A tropical wave about to emerge from Africa on Thursday was moving west to west-northwest at 15-20 mph. Although it is very early in the season to be watching such waves for development, the record-warm ocean temperatures present across much of the tropical Atlantic give this system a chance of development during the week of June 19-23. Recent runs of the European model ensemble (ECMWF) have a number of members that develop the wave into a tropical cyclone as it approaches the Leeward Islands late next week (see Tweet by Philip Klotzbach below), and the 6Z Thursday operational run of the GFS model predicted development of a tropical storm in the June 23-24 period, a few hundred miles northwest of the Leeward Islands (though the 12Z Thursday run of the model did not develop the system). In their 2 p.m. EDT Thursday Tropical Weather Outlook, the National Hurricane Center gave the wave 2-day and 7-day odds of development of 0% and 20%, respectively.

Update (8 a.m. EDT Sunday): The disturbance, designated 92L by the National Hurricane Center, has 2-day and 7-day odds of development of 80% and 90%, respectively, in the latest Tropical Weather Outlook. Sunday morning runs of the GFS and European model ensemble forecasts (Fig. 1 and Fig. 2 below) show a potential threat to the Leeward or northern Windward Islands June 22-24. In general, the forecasts of a stronger storm reaching hurricane strength had 92L taking a more northerly track missing the Leeward Islands.

Figure 1. Track forecasts out to 10 days for 92L from the 0Z Sunday, June 18, run of the European ensemble model. Individual forecasts of the 51 ensemble members are the lines color-coded by the wind speed in knots they predict for 92L; red colors correspond to a category 1 hurricane. The time in hours from the model initialization time are in grey text. The black line is the ensemble mean forecast. The more southerly ensemble members generally predicted a weaker storm that would pass through the Leeward islands between 96-144 hours from initialization time (four to six days out, or June 22-24). (Image credit: weathernerds.org)
Figure 2. Track forecasts out to 10 days for 92L from the 6Z Sunday, June 18, run of the GFS ensemble model. Individual forecasts of the 31 ensemble members are the lines color-coded by the wind speed in knots they predict for 92L; red colors correspond to a category 1 hurricane. The time in hours from the model initialization time are in grey text. The black line is the ensemble mean forecast. The model predicts a potential threat to the Leeward islands between 96-144 hours from initialization time (four to six days out, or June 22-24). (Image credit: weathernerds.org)

Tropical cyclones that form from westward-moving tropical waves that emerge from the coast of Africa have traditionally been referred to as Cape Verde-type storms; they are more properly called Cabo Verde-type storms now, since the island nation off the coast of Africa that they are named for is now called Cabo Verde.

The next name on the Atlantic list of storms is Bret. If Bret does form, it will be the third Atlantic storm of the year, following the formation of Tropical Storm Arlene on June 2 and an unnamed subtropical storm on January 16. The typical formation date of the season’s third storm is Aug. 3. The record-earliest formation date of the season’s third named storm came on June 2, 2020, when Tropical Storm Cristobal formed. That year had a record 30 named storms, and holds 26 of the 30 earliest formation date records.

Updates on this system will occur within this post daily.

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Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...