Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Remnants of Tropical Storm Harvey About to Move Over Gulf of Mexico

The remnants of former Tropical Storm Harvey are about to move over the southern Gulf of Mexico.  At 2:00 p.m. EDT on Tuesday the center of the remnants of Tropical Storm Harvey was located at latitude 20.3°N and longitude 89.8°W which put it about 45 miles (75 km) south-southwest of Merida, Mexico.  It was moving toward the northwest at 15 m.p.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 1010 mb.

A broad area of low pressure that contained the remnants of former Tropical Storm Harvey moved across the Yucatan peninsula on Tuesday.  Thin bands of showers were rotating around the broad area of low pressure over land.  Several broken bands of thunderstorms were evident on the northern and northeastern periphery of the low pressure system.  There were several smaller centers rotating around inside the larger area of low pressure, but the circulation appeared to consolidating around a center near Merida.  A few thunderstorms were forming near that center as it neared the coast.

The National Hurricane Center indicated that there is a nearly 100% chance that the low pressure system will strengthen into a tropical cyclone again once it moves over the Gulf of Mexico.  The Sea Surface Temperature (SST) in the southern Gulf of Mexico is near 31°C.  An upper level low over the northwestern Gulf of Mexico was producing some vertical shear over the top of the surface low.  The upper low is forecast to move north and weaken.  An upper level ridge over the northwestern Caribbean Sea is forecast to move over the western Gulf of Mexico.  The upper ridge will produce southerly winds which will cause some vertical wind shear.  However, those winds are expected to be weak enough to allow for intensification.  The southerly winds could actually enhance upper level divergence to the north of the low pressure system in a day or two.

Given the large size of the low pressure system and the lack of a well defined center of circulation, the system will likely start to intensify slowly.  The rate of intensification will increase once a well defined center forms.  A period of very rapid intensification could occur later this week because of very warm SSTs and little vertical wind shear.  The area of low pressure could become a tropical depression within 12 hours.  It is likely to be a tropical storm on Wednesday.  The system has a good chance of becoming a hurricane over the western Gulf of Mexico.  If the system moves slowly and rapid intensification occurs, it could become a major hurricane.

A ridge in the middle troposphere near Florida is steering the low pressure system toward the northwest and a general northwesterly motion is forecast for the next several days.  There will be more uncertainty about the future track until a well developed center of circulation forms.  However, it seems likely that this system will move toward the coast of Texas.  The system could slow and/or turn more toward the north when it nears the coast.  It has the potential to become a significant hurricane by the time it reaches the coast.  It could bring strong gusty winds, which could cause a significant storm surge at the coast.  If the system moves slowly, it could also drop very heavy rain, which would create flash floods.

Tropical Storm Harvey Weakens to a Tropical Wave

Tropical Storm Harvey weakened to a tropical wave on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Wave Harvey was located at latitude 14.3°N and longitude 71.8°W which put it about 765 miles (1230 km) east of Cape Gracias a Dios.  The wave was moving toward the west at 22 m.p.h. (35 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 1007 mb.

An upper level ridge east of Harvey produced northerly winds that blew toward the top of the former tropical storm.  A subtropical high over the Atlantic Ocean produced strong easterly winds in the lower levels of the atmosphere.  The combination of northerly winds in the upper levels and easterly winds in the lower levels produced strong vertical wind shear which disrupted the vertical structure of Harvey.  A reconnaissance plane was unable to locate a low level center of low pressure on Saturday evening and the National Hurricane Center reclassified the system as a tropical wave.

Tropical Wave Harvey will continue to move west across the Caribbean Sea during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  So, there will be sufficient energy in the ocean to support a tropical cyclone. When the tropical wave moves under the core of the upper level ridge, the wind shear will decrease.  If the tropical wave moves into a more favorable environment and slows down, a new center of circulation could redevelop.  Models are not forecasting significant redevelopment of the tropical wave at the current time, but the National Hurricane Center will continue to monitor the wave for possible redevelopment.

Tropical Storm Harvey Develops East of Barbados

A reconnaissance plane found that a center of circulation and winds to tropical storm force had developed in a tropical wave previously designated as Invest 91L and Potential Tropical Cyclone Nine.  Based on data collected by the recon plane the National Hurricane Center named the system Tropical Storm Harvey on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 13.0°N and longitude 55.8°W which put it about 250 miles (400 km) east of Barbados.  Harvey was moving toward the west 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 1004 mb.

