3 Things We Know About Invest 99-L and 2 Things We Don't Know Yet

Jonathan Belles
Published: August 27,2016

We're watching an area of storminess that has moved into the northern and central Bahamas anc could be targeting the Gulf of Mexico.
But Invest 99-L is still in development, and there are a few questions we still have, in addition to the things we already know about this system.
(FORECAST: The Latest on 99-L) 

What We Know So Far

1. Invest 99-L Will Be A Rainmaker in the Caribbean, Bahamas and Florida
The broad area of low pressure associated with a tropical wave will bring scattered areas of rain to the Bahamas, Cuba and southern Florida into Sunday.
Bands of rain have already spread into South Florida.This could result in some flooding concerns materializing, and the situation will have to be monitored.

Forecast Rainfall

2. This Disturbance Will Trek Toward the Northwest or West-Northwest
Current computer model guidance solutions are tightly packed initially, which improves our confidence that this system will move through the northern Bahamas on Saturday night and then towards the Florida Straits or Keys, or even scrape northern Cuba on Sunday.
(MORE: What is an Invest?)
The forecast gets less clear after that, but parts of the Gulf Coast will likely be in line for impacts early next week. Anything beyond that is more suitable for the "things we don't yet know" section below.

Forecast Track Models

3. Invest 99-L Continues to Fight Wind Shear, Dry Air and May Use Atlantic Heat Content To Its Advantage
The last few days, Invest 99-L has been battling dry air and wind shear on its trek across the Atlantic and parts of the Caribbean.
Wind shear around the system will continue through Saturday.
Wind shear and dry air can slow or prevent the development of tropical systems.
This wind shear and dry air could become less prevalent when the system reaches the Florida Straits and Gulf of Mexico allowing it to develop.
Deeper, warmer ocean temperatures are in the vicinity of this tropical wave. A few patches of cooler waters do exist, but the general trend will be for waters to warm as it moves toward the Gulf of Mexico. Sea surface temperatures in the Bahamas range from the mid-80s to near 90. This effect alone had been enhancing thunderstorm activity.

Conditions remain less than favorable for development.

(MORE: The Most Intense Landfalls Have Happened in this 17-Day Period)

What We Are Trying to Figure Out

1. Will 99-L become a tropical cyclone?
There remains a large array of possible outcomes in terms of intensity and even formation. Chances remain in the medium category that a tropical cyclone will form according to the National Hurricane Center.
The bottom line is that this will bring heavy rain to portions of the keys and southern Florida over the next few days whether this adds to this season's tropical tally or not.
There is still a great deal of uncertainty in the forecast.
Part of this variation is due to the lack of organization with this system so far. Hopefully this will remain the trend.
(MORE: What is a Tropical Wave?)
2. Ridge of High Pressure Will Steer This System Into the Gulf...but then where to?
 The main steering feature will become a ridge of high pressure in a day or two that is forecast to be parked over the Carolinas.

The clockwise flow around the ridge of high pressure could send it into the Gulf of Mexico through the Florida Straits or over southern Florida. This would, of course, put parts of the U.S. Gulf Coast in play for possible impacts...especially heavy rainfall. That would not likely occur until early next week, however, and the future track is uncertain.
We are also unsure of how strong this ridge of high pressure will be early next week. Some models keep this ridge stronger, which would lead to a more western route. Some models allow the ridge to break up or weaken, which would lead to a more eastern or northern route closer to Florida.
For more details, see our full forecast article at this link.
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