Back in early October, we discussed what we thought would be a formal transition to the dry season across South Florida around the middle of the month. As we have detailed, the much-anticipated transition from South Florida’s wet season to the dry season is not only a blessing for us in South Florida, but also an important milestone for all Americans living at the head of hurricane lane.

Historically, in nine out of 10 hurricane seasons over the past 60-plus years, the last hurricane to land on the U.S. mainland struck South Florida before the dry season began.

This week we see why the drier and (slightly) cooler weather in South Florida is an important step in finally curbing last month’s hurricane threat.

Starting Friday, invest 94L to cruise near or north of the islands

Invest 94L – a well-defined low pressure area moving through the central Atlantic – has a modest chance of developing as it moves westward toward the northern Caribbean islands later this week and over the weekend.

The system already has decent circulation, but dry air has limited the extent and organization of thunderstorms. As it moves into a more moist and thermodynamically robust environment (a region of tropical air and warmer water) on Thursday and Friday, we will likely see a more concerted developmental run.

It doesn’t take much organization to see a tropical depression or Tropical Storm Nadine form in the coming days.

Could 94L or the future Nadine threaten the American mainland?

This is where the kryptonite of South Florida’s dry season sets in. The intensifying cooler and drier air associated with cold fronts moving through South Florida is also increasing wind shear along U.S. coasts in the wake of major fall frontal passages.

Additionally, jet stream intrusions passing through frontal passages in Florida help steer approaching systems—particularly those approaching from the Atlantic, such as 94L—away from the United States

This is what we expect from 94L or the future Nadine. As it approaches the western Atlantic Sunday into Monday – either near or over Haiti and the Dominican Republic – it will hit the brakes as it encounters the front extending into Caribbean and western Atlantic waters.

Models suggest one of two outcomes: It dives south and west and weakens from hostile wind shear, or it is quickly thrown northeast and away from the mainland U.S. In both cases, the states are spared from any threat.

However, we need to keep an eye on the trends for Puerto Rico and the U.S. Virgin Islands this week – especially with the possibility of heavy rain if 94L or whatever comes from it lands near U.S. territories. The system could also pose a flooding threat to Haiti and the Dominican Republic by early next week if it stalls or slows in those island areas.

The unrest in the Western Caribbean quickly spread to Central America

A disturbance that is part of the broader Central American Gyre, or CAG, has been classified by the NHC as having a low probability of development in the next day or two. In general, the models have a lukewarm response to anything that forms, keeping the low pressure area wide, leaving only a limited amount of time for development before the storm spreads inland across Central America.

Regardless, heavy rain and likely flooding will occur in parts of northern Honduras, Guatemala and Belize through the weekend.