A Tropical Storm Warning is in effect for Martinique, Barbados, St. Vincent and the Grenadines, and St. Lucia.  A Tropical Storm Watch is in effect for Dominica.

The circulation of Tropical Storm Harvey became better organized on Thursday.  A low level center of circulation developed and bands of showers and thunderstorms began to revolve around the center.  Intermittent bursts of thunderstorms occurred near and to the west of the center of circulation.  The circulation of Tropical Storm Harvey is asymmetrical.  Most of the stronger thunderstorms are occurring in the western half of the circulation.  The bands in the eastern half of the circulation consist primarily of showers and low clouds.  Thunderstorms near the core of Harvey were generating some upper level divergence which was pumping mass away to the south and west of the tropical storm.

Tropical Storm Harvey will be moving through an environment that will be somewhat favorable for intensification.  Harvey will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge northeast of Puerto Rico is producing northeasterly winds which are blowing toward the top of Tropical Storm Harvey.  Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical distribution of thunderstorms.  Tropical Storm Harvey is likely to get better organized on Friday and it could strengthen.  The intensity guidance is mixed.  Some guidance forecasts that Harvey will become a hurricane as it moves over the Caribbean Sea, while other guidance weaken the tropical storm back to a tropical wave.  So far, the guidance has underpredicted the strength of Tropical Storm Harvey and so strengthen would seem more likely.

Tropical Storm Harvey is being steered quickly toward the west by the subtropical high over the Atlantic Ocean.  A general westerly or west-northwesterly track is forecast for the next few days.  On its anticipate track Tropical Storm Harvey could reach Barbados in about 12 hours.  Harvey could also reach Martinique, St. Lucia, St. Vincent and the Grenadines on Friday.  Tropical Storm Harvey will bring gusty winds and locally heavy rain to those islands when it moves over them.

Hurricane Gert Intensifies to Cat. 2 South of Nova Scotia

Hurricane Gert intensified to Category 2 on the Saffir-Simpson Scale as it sped over the Gulf Stream south of Nova Scotia on Wednesday afternoon.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Gert was located at latitude 38.7°N and longitude 62.4°W which put it about 410 miles (665 km) south of Halifax, Nova Scotia.  Gert was moving toward the northeast at 31 m.p.h. (50 km/h).  The maximum sustained wind speed was 100 mp.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 970 mb.

Although Hurricane Gert is at a fairly high latitude, it has the classic structure of a Hurricane.  There is a fairly small eye at the center of circulation.  The eye is surround by a ring of strong thunderstorm and the strongest winds are occurring in this ring of thunderstorms.  There are additional bands of showers and thunderstorms revolving around the core of the hurricane.  The circulation is symmetrical and thunderstorms in the core are producing upper level divergence which is pumping away mass to the northeast of the hurricane.  Winds to hurricane force extend out about 40 miles (65 km) primarily to the east of the center of circulation.  Winds to tropical storm force extend out about 140 miles (225 km) from the center.

Hurricane Gert is moving over the Gulf Stream which means it is moving over water where the Sea Surface Temperature (SST) is near 28.5°C.  An upper level trough west of Gert is producing southwesterly winds which are blowing toward the top of the hurricane.  However, there is not much change of wind speed with height, which means that there is little vertical wind shear.  The combination of the warm water of the Gulf Stream and little vertical shear, allowed Hurricane Gert to strengthen on Wednesday.

Hurricane Gert could intensify during the next few hours, but it will soon move into a much less favorable environment.  Gert will soon move north of the Gulf Stream where the SSTs are much cooler.  The upper level trough is moving closer to Hurricane Gert and the winds are the upper level are forecast to get stronger.  When those winds increase, there will be much more vertical wind shear.  Colder water and more wind shear will cause Hurricane Gert to weaken on Thursday.  Gert could make a transition to an extratropical cyclone in colder environment of the North Atlantic.

Southwesterly winds in the upper level trough are steering Hurricane  Gert quickly toward the northeast and that general motion is expected to continue.  On its anticipated track, Hurricane Gert will move south of Labrador and Greenland.

