energy & Environment

Relentless U.S. heat wave is likely to extend into August

Data: NOAA; Map: Erin Davis/Axios Visuals
Data: NOAA; Map: Erin Davis/Axios Visuals

The stifling heat wave that has affected large parts of the U.S. for more than a month will not loosen its grip anytime soon, forecasters warn.

Why it matters: The longer the extreme heat lasts, the greater the economic and human health effects will be. In addition, the high temperatures are expected to contribute to drought conditions in Texas and the Southwest.

  • In the Lone Star State, El Paso has gone 35 straight days with a high temperature of 100°F or higher. The unrelenting conditions dry out vegetation and can lead to rapid drought development.

The big picture: The theme of broil and repeat is likely to continue well into August for tens of millions in America.

  • The bubble of high pressure aloft over the Southwest, known as a heat dome, may shift somewhat towards the Great Basin states, according to the National Weather Service.
  • But it is still likely to maintain a broad grip from the Southeast to Southwest, while expanding at times across the Plains, Midwest and South Central states, NWS forecasts show.
  • And in Europe, where all-time record highs have been set from Spain to France to Italy and Greece, another surge of extreme heat is expected from this weekend into next week.
  • The weather pattern is expected to remain conducive to more heat throughout the rest of the summer there, according to the European Center for Medium Range Weather Forecasting.

Zoom in: In the near-term, 116 million people were under heat alerts as of Friday morning, including only the second excessive heat warning, the most serious category, to be issued for Miami to date.

  • A sultry, dangerous heat will blanket the Southeast through this weekend, the NWS warns.
  • Some of the heat will then spread north and east, covering more of the Lower 48 states before the end of July, per the NWS' Climate Prediction Center.
  • The NWS is forecasting that the Midwest will see its hottest temperatures of the summer next week into the first few days of August, for example, but there will be scant relief in the Southwest.
  • The NWS' six-to-10-day outlook shows the country awash in orange and red hues.

What they're saying: "The Southwest U.S. is one of the parts of the globe that geographically, high pressure systems like to camp out on top of, so it does take something to move them out of the way," said meteorologist John Nielsen-Gammon, director of the Southern Regional Climate Center, during a NOAA press briefing on Thursday.

  • "The Southern Tier of the U.S. and even the Pacific Northwest could end up with another period of quite warm weather and quite extreme weather during the month of August," said NOAA meteorologist Matt Rosencrans.

The intrigue: One driver of the record warmth lies in the oceans, where temperatures are also record warm.

  • This is particularly the case in the North Atlantic, where the sea surface temperatures have hurricane forecasters' attention. The Weather Company, for example, increased its hurricane season forecast on Thursday, and sees an above-average season.
  • Two factors will vie for influence of the Atlantic hurricane season — an El Niño event that may knock down the number of tropical storms and hurricanes, and the ocean temperatures. The new outlook bets that the ocean temperatures will prove more determinative.
  • The waters around South Florida are in the mid-90s°F, which is unheard of. Ocean temperatures are also above average in the Gulf of Mexico, and the Mediterranean Sea.

Between the lines: NOAA issued its highest level of coral bleaching alert for this region.

  • The unusually warm waters are influenced both by human-caused climate change and more transient weather patterns, as heat domes favor clear skies and warmer air temperatures, thereby increasing water temperatures as well.

Context: The globe is virtually certain to set a record for the warmest month on record, as well as the warmest July. This would follow the warmest June, and potentially lead into the warmest August — which would spell the warmest summer on record.

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