Tropical Storm Dexter formed along a stalled front a few hundred miles east of the North Carolina coast and about 300 miles west-northwest of Bermuda at 11 p.m. EDT Sunday, August 3. Dexter’s formation date of August 4 (in Greenwich time) comes over a week before the typical August 15 appearance of the season’s fourth named storm, based on 1991-2020 climatology.
The usual date of the Atlantic’s first hurricane is August 11, but because none of the named storms so far have strengthened into hurricanes, it’s possible we will go beyond that date in 2025 without one.
At 5 a.m. EDT Monday, Dexter was located about 255 miles (415 km) northwest of Bermuda, with top sustained winds of 45 mph (75 km/h), a central pressure of 1002 mb, and headed east-northeast at 12 mph.
Three of this year’s four Atlantic named storms have developed outside the tropics, north of latitude 30 degrees, where abnormal oceanic warmth has been concentrated this summer. Dexter’s formation was aided by warm sea surface temperatures around 29 degrees Celsius (84°F), about 1.5 degrees Celsius above average for the location and time of year. According to Climate Central’s Ocean Shift Index, human-caused climate change made the ocean temperature at this location about 400 times more likely to occur. According to an analysis by Michael Lowry (Fig. 1), these temperatures were record-warm for this time of year.
Forecast for Dexter
High wind shear of about 20 knots from strong upper-level winds out of the west will increase to over 30 knots by Monday night. The high shear and plentiful dry air should keep Dexter from becoming very strong. The National Hurricane Center predicts that Dexter’s winds will peak at 50 mph (80 km/h) on Tuesday as steering currents keep the storm well northwest of Bermuda, making it a classic “fish storm” of concern primarily to marine interests. Dexter will likely become post-tropical by Wednesday or Thursday.
An exceptionally weak one-two-three-four punch from the season’s first four named storms
Dexter is destined to be the season’s fourth-straight short-lived named storm. It follows on the heels of three other underachieving tropical storms:
- Andrea, which formed on June 24 in the remote central Atlantic between Bermuda and the Azores Islands
- Barry, which formed off the coast near Tampico, Mexico, on June 29
- Chantal, which formed a few hundred miles off the South Carolina coast on July 5.
Andrea and Barry both lasted less than a day as named storms. And although Chantal ended up causing major flooding in parts of western North Carolina and took six lives, the storm lasted just 1.25 days. The combined duration of the Atlantic’s first three named systems of 2025 was a mere 2.5 days, compared to the average value through August 2 (1991-2020) of 9.1 days. Dexter will likely last only about three days at best.
Andrea, Barry, and Chantal jointly produced an anemic 2.5 on the Accumulated Cyclone Energy or ACE scale, which may be a record for the lowest ACE from the season’s first three named storms.
Two more systems could develop in the Atlantic over the next week
Despite the tepid output of this year’s Atlantic season to date, the National Hurricane Center was tracking two areas beyond Dexter on Monday. Low pressure may develop later this week off the Southeast U.S. coast, along the stalled frontal zone that spawned Dexter, and a handful of ensemble members from the GFS and European models bring this potential disturbance into the Southeast coast toward the weekend, albeit with only modest strength. In its Tropical Weather Outlook issued at 8 a.m. EDT Monday, NHC gave this system near-zero odds of development through Wednesday but a 30% chance over the rest of the seven-day period. Regardless of development, this disturbance will likely bring two to four inches of rain late this week to the coasts of northwest Florida, Georgia, and southwestern South Carolina.
Further afield, there’s somewhat more robust support from ensemble members for a tropical wave to develop in the central tropical Atlantic by late week. It appears unlikely this system would move west into the Caribbean, but it could take enough of a west-northwest track for it to potentially approach the Bahamas and the U.S. East Coast by next week. NHC gave this system near-zero odds of development through Wednesday but a 50% chance over the rest of the seven-day period.
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