Even as Hurricane Gert speeds away over the North Atlantic three new tropical waves over the tropical Atlantic have the potential to develop into tropical cyclones.  A tropical wave about 800 miles (1290 km) east of the Lesser Antilles designated as Invest 91L showed signs of organization on Wednesday.  A few more thunderstorms developed closed to the center of circulation.  A reconnaissance plane is scheduled to investigate this system on Thursday.  A little farther to the east another tropical wave designated Invest 92L was also showing evidence or more organization.  A third tropical wave just west of Africa also has the potential to develop during the next few days.

Gert Intensifies to a Hurricane West of Bermuda

Gert intensified to a hurricane west of Bermuda on Monday.  Gert became the second Atlantic hurricane of 2017 and it is the second hurricane to form during the past six days.  Hurricane Franklin developed over the southern Gulf of Mexico last week.  At 11:00 p.m. EDT on Monday the center of Hurricane Gert was located at latitude 31.2°N and longitude 72.3°W which put it about 445 miles (720 km) west of Bermuda.  Gert was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 986 mb.

An eye appeared on satellite images of Hurricane Gert at various times on Monday and it looked more like a hurricane.  There was a somewhat elliptical eye at the center of Hurricane Gert on Monday night.  The ring of thunderstorms around the eye did not completely surround the eye.  There was a large break on the northwest side of the eye.  Additional bands of showers and thunderstorms were occurring in the southeastern half of Gert.  There were fewer showers and thunderstorms in the northwestern half of the hurricane.  Thunderstorms near the core of Gert were generating upper level divergence which was pumping out mass to the south of the hurricane.

Hurricane Gert will be an environment that will be favorable for intensification for another 24 to 48 hours.  Gert will move over water where the Sea Surface Temperature is near 28.5°C.  An upper level ridge centered northwest of Gert is producing northerly winds which are blowing toward the top of the circulation.  Those winds are producing some vertical wind shear and they may be responsible for the asymmetrical distribution of showers and thunderstorms.  However, the vertical wind shear should not be strong enough to prevent Hurricane Gert from intensifying further.  An upper level trough will approach Gert from the west, but before the trough reaches the hurricane, the wind shear will decrease and a period of rapid intensification could occur.

Hurricane Gert is moving around the western end of a subtropical high over the Atlantic Ocean.  The high is steering Gert slowly toward the north.  When the upper level trough approaches Gert, southwesterly winds will start to steer the hurricane toward the northeast.  On its anticipated track Hurricane Gert should pass northwest of Bermuda.

TD 8 Strengthens to Tropical Storm Gert

Tropical Depression Eight strengthened to Tropical Storm Gert on Sunday afternoon.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Gert was located at latitude 28.1°N and longitude 71.7°W which put it about 505 miles (810 km) west-southwest of Bermuda.  Gert was moving toward the north-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1011 mb.

The structure of Tropical Storm Gert improved on Sunday.  Numerous bands of showers and thunderstorms developed and began to rotate around the center of circulation.  The thunderstorms began to produce upper level divergence which was pumping out mass in all directions.  The circulation of Tropical Storm Gert became more circular and symmetrical.

Tropical Storm Gert will move through an environment that will be favorable for intensification during the next 24 hours.  Gert will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds over Tropical Storm Gert are weak and there is not much vertical wind shear.  There is an upper level ridge northwest of Tropical Storm Gert and the ridge is producing northeasterly winds west of Bermuda.  So, the vertical wind shear could increase when Gert moves farther north.  Tropical Storm Gert will continue to intensify during the next 24 hours.

Tropical Storm Gert is moving around the western end of the subtropical high pressure system over the Atlantic Ocean.  The high is steering Gert toward the north-northwest and a northerly motion is  expected to continue for another 24 hours.  When Gert moves west of Bermuda, it will start to encounter the westerly winds in the middle latitudes.  Those winds should turn Tropical Storm Gert toward the northeast in a day or so.  On its anticipated track Tropical Storm Gert is expected to move east of the U.S. and west of Bermuda.

Tropical Depression Eight Forms East of the Bahamas

Tropical Depression Eight formed east of the Bahamas on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Tropical Depression Eight was located at latitude 25.3°N and longitude 70.3°W which put it about 470 miles (755 km) east of Nassau, Bahamas.  It was moving toward the north-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1011 mb.

