This is the fourth consecutive year with at least one storm before the start of hurricane season on June 1.
Forecast models like the ECMWF and the GFS predict the system will be approaching the northern Gulf Coast by Sunday, potentially as a weak hurricane. The main threat from this system continues to be its heavy, flooding rain. The storm is expected to slow down when it reaches the coast, prolonging the heavy rain and other impacts.
Subtropical Storm Alberto was very disorganized on Friday morning. The storm had a robust circulation that was detected by Hurricane Hunters, but its appearance on satellite was still ragged and obviously influenced by strong winds out of the west. Tropical storms need calm upper-level winds in order to strengthen — on Friday morning, those winds were preventing Alberto from strengthening.
Conditions will become more favorable for the storm to intensify when it reaches the warm water of the Gulf of Mexico. Upper-level winds are forecast to weaken and the storm’s forward speed will slow, allowing it to linger over the Gulf and gain more energy.
Even if the storm does not strengthen significantly, the broad circulation is going to pull moisture north out of the Gulf of Mexico toward the Southeast. More than 6 inches of rain are in the forecast for parts of the Gulf Coast. The heaviest rain will probably stretch across Florida, Alabama and Georgia.
Isolated rainfall totals could reach 8 or 9 inches somewhere along the northern Gulf Coast, although it’s too early to be able to predict exactly where.
A subtropical storm is no different than a tropical storm with respect to impacts, and it is expected to transition into a tropical storm in the next day or so. As of Friday morning, the National Hurricane Center did not expect Alberto to reach hurricane status before making landfall.