Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Subtropical Storm Alberto Moves Into the Gulf of Mexico

Subtropical Storm Alberto moved over the southeastern Gulf of Mexico on Saturday.  At 11:00 p.m. EDT on Saturday the center of Subtropical Storm Alberto was located at latitude 23.9°N and longitude 84.6°W which put it about 120 miles (195 km) west-southwest of the Dry Tortugas.  Alberto was moving toward the north-northeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1001 mb.

Tropical Storm Warnings were in effect for the Dry Tortugas and the portions of the coast from Bonita Beach to Anclote River and from the Aucilla River to the border between Alabama and Mississippi.  A Tropical Storm Watch was in effect from the border between Alabama and Mississippi to the Mouth of the Pearl River.

The circulation of Subtropical Storm Alberto remained poorly organized on Saturday.  Several low level centers dissipated and new low level centers of circulation developed on the southwestern edge of an area of thunderstorms northeast of the center.  Even though the center of circulation reorganized several times, the pressure did decrease slowly during the day.  The strongest wind speeds were occurring in the area of thunderstorms northeast of the center of circulation.  The winds were weaker south and west of the center.

Subtropical Storm Alberto will move through an environment that will become more favorable for intensification during the next 48 hours.  Alberto will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over the western Gulf of Mexico was producing southwesterly winds which were blowing across the top of the circulation.  Those winds were causing significant vertical wind shear which was inhibiting the intensification of Subtropical Storm Alberto.  The shear was also preventing thunderstorms from persisting near the center of circulation, which was keeping Alberto from making a transition to a tropical storm.  An upper level ridge was forming over Florida.  The ridge was starting to enhance upper level divergence to the east of Subtropical Storm Alberto.

The upper level trough will gradually evolve into a closed upper level low.  The vertical wind shear will slowly decrease during the next several days.  When the shear decreases, it will allow Subtropical Storm Alberto to strengthen.  Less vertical wind shear will also let thunderstorms persist closer to the center of circulation.  If thunderstorms persist near the center, then Alberto could exhibit the structure of a tropical cyclone and it could be designated as a tropical storm.  Subtropical Storm Alberto could intensify into a hurricane over the northern Gulf of Mexico.

The reformations of the low level center of circulation increase the uncertainty of track forecasts.  The upper level trough is likely to steer Subtropical Storm Alberto toward the north on Sunday.  Alberto could turn more toward the north-northwest when the trough changes into an upper level low.  On its anticipated track Subtropical Storm Alberto could approach the coast of the northern Gulf of Mexico within 48 hours.  Alberto could be a strong tropical storm or a hurricane at that time.

Subtropical Storm Alberto will be capable of causing minor wind damage when it makes landfall.  Alberto will drop locally heavy rain north and east of the center of circulation.  Flood Watches have been issued for several states in the southeastern U.S.  The Gulf Coast is very susceptible to storm surge.  There will be increases in the water level along the eastern and northern Gulf Coast where the winds blow water toward the shore.

Cyclone Likely to Form Over Gulf of Mexico

A cyclone is likely to form over the Gulf of Mexico during the upcoming weekend.  A broad area of low pressure at the surface is currently centered over the Yucatan Peninsula.  The area of low pressure is currently designated as Invest 90L.  The circulation around the low pressure system is not well organized at the current time.  The center of the surface low is over the Yucatan Peninsula.  Showers and lower clouds are occurring near the center of the low.  Stronger thunderstorms are occurring on the eastern side of the low over the northwestern Caribbean Sea.  Sustained winds of 20 m.p.h. to 30 m.p.h. (30 km/h to 50 km/h) were blowing across the northwestern Caribbean Sea.  The winds were weaker over land near the center of circulation.

An upper level trough over the Gulf of Mexico was producing strong westerly winds which were blowing over the top of the surface low.  Those winds were causing strong vertical wind shear and the wind shear was one of the reasons why the stronger thunderstorms were occurring east of the center of circulation.  Sinking motion in the western portion of the upper level trough was bringing drier air to the surface and the drier air was inhibiting the formation of thunderstorms in the western side of the surface low.

