Tag Archives: Caribbean Sea

Invests 92L, 93L Monitored for Possible Development

Two weather systems designated as Invest 92L and Invest 93L are being monitored for possible development into tropical cyclones.  Invest 92L is a tropical wave that is speeding toward the Windward Islands.  At 2:00 p.m. EDT on Sunday the center of Invest 92L was located at latitude 7.3°N and longitude 49.4°W which put it about 800 miles (1290 km) east-southeast of the Windward Islands.  It was moving toward the west-northwest at 24 m.p.h. (39 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.

Invest 93L consists of a broad area of low pressure over the northwestern Caribbean Sea.  At 2:00 p.m. EDT on Sunday the surface center of Invest 93L was located at latitude 19.0°N and longitude 87.1°W which put it about 145 miles (230 km) south of Cancun, Mexico.  It was moving toward the north-northwest at 5 m.p.h. (8 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.

Invest 92L is a tropical wave and it has not yet develop a well defined surface center.  There is some evidence of cyclonic rotation on visible satellite imagery and there could be a center in the middle levels of the circulation.  Most of the stronger thunderstorms are located north and west of the center.  The are some bands of showers and thunderstorms south and west of the center.  There is some upper level divergence from the thunderstorms north and west of the center, but it is not well developed at the current time.

Invest 92L is in an environment that is moderately favorable to development of a tropical cyclone.  It is moving over water where the Sea Surface Temperature is near 28°C.  It is in a region of rapid easterly flow, but the wind speed is fairly similar at all levels.  So, there is not a lot of vertical wind shear.  The rapid easterly flow could be inhibiting the formation of a well defined center of circulation.  Invest 92L will be in a moderately favorable environment for about another 36 hours.  An upper level trough over the eastern Caribbean Sea will create increased vertical wind shear when Invest 92L reaches that location.  The National Hurricane Center is indicating that there is a 60% probability that Invest 92L will develop into a tropical cyclone during the next two days.

Invest 92L is being steered rapidly toward the west-northwest by a subtropical high north of it.  A fairly quick motion toward the west-northwest is expected to continue for the next few days.  On its anticipated track Invest 92L could be near the Windward Islands by late Monday.  Even it if does not develop into a tropical cyclone, the system will bring gusty winds and locally heavy rain to those islands.

The structure of Invest 93L is much more complicated.  There is a very broad but weak surface low pressure system over the Yucatan peninsula and the center of that low is being used as the center of the Invest.  However, there is a strong mid-level center of circulation near latitude 18.7°N and longitude 82.9°W which is about 115 miles (185 km) west-southwest of Grand Cayman.  Invest 93L is producing winds to near tropical storm force and those winds are occurring in thunderstorms associated with the mid-level circulation.  It is possible that downdrafts in those thunderstorms could transport enough momentum to the surface to generate a new surface center beneath the mid-level center.

Invest 93L is moving in an environment that will be favorable for the development of a tropical cyclone.  An upper level ridge is building between the trough over the eastern Caribbean Sea and another upper level trough over the northwestern Gulf of Mexico.  The trough over the northwestern Gulf is producing strong southwesterly winds which are causing vertical wind shear over the surface low over the Yucatan peninsula.  However, the upper level ridge is producing an area of slower winds over the mid-level center and there is less vertical wind shear there.  In fact, the upper level ridge is enhancing upper level divergence over the mid-level center.  If that continues, surfaces pressure will begin to decrease in that region.  The National Hurricane is indicating that there is a 70% probability of development of a tropical cyclone or a subtropical cyclone during the next two days.

Invest 93L is moving slowly north-northwestward around the western end of the subtropical high over the Atlantic Ocean.  A general north-northwesterly motion is expected to continue for another day or two, but there is some spread in the guidance from the numerical models.  If a cyclone forms from the surface low over the Yucatan peninsula, then the greatest risk would be to the western Gulf of Mexico.  If a new surface center forms farther east under the mid-level center, then there would be a greater risk for the central and eastern Gulf of Mexico.  Interests around the Gulf should monitor Invest 93L.

Invest 90L Meandering Over Southwest Caribbean Sea

An area of low pressure designated as Invest 90L has meandered over the southwestern Caribbean Sea during the past several days.  At 7:00 p.m. EST on Thursday the center of Invest 90L was located at latitude 12.3°N and longitude 81.3°W which put it about 170 miles (275 km) east of Bluefields, Nicaragua.  Invest 90L was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 25 m.p.h. (40 km/h) and there were wind gusts to 35 m.p.h. (55 km/h).  The minimum surface pressure was 1006 mb.

