13 September 2020

Looking ahead to two hurricane landfalls in one day with Paulette and Sally

The Atlantic continues to be crowded with active tropical cyclones: Tropical Storm Sally in the Gulf of Mexico, Hurricane Paulette southeast of Bermuda, Tropical Depression Rene and Tropical Depression Twenty in the central Atlantic.

The two landfalls coming up soon are Paulette (Bermuda on Monday morning) and Sally (Louisiana on Monday night). Both storms are forecast to be Category 1-2 hurricanes when they make landfall.

Starting with Sally, a very serious situation is unfolding -- a strengthening storm slowing down as it nears the coast will exacerbate storm surge and rainfall flooding.  Hurricane, tropical storm, storm surge, and flood warnings stretch across much of the northern Gulf coast now. Landfall will be drawn out from Monday night into Tuesday afternoon, so the storm surge will span multiple high tides and tremendous rainfall will create significant flooding.

In the coastal areas near New Orleans, a 7-11 foot storm surge is possible, and the southeast Louisiana into western Florida panhandle area could see up to two feet of rain. This combination will stress and strain the levee system protecting New Orleans, so hopefully everything holds. There are radar loops covering this area at http://bmcnoldy.rsmas.miami.edu/tropics/radar/

Paulette was upgraded to the season's 6th hurricane on Saturday night (local time) and is headed directly for Bermuda. As of this writing, it's a Category 1 hurricane, but further strengthening is expected as it reaches the island and then turns toward the northeast. It could easily reach Category 2 intensity by the time it makes landfall, and then Category 3 after that. I have two updating radar loops from Bermuda at http://bmcnoldy.rsmas.miami.edu/tropics/radar/

The two depressions are at different phases of their lives: Rene is about to dissipate, while Twenty is on the verge of becoming Tropical Storm Teddy.  Neither is close to impacting anything, and Teddy, in the longer-range forecasts, is expected to turn toward the northwest well before reaching the Lesser Antilles. I will just mention them in this post... more attention can be diverted to Teddy once the landfalling storms have passed.  Rene will probably be gone by that time.

Through the end of the 13th, the ACE (Accumulated Cyclone Energy) is hugging the average value -- just 2.5% above average using the past fifty years as the baseline.

To put that value in historical context, the value today is about 56, while eight years in the known records had values over 120 by this point in the season (2017, 2005, 2004, 1950, 1933, 1899, 1893).  This season only holds the record for the most named storms by this date.

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