What remains of Hurricane Eta is rapidly redeveloping over the warm Caribbean waters off the coast of Belize. Through the day today, the system will lift to the north and slowly strengthen. The system is quite broad, so it will take time to organize and start spinning faster. In general, the bigger the system, the longer the strengthening process takes.
The atmospheric environment over the developing system will be conducive for a new tropical storm to form. Once again, it would be called Tropical Storm Eta because it formed out of the broad rotation related to the original storm.
The system will lift north, grabbed by a sharp dip in the jet stream moving across the Gulf of Mexico. The flow around that dip will act like a scoop to push the new Eta toward Florida along with gobs of tropical moisture from the Caribbean.
The interaction between the jet stream dip and the tropical storm will be complex, difficult to precisely forecast, and will evolve over the next several days. But it’s clear that the flow from south to north over the storm will stretch the moisture toward the Florida peninsula. As a result, that dense tropical moisture will already cover South Florida while the new version of Eta is near or over the Cayman Islands and Cuba.
This means that we can’t look at the cone, and the dots in the middle of it, to forecast where the bad weather will be. The cone tracks the center of the circulation, which is much less relevant in a situation where the storm is interacting with the jet stream. In this case, imagine a large plume of moisture extending north from Eta’s center.
The National Weather Service has issued a Flood Watch for metropolitan South Florida – 6 to 10 inches of rain are forecast over the next several days. It will come in bands, so it’s impossible to know exactly where the heaviest rain will fall. The fact that the ground is saturated will aggravate the flooding problem.
In addition, it will be windy along the entire southeast coastline of Florida. The wind earlier this week was caused by the contrast in pressure between a fairly strong high-pressure system stretched over the western Atlantic to the north and Eta to the south. The bigger the contrast, the stronger our wind.