Tropical Update: Fiona and Gaston Continues to Move North, Hermine Expected to Develop This Weekend

Lead Forecaster Daniel Crawley

Good Wednesday morning to everyone, remember about a month ago when we spoke about how abnormally quiet the Atlantic Hurricane Season was to that point?

Well, things have obviously changed in recent times as we are at the peak of the Hurricane Season (September-Early October). We have powerful Hurricane Fiona pulling away from the Turks and Caicos Islands and moving north Fiona will make a close approach to Bermuda this weekend and will then accelerate north into Newfoundland where it will be Extratropical by that point. Meanwhile Gaston developed out in the middle of the Northern Atlantic and is moving north, far away from any landmass. There are additional waves exiting off the African Coastline as well.

One additional feature of interest to us is located east of the Lesser Antilles and just north of the South American Coastline. It is a disturbance that has been classified as Invest 98L. Tropical model guidance is now being executed on this feature far to the south.

Current tropical guidance shows 98L moving west and skirting along the coastline of South America for the next 48-72 hours. By this weekend, 98L will move away from the landmass and is expected to gradually develop while it moves WNW. There seems to be fairly strong support of this system being located to the South of Jamaica by Sunday.

Global computer model guidance is in strong agreement with the hurricane suite with the same general motion of the next 3-5 days with 98L, toward the WNW into the Central and Western Caribbean Sea. Posted below are individual ensemble member plots from the GFS and European Model ensemble family…

What is of most concern is that close to all guidance (Global and hurricane suite) shows a hurricane and eventually a major hurricane in the Caribbean Day 5 and beyond. What few members of the hurricane guidance suite that are not as strong is likely showing a feature that was never able to gain much latitude away from the continent of South America.

Synoptic Setup…

The setup for what could be named “Hermine” looks very supportive across the Caribbean once we get to this weekend. First off the water in the Caribbean is extremely warm. There has been little tropical activity this summer so the region is primed from that aspect. The areas in the burnt orange hues indicates positive Sea Surface Temperature Anomalies.

Sea Surface Temperature Anomalies

The other concerning aspect is that the Caribbean is going to have a very supportive wind setup to help allow any tropical system to thrive in that part of the world…upper level winds are light and divergent across the Caribbean this weekend. That works as ventilation for tropical systems to where they can grow in intensity in a quick manner.

200mb winds (Sunday Night)

The players are on the table for a rapid intensification cycle for potential Hermine should it get into the Central and Western Caribbean this weekend. Anyone who may have vacation plans for this part of the world needs to monitor future forecasts and have alternate plans in place.

US Impacts In The Long Range?

Unless we deal with a significant error in the current weather guidance, there will be a significant tropical in the Western Caribbean by early next week moving in the general area of the Gulf of Mexico. Typically, once something gets to that point its hard to avoid impact on the United States.

Looking at the 500mb charts there will be a trough across the Northeast US early next week, ridging across the Western US and some individual shortwaves sliding down the eastern extent of the ridge. This will most likely lead to a northerly heading of Hermine should it be in the position we expect by early next week.

All interests from Florida to Louisiana needs to monitor this closely and be ready to take action next week should it be necessary.

Leave a Reply

%d bloggers like this: