A DISTURBANCE TO WATCH AND A HEAVY RAIN SCENARIO FOR SOUTH FLORIDA

A bubble of upper-level winds conducive for tropical development is forecast to cover the western Caribbean Sea late in the week. At the same time, a weak tropical disturbance that is now south of the Haiti is forecast to arrive under that bubble. The combination creates a decent chance that a tropical depression or tropical storm will form over the very warm water and under favorable atmospherics east of Mexico’s Yucatán Peninsula.

Hostile upper-level winds and dry air are currently keeping the disturbance fragmented, and they should continue to inhibit development until it reaches the western Gulf about Friday. After that, it appears that the system should have a window of opportunity to organize.

In addition, as often happens in the fall, a general area of low pressure covers Central America, the southwestern Caribbean and the nearby waters of the Pacific. When it’s well developed, it’s called the Central American Gyre. This broad semi-permanent low-pressure zone should give the disturbance a little boost as it tries to form.

The computer forecast models are not yet helpful in forecasting what might happen after a depression or storm develops. The steering currents are forecast to be weak, and a cold front pressing in from the north complicates the overall pattern.

The consensus at this point is that the disturbance would stay pretty weak and drift around, but there is no consistency in the forecasts. It’s also possible that this first disturbance will drift outside of the bubble of favorable conditions, and another system will form out of the broad Central American Gyre. These broad low-pressure areas sometimes spin off disturbances on both the Atlantic and the Pacific side of Panama.

Separately, another unseasonable strong front is pushing across the Gulf and down the Florida Peninsula, driven by a sharp dip in the jet stream. The front is currently forecast to lodge over South Florida setting up a stormy pattern for late in the week.

Sometimes, jet-stream dips like this scoop disturbances out of the Caribbean and propel them north along or near the front, but current projections don’t show this scoop extending far enough south to make that happen. Instead, it appears that the disturbance, or whatever it becomes, will stay south, and tropical moisture will stream north enhancing the rain associated with the front.

The scooping flow and cold front scenario puts the possibility of heavy rain over South Florida in the forecast into the weekend, at least. That rain water on top of the extra-high tides this time of year may causing local flooding. Stay aware.

The bottom line is that nothing is expected to move fast, but there’s a pretty good chance that a system of some sort will develop in the next few days. Until the pieces come together a bit more, it’s mostly speculation based on what looks like a weather pattern conducive for development over the western Caribbean.