Tag Archives: Florida

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.

Bonnie Brings Heavy Rain and Flooding to South Carolina

Even though Bonnie weakened to a tropical depression before it made landfall near Charleston, it brought locally heavy rain and flooding to parts of South Carolina and eastern Georgia.  A portion of Interstate 95 was closed due to high water.  At 11:00 p.m. EDT on Sunday the center of Tropical Depression Bonnie was located at latitude 32.8°N and longitude 80.1°W which put it about 5 miles (10 km) west of Charleston, South Carolina.  Bonnie was slowly meandering near the coast.  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 1012 mb.

Strong southeasterly winds in the upper levels generated significant vertical wind shear that weakened Tropical Storm Bonnie to a tropical depression on Sunday morning.  However, the lower level circulation remained relatively intact as Bonnie moved onto the coast near Charleston, South Carolina.  Thunderstorms in a band west of the center of circulation dropped heavy rain in parts of southwestern South Carolina and eastern Georgia.  The heavy rain produced some flooding.

Most of the rain has tapered off to a few narrow bands of showers, which is normal at night when weaker tropical cyclones move inland.  However, daytime heating could destabilize the atmosphere and new thunderstorms could redevelop over land on Monday.  Some of those storms could also produce locally heavy rainfall and cause additional flooding.

The center of Tropical Depression Bonnie has drifted back to near the Atlantic Ocean.  Strong southeasterly winds are still blowing in the upper levels and the vertical wind shear should prevent significant redevelopment even if the center moves back over water.  Proximity to the ocean will make it easier for the circulation to pull in more moisture, which could contribute to heavier rainfall.

A high pressure system over the Atlantic and an approaching cold front will combine to produce southwesterly winds in the lower levels of the atmosphere.  Those low level winds are forecast to steer Tropical Depression Bonnie slowly toward the northeast during the next several days.  On its anticipated track Tropical Depression Bonnie is expected to move slowly along the coast of South Carolina and North Carolina.  The primary risks will be locally heavy rain, flooding and rip currents.

TD 2 Intensifies Into Tropical Storm Bonnie

Tropical Depression 2 intensified into Tropical Storm Bonnie as it passed over the warm waters of the Gulf Stream on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Bonnie was located at latitude 31.1°N and longitude 79.4°W which put it about 120 miles (195 km) south-southeast of Charleston, South Carolina.  Bonnie was moving toward the 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 wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1008 mb.  A Tropical Storm Warning remains in effect for the coast of South Carolina from the Savannah River to Little River Inlet.

Although the convection in Tropical Depression 2 dissipated when it passed over a region of slightly cooler Sea Surface Temperatures (SSTs) on Friday night, thunderstorms redeveloped and persisted when the system crossed the warmer SSTs in the Gulf Stream on Saturday.  Persistent thunderstorms produced enough increase in the wind speed to intensify Tropical Depression 2 into Tropical Storm Bonnie.

The circulation around Tropical Storm Bonnie is very asymmetrical.  Almost all of the thunderstorms are occurring in the northwestern quadrant of the storm and the strongest winds are being generated in that part of the circulation.  There are mainly thin bands of showers in the rest of the storm.  Winds to tropical storm force extend out about 60 miles (95 km) from the center in the northwest quadrant of Bonnie.

An upper level low over Florida and an upper level ridge over the western Atlantic Ocean are combining to generate southeasterly winds which are blowing over the top of Tropical Storm Bonnie.  Moderate vertical wind shear is contributing to the asymmetrical structure by tilting the circulation toward the northwest.  The wind shear is strong enough to inhibit intensification, but Tropical Storm Bonnie is extracting more energy as it passes over the Gulf Stream.  Bonnie could possibly intensify a little more while it is over the Gulf Stream.

The ridge east of Bonnie is steering the tropical storm toward the northwest and that general motion is expected to continue for another 12 to 24 hours.  An upper level trough approaching the ridge from west and the trough is expected to cause the ridge to weaken.  When the ridge weakens, the steering currents will also weaken.  Tropical Storm Bonnie could stall or meander for several days when that happens.

On its anticipated track the center of Tropical Storm Bonnie will approach the coast of South Carolina on Sunday.  The primary threats are coastal erosion, rip currents and locally heavy rainfall.  Persistent rain could create the potential for fresh water flooding.  Wind damage is likely to be minimal.  However, where the winds blow onshore, they could push water toward the coast and contribute to some coastal flooding.

Tropical Depression 2 Forms, Warning Issued for South Carolina

A reconnaissance plane investigated the system that was formerly designated Invest 91L on Friday afternoon and the plane found that the system had enough tropical characteristics to be classified as Tropical Depression 2 by the National Hurricane Center (NHC).  At 5:00 p.m. EDT on Friday the center of Tropical Depression 2 (TD2) was located at latitude 28.5°N and longitude 74.7°W which put it about 435 miles (695 km) southeast of Charleston, South Carolina.  TD2 was moving toward the west-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 wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1009 mb.  A Tropical Storm Warning has been issued for the coast of South Carolina from the Savannah River to Little River Inlet.

