Tag Archives: Bahamas

Marco Strengthens to a Hurricane, Laura Drenches Hispaniola

Former Tropical Storm Marco strengthened into a hurricane on Sunday over the Gulf of Mexico while Tropical Storm Laura dropped drenching rain on Hispaniola.  At 2:00 p.m. EDT on Sunday the center of Hurricane Marco was located at latitude 25.3°N and longitude 87.4°W which put it about 280 miles (450 km) south-southeast of the Mouth of the Mississippi River.  Marco was moving toward the north-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 992 mb.

A Hurricane Warning was in effect for the portion of the coast from Morgan City, Louisiana to the Mouth of the Pearl River, Mississippi.  Hurricane Watches were in effect for the portion of the coast from Intracoastal City, Louisiana to Morgan City and for New Orleans, Lake Pontchartrain and Lake Maurepas.  A Tropical Storm Warning was in effect from the Mouth of the Pearl River to the Mississippi/Alabama border.  A Tropical Storm Watch was in effect for the portion of the coast from the Mississippi/Alabama border to the Alabama/Florida border.

Former Tropical Storm Marco strengthened into a hurricane on Sunday.  A small eye developed at the center of circulation.  A ring of thunderstorms surrounded eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Marco.  Storms near the core generated upper level divergence which pumped mass away to the northeast of the hurricane.

The circulation around Hurricane Marco was small.  Winds to hurricane force extended out 15 miles (25 km) from the center of circulation.  Winds to tropical storm force extended out 70 miles (110 km) from the center.

Hurricane Marco will move through an environment somewhat favorable for intensification during the next 18 hours.  Marco will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the northwestern Gulf of Mexico will produce southwesterly winds which will blow toward the top of Hurricane Marco.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent Marco from strengthening during the next 18 hours.

The upper level trough and a subtropical high pressure system over the Atlantic Ocean will steer Hurricane Marco toward the north-northwest during the next day or so.  On its anticipated track Hurricane Marco will approach southeast Louisiana on Monday.  Marco will bring gusty winds and drop locally heavy rain over southeastern Louisiana and southern Mississippi.

Elsewhere, Tropical Storm Laura dropped heavy rain on the Dominican Republic and Haiti.  There were reports of flash floods.  At 2:00 pm. EDT on Sunday the center of Tropical Storm Laura was located at latitude 19.4°N and longitude 74.3°W which put it about 80 miles (130 km) southeast of Guantanamo, Cuba.  Laura was moving toward the west-northwest at 21 m.p.h. (33 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1004 mb.

Tropical Storm Warnings were in effect for the portion of the northern coast of the Dominican Republic from Samana to the border with Haiti and for the entire coast of Haiti.  Tropical Storm Warnings were in effect for the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, and the Ragged Islands.  Tropical Storm Warnings were also in effect for the Cuban provinces of Las Tunas, Holguin, Guantanamo, Santiago de Cuba, Granma, Ciego de Avila, Sancti Spiritus, Villa Carla, Cienfuegos, Matanzas, Mayabeque, La Habana, Artemisa, Pinar del Rio and the Isle of Youth.  A Tropical Storm Watch was in effect for the Florida Keys to the Isle of Youth.  Tropical Storm Watches were also in effect for the Central Bahamas and Andros Island.

Tropical Storm Marco Strengthens, Hurricane Watch for New Orleans

Tropical Storm Marco strengthened on Saturday and a Hurricane Watch was issued for a portion of the central Gulf Coast.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Marco was located at latitude 21.9°N and longitude 68.1°W which put it about 50 miles (80 km) west of the western tip of Cuba.  Marco was moving toward the north-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 992 mb.

A Hurricane Watch was issued for the portion of the coast from Intracoastal City, Louisiana to the Mississippi/Alabama border including Lake Pontchartrain, Lake Maurepas and New Orleans.  A Tropical Storm Watch was in effect for the portion of the coast from the Mississippi/Alabama border to the Alabama/Florida border.  A Tropical Storm Warning was in effect for the Cuban province of Pinar del Rio.

Tropical Storm Marco exhibited much better organization on Saturday.  Weather radar on a reconnaissance plane and from Cuba as well as visible satellite images indicated that a small eye developed at the center of Marco.  The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Tropical Storm Marco.  Storms near the core were generating upper level divergence which was pumping away to the north of the tropical storm.  The circulation around Marco was small.  Winds to tropical storm force extended out 100 miles (160 km) to the east of the center of circulation.  Winds to tropical storm force only extended out 50 miles (80 km) on the western side of the tropical storm.

