19 October 2023

Tammy forms and triggers watches & warnings in Leeward Islands

Invest 94L was upgraded to Tropical Storm Tammy on Wednesday afternoon; Tammy is the 20th named storm of this very active season.  It is forecast to become the season's 7th hurricane on Saturday as it passes over or very near the Leeward Islands.

As of Thursday morning, a tropical storm watch covers islands from Barbados up through Anguilla; the tropical storm warning and hurricane watch are for Guadeloupe.  These will definitely evolve, so stay tuned to NHC for the latest.  [link to map for a refresher on the names of the islands in the Lesser Antilles]

A useful product from NHC is the arrival time of tropical storm winds, overlaid on the probability of those winds occurring.  This too is updated every six hours, so check back on the NHC website.

The last hurricanes to pass over these islands were Maria and Irma in 2017... both at Category 5 intensity and only two weeks apart.  Thankfully, this time won't be anything remotely like that.  Intensity guidance from the models is in the tropical storm and Category 1 hurricane range when Tammy is crossing over the Leeward Islands. 

Beyond the weekend, models are in absolutely no agreement on where Tammy will go.  In one week, the ensemble spread of track forecasts from the global models spans from Haiti to Ireland and everywhere in between. So, best to just focus on 3-day forecasts for now until there's more consensus.

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