This week marks the climatological peak week of the Atlantic hurricane season, and the record-busy pace of named storms in 2020 shows no signs of slowing down. By week’s end, there could be two additional named storms, Sally and Teddy, joining Tropical Storm Paulette and Tropical Storm Rene.
Paulette and Rene pose no immediate threat to land
In the central Atlantic, Tropical Storm Paulette, featuring 65 mph winds at 11 a.m. EDT Tuesday, was headed northwest at 6 mph towards Bermuda. Paulette was experiencing high wind shear of 15 – 25 knots from an upper-level trough of low pressure to its west, and high wind shear will continue to affect the storm through the week, potentially causing Paulette to embark on a weakening trend. The high shear was forcing dry air from the Saharan Air Layer into Paulette’s circulation, slowing intensification.
Paulette could affect Bermuda by the middle of next week, and it is too early to completely dismiss the idea that the storm could affect the southeastern U.S. late next week. Hurricane Florence of 2018 took a path similar to Paulette’s and ended up making landfall in North Carolina. The Tuesday morning runs of the European and GFS ensemble forecasts did have a few of the 72 members predicting that Paulette would come close to the southeast U.S. coast late next week.
In the eastern Atlantic, Tropical Storm Rene, a minimal tropical storm with 40 mph winds at 11 a.m. EDT Tuesday, was headed west at 16 mph away from the Cabo Verde Islands. With adequately warm waters near 27 degrees Celsius (81°F), light wind shear, and a moist atmosphere, conditions appear favorable for Rene to intensify into a hurricane by week’s end. Rene is expected to turn to the northwest, and it is unlikely to affect any land areas after leaving behind the Cabo Verde Islands.
Southeast U.S. needs to watch 94L
An area of low pressure located several hundred miles southwest of Bermuda on Tuesday afternoon was headed west-northwest at 5 – 10 mph towards the Carolinas. Satellite images showed that 94L had a weak surface circulation and was producing sparse and disorganized heavy thunderstorm activity. Conditions for development through Thursday appeared favorable, with the 12Z Tuesday run of the SHIPS model predicting a moderate 5 – 15 knots of wind shear, ocean temperatures near 29.5 – 30 degrees Celsius (85 – 86°F), and a moist atmosphere with a mid-level relative humidity of 65 – 70%. In a 2 p.m. EDT Tuesday Tropical Weather Outlook, NHC gave 94L two-day and five-day odds of development of 30% and 40%, respectively. On its current track, 94L will be near the Carolinas by Thursday, leaving little time for significant strengthening to occur. An Air Force hurricane hunter aircraft is scheduled to investigate 94L on Wednesday afternoon.
The next African tropical wave is also of concern
The top models for forecasting tropical cyclone genesis are giving strong support for development to a new tropical wave predicted to emerge from the coast of Africa on Thursday.
This wave is predicted to move mostly westward at low latitude at 15 – 20 mph next week. Given its lower-latitude position compared to Paulette and Rene, this new tropical wave may be a long-range concern for the Caribbean and North America. Several ensemble members from the 0Z Tuesday, September 8, run of the European ensemble forecast showed that this new system would move through the Lesser Antilles by the middle of next week as a hurricane. In a 2 p.m. EDT Tuesday Tropical Weather Outlook, NHC gave the new wave two-day and five-day odds of development of 10% and 70%, respectively.
The next two names on the Atlantic list of storms are Sally and Teddy.
Posted on September 8, 2020 (3:40pm EDT). See update: “Tropical Storms Paulette and Rene soon could be joined by Sally (but no longer by Teddy)” posted on September 9, 2020 (1:40pm EDT).