Tropical Storm Marco will move through an environment favorable for intensification during the nextt 24 hours.  Marco will move over water where the Sea Surface Temperature is near 30°C.  It will move east of an upper level trough over the Gulf of Mexico.  The trough will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear is not likely to be enough to prevent intensification.  Tropical Storm Marco is likely to intensify into a hurricane during the next 24 hours.  Since he circulation around Marco is small, the tropical storm could strengthen or weaken quickly if the environment changes.

The upper level trough and a subtropical high pressure system over the Atlantic Ocean will steer Tropical Storm Marco toward the north-northwest during the next 36 to 48 hours.  On its anticipated track Marco could approach southeastern Louisiana by Monday afternoon.  Marco could be a hurricane when it approaches the coast.

Elsewhere, Tropical Storm Laura dropped heavy rain over Puerto Rico and it prompted the issuance of a Tropical Storm Watch for the Florida Keys.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Laura was located at latitude 18.0°N and longitude 68.1°W which put it about 125 miles (200 km) east-southeast of Santo Domingo, Dominican Republic.  Laura was moving toward the west at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1004 mb.

Tropical Storm Warnings were in effect for the U.S. Virgin Islands, Puerto Rico, Vieques and Culebra.  A Tropical Storm Warning was in effect for the northern coast of Hispaniola from Le Mole St. Nicholas, Haiti to Cabo Engano, Dominican Republic.  Tropical Storm Warnings were in effect for the Turks and Caicos, the Acklins, Long Key, Crooked Island, the Inaguas, and the Ragged Islands.  A Tropical Storm Warning was also in effect for the Cuban provinces of Las Tunas, Holguin, Santiago de Cuba, Guantanamo and Granma.

A Tropical Storm Watch was issued for the Florida Keys from Ocean Reef to Key West.  Tropical Storm Watches were in effect for the Central Bahamas and for Andros Island.

Tropical Storm Marco is forecast to move over HIspaniola and the mountains there are likely to disrupt the circulation.

TD 14 Strengthens into Tropical Storm Marco

Former Tropical Depression Fourteen strengthened into Tropical Storm Marco over the northwestern Caribbean Sea on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Marco was located at latitude 18.7°N and longitude 84.9°W which puts it about 180 miles (290 km) southeast of Cozumel, Mexico.  Marco was moving toward the north-northwest 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 1003 mb.

A Hurricane Watch was in effect for the portion of the coast from Punta Herrero to Cancun, Mexico.  A Tropical Storm Warning was in effect for the portion of the coast from Punta Herrero to Dzilam, Mexico.

An Air Force Reserve Hurricane Hunter reconnaissance aircraft found winds to tropical storm force in former Tropical Depression Fourteen and the National Hurricane Center upgraded the system to Tropical Storm Marco.  More thunderstorms developed near the center of Marco.  Many of the thunderstorms were occurring in short bands northeast of the center of circulation.  The strongest winds were occurring in those bands.  Storms near the center were generating upper level divergence which was pumping mass away to the northeast of the tropical storm.  Winds to tropical storm force extended 80 miles (130 km) to the northeast of Marco.  The winds in the other parts of the tropical storm were blowing at less than tropical storm force.

Tropical Storm Marco will move through an environment favorable for intensification during the next 24 hours.  Marco will move over water where the Sea Surface Temperature is near 29°C.  It will move east of a large upper level trough over the Gulf of Mexico.  The trough will produce southwesterly winds which will blow toward the top of Tropical Storm Marco.  Those winds will cause some vertical wind shear, but the shear will not be strong enough to prevent intensification.  Marco will intensify on Saturday and it could strengthen quickly because the circulation is small.  Tropical Storm Marco could also weaken quickly if the center moves over the Yucatan Peninsula.

Tropical Storm Marco will move around the western end of a subtropical high pressure system over the Atlantic Ocean.  The high and the upper level trough will interact to steer Marco toward the northwest during the next 24 to 36 hours.  On its anticipated track the center of Tropical Storm Marco could pass near the northeastern part of the Yucatan Peninsula on Saturday.

Elsewhere over the Atlantic Ocean, disorganized Tropical Storm Laura sped across the northern Leeward Islands on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Laura was located at latitude 17.0°N and longitude 84.9°W which put it about 195 miles (315 km) east-southeast of San Juan, Puerto Rico.  Laura was moving toward the west-northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1008 mb.

