At 2:00 PM EDT on 7/22/23, the National Hurricane Center announced that Tropical Storm Don became Hurricane Don, the first Atlantic storm to achieve hurricane-force winds this year. Not only did Don form earlier than usual, it formed farther north than usual – between New England and Europe. Hurricanes hardly ever form in that area this early in the Atlantic hurricane season.

Hurricane Don’s Current Location

Hurricane Don’s Expected Track

NHC expects Don to decrease in strength to a tropical storm on Sunday and a tropical depression on Monday as it turns toward Europe.

Higher than Normal Sea Surface Temps Contribute to Early Formation

Warmer than normal sea surface temperatures played a role in the intensification of Don. Note the dark brown to black areas off the coasts of New England and Newfoundland. Those colors indicate a whopping 4 to 5 degrees centigrade above normal. That equals 7-9 degrees Fahrenheit.

No Hurricanes Reported Forming That Far North This Early

NHC shows that in the 165 years between 1851 and 2015, no other hurricane formed as far north as Don during this 10-day period.

Average Dates of Formation for Named Storms

Usually, the Atlantic Basin doesn’t see its first named hurricane until August 11. So Don is a month ahead of schedule on that count.

Don is no threat to the Houston area. But Don’s timing may give us a clue to the type of hurricane season this will be. Both Colorado State and NOAA predicted slightly above average hurricane seasons this year.

The fourth tropical storm of the year doesn’t usually happen until August 15. And the first hurricane doesn’t usually happen until August 11.

El Niño Not a Factor in Don’s Formation

It takes the alignment of seven ingredients to form tropical cyclone. NOAA lists warm seas as #2. And we certainly have that around the world this year year, as you can see in the anomaly map above.

Wind shear from El Niño would not play a factor in deterring hurricane formation as far north as Don OR this early in the season, says Harris County’s meteorologist Jeff Lindner. “El Nino has little to no influence on our weather during the summer months (June-September),” says Lindner.

“The majority of El Nino’s influence on southern plains and Texas weather is during the fall, winter, and spring (October-May). This time of year we tend to be controlled by the sub-tropical highs around 30º N and/or the influences of the tropics from the Gulf of Mexico. This particular year the Sonoran sub-tropical high over the SW US and northern MX had thus far been the main controlling factor in our weather and El Nino has little impact on that.” 

Lindner concluded, “The wind shear associated with El Niño is mainly across the southern Gulf of Mexico, much of the Caribbean Sea, and the western deep tropical Atlantic. However, wind shear thus far this hurricane season has not been overly impressive for an El Nino summer and there are some suggestions that the very warm Atlantic waters may be lessening the impacts of El Nino and its wind shear in the Atlantic basin.”

We’re into uncharted territory, so to speak. This is where it gets interesting.

Posted by Bob Rehak on 7/23/2023

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