Tag Archives: Haiti

Tropical Storm Erika Bringing Heavy Rain to Hispaniola

Tropical Storm Erika is moving across Hispaniola and it is bringing heavy rain to parts of that island.  At 5:00 p.m. EDT the center of Tropical Storm Erika was located at latitude 17.9°N and longitude 71.2°W which put it about 95 miles (155 km) west-southwest of Santo Domingo, Dominican Republic and about 745 miles (1200 km) southeast of Miami, Florida.  Erika was moving toward the west at 21 m.p.h. (33 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 1009 mb.  Tropical Storm Warnings have been issued for the southeastern Bahamas, the Turks and Caicos, for the Dominican Republic, Haiti, for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.  Tropical Storm Watches have been issued for the northwestern Bahamas including the Abacos, Andros Island, Berry Island, Bimini, Eleuthera, Grand Bahama Island and New Providence, the Cuban provinces of Ciego de Avila, Camaguey, Las Tunas, Holguin and Guantanamo.

The circulation around Tropical Storm Erika is even less well organized today.  At times a small cyclonic rotation appeared on visible satellite images, while at other times Erika looked a lot like a very strong tropical wave.  Vertical wind shear caused by an upper level trough over the western Caribbean Sea has prevented thunderstorms from forming near the core of the circulation.  The lower part of the circulation will be significantly disrupted by the mountains of Hispaniola, but the middle portion may make it across the island.  If the middle level circulation is disrupted as well, then Erika will degenerate into a disorganized area of thunderstorms.  If the middle level circulation is still intact when it emerges west of Hispaniola, then it is possible that momentum could be transferred to the surface and a new low level center spun up.  Erika would most likely be a tropical depression at most at that time.  The water north of Cuba is very warm and if Erika still exists, it could intensify somewhat as it moves toward Florida.

The winds in the lower levels continued to push Erika toward the west-northwest on Friday and that general motion is likely continue for the next 12 to 12 hours.  Erika is getting closer to the western end of the subtropical high and it could turn more toward the north during the weekend.  On its anticipated track Erika or its remnants could be approaching the Florida Keys on Sunday afternoon.  At this time it is almost impossible to know how strong it will be at that time.  If Erika does start to reorganize when it gets west of Hispaniola, watches and/or warnings could be issued for parts of Florida.

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.

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.