Tropical Storm Warnings were in effect Saba, St. Eustatius, St. Maarten, St. Martin, St. Barthelemy, the British Virgin Islands, the U.S. Virgin Islands, Puerto Rico, Vieques, Culebra, the north coast of HIspaniola from Le Mole St. Nicholas, Haiti to Cabo Engano, Dominican Republic, the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, and the Ragged Islands.  A Tropical Storm Watch was in effect for the Central Bahamas.

Isaias Crosses Andros Island, Weakens to Tropical Storm

The center of former Hurricane Isaias crossed Andros Island on Saturday afternoon and it weakened to a tropical storm.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Isaias was located at latitude 25.1°N and longitude 78.7°W which put it about 115 miles (185 km) southeast of Ft. Lauderdale, Florida.  Isaias was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 993 mb.

A Hurricane Warning was in effect for the portion of the coast from Boca Raton, Florida to the Flagler/Volusia County Line.  A Hurricane Waning was also in effect for the Northwestern Bahamas including Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island, and Bimini.

Tropical Storm Warnings were in effect for the portions of the coast from Ocean Reef to Boca Raton, Florida and from the Flagler/Volusia County Line to Ponte Vedra Beach, Florida.  A Tropical Storm Warning was also in effect for Lake Okeechobee.  A Tropical Storm Watch was in effect for the portion of the coast from Ponte Vedra Beach, Florida to South Santee River, South Carolina.

The center of former Hurricane Isaias crossed over Andros Island on Saturday afternoon.  Normally, Andros Island does not have much of an impact on hurricanes, but combined with a less favorable environment it contributed to a temporary weakening of Isaias.   Tropical Storm Isaias consisted primarily of bands of showers and lower clouds after crossing Andros Island.  However, new thunderstorms began to develop northeast of the center of circulation during the past several hours and part of the eyewall appeared to be reforming.  Bands in the western and southern parts of Isaias still consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 90 miles (145 km) from the center of circulation.

Tropical Storm Isaias will move through an environment somewhat favorable for intensification during the next 36 hours.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the central U.S. will produce westerly winds which blow toward the top of the circulation.  Those winds will cause moderate vertical wind shear, but they are likely to only affect the very top of the tropical storm.  Tropical Storm Isaias will move into a region where there is drier air in the middle and upper troposphere.  The circulation around Tropical Storm Isaias will reorganize and it is likely to strengthen back into a hurricane.

Tropical Storm Isaias will move around the western end of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Isaias toward the northwest during the next 24 hours.  Isaias will move more toward the north later on Sunday.  The upper level trough will turn Isaias toward the northeast on Monday.  On its anticipated track Tropical Storm Isaias is will approach the southeast coast of Florida near Ft. Lauderdale and West Palm Beach on Sunday.  Isaias is likely to be a hurricane when it approaches the coast.

Hurricane Isaias Forces Hurricane Warning for Florida

The threat posed by Hurricane Isaias forced the issuance of a Hurricane Warning for Florida on Friday afternoon.  At 5:00 p.m. EDT on Friday the center of Hurricane Isaias was located at latitude 22.6°N and longitude 75.7°W which put it about 195 miles (320 km) south-southeast of Nassau, Bahamas.  Isaias was moving toward the northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 991 mb.

A Hurricane Warning was in effect for the portion of the coast from Boca Raton, Florida to the Volusia/ Brevard County Line.  Hurricane Warnings were also in effect for all of the Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands, Cat Island, the Exumas, Long Island, Rum Cay, San Salvador, Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island and Bimini.  Hurricane Watches were in effect for the portions of the coast from the Flagler/Volusia County Line to the Volusia/Brevard County Line and from Hallendale Beach to Boca Raton.  Tropical Storm Warnings were in effect for the Turks and Caicos, Ocean Reef to Boca Raton, Florida and Lake Okeechobee.  A Tropical Storm Watch was in effect for the portion of the coast from Flagler. Volusia County Line to Ponte Vedra, Florida.

The core of Hurricane Isaias exhibited greater organization on Friday afternoon.  Images from weather radar in the Bahamas and microwave sensors onboard satellites indicated that an eyewall was wrapping around the center of circulations.  The strongest winds were occurring in the ring of storms in the developing eyewall.  Storms near the center of Isaias were generating upper level divergence which was pumping mass away from the hurricane.  Bands of showers and thunderstorms were revolving around the core of Hurricane Isaias.  Winds to hurricane force extended out 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extended out 175 miles (280 km) from the center.

