The disturbance we’re tracking along the northern coast of Venezuela in the eastern Caribbean Thursday – coined Invest 98L – is expected to organize into a strengthening storm by next week and pose a potential threat to the U.S. while powerful Hurricane Fiona will bring hurricane conditions to Bermuda Thursday night into Friday before morphing into an extreme, historic, and potentially record-shattering hurricane-like storm for Nova Scotia and the Canadian Maritimes this weekend.
The immediate concern for us in Florida and the broader Gulf Coast for now is a disorganized area of spin half over land and half over water.
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With the area of low pressure partially over land and stymied by heavy shear raining down from Fiona’s upper-level outflow to the north, 98L is not going to be a fast organizer in the near term.
However, with such a robust turning of winds, it won’t take much for a tropical depression or tropical storm to form once thunderstorms are able to coalesce near the low-pressure area.
The National Hurricane Center gives 98L a high chance of developing over the next day or two.
Hurricane hunters began flying the area Wednesday to sample the atmosphere below 10,000 feet, peppering the skies with over two dozen instrument packages dropped along what aircraft crews call a “lawnmower” flight pattern, where instruments are dropped in parallel rows through the area.
These observations are fed into our computer models and used by forecasters to assess environmental factors that may affect the system ahead.
Through the weekend, 98L will be steered off to the west-northwest, gradually pulling away from South America and into the western Caribbean over the weekend.
By Sunday, forecast guidance suggests the restrictive shear should begin to abate, allowing the system to more quickly organize and strengthen while bending northward between Central America and Jamaica.
It’s worth noting, 98L is not a direct threat to areas most recently impacted by Hurricane Fiona, including Puerto Rico and the Dominican Republic.
The forecast into early and middle next week gets much hazier. We know 98L or what comes of it will get pulled northward by a dip in the jet stream. What we don’t know is how far south and west (or north and east) it’ll be positioned at that time, which will affect ultimately where it heads.
The bookends are wide right now, but we’ll likely see a strengthening storm moving toward the Gulf for next week, so interests along the U.S. Gulf Coast and Florida should continue to follow the forecasts closely.
During early stages, when a forecast contains more than the usual set of qualifiers, it can often be instructive to examine what past storms have done around this time in the season.
If we look at hurricanes that have struck the U.S. during the last week of September or first week of October going back as far as we can in the record books (to 1851), we find they generally form before or as they reach the eastern Caribbean or not until they reach the western Caribbean.
We also find U.S. landfalls this time of year that come from the south favor the north-central and eastern Gulf.
This of course doesn’t mean that’ll be the case with whatever comes of 98L – since every storm is different – but looking back at history gives us a starting place as we drill down in the days ahead.
As for the rest of the very busy tropics Thursday, Category 4 Fiona is picking up speed as it heads in the direction of Bermuda, where it’s expected to pass within about 100 miles west of the island territory by early Friday morning.
A hurricane warning is in effect for Bermuda as conditions quickly deteriorate ahead of Fiona Thursday night.
The remarkable story of Fiona, which consumed Puerto Rico on Sunday and Monday with catastrophic flooding, isn’t over. The large and powerful hurricane will get swept up by an advancing jet stream, where it will undergo a Hurricane Sandy-like metamorphosis over eastern Canada.
The extreme storm will have both characteristics of an intense wintertime low and tropical-like hurricane, and official forecasts from the U.S. Ocean Prediction Center call for a sub-940 mb storm on the eastern end of Nova Scotia by Saturday morning.
A storm of such magnitude would shatter sea-level pressure records for this time of year in Atlantic Canada (around 955 mb) and could even surpass the all-time record low pressure of 940.2 mb set in January 1977.
Needless to say, Fiona’s closing act is poised to deal a powerful and destructive punch to Nova Scotia, where it could deliver a once-in-a-generation blow to the Canadian province and surrounding Maritimes.
Elsewhere across the Atlantic, Tropical Storm Gaston is meandering near the Azores in the middle of the north Atlantic while two other systems are being monitored west of Africa in the far eastern Atlantic.
While some development is possible with these two trailing systems, the only threat they pose is stealing the next name (“Hermine”) off the tropical cyclone naming list.