• Bryan Norcross

CARIBBEAN DISTURBANCE EXPECTED TO BECOME A TROPICAL DEPRESSION SOON

The broad tropical disturbance in the western Caribbean is slowly organizing. If it can consolidate a little more, it will be designated Tropical Depression Twenty-Eight. If winds of 40 mph or higher are identified in the circulation, it would become Tropical Storm Zeta. (Yes, Zeta follows Epsilon in the Greek alphabet.)

Hurricane Hunters will fly into the storm this afternoon to get a good measure of what’s going on.


The broad disturbance’s center of rotation seems to be setting up southwest of the Cayman Islands, a little farther south than it appeared yesterday. Where the system is now, there are next-to-no steering currents at the moment. A Flood Warning is in effect for the Cayman Islands, which are stuck under the slow-moving system.

There is, however, a fairly favorable atmospheric environment for strengthening.

There are multiple players in the forecast scenario. First, there is an old front, loosely related to the moisture tail from Hurricane Epsilon, which is now moving into the North Atlantic heading toward Europe. This tail was one of the ingredients responsible for the very rainy stretch of weather in South Florida early this week.

Second, there's a dip in the jet stream moving across the northern Gulf of Mexico. This is expected to act as a scoop beginning later today to lift moisture out of the Caribbean system and push it north past the old front and into South Florida. The front will enhance the rain potential a bit.

While that plays out, the disturbance – likely as a tropical depression or Tropical Storm Zeta – is forecast to move slowly in the direction of extreme western Cuba, but stay in the Caribbean today and tomorrow.

The circulation around a system in this position can produce bands of rain rotating over South Florida, especially with the jet stream enhancing the rain potential. If things play out this way, the rainy scenario should last through Sunday.

There is low confidence in the computer forecast models, especially in the longer range, because they are locating the system farther north than it appears to be at the moment. And, as always, forecasts for weak or developing systems are iffy. But the consensus right now is that the center of the system will move into the Gulf near Mexico’s Yucatán Peninsula by Monday and then track northwest toward the northern Gulf.

Residents along the entire northern Gulf coast should stay up with the latest forecasts. Right now, it looks like the system will be fighting dry air and somewhat unfavorable upper winds in the Gulf, but like everything with this forecast, that’s subject to change.

So for South Florida, on the current schedule, the plume of rain moves south to north across the Keys and southeast Florida beginning late today or tonight. The peak of the rain would come tomorrow. And the rain would decrease on Monday as the system moves into the Gulf.

There are a lot of subtleties to this forecast plan, which are not going to be ironed out until the system develops and the position and strength are inputted into the computer forecast models.

If the system drifts farther to the west, less rain would occur on the southeast coast, though the Keys could still get the heavy rain.

If the system gets stronger sooner, it could consolidate the moisture closer to the center, which could also change the geographical spread of the heavy rain along with the track.

The bottom line is, we have to be ready for another round of heavy rain in South Florida, but this time on top of the over-saturated soil left over from the flooding rains of a few days ago. Be ready for fast-developing local flooding if the heavy rain materializes.

Next week, the consensus is that the system will track north through the Gulf, and dry air will move across the Florida peninsula from the Atlantic.

Once this system is out of the picture, a cold front is forecast to move down the peninsula. Whether it will make it to South Florida late next week is an open question. It may just be a tease.

© 2019 by Bryan Norcross Corporation

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