The unprecedented quiet in the Atlantic during what is traditionally the busiest part of the season finally ended at 5 a.m. EDT Sep. 17, with the formation of Tropical Depression Seven (TD 7) in the central tropical Atlantic. At 11 a.m. EDT Wednesday, the National Hurricane Center upgraded TD 7 to Tropical Storm Gabrielle, located about 1,085 miles (1,745 km) east of the northern Leeward Islands, moving north-northwest at 22 mph (35 km/h). Top sustained wind were 45 mph (75 km/h), and the central pressure was 1006 mb.
Satellite images showed that Gabrielle was poorly organized, with a elongated center that was exposed to view, and heavy thunderstorms confined to the east side of the center (see image at top) because of strong southwesterly winds creating high wind shear of 20-25 knots.
According to Michael Lowry, the period August 29–September 16 has never before gone without a named storm or tropical depression since satellite data began in 1966. On average, four named storms and two hurricanes form each season during this period. Lowry added: “To date, the Atlantic basin has recorded the lowest activity since 2014 and, with only one hurricane so far (Category 5 Hurricane Erin), the fewest hurricanes through September 15 since 2002.” Gabrielle’s formation date of Sep. 17 comes two weeks later than the 1991-2020 average formation date of Sep. 3 for the season’s seventh named storm. The average date of formation for the season’s second hurricane is Aug. 26, and we’ve usually had four hurricanes by this point in the season.
Forecast for Gabrielle
The steering currents for Gabrielle will carry the system to the northwest or west-northwest for the next few days. On this track, Gabrielle will pass well to the northeast of the Leeward Islands, and it appears that Bermuda will be the only land area that need be concerned with the storm. The timing and nearness of Gabrielle’s closest approach to Bermuda are both highly uncertain; the 6Z Wednesday morning run of the European model predicted this would occur Tuesday, Sep. 23, while the 6Z GFS model said this would occur on Friday, Sep. 26. Both the European and GFS runs take Gabrielle just southeast of Bermuda, which would put the islands on Gabrielle’s weaker side. However, there is plenty of spread in the ensemble output from both model runs, with a number of members taking Gabrielle closer to, and even west of, Bermuda, so it’s far too soon for any confident forecast.
Gabrielle will have to contend with periodic bouts of dry air and wind shear over the next few days, but is expected to encounter more favorable development conditions this weekend, allowing it to become a hurricane by early next week, as predicted by NHC. On this pace, Gabrielle would reach hurricane strength even later on the calendar than Isidore, the second hurricane of 2002, which became a Category 1 on September 19. Prior to that, you have to go all the way back to 1994 – just before the Atlantic kicked into the active phase that’s now run for 30 years – to find a season in which the second hurricane arrived any later. That was Florence, which didn’t reach Cat 1 strength until November 4.
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