Tropical Storm Hagupit Almost a Typhoon

Tropical Storm Hagupit intensified to almost typhoon strength east of Taiwan on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Hagupit was located at latitude 25.4°N and longitude 123.2°E which put it about 130 miles (215 km) east of Taipei, Taiwan.  Hagupit was moving toward the north-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 985 mb.

The circulation around Tropical Storm Hagupit exhibited much greater organization on Sunday night.  The inner end of a rainband wrapped around the center of circulation and an eye emerged on visible satellite imagery.  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 Hagupit.  The strongest rainbands were in the eastern half of the circulation.  Bands in the western half of the tropical storm consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 115 miles (185 km) from the center of circulation.

Tropical Storm Hagupit will move through an environment favorable for intensification during the next 24 hours.  Hagupit 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 Hagupit will intensify into a typhoon during the next 6 to 12 hours.

Tropical Storm Hagupit will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Hagupit toward the north-northwest during the next 24 to 36 hours.  On its anticipated track Hagupit will approach the coast of China south of Shanghai near Wenzhou in about 24 hours.  It will bring gusty winds and locally heavy rain to the east coast of China.  Heavy rain could cause flash floods in some locations.

Elsewhere, former Tropical Storm Sinlaku dropped locally heavy rain on northern Vietnam and Laos.  At 2:00 p.m. EDT on Sunday the center of Tropical Depression Sinlaku was located at latitude 19.7°N and longitude 103.6°E which put it about 150 miles (240 km) north of Vientiane, Laos.  Sinlaku was moving toward the west at 10 m.p.h. (16 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 996 mb.

Tropical Storm Isaias Slightly Stronger, Hurricane Watch Issued for Carolinas

Tropical Storm Isaias strengthened slightly on Sunday afternoon and a hurricane Watch was issued for a portion of the Carolinas’ coast.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Isaias was located at latitude 27.8°N and longitude 79.8°W which put it about 65 miles (105 km) southeast of Cape Canaveral, Florida.  Isaias was moving toward the north-northwest at 9 m.p.h. (15 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 994 mb.

A Hurricane Watch was issued for the portion of the coast from South Santee River, South Carolina to Surf City, North Carolina.  A Tropical Storm Warning was in effect for the portion of the coast from Sebastian Inlet, Florida to Ocracoke Inlet, North Carolina.  A Tropical Storm Watch was issued for the portion of the coast from Ocracoke Inlet, North Carolina to Watch Hill, Rhode Island including Albemarle Sound, Pamlico Sound, Long Island and Long Island Sound.

Tropical Storm Isaias strengthened a little on Sunday afternoon, but the middle level center of circulation was displaced to the northeast of the surface center.  An upper level trough over the central U.S. extended to the Gulf of Mexico and it was producing westerly winds which were blowing toward the top of Isaias.  Those winds were causing moderate vertical wind shear and they were also causing the displacement of the middle level center of Tropical Storm Isaias.  Thunderstorms continued to develop around the middle level center of circulation.  Those storms generated upper level divergence which pumped mass away to the east of the tropical storm.  Winds to tropical storm force extended out 115 miles (185 km) on the eastern side of Isaias.  Tropical Storm force winds only extended out 65 miles (105 km) on the western side of the circulation.

Tropical Storm Isaias will move through an environment somewhat favorable for intensification during the next 24 hours.  Isaias will move over water where the Sea Surface Temperature is near 30°C.  The direction of the upper level winds will shift to the southwest as the upper level trough approaches Tropical Storm Isaias.  That will cause the vertical wind shear to decrease.  Tropical Storm Isaias could strengthen into a hurricane, if the shear decreases.

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 north during the next 12 hours.  The upper level trough will steer Tropical Storm Isaias toward the northeast on Monday.  On its anticipated track Isaias will approach the coast of the Carolinas near Myrtle Beach, South Carolina on Monday night.  Isaias could be a hurricane when it makes landfall.  It will bring gusty winds and locally heavy rain to extreme eastern South Carolina, eastern North Carolina and coastal Virginia.  Isaias will cause a storm surge of 3  to 6 feet (1 to 2 meters) near and to the east of where the center makes landfall.  Tropical Storm Isaias will continue to move up the East Coast toward New England.

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.

