June 3, 2020

Newly formed tropical depression could be one for the record books


Hurricane season — which officially got underway on Monday — featured the formation of the third tropical system of the year with a tropical depression brewing over the Gulf of Mexico.

June 1 marks the official start of the Atlantic hurricane season, yet forecasters have already been busy for weeks monitoring multiple zones of disturbed weather. The season’s third tropical system has developed in the southwestern Gulf of Mexico, and it could cause a new record to be set in the basin.

Two pre-season storms, Arthur and Bertha, formed in warm waters off the Southeast coast on May 16 and May 27, respectively, and Bertha slammed into South Carolina for an early-season landfall in the United States. On Monday afternoon, Tropical Depression Three took shape in a different hotspot.

A system called the Central America gyre helped give birth to Tropical Storm Amanda over the eastern Pacific Ocean over the weekend. Amanda turned deadly after drifting inland over Central America and unleashing torrential rain, flooding and mudslides in El Salvador and Guatemala.

A gyre is a broad area of weak low pressure that rotates slowly. The Central America gyre often encompasses a thousand-mile-wide area. Since the pressure is lower and a circulation exists within the weather system, tropical storms can easily develop within the bounds of a gyre.

On Monday afternoon, the gyre spun up a new system, but this time on the Atlantic side in the region. Tropical Depression Three formed in the Bay of Campeche, located in the southwestern Gulf of Mexico. If it continues to strengthen, it will not take on its former name.

“Since the old circulation from Amanda has completely broken up, any new system that forms on the Atlantic side would garner a brand new name based on the 2020 Atlantic hurricane season list,” Dan Kottlowski, AccuWeather’s top hurricane expert, said. The next tropical storm to form in the Atlantic will be given the name Cristobal.

The water is plenty warm enough to support tropical strengthening, and wind shear, or the shifting of winds with altitude and yet another factor that favors strengthening of any system that forms, is low over the southwestern Gulf of Mexico.

This image of Tropical Storm Nadine was taken on Oct. 12, 2018, as the storm was experiencing strong vertical wind shear. Nadine appeared devoid of rainfall except in the northeastern quadrant. Clouds around the center appeared as a wispy swirl. (Earth Observing System Data and Information System [EOSDIS]/NOAA)

Should Tropical Depression Three strengthen into Tropical Storm prior to or on Thursday, June 4, it would be the earliest occurrence of three named systems in the Atlantic basin. The 2016 season holds the record for the earliest ever third tropical storm, and it was Tropical Storm Colin, which formed on June 5, that helped that year go down in the books.

June 12 is the second earliest date for a third tropical storm to generate in the basin, and forecasters say that record had stood since 1887.

“The most immediate concern is for torrential rainfall that can trigger life-threatening flooding and mudslides in southeastern Mexico, Belize and northern Guatemala much of this week,” said AccuWeather Meteorologist Courtney Travis.

Rainfall spanning Monday to Thursday is forecast to average 200 to 400 millimeters (8-16 inches) with an AccuWeather Local StormMax™ of 500 millimeters (20 inches).

Rough surf is likely to become a concern for bathers in the region, and building seas can threaten boating and fishing interests in southeastern Mexico and Belize.

Steering currents are weak around Central America at this time, so the tropical depression may move very little into Thursday.

“The circulation around the gyre is accounting for most of the steering breezes at this time, so it is plausible that it could wander southward or westward and make landfall in Mexico at midweek,” Kottlowski said.

This does not mean the United States is not at risk for impact and landfall from the tropical system. The atmosphere and weather systems are constantly changing. Ultimately, these changes will steer the tropical system in the long range.

“This new Atlantic basin feature may not move very far inland over Mexico, and it could maintain a circulation as a result,” Kottlowski explained.

Southerly steering currents are likely to pick up over the Gulf of Mexico as a belt of blocking high pressure, currently extending from the central U.S. to the Bahamas, begins to weaken later this week and into the weekend.

These southerly breezes are likely to direct the tropical system northward, away from Mexico and into the central Gulf of Mexico later this week. How quickly and how far the tropical feature moves northward later this week to early next week may determine where it strikes land next.

“If it races northward, around the time the high pressure area is weakening, it may hit the central Gulf Coast, perhaps near Louisiana as early as Sunday afternoon or Sunday night,” Kottlowski said. “If it is delayed, high pressure is forecast to rebuild over the central and southeastern U.S. this weekend, which could force the system toward Texas sometime early next week.”

People in southern Mexico and the southern U.S. as well as petroleum interests in the Gulf of Mexico are urged to monitor the strength and progress of this tropical system.

Even though the system may track into southern Mexico and weaken for a time, there is a significant chance that it could later move northward over the Gulf of Mexico, where renewed strengthening could ensue before it could track toward the U.S.

The tropical threat comes at a time of civil unrest and the ongoing COVID-19 pandemic.

“It is too early to talk with certainty about the scope and nature of impacts from the tropical system on the U.S.,” Kottlowski said.

Flooding over the Deep South is topping the list of early concerns due to the fact that the storm could slow its forward progress after moving into the U.S. next week, although the exact strength and track of the system is still unclear this far out. 

AccuWeather’s long-range forecasters led by Senior Meteorologist Paul Pastelok expressed concern for a possible June Gulf of Mexico tropical threat in their initial late-winter seasonal outlook. The team issued an update to the hurricane season outlook in early May as concerns grew for a “very active” season. In the May 6 update, Kottlowski warned that the Atlantic could spawn 14 to 20 tropical storms and seven to 11 hurricanes, four to six of which could strengthen further into major hurricanes — Category 3 or higher.

Another area of disturbed weather that forecasters had been monitoring last week over the central Atlantic failed to organize quickly enough over the weekend before encountering cold water and increasing wind shear. Development of this feature a few hundred miles east of Bermuda is no longer anticipated. Visit the AccuWeather Atlantic hurricane center for all tropical-weather-related news and information, including the full list of names for the season.

In preparation for the unique hurricane season ahead, the AccuWeather TV Network last week hosted its first-ever hurricane town hall. The exclusive one-hour event was moderated by AccuWeather Broadcast Meteorologist Brittany Boyer, who led a roundtable discussion with several of the top minds in hurricane forecasting and weather preparedness.

By Alex Sosnowski

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