Western Caribbean bears watching for tropical storm formation during late October

By Alex Sosnowski, AccuWeather senior meteorologist
October 25, 2017, 2:20:01 AM EDT

While atmospheric conditions have now become too hostile for tropical storm formation over much of the Atlantic basin, conditions over the western Caribbean may harbor development toward the end of October.

The combination of dry air, dust and strong westerly and/or southerly winds aloft will inhibit tropical storm formation over much of the Atlantic in the coming days.

However, over the far southwestern end of the Atlantic basin, or the western Caribbean Sea, some of the ingredients necessary to spawn a tropical depression or storm may come together late this week and during the last weekend of October.

Static Breeding Areas

In the western Caribbean, waters remain very warm and winds aloft are rather light, compared to much of the balance of the Atlantic basin, according to AccuWeather Senior Meteorologist Dan Pydynowski.

The area is one of several zones where tropical storms typically spin up during late October and November.

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"A tropical disturbance, currently over the south-central Atlantic is scheduled to reach the western Caribbean by the end of the week," Pydynowski said. "This may help spin up a tropical depression or storm."

In addition to these conditions, a non-tropical feature may join in late this week.

The leading edge of much cooler and less humid air, now crossing the southern United States, will push across the Gulf of Mexico this week and into the western Caribbean late in the week.

Static Caribbean

Sometimes a temperature and humidity boundary, such as this, can also help to spin up a tropical storm.

Interests from Central America and Mexico's Yucatan Peninsula to Cuba, the Florida Peninsula, the Bahamas, Hispaniola and Puerto Rico should monitor the tropical weather for the potential for increasing winds, seas and gusty thunderstorms in the coming days.

The next name on the list of tropical storms for the Atlantic in 2017 is Philippe.

Even in lieu of a strong tropical storm or hurricane, torrential downpours produced by the disturbance and temperature boundary could unleash flooding rainfall and mudslides.

Dry air and strong winds aloft are likely to prevent such a tropical storm from moving toward the central and western Gulf coast of the United States.

However, this same press of dry air may carry the threat of heavy rain and flooding toward the islands in the north-central Caribbean and the Bahamas.

Static AP Puerto Rico Barren Landscape

Trees stand barren in the aftermath of Hurricane Maria along a road in Montones Cuatro in the Piedrazul sector of Las Piedras, Puerto Rico, Monday, Oct. 2, 2017. (AP Photo/Carlos Giusti)

Much of the foliage has been stripped in these areas due to strikes from devastating hurricanes Irma and Maria in recent months. The denuded landscape increases the speed of runoff and risk of mudslides during more routine rain events.

"The steering flow will guide the feature in a general northward motion," according to AccuWeather Hurriane Expert Dan Kottlowski.

The forward speed may determine how quickly the feature strengthens.

"A slow drift may allow the most rapid strengthening, while a fast forward speed may take the feature more quickly into a zone of hostile winds that inhibits development," Kottlowski said.

Depending on how far to the east dry air pushes, there is a chance that some tropical moisture in the form of heavy rain is drawn northward along the Atlantic Seaboard of the U.S. toward the end of October.

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