Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Tropical Storm Arthur Brings Wind and Rain to Eastern North Carolina

Tropical Storm Arthur brought wind and rain to eastern North Carolina on Monday.  At 8:00 a.m. EDT on Monday the center of Tropical Storm Arthur was located at latitude 34.5°N and longitude 75.9°W which put it about 50 miles (80 km) south-southwest of Cape Hatteras, North Carolina.  Arthur was moving toward the north-northeast at 15 m.p.h. (24 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 1001 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.

Tropical Storm Arthur began to move more quickly toward the Outer Banks of North Carolina on Monday morning.  The distribution of thunderstorms and winds around Arthur was asymmetric.  The strong thunderstorms were occurring in bands in the eastern half of the circulation.  The strongest winds were occurring in those bands.  Bands in the western half of Tropical Storm Arthur consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 90 miles (145 km) in the eastern half of Arthur.  The winds in the western half of Arthur were mostly less than tropical storm force.

The asymmetric structure of Tropical Storm Arthur meant that the strongest winds were occurring east of the Outer Banks of North Carolina.  A buoy at Diamond Shoals was reporting a sustained wind speed of 33 m.p.h. (54 km/h) and wind gusts to 47 m.p.h. (76 km/h).  The wind speeds along the coast of North Carolina were much weaker.  Tropical Storm Arthur was dropping moderate rain over eastern North Carolina.   Wind blowing water toward the coast was causing the water level to rise in some locations.  Waves were causing erosion on some beaches.

A large upper level trough will approach Tropical Storm Arthur from the west.  The trough will turn Arthur more toward the east later on Monday.  On its anticipated track, Tropical Storm Arthur should move away from North Carolina on Monday afternoon.  Weather conditions should improve gradually when Arthur moves farther form the coast.

Tropical Storm Arthur Prompts Warning for North Carolina

Tropical Storm Arthur prompted the National Hurricane Center to issue a Tropical Storm Warning for a portion of the coast of North Carolina.  A Tropical Storm Warning was in effect for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.

At 11:00 a.m. EDT on Sunday the center of Tropical Storm Arthur was located at latitude 30.5°N and longitude 77.4°W which put it about 345 miles (560 km) south-southwest of Cape Hatteras, North Carolina.  Arthur was moving toward the north-northeast at 9 m.p.h. (15 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. (96 km/h).  The minimum surface pressure was 1002 mb.

The circulation around Tropical Storm Arthur exhibited more organization on Sunday morning.  Several bands of showers and thunderstorms were wrapping around the eastern and northern parts of the circulation.  Bands on the western side of Arthur still consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 115 miles (185 km) from the center of circulation on the eastern side of Tropical Storm Arthur.  The winds on the western side of Arthur were mostly below tropical storm force.

Tropical Storm Arthur will move through an environment favorable for intensification during the next 24 hours.  Arthur will move over water where the Sea Surface Temperature is near 25°C.  It will move under an upper level ridge centered off the southeast coast of the U.S.  The winds in the upper ridge are relatively weak and there will not be a lot of vertical wind shear.  Tropical Storm Arthur is likely to get stronger during the next 24 hours.

Tropical Storm Arthur will move around the western end of a high pressure system during the next 24 hours.  The ridge will steer Arthur toward the north-northeast during the next day or so.  A large upper level trough over the central U.S. will approach Tropical Storm Arthur on Monday.  The trough will steer Arthur more toward the east.  On its anticipated track Tropical Storm Arthur will approach the coast of North Carolina on Monday.  Arthur will bring gusty winds to the coast.  Wind blowing toward the shore will cause the water level to rise.  Waves will cause beach erosion.

Tropical Depression One Strengthens Into Tropical Storm Arthur

Tropical Depression One strengthened into Tropical Storm Arthur on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Arthur was located at latitude 29.4°N and longitude 77.7°W which put it about 420 miles (675 km) south-southwest of Cape Hatteras, North Carolina.  Arthur 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 1006 mb.

A Tropical Storm Watch remains in effect for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.

Surface observations and data from aircraft reconnaissance indicated that Tropical Depression One strengthened on Saturday night and the National Hurricane Center designated the system as Tropical Storm Arthur.  Thunderstorms continued to develop near the center of circulation and storms near the center generated upper level divergence which pumped mass away to the east of the depression.  Bands of showers and thunderstorms were developing.  The strongest bands were in the eastern half of the circulation.  Winds to tropical storm force extended out 80 miles (130 km) from the center in the eastern side of Tropical Storm Arthur.  Most of the winds in the western side of the circulation were less than tropical storm force.

Tropical Storm Arthur will move through an environment favorable for intensification during the next 24 hours.  Arthur will move over water where the Sea Surface Temperature is near 25°C.  An upper level trough over the eastern Gulf of Mexico and an upper level ridge east of Florida will interact to produce southerly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear but the shear will not be strong enough to prevent intensification.  Tropical Storm Arthur will strengthen on Sunday.

