Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

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.

Pablo Strengthens into a Hurricane Northeast of the Azores

Former Tropical Storm Pablo strengthened into a hurricane northeast of the Azores on Sunday.  At 11:00 a.m. EDT on Sunday the center of Hurricane Pablo was located at latitude 42.8°N and longitude 18.3°W which put it about 535 miles (865 km) northeast of Lajes, Azores.  Pablo was moving toward the north-northeast at 32 m.p.h. (52 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 983 mb.

Thunderstorms around the eye of former Tropical Storm Pablo strengthened on Sunday morning and Pablo intensified into a hurricane.  The circulation around Hurricane Pablo was still small.  Winds to hurricane force extended out about 10 miles (15 km) from the center of circulation.  Bands of showers and thunderstorms were revolving around the core of Pablo.  Winds to tropical storm force extended out 80 miles (130 km) from the center.

Hurricane Pablo was moving over water where the Sea Surface Temperature was near 18°C.  Water that cold would not normally contain enough energy to support a hurricane.  However the temperature of the air in the middle and upper troposphere is cold enough to allow for potential instability.  Convergence around the center of Hurricane Pablo generated enough rising motion to produce thunderstorms with tall, cold clouds tops around the eye at the center of the hurricane.  Enough water vapor condensed in the thunderstorms to produce a warm core which made Pablo a tropical cyclone.

Even though Hurricane Pablo is over Sea Surface Temperatures that would normal cause a hurricane to weak, Pablo could strengthen a little more during the next 12 hours.  It will move through a region where there is not a lot of vertical wind shear.  A larger low pressure system west of Pablo is likely to absorb the hurricane in a day or so.

Hurricane Pablo will move around the eastern side of the larger low pressure system.  The low will steer Pablo toward the north during the next 12 hours.  The larger low will turn Pablo toward the northwest on Monday.  On its anticipated track Hurricane Pablo is forecast to remain southwest of Ireland.

Tropical Storm Olga Develops over Gulf of Mexico, Pablo near the Azores

Tropical Storm Olga developed over the Gulf of Mexico and Tropical Storm Pablo formed near the Azores on Friday afternoon.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Olga was located at latitude 26.3°N and longitude 93.2°W which put it about 260 miles (420 km) south of Lake Charles, Louisiana.  Olga was moving toward the north-northeast at 18 m.p.h. (30 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 998 mb.

A reconnaissance plane found that former Tropical Depression Seventeen had strengthened by Friday afternoon and the National Hurricane center designated the system as Tropical Storm Olga.  More thunderstorms developed near the center of Olga and the plane found that the minimum surface pressure had decreased to 998 mb.  Bands of showers and thunderstorms were also developing around the tropical storm.  The strongest rainbands were in the eastern half of the circulation.  Bands in the western half of the circulation consisted of more showers and lower clouds.  Storms near the center were generating upper level divergence which was pumping mass away to the northeast of Tropical Storm Olga.  Winds to tropical storm force extended out about 90 miles (145 km) from the center of circulation in the northeastern quadrant of Olga.

Tropical Storm Olga could strengthen a little more during the next 12 hours.  Olga will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over the south central U.S. and Mexico will produce southwesterly winds which will blow toward the top of the circulationn. Those winds will produce moderate vertical wind shear, which will inhibit intensification.  However, the shear will not be strong enough to prevent intensification while the Olga is over the Gulf of Mexico.  The wind shear will cause Tropical Storm Olga to start a transition to an extratropical cyclone.  A cold front will move toward Olga from the northwest and the tropical storm could merge with the front during the next 24 hours.

The upper level trough will steer Tropical Storm Olga toward the north during the next several days. On its anticipated track Olga will make landfall on the coast of Louisiana during Friday night.  Tropical Storm Olga will bring  gusty winds to coastal Louisiana. Olga is likely to drop heavy rain over parts of Louisiana, Mississippi, and eastern Arkansas. The rain could cause floods in some locations.

Elsewhere over the Atlantic Ocean, visible satellite images revealed that a tiny tropical storm had developed at the center of a much larger low pressure system west of the Azores on Friday afternoon.  The National Hurricane Center designated the system as Tropical Storm Pablo.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Pablo was located at latitude 35.8°N and longitude 32.2°W which put it about 325 miles (525 km) west-southwest of the Azores.  Pablo was moving toward the east-southeast at 10 m.p.h. (16 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 990 mb.  Winds to tropical storm force extended out 35 miles (55 km) from the center of Tropical Storm Pablo.

