Why a tropical disturbance in the Caribbean will keep clear of the eastern US
By
Alex Sosnowski, AccuWeather senior meteorologist
Published Oct 20, 2020 4:19 PM EDT
People from Cuba and the Bahamas to the East Coast of the United States can breath a sigh of relief as earlier fears of a hurricane making a northward run from the Caribbean Sea are no longer warranted.
Forecasters say that development factors and changes in atmospheric conditions will work to keep a struggling system in the western Caribbean at bay this week and into the next.
The atmosphere is in a constant state of flux and conditions that may appear to be favorable for one idea 10 days out may change over time. Such is the case with an area of disturbed weather, known as the Central American gyre, over the western Caribbean that forecasters have been keeping an eye on since early in the second week of October.
This image, captured on Tuesday, Oct. 20, 2020, shows a broad area of unsettled weather over the western Caribbean and Central America. (CIRA at Colorado State/GOES-East)
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Social media began buzzing last week with some scenarios ranging from a hurricane striking the Northeast to a combination hurricane and snowstorm in the region. Because of uncertainty so far ahead, the consensus of AccuWeather meteorologists only rated the chance of the storm's formation near 50% last week.
Thanks in part to Hurricane Epsilon, about 500 miles southeast of Bermuda, an atmospheric road block is developing along the Atlantic Seaboard and in the western Atlantic. This setup will create not only a detour for any brewing system in the Caribbean, but it will also help to enhance disruptive wind shear north of the Caribbean in the coming days.
Wind shear is the increase in wind speed at progressively greater heights in the atmosphere, and it can cause established hurricanes to weaken and prevent tropical systems from developing in the first place.
Epsilon will help to build a zone of high pressure enough so that an approaching cold front will tend to weaken as it sweeps toward the East Coast later this week. South-to-north steering winds ahead of that front were key to the path a budding tropical system in the western Caribbean might take.
With those southerly winds now forecast to be much weaker, there is no longer a strong northward flow from the Caribbean to U.S. East Coast waters. Essentially, the tropical feature will miss its exit on the atmospheric highway because the exit has been closed.
Equally as important, the system in the western Caribbean will remain poorly organized and relatively weak, rather than a system that could quickly strengthen from a disturbance to a hurricane.
"Wind shear has increased so much across the northwestern Caribbean that we no longer believe this weak feature will come northward into the southeastern Gulf of Mexico or western Atlantic Ocean," according to AccuWeather Senior Meteorologist Rob Miller.
Weak systems in the tropics tend to be whisked along from east to west, rather than forging a northward path. This is because weaker disturbances are more subject to being steered by the northeast trade winds that blow across this part of the Atlantic basin during this time of year. Large, strong tropical systems tend to build up higher in the atmosphere, and thus are not normally as easily influenced by these steering winds.
Forecasters also said that there are several disturbances embedded within the overall broad area of showers and thunderstorms extending over the area from northwestern South America to southeastern Mexico, rather than just one disturbance. Competition between the weaker disturbances may prevent one from becoming more dominant.
Despite a lack of tropical development, frequent downpours are expected to develop across areas from Nicaragua to southeastern Mexico with occasional drenching downpours and gusty thunderstorms in Jamaica, the Cayman Islands, Cuba, Costa Rica, Panama and Colombia due to the ongoing unsettled pattern in place.
"The downpours could lead to incidents of flash flooding, and severe thunderstorms could cause isolated damage and power outages," Miller said.
Since the weather pattern from the western Caribbean to Central America will remain unsettled in the long-term, there is the chance for another tropical system to develop later in October and possibly during early November. As a result, AccuWeather meteorologists say that the region and other areas of the basin still have to be watched for tropical development.
