Tropical Storm Gamma becomes latest named storm in Atlantic basin

Tropical Storm Gamma became the 24th named storm in the Atlantic basin this season. Previously dubbed Tropical Depression 25, the system’s maximum sustained winds had strengthened to 40 mph by 7 p.m. PDT Friday.

Tropical Depression 25 formed late Friday morning amid an area of disturbed weather over the northwestern Caribbean that meteorologists have had their eyes on since the demise of Beta, Sally, Teddy and Paulette. The system had initially been dubbed Invest 91L by the National Hurricane Center (NHC).

As of Friday evening, the tropical storm was moving in a northwestward direction at 9 mph, about 135 miles south-southeast of Cozumel, Mexico.

Mexico’s government has issued a tropical storm warning for the country’s Yucatan Peninsula from the coastal communities of Punta Herrero to Cabo Catoche. A tropical storm watch has been issued for areas south of Punta Herrero to Puerto Costa Maya and west of Cabo Catoche to Dzilam, the NHC said.

Waters offshore of Honduras, Guatemala, Belize and Mexico’s Yucatan Peninsula have become increasingly stormy in recent days.

This zone has been experiencing low wind shear relative to the rest of the Atlantic basin. Wind shear is the increase in the speed of breezes at increasing elevation in the atmosphere and can also involve a sudden change in wind direction from one area to the next. Strong wind shear can inhibit tropical development or cause a developed tropical system to weaken.


When wind shear is weak as it is now over the northwestern Caribbean, warm waters and rising air can be enough to initiate tropical development.

AccuWeather is projecting the system to peak as a strong tropical storm before moving over land this weekend. However, strengthening could resume and extend beyond tropical storm strength if the system gets into the southern Gulf of Mexico days later.

Because of weak steering breezes in the area from the northwestern Caribbean to the southwestern Gulf of Mexico, slow forward movement of this tropical system is likely.

There are several scenarios that could develop with the most likely possibility being that the system moves northward very little during the short to medium range. However, any track the system takes will bring torrential rainfall and the risk of flooding and mudslides to the area from southeastern Mexico to Belize, Guatemala and Honduras.

But swimmers should stay out of the water and boaters should consider keeping their vessels in port over the next several days due to building seas and surf. Increasing gusty winds in thunderstorms can lead to property damage and power outages.

“The system may wander straight across the Yucatan Peninsula and then drift into the southwestern Gulf of Mexico,” AccuWeather’s top hurricane expert Dan Kottlowski said.

A storm such as this has the potential to disrupt natural gas and oil production in the western Gulf of Mexico for several days, AccuWeather meteorologists say.

In this scenario, some weakening would occur followed by possible re-strengthening over the Gulf.

“Another option is for the storm to drift on a general west-southwest path that takes it over land in Central America, never to return to warm waters,” according to AccuWeather Senior Meteorologist Adam Douty.

In that case, the system would diminish later this weekend into early next week.

A third option is for the center of the system to take a curved path around the Yucatan Peninsula and into the southwestern Gulf, avoiding most land areas.

There is also a more remote option among the scenarios AccuWeather forecasters have been considering.

“There is a low chance a non-tropical system dips southward enough to scoop up the Caribbean storm and bring it northward across Florida and perhaps along the Atlantic coast of the United States later this weekend to early next week,” Kottlowski said.

During much of next week, the northward path will be blocked due to an area of high pressure over the central and eastern U.S.

In addition to the feature already in the northwestern Caribbean, there is a second disturbance that AccuWeather meteorologists are keeping a close eye on. This second disturbance would not develop right away — and may not develop at all.

“If the system currently in the northwestern Caribbean ramps up to a strong tropical storm, like we believe it could, it might then hinder development of the other system moving in from the east,” Kottlowski said.

A strong, large system near the Yucatan Peninsula or the southwestern Gulf of Mexico would increase disruptive wind shear on its periphery.

“If the system in the northwestern Caribbean moves over land and diminishes, then the door might be opened for more robust development with the second system next week as it moves northwestward over the Caribbean,” Kottlowski explained.

Following Gamma, the next name on the list of the Greek alphabet is Delta.

Prior to the beginning of October, there have been 24 tropical depressions that have formed in the Atlantic basin this year with 23 strengthening into tropical storms. Twenty of the storms have set early-formation records.

The formation of Gamma eclipses the 24th storm on the record books, beating out Beta from Oct. 27, 2005. The majority of the former early-formation records were set during the notorious 2005 hurricane season. There was an initially unclassified storm during the 2005 season, which bumped the named storms and their numbers farther down the list that year.

The use of Greek letters this year has been just the second time recorded history that the secondary list of names has been used, with 2005 being the only other year the primary list of hurricane names was exhausted. During the 2005 season, there were 28 tropical storms that were strong enough to be named.

Despite 2020 being on record pace for formation and perhaps challenging the overall numbers of tropical storms, it is well behind a key record that is a parameter meteorologists use to measure the overall intensity of a hurricane season. That measure is called accumulated cyclone energy, or ACE.

ACE measures both the total power and duration of all tropical systems. As of Sept. 30, 2020, this measurement stood 101 units, which is above average. To put that number in perspective, however, the 2005 season finished with a record 245 units. The average for an entire season is 93 units.

AccuWeather is projecting at least one more tropical system to make landfall in the U.S. during the 2020 season.

Thus far there have been nine landfalls in the U.S., which ties the record from 1916.

Either or both of the systems in the Caribbean could later find a way to drift northward toward the U.S. toward the middle of October as steering breezes are likely to change over time.

Keep checking back on and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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