Tropical Depression Seventeen Develops over Western Gulf of Mexico

Tropical Depression Seventeen developed over the western Gulf of Mexico on Friday.  At 11:00 a.m. EDT on Friday morning the center of Tropical Depression Seventeen was located at latitude 25.6°N and longitude 94.4°W which put it about 320 miles (515 km) south-southwest of Lake Charles, Louisiana.  It was moving toward the north at 16 m.p.h. (26 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.

More thunderstorms developed near the center of a low pressure system over the western Gulf of Mexico on Friday morning and the National Hurricane Center designated the system as Tropical Depression Seventeen.  Bands of showers and thunderstorms were also developing around the depression.  The strongest rainbands were in the eastern half of the circulation.  Bands in the western half of the circulation consisted of more showers and lower clouds.  Storms near the center were generating upper level divergence which was pumping mass away to the northeast of the depression.

Tropical Depression Seventeen is likely to strengthen during the next 12 to 18 hours.  The depression will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over the south central U.S. and Mexico will produce southwesterly winds which will blow toward the top of the depression.  Those winds will produce moderate vertical wind shear, which will inhibit intensification.  However, the shear will not be strong enough to prevent intensification while the depression is over the Gulf of Mexico.  The wind shear will cause the depression to start a transition to an extratropical cyclone.  A cold front will move toward the depression from the northwest and the depression could merge with the front during the next 24 hours.

The upper level trough will steer the depression toward the north during the next several days.  On its anticipated track the depression will make landfall on the coast of Louisiana during Friday night.  The depression could be a tropical storm when it makes landfall.  It will bring gusty winds to coastal Louisiana.  The depression is likely to drop heavy rain over parts of Louisiana, Mississippi, and eastern Arkansas.  The rain could cause floods in some locations.

Tropical Storm Nestor Causes Severe Weather in Florida

Tropical Storm Nestor caused severe weather in Florida.  At 2:00 p.m. EDT on Saturday the center of Tropical Storm Nestor was located at latitude 29.7°N and longitude 85.1°W which put it about 5 miles (10 km) west of Apalachicola, Florida.  Nestor was moving toward the east-northeast at 23 m.p.h. (38 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 999 mb.

A Tropical Storm Watch was in effect for the portion of the coast from Ochlockonee River to Suwanee River, Florida.

Tropical Storm Nestor began a transition to an extratropical cyclone as it approached the coast of Florida.  Strong westerly winds in the middle latitudes created significant vertical wind shear.  In addition, the circulation around Nestor pulled cooler, drier air into the western and southern parts of the tropical storm.  The effects of the upper level westerly winds and cooler, drier air caused the strongest rising motion to occur in bands well to the east of the center of circulation.  The strongest thunderstorms occurred in bands southeast of the low level center.

The vertical wind shear was strong enough that rotation developed in some of the thunderstorms over the Florida Peninsula.  Several tornado warnings were issued on Friday night because radar indicated likely rotation.  There were reports of property damage due to possible tornadoes in Cape Coral in Lee County, near Winston in Polk County, in Plant City in Hillsborough County and in Seminole in Pinellas County.

The center of Tropical Storm Nestor officially made landfall on St. Vincent Island west of Apalachicola on Saturday afternoon.  Many of the stronger thunderstorms had moved east of Florida by Saturday afternoon.  There were still bands of showers and thunderstorms moving over the Florida Peninsula.  Flow diverging from a surface high pressure system centered over the northeastern U.S. was converging with the flow around the northern part of Tropical Storm Nestor.  The convergence was generating a large area of rising motion.  Showers and thunderstorms were occurring over northern Florida, southeastern Alabama, southern Georgia and parts of South Carolina.

Tropical Storm Nestor will move toward the northeast as an extratropical cyclone during the next several days.  On its anticipated track the center of Nestor will move across southern Georgia and near the coast of South Carolina and North Carolina.  The low pressure system will continue to drop rain over those areas.  There has been below normal rainfall over the southeastern U.S. in recent weeks.  So, the rain is unlikely to cause flooding in most places.