However, even if a tropical system were to emerge from the Caribbean later in the season, the chances for such a system to roll northward would be slim as steering winds from the west generally increase significantly across North America toward November. This typical shift in the wind would likely steer any developing Caribbean systems east of the U.S.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo
News / Hurricane
Why a tropical disturbance in the Caribbean will keep clear of the eastern US
By Alex Sosnowski, AccuWeather senior meteorologist
Published Oct 20, 2020 4:19 PM EDT
People from Cuba and the Bahamas to the East Coast of the United States can breath a sigh of relief as earlier fears of a hurricane making a northward run from the Caribbean Sea are no longer warranted.
Forecasters say that development factors and changes in atmospheric conditions will work to keep a struggling system in the western Caribbean at bay this week and into the next.
The atmosphere is in a constant state of flux and conditions that may appear to be favorable for one idea 10 days out may change over time. Such is the case with an area of disturbed weather, known as the Central American gyre, over the western Caribbean that forecasters have been keeping an eye on since early in the second week of October.
This image, captured on Tuesday, Oct. 20, 2020, shows a broad area of unsettled weather over the western Caribbean and Central America. (CIRA at Colorado State/GOES-East)
CLICK HERE FOR THE FREE ACCUWEATHER APP
Social media began buzzing last week with some scenarios ranging from a hurricane striking the Northeast to a combination hurricane and snowstorm in the region. Because of uncertainty so far ahead, the consensus of AccuWeather meteorologists only rated the chance of the storm's formation near 50% last week.
Thanks in part to Hurricane Epsilon, about 500 miles southeast of Bermuda, an atmospheric road block is developing along the Atlantic Seaboard and in the western Atlantic. This setup will create not only a detour for any brewing system in the Caribbean, but it will also help to enhance disruptive wind shear north of the Caribbean in the coming days.
Wind shear is the increase in wind speed at progressively greater heights in the atmosphere, and it can cause established hurricanes to weaken and prevent tropical systems from developing in the first place.
Epsilon will help to build a zone of high pressure enough so that an approaching cold front will tend to weaken as it sweeps toward the East Coast later this week. South-to-north steering winds ahead of that front were key to the path a budding tropical system in the western Caribbean might take.
With those southerly winds now forecast to be much weaker, there is no longer a strong northward flow from the Caribbean to U.S. East Coast waters. Essentially, the tropical feature will miss its exit on the atmospheric highway because the exit has been closed.
Equally as important, the system in the western Caribbean will remain poorly organized and relatively weak, rather than a system that could quickly strengthen from a disturbance to a hurricane.
"Wind shear has increased so much across the northwestern Caribbean that we no longer believe this weak feature will come northward into the southeastern Gulf of Mexico or western Atlantic Ocean," according to AccuWeather Senior Meteorologist Rob Miller.
Related:
Weak systems in the tropics tend to be whisked along from east to west, rather than forging a northward path. This is because weaker disturbances are more subject to being steered by the northeast trade winds that blow across this part of the Atlantic basin during this time of year. Large, strong tropical systems tend to build up higher in the atmosphere, and thus are not normally as easily influenced by these steering winds.
Forecasters also said that there are several disturbances embedded within the overall broad area of showers and thunderstorms extending over the area from northwestern South America to southeastern Mexico, rather than just one disturbance. Competition between the weaker disturbances may prevent one from becoming more dominant.
Despite a lack of tropical development, frequent downpours are expected to develop across areas from Nicaragua to southeastern Mexico with occasional drenching downpours and gusty thunderstorms in Jamaica, the Cayman Islands, Cuba, Costa Rica, Panama and Colombia due to the ongoing unsettled pattern in place.
"The downpours could lead to incidents of flash flooding, and severe thunderstorms could cause isolated damage and power outages," Miller said.
Since the weather pattern from the western Caribbean to Central America will remain unsettled in the long-term, there is the chance for another tropical system to develop later in October and possibly during early November. As a result, AccuWeather meteorologists say that the region and other areas of the basin still have to be watched for tropical development.
However, even if a tropical system were to emerge from the Caribbean later in the season, the chances for such a system to roll northward would be slim as steering winds from the west generally increase significantly across North America toward November. This typical shift in the wind would likely steer any developing Caribbean systems east of the U.S.
Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
Report a Typo