Data from satellites and NOAA buoy 41046 indicated that a low level center of circulation formed within former Invest 99L.  Based on those data the National Hurricane Center classified the system as Tropical Depression Eight.  Bands of showers and thunderstorms began to develop in Invest 99L on Saturday afternoon.  There were more bands in the eastern half of the circulation than there were in the western half.  Thunderstorms in the bands began to generate upper level divergence which was pumping away mass.  The circulation took on a more circular appearance and they system exhibited the characteristics of a tropical depression.

Tropical Depression Eight will move through an environment favorable for intensification during the next 36 to 48 hours.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper low that was inhibiting the development of Invest 99L dissipated on Saturday.  When the upper low dissipated, the upper level winds weakened.  Tropical Depression Eight will move through an area where there is little vertical wind shear.  It will likely strengthen into Tropical Storm Gert on Sunday.  It could eventually intensify into a hurricane.

Tropical Depression Eight is moving around the western end of the subtropical high over the Atlantic Ocean.  The high is steering the depression toward the north-northwest and it is forecast to move primarily toward the north during the next 24 to 48 hours.  Tropical Depression Eight will eventually reach the westerly winds in the middle latitudes and it will turn toward the northeast when that happens.  On its anticipated track Tropical Depression Eight will remain east of the Bahamas.

Hurricane Franklin Brings Wind and Heavy Rain to Mexico

Hurricane Franklin brought gusty winds and heavy rain to parts of Mexico when it made landfall on Wednesday night.  The center of Hurricane Franklin made landfall between Veracruz and Nautla near the town of Lechuguillas, Mexico.  The maximum sustained wind speed was 85 m.p.h. (140 km) at the time of landfall, which made Franklin a Category 1 hurricane on the Saffir-Simpson Scale.  Franklin weakened to a tropical storm as it moved inland during the night.

At 8:00 a.m. EDT on Thursday the center of Tropical Storm Franklin was located at latitude 19.8°N and longitude 98.3°W which put it about 60 miles (95 km) east-northeast of the Mexico City, Mexico.  Franklin was moving toward the west at 15 m.p.h. (24 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 997 mb.

A Tropical Storm Warning remains in effect for the portion of the coast from Cabo Rojo to Boca Partido, Mexico.

Franklin brought hurricane force winds to the portion of the coast north of Veracruz, Mexico.  Those winds pushed water toward the shore and created a storm surge along the coast.  The highest surge may have reached 6 to 9 feet (2 to 3 meters) near and just to the north of where the center made landfall.  Winds blowing up the slopes of mountains produced very heavy rain and flooding could be occurring in some locations.  The heavy rain will continue as Tropical Storm Franklin moves west across central Mexico.

Tropical Storm Franklin will continue to weaken as it moves across Mexico.  Heavy rain will continue to fall over portions of central Mexico and the potential for additional flooding exists.  The mountains are likely to disrupt the low level circulation.  However, the middle and upper portions of the circulation could remain intact.  Some models are forecasting that Franklin, or its remnants, could redevelop when it reaches the Eastern North Pacific Ocean.

Franklin Strengthens Into a Hurricane Northeast of Veracruz

Formerly Tropical Storm Franklin strengthened into a hurricane northeast of Veracruz on Friday afternoon.  Franklin is the first hurricane to form over the Atlantic basin in 2017.  At 5:00 p.m. EDT the center of Hurricane Franklin was located at latitude 20.1°N and longitude 94.9°W which put it about 105 miles (170 km) northeast of Veracruz, Mexico.  Franklin was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 984 mb.

A Hurricane Warning is in effect for the portion of the coast from Puerto de Veracruz to Cabo Rojo, Mexico.  A Hurricane Watch is in effect for the portion of the coast from Cabo Rojo to Rio Panuco.  A Tropical Storm Warning is in effect for the portion of the coast from Puerto Dos Bocas to Puerto de Veracruz and from Tuxpan to Barra del Tordo.

An elliptical eye formed at the center of Hurricane Franklin and a reconnaissance plane detected surface winds in excess of 74 m.p.h. (119 km/h).  Based on data from the plane and an improved appearance on satellite imagery, the National Hurricane Center upgrade Franklin to hurricane status in its 5:00 p.m. EDT advisory.

