Monitoring Possible Tropical Development in the Gulf Next Week

Metro Miami-Dade and Broward catch a break from the deluge on Thursday

Typically over the past 50 years, the first named storm in the Atlantic has formed around this time in June. It’s no surprise then that the first bona fide attempt at tropical development looks to be next week in the southern Gulf of Mexico.

We began previewing this development scenario in our newsletter last Monday, and forecast models have started sharpening their sights on the Bay of Campeche, tucked away in the lower reaches of the southwestern Gulf. The National Hurricane Center – which added this area to its tropical weather outlook on Wednesday – continued to bump up development odds on Friday.

The genesis of this disturbance will take shape within a wider region of spin rotating about Central America known as the Central American Gyre or CAG. CAG-spawned systems tend to occur on the shoulders of hurricane season, namely in May and June and again from September through November.

Monthly occurrence of the Central American Gyre or CAG from 1980-2010 (top) and most common formation locations of the CAG (bottom), with warmer colors indicating a higher chance of occurrence. Credit: Philippe Papin

Within the larger orbit of the CAG, smaller circulations often pinwheel in and those embedded swirls can get a boost from all the extra background spin, growing into tropical depressions or storms.

This is the scenario depicted by our forecast models come next Monday into Tuesday, as spin from the eastern Pacific and southern Caribbean pivot toward the Yucatán Peninsula and southern Gulf of Mexico within the broader CAG. Any organizing low-pressure area will benefit from lighter winds aloft which should help to promote persistent storminess.

It’s still uncertain where exactly the dominant circulation will set up, but regardless, the steering pattern will guide anything that forms westward toward Mexico or the south Texas coast. This will not be a threat for us in South Florida.

Low-pressure tracks from the European model ensemble system through next Thursday, June 20^th. A high-pressure heat dome anchored over the eastern U.S. next week will block any developing system from moving east toward South Florida. Credit: Weathernerds.org

Another credible scenario is that the CAG births a second system behind the initial one into the following weekend (June 22^nd). This is still questionable and more than a week out, so let’s give it some time to shake out. We’ll revisit next week once we see how these multiple areas of spin evolve over the coming days.

Invest 90L pulling away as South Florida rains slowly subside

Mercifully, the area of low pressure designated 90L is accelerating away from Florida and now offshore the coast of North Carolina.

The long tail of tropical moisture associated with 90L will stick around into the weekend for South Florida, but the coverage of storms should be less widespread as earlier in the week. With grounds already water-logged, it would take very little additional rainfall to cause flood issues today and tomorrow. The Flood Watch remains in effect for South Florida at least through Friday evening.

As for as the future of 90L, it’s merging with a front and the development window will soon close as it’s quickly whisked away from the U.S. this weekend.