The National Hurricane Center (NHC) indicated in a Special Tropical Weather Outlook at 2:00 p.m. EDT on Thursday that there is a 70% probability of the formation of a subtropical or tropical depression during the next 48 hours.  NHC has tentatively tasked a reconnaissance aircraft to investigate the low pressure system on Friday afternoon if necessary.

The wind speeds are slower near the axis of the upper level trough.  If the surface low pressure system moves under the axis of the upper level trough, then there would be less vertical wind shear and a cyclone could form.  If thunderstorms develop near the center of circulation after the center moves over the northwestern Caribbean Sea or southeastern Gulf of Mexico, then NHC would likely designate the system as a tropical depression.  If the thunderstorms develop farther away from the center of circulation and the circulation does not exhibit a tropical appearance, then NHC could classify the system as a subtropical depression.  NHC would issue advisories on the cyclone even if it is designated a subtropical depression.

There is a strong high pressure system over the Atlantic Ocean and the high is likely to steer the surface low toward the north.  The Sea Surface Temperature of the water in the southeastern Gulf of Mexico is near 27°C.  So, there is enough energy to support the formation of a tropical cyclone.  Most of the stronger thunderstorms are likely to continue to form in the eastern side of the circulation because of the vertical wind shear and drier air to the northwest of the surface low.  The low pressure system could slowly organize into a tropical storm during the weekend.

Heavy rain and the potential for flooding are the greatest risks with this low pressure system.  There will be some storm surge along the eastern and northern coasts of the Gulf of Mexico as counterclockwise rotation around the low blows water toward the shore.

System Could Bring Heavy Rain to Southeast U.S.

A weather system over the southeastern Gulf of Mexico could bring heavy rain to the southeastern U.S. this week.  An upper level low over the eastern Gulf of Mexico could transfer enough kinetic energy down to the lower troposphere to spin up a low at the surface.  Air flowing around the eastern side of the low is contributing to upper level divergence over Florida.  The divergence enhanced rising motion over Florida and rain fell over parts of the southern and central portions of that state.

The weather system is forecast to move slowly northward during the next several days.  The Sea Surface Temperatures in the southeastern Gulf of Mexico are 24°C to 26°C.  There is enough energy in the upper levels of the water to support the formation of a tropical cyclone.  The upper level low will create southerly winds which will cause moderate vertical wind shear.  The shear will inhibit development, although those winds could contribute to upper level divergence to the east of the weather system.  Upper level divergence could allow the surface pressure to decrease and a low pressure system could form at the surface.  The National Hurricane Center (NHC) issued a special Tropical Weather Outlook on Sunday afternoon on the weather system.  NHC indicated the probability was 40% that a tropical or subtropical cyclone could form during the next five days.

Guidance from numerical models suggest that the weather system will move slowly northward over the eastern Gulf of Mexico during the next few days.  Counterclockwise rotation around the low will transport moist air northward on the eastern side of the low.  The moist air combined with upper level divergence will create the potential for locally heavy rainfall over the southeastern U.S.  Heavy rain could result in floods in some locations.

System to Bring Wind, Rain to Bahamas and South Florida

A complex weather system near the Bahamas is forecast to move westward and it will bring gusty winds and locally heavy rain to parts of the Bahamas and South Florida during the weekend.  The circulation is strongest in the middle and upper troposphere.  An upper level low is centered near the Bahamas.  Showers and thunderstorms are occurring north and east of the upper low.  There is not a distinct center of circulation in the lower troposphere or at the surface.  There is a small upper level ridge to the east of the upper low and the ridge is producing some upper level divergence which is pumping mass away to the east of the system.

The system will move through an environment that is only marginally favorable for the development of a tropical cyclone.  It will move over water where the Sea Surface Temperature is near 26°C.  So, there is potentially enough energy in the upper ocean to support the development of a minimal tropical cyclone.  The upper low and the ridge to the east are southerly winds near the Bahamas and westerly winds southeast of the Bahamas.  Those winds are causing strong vertical wind shear.  The winds are weaker near the center of the upper low, but there are no thunderstorms in that region at the current time.  If a surface low were to develop under the center of the upper low, then there would be the possibility of some slow development.  A second, possible scenario is that a subtropical cyclone develops north and east of the upper low where the showers and thunderstorms are forming.

