Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Small Low Forms East of Florida

A small surface low pressure system formed just north of the Bahamas on Thursday and the National Hurricane Center has designated this system Invest 92L.  At 8:00 p.m. EDT on Thursday the low was centered at latitude 27.2°N and longitude 79.1°W which put it about 70 miles east-northeast of Ft. Lauderdale, Florida.  The low was moving toward the west at 7 m.p.h.  The maximum sustained wind speed was 30 m.p.h. and the minimum surface pressure was 1012 mb.

An east-west upper level ridge over the southeastern U.S. and an upper low east of the Carolinas were combining to produce strong northerly winds over the surface low.  Those winds were creating considerable wind shear and were blowing much of the thunderstorm activity to the south of the low.   The shear is likely to continue for the next day or two and it is likely to inhibit significant intensification of the low.  The northerly winds were diverging on the south side of the low and the upper level divergence did cause the surface pressure to decrease by several millibars on Thursday.

The low is likely to move across south Florida during the weekend and it could enhance the rainfall in that area.  If the surface low remains intact and moves out over the Gulf of Mexico, it could move into an area where the wind shear is less.  Some models are suggesting that the low could become a tropical cyclone over the Gulf of Mexico, but that is contingent on its circulation retaining its integrity and the shear decreasing.  If a tropical cyclone does form, it could move toward the western or northwestern Gulf Coast during the early part of next week.

This low bears watching because of its proximity to the U.S., but it’s future is highly uncertain.  The wind shear could cause the system to dissipate as it crosses over Florida.  On the other hand, the low could move just far enough south to get away from the strongest upper level winds and then the low could emerge over the Gulf of Mexico in a couple of days.  There is time to watch the evolution of this system.

 

Tropical Storm Edouard Forms over the Eastern Atlantic

A core region of convection developed in the center of a large low pressure system associated with the northern portion of a tropical wave and the system was classified as Tropical Storm Edouard.  At 11:00 p.m. EDT the center of Edouard was located at latitude 17.3°N and longitude 39.4°W which put it about 1020 miles west of the Cape Verde Islands and about 2700 miles east-southeast of Miami, Florida.  Edouard was moving toward the west-northwest at 13 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and the minimum surface pressure was 1005 mb.

Edouard is likely to move in a general west-northwest to northwest track during the next several days before taking a more northward turn early next week.  This track would keep Edouard out in the middle of the Atlantic Ocean during the next five days where it will pose no immediate threat to any land areas.

The Sea Surface Temperatures in the subtropical Atlantic Ocean are several degrees above normal and Edouard should be able to extract plenty of energy from the ocean.  As long as the upper level winds are not too strong Edouard should be able to intensify and it is likely to become a hurricane.

 

TD 5 becomes Tropical Storm Dolly

Tropical Depression Five intensified into Tropical Storm Dolly during the overnight hours.  An Air Force Reserve Hurricane Hunter reconnaissance aircraft found that the maximum sustained wind speeds around Tropical Depression Five had increased to tropical storm force and the National Hurricane Center upgraded the system to Tropical Storm Dolly.  The plane also found that a new center of circulation had developed farther to the north of the previous center and the government of Mexico extended the Tropical Storm Warning northward to Barra El Mezquital.

At 8:00 a.m. EDT on Tuesday the center of Tropical Storm Dolly was located at latitude 23.0°N and longitude 95.7°W which put it about 145 miles east-southeast of La Pesca, Mexico and about 220 miles south-southeast of Brownsville, Texas.  Dolly was moving toward the west-northwest at 13 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and the minimum surface pressure was 1005 mb.  A Tropical Storm Warning is in effect from Tuxpan to Barra El Mezquital, Mexico.

Dolly is expected to continue to move toward the west-northwest and it could make landfall in northern Mexico later today.  The Sea Surface Temperatures in the western Gulf of Mexico are very warm and some further intensification is likely.   Locally heavy rains are possible after Dolly makes landfall.

