Bryan Norcross: Watching Atlantic tropical disturbance for development in Caribbean

Updated at 9 a.m. on Sunday, Sept. 1, 2024.Tropical Disturbance #2 east of the Caribbean islands is showing no signs of development yet. Every time it looks like a circulation might be developing, the system can’t sustain it. The disturbance will likely move across the eastern Caribbean islands as a moisture surge tomorrow and Tuesday. Heavy rain and some gusty squalls are possible.Puerto Rico and the Virgin Islands will feel the northern end of the disturbance. Watch for some periods of heavy rain.The National Hurricane Center is keeping the odds of development in the medium range. The computer model forecasts show a wide variety of possibilities for the future of the system. At one extreme, some forecasts show a hurricane developing in the western Caribbean, while others show little or no development as the disturbance moves west into the southern Gulf of Mexico or Central America.The tropical disturbance is dragging some Saharan dust with it, which is probably one of the factors slowing down development. If it attains a well-defined circulation, it should push that dust away, so the big question is, when will it organize? Or will it organize at all?The computer forecast models we depend on are not especially good at predicting when a poorly organized system will pull itself together. That’s why the National Hurricane Center looks at multiple models to come up with the odds of minimal development into a tropical depression.On the current schedule, the possible storm will be in the western Caribbean late in the week and possibly in the Gulf after that. If the system organizes and strengthens in the Caribbean, it would logically be pulled to the north by a dip in the jet stream. If, however, it stays relatively weak, it appears more likely to take a southerly track into Mexico.Long-range computer forecasts have been jumping all over the place, which is expected when a defined circulation has not yet formed. Let’s see where we are midweek.IN THE GULF, there is still a slight chance that Disturbance #1 will take on some tropical characteristics while it’s hanging around the Texas and Louisiana coasts. The National Hurricane Center has the odds in the low range. The disturbance is a non-tropical system related to an upper-level low and a surge of tropical moisture.In any case, a heavy rain threat will continue along the coast from Galveston to south of New Orleans. Most of the heavy rain will fall south of I-10, although some downpours will spread north as the system meanders. Stay aware of local information and instructions. Extreme rainfall will likely cause flooding in some areas.NEAR THE AFRICAN COAST, Potential Disturbance #3 is about to move into the Atlantic. The atmospheric pattern looks marginally conducive for development, so the National Hurricane Center has the development odds in the low range over the next week. There is no apparent threat to land at the current time.