Tropical Storm Nestor Speeds Toward Northwest Florida

Tropical Storm Nestor sped toward northwest Florida on Friday afternoon.  The National Hurricane Center designated a strong low pressure system over the Gulf of Mexico as Tropical Storm Nestor on Friday afternoon.  At 2:00 p.m. EDT on Friday the center of Tropical Storm Nestor was located at latitude 26.3°N and longitude 89.5°W which put it about 355 miles (570 km) southwest of Panama City, Florida.  Nestor was moving toward the northeast at 22 m.p.h. (35 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 1001 mb.

Tropical Storm Warnings were in effect for the portions of the coast from Grand Isle, Louisiana to the mouth of the Pearl River, Mississippi and from the Mississippi/Alabama border to Yankeetown, Florida.  A Storm Surge Warning was in effect for the portion of the coast from Indian Pass to Clearwater Beach, Florida.

Tropical Storm Nestor exhibited an asymmetrical structure that is commonly seen in late season tropical storms over the Gulf of Mexico.  The strongest thunderstorms were occurring in bands in the eastern side of Nestor.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  The tropical storm force winds were occurring in the eastern half of Tropical Storm Nestor.  Winds to tropical storm force extended out 175 miles (280 km) in the eastern side of the circulation.  The winds in the western half of Nestor were mostly less than tropical storm force.

Drier air was being pulled around the western side of Tropical Storm Nestor.  In addition, an upper level trough over the western Gulf of Mexico was producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were causing moderate vertical wind shear.  The combination of the drier air and the vertical wind shear was responsible for the asymmetrical distribution of thunderstorms and strong winds in the eastern half of the circulation.

Tropical Storm Nestor will move through an environment only marginally favorable for further intensification during the next 12 hours.  Nestor will move over water where the Sea Surface Temperature is near 29°C.  So, there is plenty of energy in the upper part of the Gulf of Mexico to support intensification.  However, the drier air and wind shear will inhibit intensification.  Tropical Storm Nestor will start a transition to an extratropical cyclone on Saturday.  Nestor could strengthen somewhat during the extratropical transition, but it could be over land before that occurs.

The upper level trough over the Western Gulf of Mexico will steer Nestor quickly toward the northeast during the next 48 hours.  On its anticipated track Tropical Storm Nestor could make landfall on the coast of northwest Florida between Panama City and Apalachicola.  Nestor will bring gusty winds to northern Florida on Saturday.  Strong southerly winds on the eastern side of Tropical Storm Nestor will push water toward the coast and a storm surge of 3 to 6 feet (1 to 2 meters) will occur around the northeastern Gulf of Mexico.  Nestor could drop locally heavy rain over parts of northern Florida, southeast Alabama, southern Georgia and South Carolina.  Tropical Storm Nestor will make landfall near where Hurricane Michael did so much damage in 2018.  Recovery efforts have been slow in that area and Nestor could set back the ongoing recovery from Hurricane Michael.

Low Pressure System Forms Over Southwest Gulf of Mexico

A surface low pressure system formed over the southwestern Gulf of Mexico on Wednesday.  At 8:00 p.m. EDT on Wednesday the center of the low pressure system was located at latitude 20.8°N and longitude 95.4°W which put it about 70 miles (110 km) east-southeast of Nautla, Mexico.  The low was moving toward the north at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1009 mb.

The northern end of a trough of low pressure moved over the Bay of Campeche on Wednesday and a surface low formed when the trough moved over the southwestern Gulf of Mexico.  More thunderstorms developed near the center of the low pressure system.  Divergence from a surface high pressure system over the U.S. was converging with the northern periphery of the circulation around the surface low and a band of showers and thunderstorms was occurring over the west central Gulf of Mexico.  Storms near the center of the low were starting to generate some upper level divergence.

The low pressure system will move through an environment that will be favorable for intensification during the next 24 to 36 hours.  The low will move over water where the Sea Surface Temperature is near 29°C.  It will move under an upper level ridge where the winds are weak and divergent.  The low could intensify slowly if it gets better organized on Thursday.  The National Hurricane Center is indicating that there is a 60% probability of formation of either a tropical or subtropical storm.  A reconnaissance plane has been tentatively tasked to investigate the low pressure system on Thursday afternoon.

The upper level ridge over the surface low pressure system will steer the low toward the northeast during the next several days.  On its anticipated track the low could approach the northeastern coast of the Gulf of Mexico on Friday.  The low will bring gusty winds and locally heavy rain.  The winds will generate higher waves and there could be a storm surge of 3 to 6 feet (1 to 2 meters).