Invest 97L Likely to Become a Tropical Depression or Tropical Storm Matthew Soon; Reaches Windward Islands Wednesday

Tom Moore and Jonathan Erdman
Published: September 27,2016
Invest 97L, a strong tropical disturbance east of the Windward Islands will likely develop into the next Atlantic tropical depression or storm soon. 97L will pose a threat into next week in the Caribbean basin and may eventually threaten parts of the U.S. as soon as later next week.
(MORE: What is an Invest?)
This strong tropical wave is located about 250 miles east of Barbados. Hurricane Hunters were unable to find any winds coming out of the west on Tuesday afternoon, which means that winds at the surface do not exhibit a closed low-pressure circulation, but rather shift from northeasterly ahead of the wave to southeasterly behind the wave.
(MORE: Why Tropical Waves Are Important in Hurricane Season)
At that point, depending on the strength of the surface winds, 97L would then become either Tropical Depression Fourteen or Tropical Storm Matthew.

First Stop: Windward Islands

Steered by the subtropical ridge of high pressure known as the Bermuda-Azores high, this system will arrive in the Windward Islands, bringing showers, some locally heavy rain and strong winds beginning Wednesday. Many of the Windward Islands have already experienced scattered showers.

Five Day Possible Formation Area

Some bands of rain may reach as far north as the Leeward Islands, Puerto Rico and the Virgin Islands, and may persist into Thursday in the Windward Islands.
It should be noted this disturbance is starting out at a fairly low latitude, just north of 10 degrees. Therefore, locally heavy rain and gusty winds are expected in such locations as St. Vincent and the Grenadines, Grenada, Trinidad and Tobago, perhaps even coastal Venezuela.
(MORE: Hurricane Central)

Caribbean Questions

By Thursday, the system will be in the eastern Caribbean Sea.
Again, given the southern track, there could be locally heavy rain and strong winds in the typically drier "ABC Islands" – Aruba, Bonaire and Curaçao – as well as parts of coastal Venezuela and Colombia Thursday through early Saturday.
Beyond that, uncertainty is still very high on this system's future.
First of all, west to northwest winds aloft over the Caribbean Sea are providing some wind shear, which is typically hostile to the development and intensification of tropical cyclones.

Current Satellite, Wind Shear

However, that Caribbean wind shear is roughly average for late September. Assuming the shear diminishes, the "future Matthew" should be able to intensify in the Caribbean Sea.
(MORE: Just Because It's Fall Doesn't Mean We Shouldn't Pay Attention to the Tropics)
In general, models being run on the "future Matthew" have shown that it may make a northwest or even northward turn in the Caribbean Sea this weekend, which could threaten Hispañola, Jamaica or parts of eastern Cuba as soon as early next week.
Again, the timing and track of this remain uncertain at this time.

U.S. Threat?

Beyond that, it is far too soon to determine which parts of the U.S. may be in danger from this "future Matthew".
As the Weather Channel hurricane expert, Michael Lowry eloquently put it in a recent blog post:

"The science tells us there’s no skill in seven-to-ten day forecasts of tropical systems that haven’t formed (like invests)."

Ensemble forecast guidance includes scenarios where "future Matthew" moves north, then northeast remaining well off the East Coast, but also includes tracks into the Gulf of Mexico next week.
(MORE: Why Long-Range Model Forecasts For the Tropics Can't Often Be Trusted)
The track will depend, in part, on the steering currents in the atmosphere, including whether a piece of the "closed-low" upper-level system that will soak the East the next few days will hang in place over the southeast U.S. and Gulf of Mexico next week to help pull "future Matthew" northward, and to what degree.
It's also worth noting interaction with land, including mountainous terrain in the Caribbean, which may also play a significant role in this system's future.
Colorado State University tropical scientist, Dr. Phil Klotzbach noted 60 percent of landfalling U.S. hurricanes from September 27 and beyond since 1900 have occurred in Florida. However, while lower probability, there have been landfalls this late in the season as far west as the Texas Gulf Coast.

Typical October named storm origin locations and tracks.

For now, all interests in the Caribbean Sea, Gulf of Mexico, Bahamas and U.S. East Coast should monitor the progress of this system. Check back with us frequently at weather.com for any important forecast updates.
Now is a good time to make sure you're prepared before the storm. Are you #HurricaneStrong?
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