The National Hurricane Center is giving an area of low pressure drifting south across the Florida panhandle a 50 percent chance of developing into a tropical depression or storm over the next two days. The disorganized system will emerge over the eastern Gulf of Mexico sometime Tuesday and is expected to move westward across the Gulf along the edge of a high pressure system.
Unfortunately, numerous questions still remain with this system.
Will it develop into a tropical storm or hurricane?
The odds remain pretty low that it will reach hurricane strength. The Gulf is certainly warm enough to sustain and strengthen a tropical system, but it will only be over water for a couple days, not enough time to fully organize given how disorganized it is at the moment. It could reach tropical storm status, but even that isn't a given. None of the forecast models are calling for more than a tropical storm at landfall.
Where will it go (i.e. will it reach Houston?)?
The key steering mechanisms for this storm are high pressure to the north and a trough of low pressure sweeping across the United States this week from west to east. The sooner that trough interacts with the storm, the sooner it will turn the storm north and ultimately northeast. The most recent runs of the most reliable forecasting models seem to be trending eastward toward the central coast of Louisiana, but without a formed center of circulation, it is hard to know.
Why do we need a center of circulation to know where it will go?
Tropical systems spin counterclockwise around a center of low pressure. When a system is forming the establishment of that center is critical because it can sometimes form well way from the disturbed weather wrapping around it. If it manages to form farther south in the Gulf, for example, it would likely spend more time over water, grow a bit stronger and travel farther to the west. If it formed closer to the coast, it could hug the coastline, inhibiting any development at all.
What are the possible impacts on Houston?
At this point, we could see some rain, a lot of rain or rather dry conditions. If the storm manages to organize and make landfall near Houston as a tropical storm, we would have all the things associated with it including heavy rain, winds and high tides. Rainfall totals could reach 10 inches-plus over two days. If it remains disorganized but continues to drift this direction, lower tides, lighter winds and much less rainfall would result. If it goes on shore in western Louisiana, the storm could actually impact our weather in the opposite direction bringing loads of sunshine, dry conditions and high temperatures up near 100.
What is the timing of landfall?
At this point, it looks like landfall of the storm will be sometime between early Friday and early Saturday depending on where it goes on shore. It could be a soggy weekend...or not.
Will it linger...as in will it be another Allison or Harvey?
Highly unlikely. This is more like a typical tropical system in that it will rain a lot, but it should move out of the area of landfall very quickly. This would be a 24-hour event, not a three- or four-day one.
When will we know more?
By tomorrow morning, we should have a center of circulation over water and the forecast models should begin to come into better agreement on track and intensity. Be prepared regardless.