23 October 2020

As Epsilon passes by Bermuda, Zeta could form in western Caribbean

Hurricane Epsilon is now a Category 1 hurricane with peak winds of 85 mph... it's centered about 200 miles east-northeast of Bermuda.  It should remain a strong tropical cyclone through the weekend, but will gradually transition to an extratropical cyclone as it passes east of Newfoundland on Sunday. Then, it could actually be a pretty powerful storm for the British Isles by the middle of next week.

The area of disturbed weather in the western Caribbean is now labeled Invest 95L.  Although still not a tropical depression, its organization has improved drastically in the past day, and NHC is giving it a 60% probability of formation.  It's presently centered near the Cayman Islands, but is broad and messy.  

Any activity in the western Caribbean in October is cause for concern; some very notorious hurricanes have explosively developed there.  In this map of ocean heat content, high values over the entire western Caribbean mean that there is a nearly endless supply of very warm water at its disposal.  If this develops, it would be Tropical Depression 28 and then Tropical Storm Zeta. You may recall that the record 2005 season finally ended with Zeta, which formed on December 30th.

Model guidance is generally not aggressive with it (yet). We also need to interpret the guidance with caution, because models are not great with these broad and disorganized low pressure systems.  The overall consensus is for it to track toward the northwest, bringing it into the Gulf of Mexico early next week, perhaps as a tropical depression or tropical storm.  

But there are some notable outliers in both the global model ensembles and in regional hurricane models -- those outliers bring it north over Cuba and into south Florida or the western Bahamas on Monday-Tuesday. Those also happen to be the quicker and stronger solutions (this particular HMON run shown below ("HMNI") has a Category 1-2 hurricane just east of south Florida on Tuesday morning, for example). Given that this outcome would bring at least tropical storm conditions to urban southeast Florida starting Monday afternoon, it's worth keeping a very close eye on it.

With such a track spread, it's basically impossible to come up with a meaningful rainfall forecast. But Jamaica, Cuba, the Yucatan peninsula, the western Bahamas, and south Florida could easily see multiple days of heavy rain from today through Monday. Check https://www.nhc.noaa.gov/ for the latest forecasts.

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