AccuWeather meteorologists eyeing waters near US for late-May tropical activity
Tropical systems have developed ahead of hurricane season in May in recent years and there is the potential for just that in waters close to the southeastern coast of the United States prior to the end of the month.
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Pre-season tropical development has become all the rage in recent years, and following a post-verified storm from January, AccuWeather meteorologists are closely monitoring waters surrounding the southeastern United States during the last week of May and into early June for possible tropical activity. In lieu of any tropical development, an extended period of stormy weather is in store.
During the middle of January, analysis of a storm that formed just off the coast of the northeastern U.S. that was on AccuWeather's watchful eye revealed to meteorologists at the National Hurricane Center (NHC) that the system was indeed tropical. Since the storm was confirmed months after dissipating over Atlantic Canada, it did not acquire a name but was the first tropical depression and storm of the 2023 season.
A zoomed-in view of the subtropical storm that formed over the Atlantic Ocean in January of 2023. (NASA Worldview)
When AccuWeather released its first forecast for the 2023 Atlantic hurricane season, the team of meteorologists expressed concern for more pre-season and early-season development possible near the southeastern U.S. coast. Warmer-than-historical average water temperatures were one factor with this potential. An evolving pattern through the Memorial Day weekend in the Southeast also supports that concern raised months earlier.
"While hurricane season doesn't officially begin until June 1, a tropical system in May is far from rare," AccuWeather Meteorologist Andrew Johnson-Levine said. "Since 2010, a majority of years have seen a tropical depression or storm in the month of May, and this year may continue that trend." The most recent May tropical storm was Ana in 2021, which formed and dissipated within a few hundred miles of Bermuda. Two tropical storms -- Arthur and Bertha -- formed in May of 2020.
Peak Timing / Frequency of Hurricane Season
Water temperatures surrounding Florida generally range from the 70s to the lower 80s F, warm enough to support a tropical system. A temperature of 77-78 degrees Fahrenheit is the agreed-upon approximate cutoff amongst the meteorological community for full tropical development. However, there are exceptions to every rule. Farther north, waters trend cooler, but as with the tropical storm in January over the northwest Atlantic, water temperatures were significantly lower than the threshold.
In the case of potential tropical development during the last week or so of May to early June in the Southeast coastal waters, a broad southward dip in the jet stream will develop and persist.
This pattern will help to lower atmospheric pressure in the region. Rising air generated by the lower pressure will cause pockets of showers and thunderstorms to erupt over land and sea in the region. Any one of these clusters may slowly develop circulation and evolve into a tropical or subtropical system. A subtropical storm has both tropical and non-tropical characteristics.
It isn't out of the question that more than one system may try to form over the same period and into early June.
AccuWeather meteorologists have assigned two areas with a low chance of tropical development in the western Atlantic for the last week or so of May. One area was located just east of the Bahamas as southerly steering winds in the zone would likely keep any system that develops in this area away from the U.S. The development window for this feature ranges from May 23-24. A second area that could evolve into a brief tropical system was just off the Southeast coast of the U.S. The development window for this feature is from May 26-27.
The first two names on the list of tropical storms for the 2023 Atlantic hurricane season are Arlene and Bret.
"Regardless of whether disturbances in the pattern are linked to the tropics or not, impacts along the southern Atlantic coast could be particularly disruptive for outdoor activities in the days prior to and during the extended Memorial Day weekend," Johnson-Levine said.
Areas of rain, gusty thunderstorms and building seas and rough surf are likely as the broad area of low pressure develops in the region this week. Downpours and thunderstorm activity will extend well beyond the southern Atlantic coast and perhaps as far to the west as the southern Appalachians, the central Gulf coast and perhaps into the Carolinas.
The counterclockwise circulation around the broad area of low pressure will create long-lasting, stiff onshore winds along portions of the southern Atlantic and Florida Gulf coasts. The persistent fetch of these winds over the water will create rough seas, building surf and frequent and strong rip currents. It is possible that swimming may be prohibited by officials at some of the beaches in the region due to the dangerous conditions.
Beach erosion and coastal flooding at times of high tide are likely in some communities. The conditions could require extensive repair by officials leading into the heart of the summer vacation season.
In addition to the generally unsettled conditions, any tropical system can make matters much worse at the local level in terms of rain, wind and rough surf, Johnson-Levine said. Should a full-blown tropical or subtropical storm make landfall, there may be power outages and property damage due to strong winds and possible tornadoes or waterspouts that spin ashore.
Coastal communities, as well as offshore fishing, cruise and shipping interests, should monitor the progress of the situation, forecasters advise.
Despite the grim appearance of the forecast scenario, it is not likely to rain or thunderstorm every day at every location in the region. Episodes of dry weather are likely to unfold and may even last for a few days in some areas of the Southeast. The details will unfold as the pockets of showers, thunderstorms and any tropical activity develop.
Rain would not be bad if it were not coming around the time of the holiday weekend as portions of Florida are in severe drought and abnormally dry conditions have been expanding in the Southeast (and Northeast) states in recent weeks, according to the United States Drought Monitor.
Away from the influence of the jet stream dip and tropical moisture in the Southeast, a broad zone of dry weather and sunny conditions are likely for days from New England to the Upper Midwest and much of the Mississippi Valley this week and perhaps into the Memorial Day weekend.
AccuWeather will continue to provide updates on potential tropical development as the situation warrants in the coming days.
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