Invest 90L consists of a broad area of low pressure over the southwestern Caribbean Sea.  There is a definite area of counterclockwise rotation, but the is no well defined core at the center of the low.  There is a swirl of low clouds and showers at the center of Invest 90L, but there are no thunderstorms near the center.  Thunderstorms form and dissipate in bands around the periphery of the circulation.

The environment around the southwestern Caribbean Sea is not as favorable for the development of a tropical cyclone as it was earlier this week.  Invest 90L is moving over water where the Sea Surface Temperature is near 29°C.  However, northerly winds blowing across the Gulf of Mexico have transported drier air over the northwestern Caribbean Sea.  The drier air has not reached Invest 90L, but the drier air is just to the northwest of the low pressure system.  An upper level trough over the Gulf of Mexico is producing southwesterly winds which are blowing over the top of Invest 90L.  Those winds are generating moderate vertical wind shear which is inhibiting the organization of the low pressure system.  Even with the inhibiting factors the National Hurricane Center is indicating that the probability of the formation of a tropical cyclone during the next five days is 70%.

The fact that there is only a low level circulation means that Invest 90L is being steering by winds closer to the surface.  The winds in the lower levels have been pushing the low pressure system very slowly toward the west.  Guidance from numerical models suggests that Invest 90L could meander over the southwestern Caribbean Sea for several more days.

Possible Tropical Development Over the Southwest Caribbean Sea

A weak trough of low pressure over the Southwestern Caribbean Sea has the potential to develop into a tropical cyclone during the next few days.  The National Hurricane Center is stating that there is a 70% probability of the formation of a tropical cyclone during the next five days.  A broad trough of low pressure stretches from near Panama to east of Nicaragua.  There is not a well defined center of low pressure within the broader trough.  There were more thunderstorms earlier today, but many of them weakened on Monday evening.  A few more thunderstorms developed north of Panama during the past several hours.

The environment over the southwestern Caribbean Sea is favorable for intensification.  The Sea Surface Temperature of water in that part of the Caribbean Sea is around 29°C.  There is an upper level ridge over the area.  The winds are weaker in the center of the ridge and there is little vertical wind shear in that part of the atmosphere.  The ridge providing a source of upper level divergence which is allowing the surface pressure to decrease slowly.

Several numerical models are suggesting that a tropical cyclone could develop during the next few days.  The models do differ on exactly when and where the tropical cyclone could form.  The probability of development will be higher if the area of lower pressure remains over the water.  However, if the trough of low pressure drifts closer to the coast of Nicaragua, then the interaction of the circulation with land could inhibit the formation of a tropical cyclone.  Even if a tropical cyclone does not form, the trough could produce locally heavy rain over parts of Panama, Nicaragua and Honduras.

Tropical Storm Matthew Develops Near the Windward Islands

The National Hurricane Center determined that a surface circulation center formed within Invest 97L on Wednesday morning and it designated the system as Tropical Storm Matthew.  At 11:00 a.m. EDT on Wednesday the center of Tropical Storm Matthew as located at latitude 13.4°N and longitude 60.7°W which put it about 35 miles (55 km) southeast of St. Lucia.  Matthew was moving toward the west at 21 m.p.h. (33 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 1008 mb.

Tropical Storm Warnings have been issued for Guadeloupe, Martinique, Barbados, Dominica, St. Lucia, and St. Vincent and the Grenadines.

The circulation of Tropical Storm Matthew is still organizing and it appears as if the surface center is located southwest of the mid-level center.  There are many more thunderstorms north and east of the center and there are fewer thunderstorms south and west of the center.  The strongest winds are occurring in the bands of thunderstorms northeast of the center of circulation.  The winds are much weaker in the western half of Tropical Storm Matthew.  The stronger thunderstorms northeast of the center of circulation are generating upper level divergence which is pumping mass out to the north and east of Matthew.

Tropical Storm Matthew will be moving into an environment that is favorable for intensification The Sea Surface Temperatures in the eastern and central Caribbean Sea are near 30°C.  The upper level winds are weak and there is not much vertical wind shear.  Even with those favorable conditions, several factors could slow the rate at which Tropical Storm Matthew intensifies.  First, it is moving west at 21 m.p.h. (33 km/h).  Sometimes tropical cyclones generate low level vertical wind shear when they move that quickly.  Second, the asymmetrical distribution of thunderstorms around the circulation of Matthew could prevent the tropical storm form efficiently using the energy it extracts from the ocean.  In addition, if Tropical Storm Matthew moves too close to the northern coast of South America, it could pull in some drier air, which would also slow the rate of intensification.  Even with those potential inhibiting factors, Tropical Storm Matthew is likely to become a hurricane by the end of the week and it could become a major hurricane while it is over the Caribbean Sea.