Hurricane Isaias will move through an environment favorable for intensification during the next 24 hours.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Hurricane Isaias will strengthen on Saturday and it could intensify more rapidly once the inner core is fully formed.  Isaias could intensify into a major hurricane while it moves over the Bahamas.

Hurricane Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the northwest during the next 24 hours.  It will turn the hurricane more toward the north during the weekend when Isaias reaches the western end of the high pressure system.  On its anticipated track Hurricane Isaias will move over the Central Bahamas on Friday night.  Isaias could approach southeast Florida on Saturday.  Hurricane Isaias could approach the coast of the Carolinas on Monday.  Hurricane Isaias will bring strong winds to the southeast coast of Florida.  Those winds will blow the water toward the coast and they will create a dangerous storm surge.  Isaias will continue to produce strong winds and locally heavy rain in the Turks and Caicos and the Bahamas. Heavy rain could cause flash floods. Hurricane Isaias will also generate a dangerous storm surge in parts of the Bahamas.

Isaias Rapidly Intensifies into a Hurricane Southeast of the Bahamas

Former Tropical Storm Isaias rapidly intensified into a hurricane southeast of the Bahamas on Thursday night.  At 11:40 p.m. EDT on Thursday the center of Hurricane Isaias was located at latitude 20.3°N and longitude 72.1°W which put it about 70 miles (110 km) east-southeast of Great Inagua.  Isaias was moving toward the northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 995 mb.

Hurricane Warnings were issued for all of the Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands, Cat Island, the Exumas, Long Island, Rum Cay, San Salvador, Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island and Bimini. Tropical Storm Warnings were in effect for the entire coast of the Dominican Republic, Le Mole St. Nicholas, Haiti to the northern border with the Dominican Republic, the Turks and Caicos.  A Tropical Storm Watch was in effect for the portion of the coast from Ocean Reef to Sebastian Inlet, Florida.

A reconnaissance plane sampling former Tropical Storm Isaias on Thursday night found winds to hurricane force and a decrease in surface pressure.  The core of Hurricane Isaias organized quickly after it moved over the warm water north of the Dominican Republic.  A band of strong thunderstorms wrapped around the western side of the center of circulation.  Winds to hurricane force extended out about 30 miles to the northeast of the center of circulation.  Winds to tropical storm force extended out 240 miles (390 km) to the north and east of Isaias in the parts of the circulation that were over water.  Thunderstorms near the center of circulations were generating upper level divergence which pumped mass away from the tropical storm and allowed the pressure to decrease.   Brands of thunderstorms were wrapping around the eastern and northern sides of the circulation.

Hurricane Isaias will move through an environment favorable for intensification during the next 36 hours.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Hurricane Isaias will strengthen on Friday and it could intensify more rapidly once an inner core consolidates.  Isaias could intensify into a major hurricane while it moves over the Bahamas.

Hurricane Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the northwest during the next 36 hours.  It will turn the hurricane more toward the north on the weekend when Isaias reaches the western end of the high pressure system. On its anticipated track Hurricane Isaias will move over the Southeastern Bahamas on Friday morning.  Isaias will move over the Central Bahamas later on Friday and it could approach southeast Florida on Saturday.  Hurricane Isaias could approach the coast of the Carolinas on Monday.  Hurricane Isaias will bring strong winds and locally heavy rain to the Turks and Caicos and the Bahamas.  Heavy rain could cause flash floods.  Hurricane Isaias will also generate a dangerous storm surge in the Bahamas.

Tropical Storm Isaias Reorganizes North of Dominican Republic, Watch Issued for South Florida

The circulation around Tropical Storm Isaias reorganized near the northern coast of the Dominican Republic on Thursday afternoon and Tropical Storm Watches were issued for part of the coast of southeast Florida.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Isaias was located at latitude 19.5°N and longitude 70.6°W which put it about 25 miles (40 km) southeast of Puerto Plata, Dominican Republic.  Isaias was moving toward the northwest at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 999 mb.

Tropical Storm Warnings were in effect for the entire coast of the Dominican Republic, Le Mole St. Nicholas, Haiti to the northern border with the Dominican Republic, the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands, Cat Island, the Exumas, Long Island, Rum Cay, San Salvador, Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island and Bimini.  A Tropical Storm Watch was in effect for the portion of the coast from Ocean Reef to Sebastian Inlet, Florida.