The National Hurricane Center (NHC) issued a special Tropical Weather Outlook on this system at 10:45 a.m. EDT on Friday.  NHC indicated that “no significant development” is expected and it gives a 0% probability of the formation of a tropical cyclone.

The upper level low is forecast to move south-southwest over the northwestern Caribbean Sea during the next 72 hours.  The surface and lower parts of the system are forecast to move across the Bahamas toward South Florida during the weekend.  Since the showers and thunderstorms are occurring north and east of the upper low, this could bring gusty winds and locally heavy rain to parts of the Bahamas and South Florida during the weekend.  Some of the humid air on the northeastern periphery of the system could be pulled toward the Carolinas ahead of an approaching cold front.  The moist air could enhance rainfall in eastern South Carolina and eastern North Carolina when the cold front moves through those places and lifts the air.

Tropical Depression 19 Strengthens to Tropical Storm Rina

Tropical Depression Nineteen strengthened into Tropical Storm Rina on Monday night.  At 10:00 p.m. EST on Monday the center of Tropical Storm Rina was located at latitude 30.4°N and longitude 49.9°W which put it about 890 miles (1430 km) east of Bermuda.  Rina was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1010 mb.

Although an upper level low northwest of Tropical Depression Nineteen continued to produce westerly winds which caused moderate vertical wind shear, stronger thunderstorms developed east of the center of circulation.  Downdrafts in those storms were able to transport stronger winds to the surface and winds to tropical storm force were occurring at the surface.  The National Hurricane Center upgraded Tropical Depression Nineteen to Tropical Storm Rina on Monday night.

The circulation of Tropical Storm Rina is asymmetrical.  The stronger storms are occurring east of the center of circulation.  The winds to tropical storm force are occurring northeast of the center.  Winds to tropical storm force extend out about 60 miles to the northeast of the center of circulation.  The bands west of the center consist primarily of lower clouds and showers.  The upper level westerly winds are tilting the circulation toward the east with height.

The moderate vertical wind shear will continue to inhibit the intensification of Tropical Storm Rina.  Rina will move over water where the Sea Surface Temperature is near 25°C.  Although the water is cooler than it is in the tropical, colder air in the upper levels will make the atmosphere unstable enough to allow thunderstorms to continue to develop.  The vertical wind shear could decrease during the next 24 to 36 hours and some intensification is possible.  When Tropical Storm Rina moves farther north, it will move over colder water.

The upper level low to the northwest of Tropical Storm Rina and a ridge to the east of Rina are steering the tropical storm toward the north.  A general motion is expected to continue for another day or two.  On its anticipated track Tropical Storm Rina will pass between Labrador and the Azores.

Tropical Depression Nineteen Forms East of Bermuda

Tropical Depression Nineteen formed east of Bermuda on Monday.  At 10:00 a.m. EST on Monday the center of Tropical Depression Nineteen was located at latitude 29.5°N and longitude 50.4°W which put it about 875 miles east of Bermuda.  It was moving toward the north-northeast at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1013 mb.

A small low pressure system has been meandering over the Atlantic Ocean between Bermuda and the Azores.  More showers and thunderstorms formed near the center of the the low and the circulation became more circular.  Because the low pressure system developed the characteristics of a tropical cyclone, the National Hurricane Center designated the system as Tropical Depression Nineteen on Monday morning.

The circulation of Tropical Depression Nineteen is being affected by vertical wind shear.  An upper level low located to the northwest of the system is producing easterly winds which are blowing across the top of the depression.  Those winds are producing moderate vertical wind shear shear which is tilting the upper portion of the circulation to the east.  The surface center of circulation was exposed on visible satellite images.  Most of the showers and thunderstorms were occurring to the east of the center.

Tropical Depression Nineteen is forecast to intensify into a tropical storm.  The depression will move over water where the Sea Surface Temperature is near 25.5°C, which is marginally warm enough to support intensification.  The upper level low will continue to produce vertical wind shear which will inhibit intensification during the next 12 to 24 hours.  The shear is forecast to decrease on Tuesday and Tropical Depression Nineteen could strengthen into a tropical storm before it moves over colder water.