A subtropical high pressure system to the north of Matthew is steering the tropical storm toward the west and that general motion is expected to continue for several more days.  Tropical Storm Matthew is likely to slow down over the weekend as it gets closer to the western end of the subtropical high.  Matthew will likely turn toward the north during the weekend.  There is a great deal of variability in how quickly and sharply the models predict the turn will be.  Some models forecast a quick sharp turn toward the north that could eventually carry Matthew near Bermuda.  Other models forecast a later slower turn that occurs over the western Caribbean Sea and could take take Matthew closer to the U.S.  It is too early to know which scenario will be the right one.

Tropical Storm Matthew will bring gusty winds and locally heavy rain to the Windward Islands and southern Leeward Islands.  Interests in other parts of the Caribbean Sea, the Bahamas, U.S. and Bermuda should monitor the progress of Tropical Storm Matthew.

Invest 97L Poses Risk for Caribbean Sea

A tropical disturbance designated as Invest 97L poses a potential risk for locations around the Caribbean Sea.  At 8:00 p.m. EDT on Tuesday the center of Invest 97L was located at latitude 13.1°N and longitude 55.3°W which put it about 285 miles (460 km) east of Barbados.  Invest 97L was moving toward the west at 19 m.p.h. (31 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. (70 km/h).  The minimum surface pressure was 1008 mb.

A U.S. Air Force Reserve Hurricane Hunter aircraft flew a reconnaissance mission into Invest 97L on Tuesday afternoon.  The plane found the there were winds to near tropical storm force, but it could not identify a closed circulation.  The winds on the western side were weaker and the plane was unable to find a surface center.  There does seem to be cyclonic rotation above the surface at least on infrared satellite imagery.

The circulation in Invest 97L is still organizing.  Many of the stronger thunderstorms are forming north and east of the apparent center on satellite imagery.  Rainbands are also forming north and east of the center.  Recent satellite images suggest that some thunderstorms could be developing closer to the center of cyclonic rotation.  The current thunderstorms are generating upper level divergence which is pumping out mass to the north and east of the system.

Invest 97L is moving through an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds over the majority of the circulation are relatively weak.  An upper level trough over the Caribbean Sea is generating vertical wind shear over the northern fringe of the circulation.  Invest 97L could become a tropical storm at any time.

A subtropical high pressure system to the north of Invest 97L is steering it toward the west and that general motion is expected to continue for another day or two.  On its anticipated track Invest 97L will move through the Windward Islands near Barbados, St. Lucia, Martinique, and Dominica on Wednesday.  It could bring gusty winds and locally heavy rain to those locations.

Disturbance Near Yucatan Could Develop Over Gulf of Mexico

A tropical disturbance over the northwestern Caribbean Sea near the Yucatan peninsula is moving northwest and it could develop into a tropical cyclone when it moves over the southern Gulf of Mexico.  The National Hurricane Center (NHC) has designated the disturbance as Invest 93L and NHC is putting the probability of development into a tropical cyclone during the next two days at 80%.  At 8:00 p.m. EDT the center of Invest 93L was located at latitude 18.5°N and longitude 87.5°W which put it about 170 miles (270 km) south of Cancun, Mexico.  Invest 93L was moving toward the northwest at 11 m.p.h. (17 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. (70 km/h).  The minimum surface pressure was 1005 mb.

Invest 93L consists of a broad area of low pressure at the surface.  Several bands of thunderstorms are occurring in the eastern and northern parts of the circulation.  There is no well defined center of circulation and there are fewer thunderstorms in the inner portion of the circulation.  The strongest winds are occurring in the bands of thunderstorms north and east of the center.  There is some upper level divergence to the east of Invest 93L.

The environment around Invest 93L is not totally favorable for development.  The Sea Surface Temperature in northwest Caribbean Sea is near 30°C, which means there is plenty of energy in the upper ocean.  However, an upper level low near Texas and an upper level ridge east of Invest 93L are combining to generate strong southwesterly winds that are blowing over the top of the disturbance.  Those winds are creating significant vertical wind shear which is inhibiting the development of Invest 93L.  The upper level ridge is enhancing the upper level divergence to the east of the disturbance which allowed the pressure to fall several millibars on Saturday.  The upper winds are lighter near the axis of the ridge which is why the stronger bands of thunderstorms are persisting in that area.