The upper level trough and upper level ridge will steer Tropical Storm Arthur toward the north-northeast during the next 36 to 48 hours.  On its anticipated track Tropical Storm Arthur will approach the coast of North Carolina on Monday.  It will bring gusty winds and heavy rain to parts of the coast.  Wind blowing water toward the coast will cause the water level to rise and there will be erosion of the beaches.

Tropical Depression One Forms East of Florida

Tropical Depression One formed east of Florida on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Depression One was located at latitude 28.4°N and longitude 78.6°W which put it about 125 miles (200 km) east of Melbourne, Florida.  The depression was moving toward the north-northeast at 13 m.p.h. (20 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 1008 mb.

A Tropical Storm Watch was issued for the portion of the coast from Surf City to Duck, North Carolina including Pamlico and Albemarle Sounds.

Surface observations and data from aircraft reconnaissance indicated that a distinct low pressure system formed east of Florida on Saturday and the National Hurricane Center designated the system as Tropical Depression One.  More thunderstorms developed near the center of circulation.  Storms near the center began to generate upper level divergence which pumped mass away to the east of the depression.  The strongest winds were occurring in the inner part of the circulation, which was consistent with the typical structure of a tropical cyclone.  Bands of showers and thunderstorms were developing.  The strongest bands were in the eastern half of the circulation.

Tropical Depression One will move through an environment favorable for intensification during the next several days.  The depression will move over water where the Sea Surface Temperature is near 25°C.  An upper level trough over the eastern Gulf of Mexico and an upper level ridge east of Florida will interact to produce southerly winds which will blow toward the top of the circulation.  Those winds will cause some vertical wind shear but the shear will not be strong enough to prevent intensification.  Tropical Depression One will strengthen into a tropical storm.

The upper level trough and upper level ridge will steer Tropical Depression One toward the north-northeast during the next 36 to 48 hours.  On its anticipated track Tropical Depression One will approach the coast of North Carolina on Monday.  It will be a tropical storm by that time.  It will bring gusty winds and heavy rain to parts of the coast.  Wind blowing water toward the coast will cause the water level to rise and there will be erosion of the beaches.

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.

Possible Development Near the Bahamas

A low pressure system could develop near the Bahamas on Friday or Saturday.  The National Hurricane Center is indicating that there is a 70% probability that the low pressure system could develop into a subtropical cyclone.

A stationary frontal boundary extends from south of Florida across the Bahamas.  A small upper level trough called a shortwave over the southwestern U.S. will move east toward the stationary front later this week.  When the upper level trough approaches the stationary front, a low pressure system is likely to develop near the Bahamas.  If thunderstorms develop near the center of the low pressure system, then it could exhibit the structure of a tropical or subtropical cyclone.  The Sea Surface Temperature near the Bahamas is near 26°C.  So, the water will be warm enough to support the development of a tropical cyclone.  However, the winds blowing around the upper level trough will cause moderate vertical wind shear.  The wind shear may be strong enough to inhibit the development of a tropical cyclone.  However, the shear may not be strong enough to prevent the development of a subtropical cyclone.  If the low pressure system strengthens into a subtropical storm, it will be designated Subtropical Storm Arthur.

Tropical Storm Sebastien Speeds East

Tropical Storm Sebastien sped eastward across the Atlantic Ocean on Friday.  At. 4:00 p.m. EST on Friday the center of Tropical Storm Sebastien was located at latitude 26.2°N and longitude 53.7°W which put it about 815 miles (1315 km) northeast of the Leeward Islands.  Sebastien was moving toward the east-northeast at 16 m.p.h. (26 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.

An upper level trough over the western Atlantic Ocean was producing strong southwesterly winds which were blowing toward the top of Tropical Storm Sebastien.  Those winds were producing moderate vertical wind shear.  The shear was contributing to an asymmetrical distribution of thunderstorms around Sebastien.  Stronger thunderstorms were occurring in bands north and east of the center of circulation.  Bands south and west of the center consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out 200 miles (325 km) from the center of circulation.

Tropical Storm Sebastien will move through an environment that could permit it to maintain its intensity for another day or so.  Sebastien will move over water where the Sea Surface Temperature is near 25.5°C.  The upper level trough over the western Atlantic will continue to cause moderate vertical wind shear, which will inhibit intensification.  Sebastien will move over cooler water during the weekend and it should start to weaken at that time.

The upper level trough will steer Tropical Storm Sebastien toward the northeast during the weekend.  On its anticipated track Sebastien will move toward the Azores.  Sebastien is forecast to merge with a cold front before it reaches the Azores.

