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Low Pressure System Forms Over Caribbean Sea

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A low pressure system formed over the Caribbean Sea on Wednesday.  The low pressure system was designated as invest 99L.  At 10:00 a.m. EST on Wednesday the center of Invest 99L was located at latitude 16.1°N and longitude 77.6°E which put the center about 140 miles (225 km) south-southwest of Kingston Jamaica.   Invest 99L was moving toward the west at 5 m.p.h. (8 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 1007 mb.

The circulation around Invest 99L was large, but it was not well organized.  There were at least three smaller counterclockwise circulations revolving around inside the larger circulation.  One of the smaller circulations was north of Honduras.  A second smaller circulation was southwest of Jamaica and the third smaller circulation was southeast of Jamaica.  Bands of showers and thunderstorms were revolving around each of the smaller circulations.

Invest 99L will move through an environment favorable for the formation of a tropical cyclone during the next 24 hours.  Invest 99L will move over water where where the Sea Surface Temperatures are near 29°C.  It will move under the middle of an upper level ridge over the Caribbean Sea.  The upper level winds are weak near the middle of the upper level ridge.  Invest 99L is likely to develop into a tropical depression or a tropical storm during the next day or two.

Invest 99L will move around the southern part of a high pressure system over the western Atlantic Ocean.  The high pressure system will steer Invest 99L slowly toward the west during the next 24 hours.  On its anticipated track, Invest 99L will move slowly toward Nicaragua and Honduras.

Tropical Cyclone Likely to Form over Western Caribbean

A tropical cyclone is likely to form over the western Caribbean Sea during the next few days. At 8:00 a.m. EDT on Wednesday the center of Invest 99L was located at latitude 12.5°N and longitude 75.4°W which put it about 100 miles (160 km) north of Barranquilla, Colombia. Invest 99L was moving toward the west-northwest at 25 m.p.h. (40 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 1006 mb.

A tropical cyclone is likely to form from a tropical wave, currently designated as Invest 99L, that is over the Caribbean Sea north of Colombia. There is currently no low level center of circulation in the tropical wave. Visible satellite images were providing evidence of some rotation in the middle troposphere on Wednesday afternoon. The wave is currently in an environment that is unfavorable for the formation of a tropical cyclone. The wave is over water where the Sea Surface Temperatures are near 29°C. However, an upper level low centered near the Bahamas is producing strong southwesterly winds that are blowing across the western part of the tropical wave. Those winds are causing moderate vertical wind shear and they are inhibiting the development of the wave. Easterly winds in the lower troposphere are pushing lower section of the tropical wave quickly toward the west-northwest, which is also inhibiting development.

The tropical wave will move into an environment more favorable for the development of a tropical cyclone during the next several days. The upper low near the Bahamas is forecast to move toward the northwest and to weaken. When the upper low weakens, the vertical wind shear will decrease around the tropical wave. In addition, the wave is forecast to move more slowly when it reaches the western Caribbean Sea. The National Hurricane Center (NHC) is indicating that there is a 50% probability that a tropical depression will form from the tropical wave in the next 48 hours. NHC is indicating there is a 80% probability that a tropical wave will form during the next five days.

The tropical wave will move around the southwestern part of a subtropical high pressure system over the Atlantic Ocean. The high will steer the tropical wave toward the west-northwest during the next several days. On its anticipated track the tropical wave will approach Nicaragua and Honduras on Thursday. The system could be near the northeastern part of the Yucatan Peninsula on Friday evening. It could move over the Gulf of Mexico during the weekend. The conditions over the Gulf of Mexico could be favorable for intensification during the weekend. The Sea Surface Temperatures in the Gulf of Mexico are near 30°C. An upper level ridge is forecast to be over the Gulf. The upper level winds will be weak in the ridge and there will be little vertical wind shear. If Invest 99L is in the Gulf of Mexico during the weekend, it could strengthen to a hurricane. If it develops into a hurricane with a well formed inner core, then a period of rapid intensification could occur.

