AccuWeather meteorologists closely watching potential for 'homebrew' tropical system
Areas of concern include stormy weather along the Southeast coast of the U.S. through the Memorial Day weekend.
A stormy pattern will bring persistent showers, thunderstorms and rough surf to the southeastern U.S. coast this week.
As Memorial Day travel will be near pre-pandemic levels with AAA predicting 42.3 million travelers this year, there could be some trouble brewing in the tropics. Americans may not only have to dodge downpours and deal with rough surf but also remain aware of the risk of tropical development along the United States' southern Atlantic coast, AccuWeather meteorologists warn.
AccuWeather's team of long-range meteorologists and tropical experts have been warning since late March that conditions could become favorable for development ahead of the official start of the 2023 Atlantic hurricane season, which begins on June 1.
"During the next several weeks, very warm water will be in place off the southeast Atlantic coast of the U.S., in the Gulf of Mexico and the Caribbean Sea," AccuWeather Hurricane Expert Dan Kottlowski said. "These are natural areas where a front can drop in or a storm in the upper part of the atmosphere can take advantage of the warm water and slowly lead to tropical development."
Clock ticking for system east of Bahamas
One area of concern was a broad area of tropical moisture situated just east of the Bahamas. Downpours have been leading to localized flooding in Puerto Rico and Bermuda in recent days. This feature could develop a circulation through the middle of this week.
The problem with this system is the lack of low pressure in the mid-levels of the atmosphere despite low pressure at the surface, Kottlowski explained. "It's a very shallow feature that is going to move northward into drier air and increasing wind shear." because of these limiting factors, tropical development is not expected with this system.
Wind shear is the change in breezes at different heights of the atmosphere or across the sea surface. When the winds increase significantly or change abruptly, it can often be a deterrent for tropical development.
This image from Tuesday, May 23, 2023, of the southeastern United States and parts of the western Atlantic, Gulf of Mexico and the Caribbean shows a zone of clouds, showers and thunderstorms east of the Bahamas. AccuWeather Enhanced RealVue™ satellite.
"You can get multiple areas of low pressure to develop at the surface, but in order to get a tropical system to develop, there needs to be some development in the vertical part of the atmosphere as well," Kottlowski said.
With this forecast path, the system east of the Bahamas and its direct impacts will remain east of the U.S., but it can enhance showers and thunderstorms near Bermuda this week.
Homebrew system bears watching late this week
A primary zone of potential tropical development AccuWeather meteorologists have been focusing on is much closer to the U.S. shore, with the best chance of forming from Friday to Sunday.
Some data indicate that a cluster of thunderstorms will try to develop this week over the warm waters of the Gulf Stream right along the southern Atlantic coast. There is a narrow zone where surface water temperatures are near 80 degrees Fahrenheit. The critical minimum temperature for tropical development is 77-78 F.
The question is, will the system have enough time to develop?
"It sometimes takes two to three days for a complex of thunderstorms to develop into a tropical system, and it looks like the setup will not allow the system to have enough time to do so," Kottlowski said.
However, should the system be given a little extra time to linger over the warm waters, development would become more likely. Should the system spiral inland quickly, development would not occur. But if the center manages to stay offshore for more than a couple of days, there is a better chance of evolving into a tropical depression or storm.
Kottlowski pointed out that Tropical Storm Colin formed along the Southeast coast very quickly last year, but that was during the late summer when waters were warm through a deep layer and not just at the surface.
A satellite image showing Tropical Storm Colin not long after it formed early on Saturday, July 2, 2022.
"Currently, Gulf Stream waters are warm enough off the Southeast coast but not through a deep layer of the ocean," Kottlowski said. "Waters were warm through a deep layer for Colin."
The first two names of tropical storms for the 2023 Atlantic hurricane season are Arlene and Bret. A recent analysis by the National Hurricane Center revealed that a tropical storm formed east of New England before moving inland in Atlantic Canada during January. Since this was not determined until well after the system formed, no name was ever assigned.
Meanwhile, in the middle of the Pacific Ocean, the Island of Guam is bracing for a direct hit by a monster storm named Typhoon Mawar. The typhoon will hit the island late Tuesday night or early Wednesday with the strength of a Category 4 or 5 hurricane.
Bad beach days
Regardless of tropical storm formation, an extended period of stormy conditions will evolve along the southern Atlantic coast this week with the likelihood of cloudy and wet conditions farther north along the Eastern Seaboard for the Memorial Day weekend.
As a dip in the jet stream persists this week then amplifies into a storm high in the atmosphere, much of the Southeast will be uncommonly cool for late May, AccuWeather Senior Meteorologist Joe Lundberg said.
By midweek, the inland areas of the Southeast will get somewhat of a respite with little rain, but the coast will likely remain stormy.
"On Thursday, Friday and Saturday, coastal areas from the Carolina beaches on south to northeastern and central Florida will likely become stormy with stiff winds, rough seas and surf and pockets of showers and thunderstorms," Lundberg said. "Some beach erosion and minor coastal flooding at times of high tide are likely."
If a system forms along the coast, tropical or not, conditions may become very stormy with heavy rain, strong winds, severe thunderstorms, isolated tornadoes and waterspouts and moderate coastal flooding.
As jet stream energy feeds into the broad storm in the upper atmosphere over the Southeast, it could strengthen the system enough to allow rain and wind to spread into the mid-Atlantic region over the extended holiday weekend, Lundberg said.
"With the approach of Memorial Day weekend, many people normally head to the coast for a vacation with just some beach time or pleasure boating," Lundberg said. "However, this setup is likely to be bad for business as the weather may thwart many people's plans along much of the Mid-Atlantic and Southeast coast."
Some of the moisture may expand westward to the central and southern Appalachians. Dry air may hold through Memorial Day across the northern tier of the Northeast from upstate New York to parts of New England.
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