Tropical storms Humberto and Imelda are likely to form later this week and could be a threat to parts of the Southeast U.S., the Bahamas and Bermuda as the Atlantic Basin’s active period continues following Hurricane Gabrielle.
There is still considerable uncertainty as to the details of how this will all shake out into next week, so please check back with us at weather.com for important updates in the days ahead as the forecast gradually becomes clearer.
Here’s our latest thinking, including a potentially weird wild card to the forecast.
The Two Areas
The map below shows the two areas where tropical development is likely in the next few days, according to the National Hurricane Center.
Both are well-defined ripples of low pressure known as tropical waves, which are often seeds of future tropical storms during the Atlantic hurricane season.
NHC Development Chance
Easternmost area: This tropical wave — designated as Invest 93L — is still about 700 miles east of the Leeward Islands. Most model forecasts suggest this wave could develop first, and eventually strengthen to a hurricane that could be of some threat to Bermuda early next week.
Westernmost area: This second tropical wave — designated as Invest 94L — will bring showers with locally heavy rain to Puerto Rico and the Virgin Islands through early Friday, then Hispaniola, eastern Cuba and the Bahamas. It may take a bit longer to develop, but is now likely to do so by this weekend when it’s somewhere near the Bahamas.
(MORE: What An ‘Invest’ Means In Hurricane Season)
Hurricane Hunter reconnaissance aircraft missions into this system could begin as soon as Wednesday afternoon, or whenever it’s showing enough organization to merit a further look.
There is a lot of uncertainty in the forecast for this system.
Some computer forecast models pull this system north near or over and western Bahamas and off the Southeast U.S. coast from Florida to North Carolina early next week. It may either stall offshore for a few days or landfall some time Monday – Tuesday. It may either be a tropical storm or hurricane at that time.
Most of the models eventually shove this system eastward into the Atlantic by mid-late next week, but that eastward shove could propel it toward Bermuda, meaning it could be the second system to affect Bermuda in just a few days’ time next week.
Even if this system doesn’t ever make a landfall in the U.S., days of onshore winds are likely to generate dangerous high surf, rip currents and at least some coastal flooding up and down the Eastern Seaboard from Florida to New England next week.
All interests in the Bahamas, the U.S. East Coast (especially from Florida to North Carolina) and Bermuda should closely monitor the progress of this forecast.
As usual for late September, there is plenty of deep, warm ocean water that could fuel tropical development in this area, as was the case with Hurricane Gabrielle.
Ocean Heat Content
A Weird Possibility
One other outcome suggested by some computer models is that both systems could be close enough to each other to do a kind of circular dance, what meteorologists call the Fujiwhara effect.
Sometimes the larger system can grab hold of the smaller one and absorb it. Other times, both systems can creep closer and spin around each other before going on their own paths.
This happened in recent years most often in the Pacific Basin, including last year with tropical storms Emilia and Fabio.
We’ll keep an eye on this possibility in the coming days and spell out what it could mean for you if this “dance” becomes imminent.
Check back with us at weather.com for the latest on these systems.