 

Tropical Depression Five

A low pressure system over the southern Bay of Campeche has been classified as Tropical Depression Five (TD5).  At 5:00 p.m. EDT on Sunday the center of TD5 was located at latitude 20.1°N and longitude 93.6°W which put it about 255 miles east-southeast of Tuxpan, Mexico and about 465 miles south-southeast of Brownsville, Texas.  TD5 was moving toward the west-northwest at 13 m.p.h.  The maximum sustained wind speed was 30 m.p.h. and the minimum surface pressure was 1009 mb.  A Tropical Storm Warning has been issued for the portion of the coast from Tuxpan to La Pesca, Mexico.

TD5 is expected to move toward the west-northwest and intensify into tropical storm Dolly before it makes landfall.  The circulation of TD5 is interacting with a small upper level low north of the system, which is creating some northwesterly shear over it.  The shear is causing most of the thunderstorms and stronger winds to occur southeast of the center.  The shear will also limit intensification over the short term.  Heavy rain may be possible to the north of the center when the system makes landfall.

Possible Bay of Campeche TC

An area of low pressure associated with the northern edge of a tropical wave has moved out over the southern Bay of Campeche.  An Air Force Reserve Hurricane Hunter reconnaissance aircraft is flying through the the system and the plane has found southwesterly winds to 35 m.p.h. on the south side of the disturbance.  The strongest winds are currently on the southern side of the circulation.  If the plane is able to identify a well defined center of circulation at the surface, then the system could be classified as a tropical depression or tropical storm at 5:00 p.m. EDT.

The low pressure system is moving toward the west-northwest at 13 m.p.h.  Many models are predicting that the motion will continue and the system will make landfall in Mexico in the 36-48 hours.  Some intensification is predicted before the system makes landfall.  However, confidence in the model forecasts will increase once a center of circulation is identified and is used to initialize the models.

 

TD4 becomes Tropical Storm Cristobal

Reconnaissance aircraft found that the maximum sustained wind speed in Tropical Depression Four has increased to 45 m.p.h. and it has been upgraded to Tropical Storm Cristobal.  At 8:00 a.m. EDT the center of Cristobal was located at latitude 23.0°N and longitude 73.0°W which put it about 135 miles east-southeast of Long Island in the Bahamas and about 480 miles east-southeast of Miami, Florida.  Cristobal was moving toward the northwest at 9 m.p.h.  The minimum surface pressure was 1002 mb.  Tropical Storm Warnings remain in effect for the Southeastern and Central Bahamas and the Turks and Caicos.

Upper level winds from the northwest appear to be creating wind shear over Cristobal.  Most of the convection is occurring east and south of the center.

Tropical Depression Four

A reconnaissance aircraft found westerly winds in the southeastern side of a low pressure system over the Southeastern Bahamas and was able to close off a center of circulation.  As a result the National Hurricane Center classified the low as Tropical Depression Four (TD4).  At 5:00 p.m. EDT on Saturday the center of TD4 was located at latitude 21.8°N and longitude 72.3°W which put it about 75 miles northeast of Great Inagua Island in the Bahamas and about 560 miles east-southeast of Miami, Florida.  TD4 was moving toward the northwest at 12 m.p.h.  The maximum sustained wind speed was 35 m.p.h. and the minimum surface pressure was 1005 mb.

Tropical Storm Warnings have been issued for the Southeastern Bahamas including The Acklins, Crooked Island, Long Cay, The Inaguas, Mayaguana and the Ragged Islands as well as The Turks and Caicos Islands and the Central Bahamas including Cat Island, The Exumas, Long Island, Rum Cay and San Salvador.

A small upper low north of Cuba is causing some wind shear over the western portion of TD4.  On the other hand the Sea Surface Temperatures around The Bahamas are very warm and TD4 is very likely to intensify into Tropical Storm Cristobal and eventually into a hurricane.  Since the center has just formed the motion and future track are still highly uncertain, although a general motion toward the southeastern U.S. seems likely.