Tropical Depression Nineteen is currently in an area where the steering currents are weak.  The circulation around the upper level low to the northwest of the Tropical Depression is being deflected around an upper level ridge to the east of the depression.  Some of the flow is turning northward and the rest of the flow is turning toward the south.  The orientation of the upper low and ridge is forecast to change and the two systems are forecast to steer the depression toward the northeast later this week.  However, if the wind shear stays strong enough to prevent the circulation of the depression from growing vertically, then the winds in the lower level could steer the depression more toward the west.

Tropical Storm Philippe Brings Wind, Rain to Cuba and South Florida

Tropical Storm Philippe brought wind and rain to parts of Cuba and south Florida on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Philippe was located at latitude 24.8°N and longitude 82.1°W which put it about 25 miles (40 km) northwest of Key West, Florida.  Philippe was moving toward the north-northeast at 24 m.p.h. (39 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1003 mb.

Tropical Storm Warnings were in effect for the Cuban provinces of Isla de la Juventud, La Habana, Ciudad de la Habana, Matanzas, Cienfuegos and Villa Clara.  Tropical Storm Warnings were in effect for the northwestern Bahamas including the Abacos, Andros Island, Berry Island, Bimini, Eleuthera, Grand Bahama Island and New Providence.  Tropical Storm Watches were in effect for the portion of the coast from Craig Key to Golden Beach, Florida.  Tropical Storm Watches were also in effect for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.

The circulation is of Tropical Storm Philippe is not well organized.  The appear to be multiple smaller centers of counterclockwise rotation moving around inside the broader circulation.  One center of circulation is in northwest of Key West.  Showers and thunderstorms were primarily northeast of that center of rotation.  There were low clouds west of that center.  Another center of rotation was just north of the coast of Cuba.  A primary band of showers and thunderstorms wrapped around the eastern side of this second center.  The middle and upper level circulation of Tropical Storm Philippe appeared to be associated with the center near Cuba.

Tropical Storm Philippe will move through an environment that will be somewhat favorable for intensification.  Philippe will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough approaching Tropical Storm Philippe from the west is producing strong southwesterly winds which are causing significant vertical wind shear.  The shear is inhibiting the organization of the circulation.  Tropical Storm Philippe could intensify on Sunday if the center of circulation near Cuba becomes the dominant center, since it has a more complete vertical structure.

The upper level trough will continue to steer Tropical Storm Philippe quickly toward the northeast on Sunday.  On its anticipated track Tropical Storm Philippe will move through the Upper Florida Keys and over the Northwestern Bahamas on Sunday.   It will bring gusty winds and locally heavy rains to those areas.

Potential Tropical Cyclone Eighteen Prompts Warnings for Cuba and Bahamas

Potential Tropical Cyclone Eighteen prompted the governments of Cuba and the Bahamas to issue Tropical Storm Warnings and Watches for portions of those countries on Friday afternoon.  At 5:00 p.m. EDT on Friday the center of Potential Tropical Cyclone Eighteen was located at latitude 17.5°N and longitude 84.5°W which put it about 415 miles (670 km) south-southwest of Havana, Cuba.  It was moving toward the north-northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1006 mb.

Tropical Storm Warnings were issued for the Cuban provinces of Isla de la Juventud, La Habana, Ciudad de la Habana, Matanzas, Cienfuegos, and Villa Clara.  Tropical Storm Warnings were also issued for the northwestern Bahamas including the Abacos, Andros Island, Berry Island, Bimini, Eleuthera, Grand Bahama Island and New Providence.  Tropical Storm Watches were issued for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.

An Air Force Reserve Hurricane Hunter reconnaissance plane investigated the system formerly known as Invest 93L on Friday afternoon.  The plane found sustained winds to tropical storm force.  The plane also found a broad circulation center with several smaller centers of circulation revolving around inside the broader center.  Based on the observations from the plane, the National Hurricane Center (NHC) chose not to upgrade the system to Tropical Storm Philippe in its 5:00 p.m. EDT advisory.  However, NHC did change the designation of the system from Invest 93L to Potential Tropical Cyclone Eighteen.  If a more well defined center of circulation develops, then NHC could still change designation of the system to Tropical Storm Philippe.

