TD 9 Forms - Eyeing the Big Caribbean Islands and the United States
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Tropical Depression #9 has formed from Invest 94L east of the lesser Antilles. The system has displayed an increase in convection since last night, unsurprising since it has crossed 50W into an area of warmer water. Convective coverage remains low overall, and the northeastern semicircle of the storm is mostly void of thunderstorms. This should change as the system leaves its genesis area within the eastern Atlantic monsoon flow, and thunderstorm activity should gradually fill out during the next couple of days. TD 9 should steadily intensify as it enters the eastern Caribbean, bringing tropical storm conditions to the northern Antilles as far south as St. Lucia. By the time it nears Hispaniola in about 3 days, I expect it will be a moderate-strong tropical storm. This is not aggressive as the NHC forecast which takes TD 9 to a Cat 2 hurricane near Haiti. I am less bullish with the intensity through Day 3 due to the still less than ideal environment in the eastern Caribbean with continued fast trade winds and sinking air ahead of the storm.
The track forecast reasoning remains unchanged. The subtropical ridge directly north of TD 9 right now should continue to direct it westward or WNW for the next 48 hours or so. Thereafter, this ridge will be shifting eastward and a weakness will develop north of the Bahamas, inducing a more northwesterly motion near or over the island of Hispaniola. This motion should then continue, bringing TD 9 in the vicinity of the Bahamas and Florida within 5 days. The 0z ECMWF takes TD 9 south of Cuba and into the eastern Gulf of Mexico as a major hurricane. This is the western outlier of the model guidance envelope, and is being discounted as too far west at this time. The track has been nudged slightly to the left, and is in best agreement with the 06z GFS ensemble mean.
Overall, this storm is now developing, and we should start to get a better handle on the track as the models become better able to resolve the situation. The northern Antilles, Puerto Rico, Hispaniola, and eastern Cuba could all face impacts from this storm during the next few days. The Bahamas and the southeast United States are very likely to be impacted as well, but there is still uncertainty on the details given that a potential U.S. landfall is still at least 6-7 days away.
Elsewhere....Invest 95L in the western Gulf of Mexico has not developed significantly since yesterday, mainly due to the frontal boundary to the northeast being too strong to allow much consolidation. 95L still has another day or so over water and could still wind up just before moving ashore, but should not be more than a rain maker for northern Mexico and extreme south Texas.
We shall see what happens!

Reader Comments
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Not relevant while it is days away from the islands and TD 9 is right on the doorstep. I keep a close focus on the systems impacting land and tend to ignore the ones way out in the middle of nowhere until they become an issue.
Fairly unlikely now. This looks like a pretty much guaranteed continental landfall.
Ok thanks Levi.
This is the time of the year when I count on you the most, my friend. Thank you for your analysis and commentary. I suppose maybe tomorrow, you can tell me just exactly when I (might) need to head out of town!
With the 12z and the 18z runs out now, do you see your track shifting significantly? Are you seeing more of an east coast or Florida event? I feel like historically, more of an east coast storm would be favored, but I realize every storm is different.
Thanks!
I prefer to see if the models continue a westward trend through tonight and early tomorrow morning. Shifting the track with every run of the models is too reactive for me. Florida is certainly right in the thick of it, even though my track is still just to the east. The gulf coast should be monitoring the situation closely as well. I'll be updating my track tomorrow morning.
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