The last National Hurricane Center advisory on Harvey has been issued, but the tropics remain active nonetheless, with three different systems being monitored across the Atlantic Basin: Major Hurricane Irma, a tropical wave off of Africa, and an area of low pressure that is expected to form over the Southwest Gulf this weekend.
Irma
Irma developed yesterday, and rapidly intensified into the second major hurricane of the 2017 Atlantic Hurricane Season this afternoon.
11 PM EDT Advisory Info: As of the 11pm EDT advisory, Irma was a category 3 hurricane, located 17.8 degrees north 35.9 degrees west, with maximum sustained winds of 115mph and a minimum central pressure of 967 millibars, and was moving west-northwest at 12mph.
Track Forecast (Next 5 days): Irma will generally track to the west, towards the Northeast Caribbean, over the next 5 days.
The current west-northwest motion will continue over the next day or so. Then, by Monday, Irma will begin to move west-southwest as an upper-level ridge builds south and west, with a west west-northwesterly motion likely to resume on Tuesday.
Intensity Forecast (next 5 days): With the exception of 26 – 27 degree Celsius sea surface temperatures over the next day or two, environmental conditions are expected to remain generally conducive for continued intensification of Irma over the next 5 days, and Irma is likely to become a category 4 (or possibly 5) hurricane by early next week.
Long Range: As of now, there is still a great deal of uncertainty regarding what will happen with Irma beyond early this week.
Major Hurricane Irma now … I’d be surprised if storm didn’t become Cat 5 during next 5-7 days. Many EPS ensembles are very intense. pic.twitter.com/EyjSojsG6r
— Ryan Maue (@RyanMaue) August 31, 2017
The ECMWF and its ensembles (which the National Hurricane Center appears to be putting more weight on in the 5 day forecast) are forecasting the western flank of the Bermuda high to nose into the Southwest Atlantic, causing Irma to be pushed into the vicinity of Cuba and the Bahamas as a major hurricane late next week.
Meanwhile, the GFS and its ensembles are forecasting the western flank of the Bermuda high to be weaker, allowing Irma to track about midway between the Bahamas and Bermuda as a major hurricane towards the end of next week.
African Wave
A new tropical wave emerged off of Africa and into the far Eastern Atlantic this morning.
Chance of Development: Overall, environmental conditions appear conducive for development of this wave over at least the next 5 days or so.
In its 8 PM EDT tropical weather outlook the National Hurricane Center this wave a 40% chance of developing over the next 5 days.
Model Guidance: All three of the reliable global models best at predicting tropical cyclone genesis — the ECMWF, UKMET, and GFS — are forecasting development of this wave (as of their latest runs that is).
If this wave were to develop, a west to west-northwest track towards the Caribbean seems most likely at this time.
Potential Gulf Development
There is still potential for tropical development in the Southwest Gulf next week, as an area of low pressure is expected to form in the Bay of Campeche next week.
However, all of the models have now dropped the idea of development. It is still something worth keeping an eye on though.
In its 8 PM EDT tropical weather outlook the National Hurricane Center placed the odds of development occurring in the Southwest Gulf next week at 10%.
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