TROPICAL STORM GAMMA’S INTERACTION WITH ANOTHER DISTURBANCE MAKES FORECASTS UNUSUALLY UNCERTAIN

Tropical Storm Gamma is intensifying as it approaches the Mexican coast just south of Cancún. The broad circulation of the storm will cover the entire Yucatán Peninsula of Mexico. Flooding is the biggest threat, especially in the more mountainous areas. Although Gamma's peak winds will be near or at hurricane strength when it makes landfall.

Over the weekend, as Gamma is meandering near or over the northern part of the Yucatán, a dip in the northern jet stream is going to reach down and try to pull the system north. At this time, it appears it will only pull moisture out of Gamma, however, and the system will stay to the south over Mexico.

That moisture will continue to spread over South Florida producing cloudiness and periods of heavy rain into tomorrow, before the jet-stream dip lifts away. The Flood Watch continues in effect, which is the National Weather Service’s alert for the possibility of torrential downpours that cannot drain off due to saturated ground and extra-high tides on top of the heavy rain.

Over Central America, A broad underlying low-pressure area called the Central American Gyre is creating an arcing steering flow, which should slowly lift Gamma north over the Yucatán and then back to the south as the storm drifts into the southwestern Gulf of Mexico.

It’s best chance to intensify would seem to be right now, before it makes landfall. After that, land interaction, somewhat hostile upper winds, and dry air should take a toll on Gamma. As a result, the National Hurricane Center is forecasting the storm to weaken with time.

Complicating the long-range forecast for Gamma is Tropical Disturbance #1, which has a good chance of organizing into at least a tropical depression. While Gamma is dawdling near the Yucatán, Disturbance #1 is maintaining its forward speed toward the same area. There’s a decent chance that the two systems will get close enough to deflect each other – Gamma to the south and the disturbance, or whatever it becomes, to the north.

Exactly how these systems will interact is impossible to forecast. It depends on their relative strengths, diameters, how close they try to get, and other atmospheric factors. The bottom line is, the interaction could deflect an organized version of Disturbance #1 into the central Gulf of Mexico around the middle of next week.

Everybody around the Gulf coast needs to stay aware since the forecast is guaranteed to change. Until we know if Disturbance #1 is going to reach the western Caribbean as a well-organized system, its future track and intensity will remain very uncertain.

In any case, Disturbance #1 is not expected to be a threat to land through the middle of next week, if it ever is.

Farther out in the Atlantic, the National Hurricane Center is taking note of two other disturbances, but neither appears to be a threat to land.