The circulation of Potential Tropical Cyclone Eighteen is still organizing.  As mentioned above, there is a broad center of counterclockwise rotation.  There are also several smaller counterclockwise swirls within the broader center.  More showers and thunderstorms developed closer to the center of circulation on Friday afternoon.  The storms closer to the center of circulation were generating some upper level divergence which was pumping away mass to the northeast of the system.  Some bands of showers and thunderstorms were developing in the outer portions of the circulation.

Potential Tropical Cyclone Eighteen will move through an environment somewhat favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The system is embedded in a flow over warm moist air.  However there is a stationary front northwest of the system and there is cooler, drier air north of the stationary front.  The system is currently under the western side of an upper level ridge.  The upper level winds are weak and there is not much vertical wind shear.  Potential Tropical Cyclone Eighteen could slowly intensify during the next 24 hours as the circulation becomes more well organized.

The ridge east of Potential Tropical Cyclone Eighteen is steering the system toward the north-northwest.  That general motion should continue for another six to twelve hours.  An upper level trough will approach the system from the west on Saturday and the trough will start to steer it more toward the northeast.  On its anticipated track Potential Tropical Cyclone Eighteen will approach Cuba on Saturday afternoon.  The center of the system will move south of the Florida Keys on Saturday night and it could move across the northwestern Bahamas on Sunday.

The system will bring gusty winds and locally heavy rain to those locations.  The locally heavy rain could cause flooding.  There could be a storm surge of several feet (one to two meters) on parts of the south coast of Cuba, where the wind blows the water toward the coast.  There could also be some storm surge along the coasts of the Florida Keys.

Low Pressure Forms Near Northwest Caribbean Sea

An area of low pressure formed near the northwestern Caribbean Sea on Monday and the system has been designated as Invest 93L.  At 8:00 p.m. EDT on Monday the center of Invest 93L was located at latitude 14.0°N and longitude 83.0°W which put it about 75 miles (120 km) south-southeast of Cabo Gracias a Dios.  It was moving toward the north at 6 m.p.h. (9 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1006 mb.

An area of low pressure formed in the southern portion of an area of showers and thunderstorms that has persisted over the western Caribbean Sea for several days.  The circulation of Invest 93L is not well organized.  There is no well organized center of circulation nor are there well organized rainbands.  Most of the showers and thunderstorms are occurring in the northern portion of the circulation.  There are not many showers or thunderstorms in the southern half of the circulation.  Much of the western half of the circulation is over Nicaragua and Honduras.

Invest 93L will move through an environment mostly favorable for the development of a tropical cyclone during the next few days.  It will move over water where the Sea Surface Temperature is near 30°C.  Invest 93L is near the axis of an upper level ridge.  So, the upper level winds are weak over the system.  There are stronger winds farther north over the northern Caribbean Sea.  Invest 93L will be slow to develop as long as almost half of the circulation is over land.  Development will be more likely when the center moves farther away from land.

Invest 93L is just west of the axis of the ridge, which is steering the system slowly toward the north.  That general motion is forecast to continue for several more days.  On its anticipated track Invest 93L will move over the northwestern Caribbean Sea later this week.  Invest 93L will drop locally heavy rain over Nicaragua and Honduras and it could cause flash floods in some areas.

Former Hurricane Ophelia Brings Strong Winds to Ireland

Former Hurricane Ophelia brought strong winds to Ireland and parts of the United Kingdom on Monday.  Although former Hurricane Ophelia had made a transition to an extratropical cyclone before it reached Ireland, it was still a very powerful storm when it moved across that region.  There were reports of several fatalities, damage and power outages across Ireland.  Met Eireann (the Irish meteorological agency) reported the following wind gusts during the passage of former Hurricane Ophelia.

At the Fastnet Lighthouse (anemometer at 200 feet [61 meters] ) there was a gust of 191 km/h (118 m.p.h.).  Sherkin Island reported a wind gust of 135 km/h (84 m.p.h.) before the power went out.  Cork airport reported a wind gust of 126 km/h (78 m.p.h.) before the power went out. Shannon airport reported a wind gust of 122 km/h (76 m.p.h.).  Roches Point reported a wind gust of 156 km/h (97 m.p.h.).  The Kinsale Platform reported a wind gust of 141 km/h (87 m.p.h.) and the Dublin airport reported a wind gust of 104 km/h (65 km/h).