The low level center of Tropical Storm Isaias moved across the eastern part of the Dominican Republic on Thursday.  The middle and upper parts of Isaias skirted along the east coast of Hispaniola.  The various levels of Tropical Storm Isaias appeared to be reconsolidating near the northern coast of the Dominican Republic just to the east of Puerto Plata.  New thunderstorms were forming near the reorganizing center of Isaias.  Those storms were generating upper level divergence which pumped mass away from the tropical storm and allowed the pressure to decrease.  Brands of thunderstorms were wrapping around the eastern and northern sides of the circulation.  The strongest winds were occurring in the portions of those bands over water.  The circulation around Tropical Storm Isaias tightened up on Thursday.  Winds to tropical storm force extended out 240 miles (390 km) to the north and east of Isaias in the parts of the circulation that were over water.

Tropical Storm Isaias will move through an environment favorable for intensification once it moves past Hispaniola.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Isaias will intensify when it moves north of Hispaniola and it could intensify rapidly once an inner core consolidates.  Isaias could intensify to a hurricane on Friday and it could strengthen into a major hurricane during the weekend.

Tropical Storm Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the northwest during the next 36 hours.  It will turn the tropical storm more toward the north on the weekend when Isaias reaches the western end of the high pressure system.  On its anticipated track Tropical Storm Isaias will move over the Turks and Caicos by Friday morning.  Isaias will move over the the Bahamas on Friday and it could approach southeast Florida on Saturday.  Tropical Storm Isaias could approach the coast of the Carolinas on Monday.  Tropical Storm Isaias will bring gusty winds and locally heavy rain to the Turks and Caicos and the Bahamas.  Heavy rain could cause flash floods.

Tropical Storm Isaias Drops Heavy Rain on Puerto Rico

Tropical Storm Isaias dropped heavy rain on Puerto Rico on Thursday.  At 8:00 a.m. EDT on Thursday the center of Tropical Storm Isaias was located at latitude 17.6°N and longitude 68.5°w which put it about 105 miles (165 km) east- southeast of Santo Domingo, Dominican Republic.  The center was about 80 miles (130 km) south of Cabo Engano.  Isaias was moving toward the northwest at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 1003 mb.

Tropical Storm Warnings were in effect for Puerto Rico, Culebra, Vieques, the U.S. Virgin Islands, the British Virgin Islands,  the entire coast of the Dominican Republic, Le Mole St. Nicholas, Haiti to the northern border with the Dominican Republic, the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands, Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.  Tropical Storm Watches were in effect for Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island and Bimini.

Bands on the eastern side of Tropical Storm Isaias were dropping heavy rain over parts of Puerto Rico on Thursday morning.  Flash Flood Warnings were in effect for parts of the island.  Isaias was also causing winds to tropical storm force in parts in Puerto Rico.  A station at Yabucoa Tanque de Agua reported a sustained wind speed of 46 m.p.h. (74 km/h) and a wind gust to 56 m.p.h. (91 km/h).  A station at Las Mareas reported a sustained wind speed of 3 m.p.h. (69 km/h) and a wind gust of 54 m.p.h. (87 km/h).

The circulation around Tropical Storm Isaias exhibited much more organization on Thursday morning, although the mid-level center did appear to be displaced to the north of the low level center.  There was a center of circulation but the distribution of thunderstorms was asymmetrical.  Most of the stronger thunderstorms were occurring in bands in the eastern side of Tropical Storm Isaias.  Storms near the center of circulation were generating upper level divergence which was pumping mass away from the tropical storm.  Bands in the western half of Isaias consisted primarily of showers and lower clouds.  Northerly winds on that side of the circulation were sinking over the southern part  of Hispaniola and that could have been suppressing the development of thunderstorms in that region.  The circulation around Tropical Storm Isaias was very still very large.  Winds to tropical storm force extended out 415 miles (665 km) on the northern side of Isaias.

Tropical Storm Isaias could weaken when the low level center of circulation moves across the eastern part of the Dominican Republic.  The low level circulation will be disrupted by the terrain but it looks like Isaias will pass east of the tallest mountains on Hispaniola.  The mid-level center of Tropical Storm Isaias appears to be passing very close to the eastern end of Hispaniola.  The middle and upper portions of the circulation are likely to remain intact and a new low level circulation could form north of Hispaniola.  Tropical Storm Isaias will move through an environment favorable for intensification once it moves past Hispaniola.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Isaias is likely to intensify when it moves north of Hispaniola and it could intensify rapidly once a new low level center of circulation develops.