Invest 93L is forecast to move toward the Yucatan peninsula on Sunday.  If the broad area over low pressure moves over land that will prevent it from developing until it moves back over water.  Numerical models are guiding that the disturbance will develop into a tropical cyclone when the area of low pressure moves over the southern Gulf of Mexico.  The upper level ridge is forecast to extend over the southeastern Gulf and if that happens the wind shear could decrease enough to allow development to occur.  Invest 93L could become a tropical depression or a tropical storm over the Gulf of Mexico.

The southwesterly flow over the Gulf of Mexico is forecast to turn Invest 93L toward the northeast.  On its anticipated track the system could reach the west coast of Florida near Cedar Key late Monday or early Tuesday.  The primary risk is likely to be locally heavy rain.  However, the coast in that area is very susceptible to storm surge and there could be some rise in the water level.  The National Hurricane Center has tentatively tasked a reconnaissance plane to investigate Invest 93L on Sunday, if necessary.

Erika Bringing Heavy Rain to the Northeastern Caribbean

Although it is not very well organized, Tropical Storm Erika brought heavy rains to parts of the northeastern Caribbean Sea on Thursday and it caused flooding on Dominica.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Erika was located at latitude 16.6°N and longitude 65.3°W which put it about 135 miles (215 km) south-southeast of San Juan, Puerto Rico and about 1145 miles (1850 km) east-southeast of Miami, Florida.  Erika was moving toward the west at 17 m.p.h. (28 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1008 mb.  Tropical Storm Warnings have been issued for Puerto Rico, Vieques, Culebra, the U.S. Virgin Islands, the British Virgin Islands, the southeastern Bahamas, the Turks and Caicos, the coast of the Dominican Republic from Isla Saona to the border with Haiti, St. Barthelemy and St. Martin.  Tropical Storm Watches have been issued for the Central Bahamas and the coast of the Dominican Republic from Isla Saona to Punta Palenque.

The circulation around Tropical Storm Erika is poorly organized to due persistent upper level winds from the west which are causing vertical wind shear.  The low level circulation consists of a large diffuse center with at least once smaller mesoscale center rotating around inside the larger diffuse center.  The mesoscale center could have been produced by one of the thunderstorm clusters that form nightly in the southeastern portion of the circulation.  Again on Thursday the strongest thunderstorms occurred east of the center of circulation.  Those thunderstorms produced a lot of upper level divergence but the upper level westerly winds pushed that divergence east of the low level center.  As a result, the surface pressure actually rose a couple of millibars on Thursday.  Stronger thunderstorms are forming southeast of the center of Erika again tonight.  So, the pattern of the past several nights appears to be repeating itself again.

An upper level trough over the western Caribbean Sea is causing the westerly winds that are the source of vertical wind shear over Erika.  That trough is expected to drift west and slowly weaken.  If it does weaken in a couple of days, then the upper level wind pattern could be more favorable for intensification.  However, the center of Erika could pass over or very near Hispaniola.  It is likely that the mountains on that island would significantly disrupt the low level circulation.  If the low level circulation maintains its integrity, the Sea Surface Temperatures around the Bahamas and south Florida are very warm.  If Erika still has a coherent circulation at that time it could organize quickly.

A subtropical ridge is steering Erika toward the west.  Erika is nearing the western end of the ridge and a turn toward the west-northwest is possible.  If Erika gets stronger and the circulation is taller, then the upper level trough could push it more toward the north.  On the other hand, if the circulation of Erika stays weaker and shorter, then lower level flow could push it farther west.  Erika is likely to pass near or over Hispaniola on Friday and on its anticipated track it could be approaching south Florida in about 72 hours.

Even if Erika is a disorganized tropical storm it is capable of producing heavy rains and flooding on any island it crosses.

Tropical Storm Erika Prompts Warnings for the Caribbean

The imminent approach of Tropical Storm Erika prompted the issuance of watches and warnings for locations in the northeastern Caribbean Sea.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Erika was located at latitude 16.0°N and longitude 54.4°W which put it about 495 miles (800 km) east of Antigua and about 1780 miles (2870 km) east-southeast of Miami, Florida.  Erika 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 1006 mb.  Tropical Storm Warnings have been issued for Anguilla, Saba, St. Eustatius, and St. Maarten.  Tropical Storm Watches have been issued for Puerto Rico, the U.S. Virgin Islands, the British Virgin Islands, Montserrat, Antigua, Barbuda, St. Kitts, Nevis, Guadeloupe, St. Martin and St. Barthelemy.

