22 July 2020

Watching two systems in the tropics... could become Gonzalo and Hanna?

Tropical Depression 7 formed on Tuesday afternoon from an easterly wave that left the African coast back on July 15th. As of Wednesday morning, it's centered about 1250 miles east of the Windward Islands and moving toward the west-northwest at 12 mph.  It is very close to tropical storm intensity, and when that happens, it will be named Gonzalo.

If this indeed becomes a tropical storm today or tomorrow, it will be the earliest 7th named storm formation on record, beating Gert from July 24, 2005. It's also worth pointing out that this is the first tropical cyclone to develop in the deep tropics this season.

Most model guidance shows some further strengthening in the next 3-4 days, but then weakening (or even dissipating) as it enters the high wind shear environment in the Caribbean. The storm, most likely at tropical storm intensity, will reach the Windward Islands on Saturday.  The National Hurricane Center's forecast is in line with this. This product is not the cone of uncertainty, but rather, the tropical storm force wind speed probabilities and their most likely time of arrival.

Beyond that timeframe, uncertainty continues to increase, naturally. The American and European global model ensembles are in fairly good agreement on it staying in the Caribbean (and weakening), though there are a few outliers that bring it north of the Greater Antilles. These maps depict the track density from the ensemble members (50 for ECMF and 20 for GEFS). Don't focus on exact tracks from long-range ensemble forecasts, they're just useful to look for patterns and probabilities.

Elsewhere, a tropical wave in the central Gulf of Mexico has a decent shot at becoming a tropical cyclone before it reaches Texas later on Friday. If it becomes a Tropical Depression, it would be the 8th, and if it gets named, it would be Hanna.

The environment ahead of it is marginal for development, but regardless of formation, it will be a rain-maker as they all are.  This map shows the accumulated rainfall forecast through the next week.

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