Two Tropical Disturbances Could Develop in the Caribbean Sea; Flood Danger in Mexico, Central America

A pair of tropical disturbances in the Caribbean Sea each may become either a tropical depression or tropical storm in the days ahead, with flooding rain a major concern in parts of Mexico and Central America.

One disturbance is in the western Caribbean Sea and is now referred to as Invest 91L, a naming convention used by the National Hurricane Center to identify features they are monitoring for possible development.

(MORE: What is an Invest?)

The other disturbance is now pushing into the eastern Caribbean Sea.

Invest 91L – Western Caribbean Concern

The westernmost tropical disturbance is spreading showers and thunderstorms from the Cayman Islands to parts of Central America and continues to become better organized.

Invest 91L will track generally toward Mexico’s Yucatan Peninsula, including Cancún and Cozumel, Belize or the far southern Gulf of Mexico into this weekend.

With a lack of shearing winds and deep, warm water, Invest 91L is expected to become a tropical depression or tropical storm if it remains over the waters of the northwestern Caribbean Sea or the southern Gulf of Mexico.

A Hurricane Hunter mission is scheduled to investigate the disturbance Friday afternoon.

Its future after that remains uncertain.

Track outcomes range from a more southern track into Mexico and Central America, to a stall for a time over the northwestern Caribbean Sea or southern Gulf of Mexico, to an eventual turn toward the west or west-southwest into the southwest Gulf of Mexico or Bay of Campeche.

The intensity forecast is complicated by the system’s proximity to land, the aforementioned deep, warm water, the potential for it to ingest some drier air over the western Gulf of Mexico and potential wind shear it could face in the southern Gulf of Mexico.

While not an immediate, apparent threat, it’s too soon to rule out any eventual U.S. Gulf Coast impact.

For now, all interests in Mexico’s Yucatan Peninsula, western Cuba and Belize should monitor the progress of this system.

Second Caribbean System

The second area being monitored is a tropical wave that is moving across the eastern Caribbean Sea.

This disturbance will continue to push westward over the next several days and, for now, has a low chance of development by early next week as it tracks toward the western Caribbean Sea.

It’s too soon to determine if this system will develop, where it might track and how strong it may become.

Interests in the western Caribbean should monitor the progress of this system.

The next tropical storm to form in the Atlantic would be named Gamma.

(MORE: All the Records the 2020 Hurricane Season has Broken So Far)

Central American Gyre – Flood Threat

Regardless of whether one or both of these disturbances develop, computer forecast models suggest something called a Central American Gyre, or CAG, could form.

This “gyre” is a large, broad area of low pressure that often forms in late spring and early fall over Central America and the western Caribbean Sea.

What’s important about the CAG is that it can instigate the development of tropical storms, often as spokes of energy rotating around it.

Such was the case with Tropical Storm Cristobal – and its eastern Pacific companion, Tropical Storm Amanda – in late May and early June. Another example of a recent CAG-spawned storm was Hurricane Nate in early October 2017.

The other important note about a CAG is it often is a prolific rain producer in Central America.

So, this setup could lead to dangerous flash flooding in parts of eastern Mexico, Belize, Guatemala, El Salvador, Honduras and Nicaragua regardless of whether a tropical depression forms or not.

Also, moisture-laden winds on the eastern flank of the CAG intercepting a stalled frontal boundary could wring out heavy rain in parts of the Florida Peninsula, leading to flooding which may also combine with high astronomical tides.

Even though the climatological peak of the hurricane season – Sept. 10 – has passed, residents along the Gulf and East coasts need to remain prepared for a hurricane.

Roughly one-fifth of all U.S. hurricane landfalls have occurred in October and November.

(MORE: What the Busiest Hurricane Seasons Have Delivered in October)

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