Invest 96L

The circulation around the tropical disturbance designated 96L has been disrupted by the mountains on Hispaniola.  There a appears to be a broad low level center near the northern coast of Haiti.  There are several smaller vorticies rotating around within the broader area of low pressure.  The strongest winds are occurring north and east of the center and several reconnaissance flights found winds to tropical storm force north of the center.  The broad center appears to be moving toward the west-northwest at 10-15 m.p.h.   The area of low pressure has produced heavy rain on some of the islands of the northern Caribbean Sea.

It is still possible that 96L could organize into a tropical cyclone as it moves away from Hispaniola.  Once it gets away from the mountains, it will be easier for the flow to consolidate around one primary circulation center.  The Sea Surface Temperatures (SSTs) are very warm around the Bahamas and the upper level winds are not too strong.

There is a large amount of uncertainty about the future track of this system and that will continue until a well defined center of circulation exists.  It appears that the low has been initialized too far to the northeast in some runs of numerical models and that has produced some forecast tracks that are also too far north and east.  It is still possible that this system could head in the general direction of the southeastern U.S.

Development will possibly be slow to occur until the system becomes better organized.  Tropical cyclones can intensify rapidly over the Bahamas and people would be wise to monitor future developments with 96L.

Update on Invest 96L

A tropical disturbance approaching the Lesser Antilles was designated Invest 96L by the National Hurricane Center (NHC).  The disturbance appears to consist of a tropical wave, a broad surface low centered east of Guadaloupe and a small cyclonic meso-vortex rotating around the northeastern portion of the broader low pressure system.  The overall system is moving toward the west-northwest at 21 m.p.h.  There appears to be a broad area of light winds within the surface low and stronger winds on the north side of the small meso-vortex.  A reconnaissance aircraft did find winds to tropical storm force on the north side of the system, but it also reported that the overall circulation was poorly defined.

This disturbance has a complicated origin which is linked to its slow development.  The disturbance originally consisted of two tropical waves moving north of a broad but weak low pressure system located within the Intertropical Convergence Zone/monsoon trough.  The complex structure inhibited the development of a dominant center of circulation and several clusters of thunderstorms have produced small meso-vortices like the one mentioned previously.  It appears that there has been a slight increase in organization today as the broad area of low pressures appears to have a more symmetrical shape.  It is unclear if an upper low to the northwest of the system is creating wind shear over the top of it.

NHC is giving a 70% chance that a tropical cyclone will form out of this system within the next five days.  As broad low pressure system moves west-northwest it will affect the weather over the northeastern Caribbean Sea during the next several days.  Another reconnaissance aircraft is scheduled to investigate the disturbance tomorrow afternoon, if necessary.

 

Possible Tropical Development

For the first time this hurricane season the Global System Forecast (GFS) Model is suggesting a classical development of a tropical cyclone east of the Lesser Antilles might occur and that resulting storm could effect the U.S.  A tropical wave is about 600 miles east of the Lesser Antilles and there may be a low pressure center near latitude 10°N and longitude 50°W.  Thunderstorm activity has increased with this system today as it moves westward.

The 0600 UTC run of the GFS model developed a tropical cyclone from this wave and moved it through the Caribbean Sea and into the Gulf of Mexico near Texas by a week from Friday.  The following (1200 UTC) run also developed a tropical cyclone and moved it into the northern Gulf of Mexico by a week from Wednesday evening.  At this time it is prudent to ask if these runs represent model false alarms or a possible depiction of future reality.  If the development of a tropical cyclone does occur, then it may be that a hurricane could approach the coast of the U.S. during the second half of next week.  The first indication that the GFS forecast might verify would be the development of tropical depression east of the Lesser Antilles.

This far out in advance the uncertainty of a track or intensity forecast is very high.  If there was a cone of uncertainty for the track, it might extend from Cancun to Cape Hatteras.  If a center of low pressure organizes, then the model guidance will improve and the uncertainty will decrease.

People along the coast of the U.S. should be aware of this system and maintain a cautious vigilance until we see if it does develop,