Tropical Storm Sebastien Forms Northeast of the Leeward Islands

Tropical Storm Sebastien formed northeast of the Leeward Islands on Tuesday morning.  At 10:00 a.m. EST on Tuesday the center of Tropical Storm Sebastien was located at latitude 20.1°N and longitude 58.7°W which put it about 275 miles (445 km) northeast of the Leeward Islands.  Sebastien was moving toward the north-northwest at 8 m.p.h. (13 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.

More thunderstorms developed closer to the center of a low pressure system northeast of the Leeward Islands on Tuesday morning and the National Hurricane Center designated the system as Tropical Storm Sebastien.  There was a distinct low level center of circulation evident on visible satellite imagery.  However, the distribution of thunderstorms was asymmetrical.  The stronger thunderstorms were occurring in bands in the eastern half of the circulation.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Storms near the center were generating upper level divergence which was pumping mass away to the east of the tropical storm.  Winds to tropical storm force were occurring primarily in the northeastern quadrant of Sebastien.  Those winds extended out 100 miles (160 km) from the center of circulation.

Tropical Storm Sebastien will move through an environment marginally favorable for intensification during the next day or two.  Sebastien will move over water where the Sea Surface Temperature is near 28°C.  So, there will be sufficient energy in the upper ocean to support intensification.  An upper level trough near the east coast of the U.S. will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will create moderate vertical wind shear and they are probably contributing to the asymmetrical distributions of thunderstorms.  Tropical Storm Sebastien could strengthen if the shear does not increase.  However, if the upper level winds get stronger, then wind shear will cause Sebastien to weaken.

The upper level trough near the east coast of the U.S. and a subtropical high pressure system over the Atlantic Ocean will interact to steer Tropical Storm Sebastien toward the north during the next 24 to 36 hours.  On its anticipated track Sebastien will move away from the Leeward Islands and it is forecast to stay southeast of Bermuda.

Low Pressure Developing East of the Leeward Islands

A low pressure system was developing east of the Leeward Islands on Sunday night.  The low pressure system was centered about 550 miles (890 km) east of the Leeward Islands.  The structure of the low pressure system was still organizing.  Thunderstorms were forming in bands southeast of the low level center of circulation.  Bands in the other parts of the circulation consisted primarily of showers and lower clouds.

The low level center appeared to be located east of a small upper level low.  The upper low was causing southerly winds which were creating vertical wind shear over the western half of the surface center.  Some upper level divergence appeared to be occurring over the eastern half of the low level circulation.  The upper level divergence could be contributing to the development of the thunderstorms in that region.

The low pressure system will move through an environment somewhat favorable for development during the next several days.  The low will move over water where the Sea Surface Temperature is near 28°C.  It will move into a region where the upper level winds will not be too strong and there will not be too much vertical wind shear.  The National Hurricane Center is indicating that there is a 50% probability that a tropical or subtropical cyclone forms during the next five days.

The upper level low will steer the developing low pressure system toward the northwest on Monday.  A much large upper level trough off the east coast of the U.S. will steer the low pressure system more toward the north on Tuesday and Wednesday.  On its anticipated track the low pressure system will pass northeast of the Leeward Islands early next week.

Subtropical Storm Rebekah Forms West of the Azores

Subtropical Storm Rebekah formed west of the Azores on Wednesday afternoon.  At 5:00 p.m. EDY on Wednesday the center of Subtropical Storm Rebekah was located at latitude 38.3°N and longitude 40.7°W which put it about 745 miles (1195 km) west of the Azores.  Rebekah was moving toward the east at 13 m.p.h. (20 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 987 mb.

Subtropical Storm Rebekah formed in a manner very similar to the way Hurricane Pablo developed last week.  A small center of circulation developed in the middle of a much larger, extratropical cyclone.  Thunderstorms developed around the center of the small low pressure system.  Even though the small low was over water where the Sea Surface Temperature is near 22°C, cold air in the upper troposphere generated enough instability to allow the thunderstorms to grow upward.  Bands of showers and thunderstorms developed and began to revolve around the small low pressure system, and the National Hurricane Center designated the system at Subtropical Storm Rebekah.  Winds to tropical storm force extended out 90 miles (145 km) from the center of Rebekah.

Subtropical Storm Rebekah could strengthen during the next 24 hours.  Although Rebekah will move over water where the Sea Surface Temperature is near 22°C, colder air in the middle and upper troposphere will keep enough potential instability in the atmosphere to allow for the continued development of thunderstorms.  Since Rebekah is at the center of the larger low pressure system, the vertical wind shear will be less.  Subtropical storm Rebekah may intensify during the next day or so and it could make a transition to a tropical storm.

Subtropical Storm Rebekah will move eastward along with the larger low pressure system that surrounds the much smaller subtropical storm.  Southerly winds blowing around the eastern side of the larger low could push Rebekah toward the north at times.  On its anticipated track Subtropical Storm Rebekah could approach the western Azores on Friday.