Tracking the tropical disturbance approaching the Caribbean. T.S. Fred may be on the board soon.
We are carefully watching Invest 94L, the tropical disturbance approaching the Lesser Antilles and the eastern Caribbean. The system has been showing signs of increasing organization of the thunderstorms associated with the mid-level center of circulation, and the overall upper-level outflow pattern has been improving. However, the system has not yet been able to close off an organized low-level circulation center. For that reason, we have not yet gotten Tropical Depression 6, but there is a high chance of that happening either later today, tonight, or the first half of tomorrow. Should this system become a tropical storm, its name will be Fred.
The short-term environment ahead of this disturbance isn't the most perfect in the world, but at least has the potential to allow for some intensification. There is still some dry air to the north that is being wrapped around the west side of the system. This will likely give way with time. As that does, the system will be moving into warmer water, and that warmer water is fairly deep. That provides plenty of latent heat to be released, which is the fuel source for tropical development. Shear won't be overly strong as the system moves into the northeastern Caribbean either, although there will still be some shear present. These evolving conditions over the next couple of days may allow the system to develop into an organized tropical storm.
One of the main problems for more significant development with this system down the road is the expectation of interaction with the mountainous islands in the Caribbean. Hispaniola and Cuba are notorious for their mountains causing tropical systems to weaken. That could very well be the case here. Some systems never survive their encounter with these islands and fall apart. That is very possible. However, we need to caution a few things before you instantly assume that will be the case:
Weaker systems (like this may be) can sometimes do a better job of "surviving" their encounter with these mountainous islands and then go on to intensify down the road in an area with more favorable conditions. Frederic did that in a huge way in 1979, and Laura did that in an even more dramatic way just last year. Determining whether that may happen, however, is a blind guess at this stage in the game.
If the system struggles to organize and intensify over the next couple of days, it is more likely to take a track more westward through the Caribbean, south of the islands and south of where the current model projections have it going. The system has already been leaning on the south side of the model guidance already. Weaker systems in this area will track more westward because they are more shallow and embedded in the low-level easterly trade winds AND they are less impacted by the poleward pull of the Coriolis force. Such a scenario as this would also open the door for the system to limp along for a while until it gets into the western Caribbean and much more favorable conditions for intensification.
Regardless of whether the system tracks up the islands and is weaker or stays more westward in the short-term and goes south of the islands, it looks like there is a decent shot that the system (or whatever is left of it) gets into the Gulf of Mexico toward the end of the weekend and the start of early next week. What will determine any potential U.S. impact beyond that will be the environmental conditions after the system moves into the Gulf.
Nobody can deny that water temperatures across the Gulf are favorable for intensification of a tropical system. Sea surface temperatures are in the mid to upper 80s everywhere, and a few locations have been running near 90 degrees. However, there will be an upper-level trough ahead of this tropical system that will be retrograding westward in tandem with the tropical system's westward movement. Strong upper-level winds on the east side of that trough will provide a hostile shear environment for anything that is approaching. The key for this tropical system to have a chance to not be impacted by that is its specific timing and location in comparison to that trough. There will be a window of opportunity where the tropical system can be placed far enough east of the trough to not feel the shear and have a chance at intensification in the Gulf. However, if the tropical system trends faster as it approaches the Gulf, it will lose this opportunity and will likely move into more hostile wind shear. This is something that we won't have a good handle on until at least the latter part of this week.
These are all the internal moving parts of what we're watching with this tropical system. This IS a system that needs to be monitored along the U.S, coastline, especially in the Gulf and in south Florida. However, there is way too much uncertainty at this stage in the game to try to say what impacts (if any) there may be to the U.S. coastline. We will know more in the coming few days as this system progresses and we get a better handle on its track in relation to the Caribbean vs the mountainous islands and its timing with approaching the Gulf of Mexico. Our advice right now, even if you live along the Gulf Coast, is don't panic... don't worry... but monitor the forecast for the latest information and any changes... and prepare just in case we do have an organized system moving into the Gulf at the start of next week. And for those of us in the Tennessee Valley, we need to monitor forecasts in the coming days as well. As we saw several times just last year alone, tropical systems in the Gulf CAN produce impactful weather in our local area. We will be watching carefully and keeping you updated in the days ahead!