For much of Monday the circulation around Tropical Storm Erika consisted of a large swirl of low level clouds and a few thunderstorms well to the southeast of the center.  The minimum surface pressure rose several millibars which was indicative of a weakening storm.  In the past several hours satellite imagery suggests that a few new thunderstorms could be forming closer to the center of circulation.  Erika is moving over water where the Sea Surface Temperature (SST) is between 28°C and 29°C.  So there is plenty of energy in the upper ocean.  The circulation could be pulling in some drier air from farther north of the storm.  There is also some vertical wind shear which may also be inhibiting intensification.    The combination of positive environmental factors like SST and negative environmental factors like drier air and wind shear make the intensity forecast challenging.  Guidance from numerical models is divergent.  Some models predict intensification while others predict that Erika will dissipate like Danny did.  If more thunderstorms continue to develop around the center of circulation, then intensification would be more likely.  On the other hand, if the recently formed thunderstorms dissipate in a few hours, the Erika could weaken to a tropical depression.

A subtropical ridge is steering Erika a little north of due west and that general motion is expected to continue during the next several days.  On its anticipated track Erika would approach the northern Leeward Islands in about 24 hours and it could be near Puerto Rico in less than two days.

Danny Dissipates But Erika Forms Behind It

Vertical wind shear weakened Tropical Storm Danny as it entered the eastern Caribbean Sea and its circulation degenerated into a weak area of low pressure.  However, a new tropical storm formed about a thousand miles east of the remnants of Danny and the National Hurricane Center designated it as Tropical Storm Erika.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Erika was located at latitude 14.4°N and longitude 47.7°W which put it about 955 miles (1535 km) east of the Leeward Islands and about 2240 miles (3600 km) east-southeast of Miami, Florida.  Erika was moving toward the west at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1003 mb.

The circulation around Erika is a little larger than the circulation around Danny was.  There are several bands of thunderstorms near the center of circulation and the thunderstorms are generating upper level divergence in all directions.  Erika is moving over water where the Sea Surface Temperature is near 27.5°C and it will gradually move over warmer SSTs as it moves west.  Erika is moving at 20 m.p.h. and that is about the upper limit for storms that intensify over the tropical Atlantic Ocean.  Currently the low level winds and upper level winds are blowing at nearly the same speed.  So, there is not much vertical wind shear.  However, if Erika were to move toward the west faster, then vertical wind shear could be more significant.  As long as Erika does not move too fast, the environment is favorable for intensification and Danny intensified rapidly over the same region a few days ago.  When Erika enters the Caribbean Sea in two or three days, it could encounter the same upper level trough that sheared Danny apart.

A subtropical ridge is steering Erika quickly toward the west and that same general steering motion is expected to continue for the next two or three days.  Erika could be approaching the northern Leeward Islands in about 48 hours.

Tropical Storm Danny Approaching Dominica and Guadeloupe

Tropical Storm Danny weakened on Sunday but it was maintaining its status as a tropical storm as it approached Dominica and Guadeloupe.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Danny was located at latitude 15.6°N and longitude 59.8°W which put it about 115 miles (240 km) east-southeast of Guadeloupe and about 1415 miles (2280 km) east-southeast of Miami, Florida.  Danny 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 1009 mb.  Tropical Storm Warnings have been issued for Antigua, Barbuda, Montserrat, St. Kitts and Nevis.  Tropical Storm Watches have been issued for Saba, St. Eustatius and St. Maarten.

Strong southwesterly winds in the upper levels created vertical wind shear which pushed the stronger thunderstorms northeast of the center of circulation.  The core of Tropical Storm Danny consisted of an area of low clouds rotating cyclonically for much of the Sunday, but satellite images and radar indicate that a few more showers and thunderstorms formed during the past few hours.  Danny still has a well defined low level circulation.  Thunderstorms northeast of the center were producing winds to tropical storm force and Danny was still classified as a Tropical Storm at 11:00 p.m. EDT on Sunday.

Upper level southwesterly winds are forecast to continue over the eastern Caribbean Sea.  The resulting vertical wind shear will make it difficult for thunderstorms to persist near the center of Tropical Storm Danny and it could weaken to a tropical depression at any time.  However, it is moving over warm water and a reduction in wind shear could allow for the circulation to maintain itself for a longer period if that happens.

A subtropical ridge north of Danny is steering the tropical storm toward the west and that general motion is expected to continue.  Danny will enter the eastern Caribbean Sea on Monday.  On its anticipated track Danny will pass south of Puerto Rico and it is unlikely to bring much rain to help alleviate the drought conditions there.  Danny could bring some wind and rain to the southern Leeward Islands as it passes over them during the next few hours.