21 August 2023

Emily, Franklin, Gert, and soon-to-be Harold bring the Atlantic to life

In a surge of activity, nearly every area of interest over the past few days has become a tropical cyclone or is about to.  Since Saturday's post, TD6 became TS Gert, Invest 98L became TS Emily, Invest 90L became TS Franklin, Invest 91L became TD 9, and the easterly wave near Cabo Verde is now Invest 92L.  You have every right to be confused.

While that is a long list, it will be easy to knock a few out right away.  TS Emily dissipated on Monday morning, and Gert is barely clinging to tropical depression status and will dissipate shortly.  The wave near Cabo Verde is not too close to development today, so for this update I'll just mention it but not go into any depth.

Moving on to Tropical Storm Franklin... on Monday afternoon it is located in the Caribbean Sea roughly 300 miles south of Hispaniola and about to make a turn toward the north.  That will bring it to Hispaniola on Wednesday; tropical storm warnings are in place and as always in mountainous areas, heavy rainfall is a significant concern (this includes Puerto Rico).

Models are in good agreement on a track across Hispaniola then into the open Atlantic where it has a decent chance of becoming the season's second hurricane.  The plot below shows the track density from an ensemble of four global model ensembles (LOTS of members!).

Tropical Depression 9 is in the central Gulf of Mexico and racing west toward the south Texas coast.  Although the water temperature in the Gulf is extremely/anomalously warm, this storm thankfully will not have enough time to get its act together.  It is expected to become a tropical storm soon (the next name is Harold), and reach the Texas coast midday Tuesday.  Wind and storm surge will be minimal threats, and it's moving fast enough that it won't be able to dump too much rain either.  You can view the latest suite of hazard products at https://www.nhc.noaa.gov/graphics_at4.shtml?start#contents

Gert was the season's 8th named storm, and from the 1991-2020 climatology, the average date of 8th named storm formation is September 9.  And if Harold forms on Tuesday from TD 9, it would be the 9th named storm and be 3.5 weeks ahead of average.

The Accumulated Cyclone Energy (ACE) is trickling in from the weak named storms, but not even fast enough to keep pace with climatology this time of year!  As of the 21st, it's at about 93% of average for the date.

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