The structure of Hurricane Franklin improved on Friday.  An elliptical eye oriented north to south formed at the center of circulation.  A ring of thunderstorms completely surrounded the eye.  The strongest winds were occurring in the northeastern part of the ring of storms.  Storms in the core of the circulation were generating upper level divergence which was pumping out mass and allowing the surface pressure to decrease.  A primary band of showers and thunderstorms coiled inward toward the core of Hurricane Franklin,  Additional bands of showers and thunderstorms were revolving around the core of Franklin.  Winds to hurricane force extended out about 35 miles (55 km) northeast of the center of circulation.  Winds to tropical storm force extended out about 140 miles (225 km) on the northern side of Franklin and about 100 miles (160 km) on the southern side of the hurricane).

Hurricane Franklin could intensify further before it makes landfall.  It is moving over water where the Sea Surface Temperature is near 30°C.  An upper level ridge over northern Mexico is generating northerly winds which are blowing toward the top of the circulation.  However, those winds are not very strong and the vertical wind shear is minor and it did not prevent Franklin from becoming a hurricane.  Hurricane Franklin has about another 6 to 12 hours to strengthen.  Once Franklin makes landfall and moves into the mountains, the surface circulation will weaken quickly.

A subtropical ridge is steering Hurricane Franklin toward the west and that general motion is expected to continue.  Hurricanes often turn slightly south of west when the approach the coast of the southwestern Bay of Campeche.  On its anticipated track the center Hurricane Franklin could make landfall on the coast of Mexico north of Veracruz in less than 12 hours.  The most likely landfall would be between Veracruz and Nautla.

Hurricane Franklin will bring strong gusty winds, a storm surge and heavy rain at the coast.  The storm surge could reach 6 to 9 feet (2 to 3 meters) near and just to the north of where the center makes landfall.  Franklin could produce very heavy rain when it reaches the mountains and flash flooding is a serious risk.

Tropical Storm Franklin Moves Over Bay of Campeche and Strengthens

Tropical Storm Franklin moved off the Yucatan peninsula over the Bay of Campeche and began to strengthen on Tuesday night.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Franklin was located at latitude 20.3°N and longitude 91.3°W which put it about 325 miles (525 km) east-northeast of Veracruz, Mexico.  Franklin was moving toward the west-northwest at 10 m.p.h. (16 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 996 mb.

A Hurricane Warning was in effect for the portion of the coast from Puerto de Veracruz to Tuxpan, Mexico.  A Hurricane Watch was in effect for the portion of the coast from Tuxpan to Rio Panuco.  A Tropical Storm Waring was in effect for the portion of the coast from Celestun to Puerto de Veracruz and from Tuxpan to Rio Panuco.

Although Tropical Storm Franklin weakened as it moved across the Yucatan peninsula on Tuesday, its circulation maintained its structural integrity.  In fact, a tighter inner core developed at the center of the circulation while the tropical storm moved over land.  New thunderstorms began to form near the center of Tropical Storm Franklin as soon as the center moved back over water.  A primary band of thunderstorms began to wrap tightly around the eastern and northern sides of the center.  Additional bands of showers and thunderstorms began to form over the Bay of Campeche.  Thunderstorms in the core were generating upper level divergence which is pumping away mass.

Tropical Storm Franklin will move over an environment very favorable for intensification on Wednesday.  Franklin will move over water where the Sea Surface Temperature is near 30°C.  The upper level winds are weak and there is little vertical wind shear.  An upper level trough over the Bahamas may enhance the upper divergence by creating an outflow channel to the east of Franklin.  Tropical Storm Franklin will intensify on Wednesday and there could be a period of rapid intensification.  Franklin is likely to become a hurricane.

Tropical Storm Franklin is being steered to the west by a subtropical high to its northeast.  A general westerly motion is expected to continue for another day or two.  On its anticipated track Tropical Storm Franklin will approach the coast of Mexico north of Veracruz on Wednesday night.  Franklin will bring gusty winds, heavy rain and a storm surge at the coast.  When Franklin moves inland the mountains will enhance the rising motion and very heavy rain could fall.  The heavy rain could cause flash floods.