Tropical Storms Sinlaku & Hagupit Form over West Pacific

Tropical Storms Sinlaku and Hagupit formed over the Western North Pacific Ocean on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Sinlaku was located at latitude 19.4°N and longitude 107.1°E which put it about 90 miles (145 km) southeast of Nam Dinh, Vietnam.  Sinlaku was moving toward the northwest at 12 m.p.h. (19 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 993 mb.

The circulation around a low pressure system near Vietnam exhibited greater organization on Saturday and the Japan Meteorological Agency designated the system as Tropical Storm Sinlaku.  Bands of showers and thunderstorms were revolving around the center of Sinlaku.  There were more thunderstorms in the bands on the western side of the circulation.  Winds to tropical storm force extended out 110 miles (185 km) from the center of circulation.

Tropical Storm Sinlaku has about 12 hours to strengthen before it makes landfall in northern Vietnam.  Sinlaku will move over water where the Sea Surface Temperature is near 30°.  It will move under the southeast part of an upper level ridge over Asia.  The ridge will produce easterly winds which will blow toward the top of Sinlaku.  Those winds will cause moderate vertical wind shear and the shear will limit intensification.  Tropical Storm Sinlaku will bring gusty winds and rain to northern Vietnam on Sunday.

The circulation around a second low pressure system east of Taiwan also exhibited more organization on Saturday and the Japan Meteorological Agency designated that system as Tropical Storm Hagupit.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Hagupit was located at latitude 21.8°N and longitude 126.5°W which put it about 220 miles (350 km) southeast of Ishigaki, Japan.  Hagupit was moving toward the 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.

The circulation around Tropical Storm Hagupit was still organizing on Saturday.  Thunderstorms were developing in bands in the eastern half of Hagupit.  Bands in the western side of the circulation consisted primarily of showers and lower clouds.  Storms near the center of Hagupit were generating upper level divergence which was pumping mass away to the east of the tropical storm.

Tropical Storm Hagupit will move through an environment favorable for intensification.  Hagupit will move over water where the Sea Surface Temperature is near 30°C.  Hagupit will move into a region where the upper level winds are weaker and there will not be a lot of vertical wind shear.  Tropical Storm Hagupit is likely to intensify during the next 24 to 36 hours.

Tropical Storm Hagupit will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high will steer Hagupit toward the northwest during the next several days.  On its anticipated track the center of Tropical Storm Hagupit will pass near Ishigaki, Japan in about 24 hours.  Hagupit will approach the coast of China south of Shanghai in about 48 hours.

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.

Potential Tropical Storm Prompts Warnings for Puerto Rico, Virgin Islands, Leeward Islands

A low pressure system that has the potential to organize into a tropical storm prompted the issuance of Tropical Storm Warnings for Puerto Rico, the Virgin Islands and many of the Leeward Islands on Tuesday morning.  At 11:00 a.m. EDT on Tuesday the center of Potential Tropical Cyclone Nine was located at latitude 13.8°N and longitude 53.7°W which put it about 585 miles (940 km) east-southeast of the Leeward Islands.  It was moving toward the west at 23 m.p.h. (37 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 1007 mb.

Tropical Storm Warnings were issued for Puerto Rico, Culebra, Vieques, the U.S. Virgin Islands, Antigua, Barbuda, the British Virgin Islands, Montserrat, St. Kitts, Nevis, Guadeloupe, Martinique, St. Martin, Saba, St. Eustatius, and St. Maarten.

The circulation around Potential Tropical Cyclone Nine was very broad and it stretched from the southwest toward the northeast.  The stronger thunderstorms were occurring in the southwestern and northeastern ends of the circulation.  There were few thunderstorms or bands in the broad middle of the low pressure system.  Winds to tropical storm force extended out 200 miles (320 km) on the northern side of the circulation.  The winds in the southern half of the low pressure system were blowing at less than tropical storm force.

Potential Tropical Cyclone Nine will move through an environment favorable for intensification during the next two days.  It will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  The large broad circulation will contribute to a slow, gradual intensification.  If thunderstorms consolidate around a center of circulation and an inner core begins to form, then the system may be designated as a tropical storm.

Potential Tropical Cyclone Nine will move south of a subtropical high pressure system over the North Atlantic Ocean.  The high will steer the potential tropical storm toward the west-northwest during the next several days.  On its anticipated track Potential Tropical Cyclone Nine could approach the Leeward Islands on Wednesday morning.  It could approach the Virgin Islands and Puerto Rico by Wednesday night.  The large circulation means that Potential Tropical Nine will bring a prolonged period of gusty winds.  It could also drop heavy rain and cause flash floods on some islands.