Tropical Storm Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the northwest during the next 48 hours.  it will turn the tropical storm more toward the north on the weekend when Isaias reaches the western end of the high pressure system.  On its anticipated track Tropical Storm Isaias will move across the eastern part of the Dominican Republic today.  Isaias will move over the Bahamas on Friday and it could approach southeast Florida on Saturday.  Tropical Storm Isaias will bring gusty winds and locally heavy rain to Puerto Rico, Hispaniola and the Bahamas.  Flash floods could occur.

Tropical Storm Isaias Develops South of Puerto Rico

Tropical Storm Isaias developed south of Puerto Rico on Wednesday night.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Isaias was located at latitude 15.8°N and longitude 67.0°W which put it about 155 miles (250 km) south of Ponce, Puerto Rico.  Isaias was moving toward the west-northwest at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1004 mb.

Tropical Storm Warnings were in effect for Puerto Rico, Culebra, Vieques, the U.S. Virgin Islands, the British Virgin Islands, St. Martin, St. Barthelemy, Saba, St. Eustatius, St. Maarten, the entire coast of the Dominican Republic, Le Mole St. Nicholas, Haiti to the northern border with the Dominican Republic, the Turks and Caicos, the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands, Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.  Tropical Storm Watches were in effect for Andros Island, New Providence, Eleuthera, the Abacos, the Berry Islands, Grand Bahama Island and Bimini.

Data from a scatterometer onboard a satellite and observations from a buoy south of Puerto Rico indicated that a distinct center of circulation formed within a large low pressure system over the northeastern Caribbean Sea and the National Hurricane Center designated the system as Tropical Storm Isaias.  The center of circulation formed about 150 miles (240 km) south of Puerto Rico on Wednesday night.  More thunderstorms were developing near the newly formed center.  Many of those thunderstorms were southeast of the center.  Storms near the center were generating upper level divergence which pumped mass away from the tropical storm.  Bands of showers and thunderstorms were also located on the northern periphery  of the circulation and the strongest winds were occurring in those bands.  Winds to tropical storm force extended out 300 miles (485 km) to the northeast of the center of circulation.  Winds to tropical storm force also extended out 130 miles (215 km) to the northwest of the center.  The winds south of the center of Isaias were blowing at less than tropical storm force.

Tropical Storm Isaias will move through an environment favorable for intensification during the next 12 hours.  Isaias will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Isaias will get better organized and strengthen during the first half of Thursday.  A portion of the circulation around Isaias will move over Hispaniola later on Thursday.  Mountains on that island will disrupt the circulation and Tropical Storm Isaias will weaken while the center moves over land.

Tropical Storm Isaias will move around the western end of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer Isaias toward the west-northwest on Thursday.  On its anticipated track Tropical Storm Isaias will move across Hispaniola on Thursday.  Isaias will cause gusty winds and it will drop locally heavy rain when it moves over Hispaniola.  Heavy rain could cause flash floods.

Disturbance South of Florida Keys

A disturbance south of the Florida Keys is currently designated at Invest 90L.  The disturbance could develop into a tropical or subtropical cyclone during the next few days.  At 8:00 p.m. EDT on Thursday the center of Invest 90L was located at latitude 23.9°N and longitude 81.2°W which put it about 55 miles (85 km) south of Marathon, Florida.  It was moving toward the east-northeast at 5 m.p.h. (8 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 trough in the middle troposphere moved over a stationary front south of the Florida Keys on Thursday.  Satellite images and radar loops detected rotation in the middle troposphere.  There was a broad counterclockwise rotation south of the Keys and radar loops also revealed several small counterclockwise rotations within the broader mid-level circulation.  However, there did not appear to be a distinct center of circulation with lower pressure at the surface.

Invest 90L is forecast to move toward the northeast during the next several days.  It will move into an environment more favorable for development into a tropical or subtropical cyclone.  Invest 90L will move over water where the Sea Surface Temperature is near 27°C.  There will be an upper level trough over the eastern Gulf of Mexico, but a small upper level ridge will develop east of Florida.  The combination of the upper level trough and the upper ridge will produce a region of upper level divergence east of Florida.  The upper level divergence will pump mass away and the surface pressure will decrease in that area.  A surface low pressure system is likely to form on Friday or Saturday.  The National Hurricane Center is indicating that there is an 80% probability of the formation of a tropical or subtropical cyclone.  A reconnaissance plane is tentatively scheduled to investigate the system on Friday afternoon, if necessary.