18 November 2019

Disturbance near Leeward Islands could become 18th named storm

With twelve days remaining in the official hurricane season, the Atlantic may not have run out of steam yet.  A lingering low pressure system east of the Leeward Islands is getting better organized and could become the 18th named storm of the season this week: Sebastien.  It has been sitting nearly stationary for at least a week now in an area of very weak steering flow.  By the way, the last time we reached the "S" name in a list was 2012 (Sandy).

It's still not even a Depression, and as you can see in the satellite image above, it's not looking too impressive today. However, environmental conditions are marginally favorable today through Wednesday.  All models agree on a northwestward track, then recurve to the northeast as it gets picked up by a cold front.  It will not affect any land.

It only has a brief window of opportunity to develop before strong vertical wind shear comes along on Wednesday-Thursday and it transitions to a strong extratropical low pressure system.  This also means that if it develops and earns a name, it would be the *9th* storm to be named for two days or less this season! You read that right: if this forms and dissipates shortly thereafter, half of the season's storms (9 of 18) will have been a tropical storm or hurricane for two days or less.

Here is a map of the season's activity through today... if Sebastien forms it would be near where Karen dissipated in late September.  One feature that looks quite obvious on that map is the lack of activity in the Caribbean Sea and Gulf of Mexico.  Only Barry and Dorian were hurricanes in those two regions, and for a combined total of just a few hours, and both as Category 1 hurricanes.

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