Reconnaissance planes are tentatively scheduled to begin to investigate the tropical wave on Thursday afternoon, if necessary. Invest 99L has the potential to pose a serious threat to the northwestern Gulf of Mexico. Interests in Texas, Louisiana, Mississippi, Alabama and Florida should monitor progress of the system.

Strong Tropical Wave Brings Wind and Rain to Windward Islands

A strong tropical wave was bringing wind and rain to the Windward Islands.  At 8:00 p.m. EDT on Saturday the center of the tropical wave was located at latitude 11.9°N and longitude 59.5°W which put it about 75 miles (120 km) northeast of Tobago.  The wave was moving toward the west at 20 m.p.h. (32 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 1009 mb.

The axis of the tropical wave stretched from near Barbados to just east of Trinidad and Tobago.  More thunderstorms developed near the axis of the wave on Saturday night and there were indications that a center of circulation could be forming northeast of Trinidad and Tobago.  There were winds to near tropical storm force.  The National Hurricane Center issued a special Tropical Weather Outlook on Saturday night and indicated that tropical storm watches and warnings might need to be issued on Sunday.  The wave is forecast to move over the Windward Islands and into the eastern Caribbean Sea on Sunday.

Elsewhere over the Atlantic Ocean, Tropical Storm Jerry was located north of Puerto Rico.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Jerry was location at latitude 24.1°N and longitude 66.3°W which put it about 575 miles (925 km) south of Bermuda.  Jerry was moving toward the northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 1002 mb.

NHC Monitoring Two Areas for Tropical Development

The National Hurricane Center (NHC) was monitoring two areas for possible tropical development on Thursday afternoon.  A strong tropical wave was moving through the southeastern Caribbean Sea and the wave was designated as Invest 90L.  At 2:00 p.m. EDT on Thursday the center of Invest 90L was located at latitude 12.2°N and longitude 65.8°W which put it about 160 miles (260 km) east of Bonaire.  The tropical wave was moving toward the west at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 35 m.p.h. (55km/h) and there were gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1011 mb.

Another tropical wave moved off the coast of West Africa on Thursday and NHC designated that wave as Invest 99L.  At 2:00 p.m. EDT on Thursday the center of Invest 99L was located at latitude 10.2°N and longitude 20.9°W which put it about 370 miles (595 km) south-southeast of the Cabo Verde Islands.  The tropical wave was moving toward the west at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1010 mb.

The tropical wave over the southeastern Caribbean Sea will have the most immediate impact to land.  The wave could bring gusty winds to Aruba, Bonaire and Curacao within 24 hours.  The circulation of Invest 90L is elongated in an east-west direction and that is probably because of strong easterly winds blowing in the lower atmosphere.  There are some indications of a counterclockwise rotation on loops of visible satellite imagery, but it is not clear if the rotation extends all the way down to the surface.  The tropical wave is generating winds to near tropical storm force in the northern portion of the wave.  There are numerous thunderstorms developing along the axis of the wave.

Invest 90L is moving under the western end of an upper level ridge.  The ridge is producing southerly winds which are blowing over the top of the tropical wave and those winds are contributing to moderate vertical wind shear.  The strong easterly winds in the lower levels are also contributing to the shear.  Invest 90L could develop into a tropical cyclone when it moves farther west.  The shear could diminish and the Sea Surface Temperatures in the western Caribbean Sea and Bay of Campeche are very warm.  NHC is indicating that there is a 20% probability Invest 90L will become a tropical cyclone during the next five days.

The tropical wave over the far eastern Atlantic has a better chance of developing into a tropical cyclone.  Invest 99L is moving over water where the Sea Surface Temperature is near 28°C.  It is moving under the eastern end of an upper level ridge.  The ridge is causing northeasterly winds which are blowing toward the top of the tropical wave.  Those winds are producing moderate vertical wind shear.  When the wave moves farther west, it will move under weaker winds and the wind shear will decrease.  NHC is indicating that there is a 70% probability that Invest 99L will become a tropical cyclone during the next five days.