The circulation in Tropical Depression 2 became better organized on Friday, but it would not yet be considered well organized.  More thunderstorms formed near the center of circulation and a primary rainband now curls around the the northern and western sides of the center.  However, there are only thin bands of showers in much of the eastern half of the circulation.  With persistent thunderstorms near the core of TD2, it possess enough tropical characteristics to be considered a tropical cyclone.

An upper level low near Cuba and an upper level ridge northeast of TD2 are combining to generate northerly winds over the top of the circulation.  Those winds are causing moderate vertical wind shear.  TD2 will also be moving over slightly cooler Sear Surface Temperatures (SSTs) during the next 12 to 18 hours.  The combination of the vertical wind shear and cooler SSTs could keep TD2 from intensifying much during that time period.  TD2 will move over the warmer SSTs of the Gulf Stream later on Saturday.  The vertical wind shear could also decrease somewhat.  Warmer SSTs and less wind shear could allow TD2 to intensify into Tropical Storm Bonnie later on Saturday.

A ridge northeast of TD2 is steering the tropical depression toward the west-northwest and a general motion in that direction is expected for another 36 to 48 hours.  After about two days the steering currents could weaken.  On its anticipated track TD2/Tropical Storm Bonnie is expected to approach the coast of South Carolina on Sunday.  Coastal erosion, rip currents and locally heavy rain are the primary risks.  Wind damage is likely to be minimal.

 

Invest 91L Slightly Stronger, Moving Toward U.S.

The circulation of the low pressure system designated as Invest 91L strengthened slightly on Thursday.  At 8:00 p.m. EDT on Thursday the center of Invest 91L was located at latitude 27.4°N and longitude 70.9°W which put it about 410 miles (660 km) east-northeast of Great Abaco Island, Bahamas and about 675 miles (1090 km) south-southeast of Charleston, South Carolina.  Invest 91L was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to near 45 m.p.h. (70 km/h).  The minimum surface pressure was 1013 mb.  The center of Invest 91L was near NOAA buoy 41047 which reported observations consistent with those numbers.

The organization of Invest 91L improved slightly on Thursday.  A few thunderstorms formed northeast of the center of circulation and they persisted throughout the day.  However, there are few thunderstorms in other parts of Invest 91L.  The circulation became slightly more circular although it is still elongated.  The surface pressure decreased slowly, but steadily throughout the day.

The environment around Invest 91L is only marginal for intensification.  It is over water where the Sea Surface Temperature is near 26°C to 27°C.  However, an upper level low near Cuba and an upper level ridge near the east coast of the U.S. are combining to create southerly winds over the top of Invest 91L.  Those winds are causing moderate levels over vertical wind shear which is inhibiting the development of the system.  The magnitude of the wind shear decreased during the past 24 hours and it could decrease a little more on Friday as the upper level ridge moves farther east.

If more thunderstorms develop near the center of circulation, the system could be classified as a tropical depression or tropical storm.  The National Hurricane Center (NHC) is indicating that there is an 80% probability that the Invest 91L will become a tropical cyclone or subtropical cyclone within 48 hours.  NHC has tentatively tasked a reconnaissance plane to investigate the system on Friday.

The vertical wind shear is limiting the strongest part of the circulation of Invest 91L to the lower half of the troposphere.  Thus, the system is being steered toward the west-northwest by a surface pressure system over the western Atlantic Ocean.  That general motion is expected to continue with a slow northward turn.  On its anticipated track Invest 91L could approach the southeast coast of the U.S. in 48 to 72 hours.

The primary risks with Invest 91L remain coastal erosion, rip currents and locally heavy rainfall.  Some wind damage will be possible, but it is likely to be minimal.

Low Pressure Forms East of the Bahamas

A small area of low pressure developed east of the Bahamas on Wednesday afternoon and the National Hurricane Center designated the system as Invest 91L,  At 8:00 p.m. EDT on Wednesday the center of Invest 91L was located at latitude 26.6°N and longitude 67.7°W which put it about 625 miles (1005 km) east of Great Abaco Island in the Bahamas and about 895 miles (1445 km) south-southeast of Charleston, South Carolina.  Invest 91L was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was he 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 1015 mb.

The circulation of Invest 91L is not well organized at the current time.  A small center of circulation was evident on late afternoon visible satellite imagery.  Several thin bands of showers are on the eastern side of the center of circulation.  However, there are very few taller thunderstorms and the circulation probably does not have a warm core at the moment.

Although Invest 91L is over water where the Sea Surface Temperature is between 26°C and 27°C, the atmospheric environment is currently unfavorable for further development.  An upper level trough near Florida is causing strong southwesterly winds to blow over the top of Invest 91L and there is significant vertical wind shear.  The wind shear is quickly dissipating any thunderstorms that start to form.  Invest 91L is forecast to move west-northwest into a more favorable environment in about a day or two.  If the system moves west, it will move into an area where the upper level winds are not as strong.  If the surface circulation is still intact at that time, less vertical wind shear could allow for the system to intensify.  The National Hurricane Center places the probability of development of a tropical cyclone or subtropical cyclone within the next five days at 60%.

Since Invest 91L primarily exists in the lower levels, it will be steered by winds in the lower troposphere.  A surface high pressure system centered off the southeast coast of the U.S. is forecast to move north of Invest 91L and the high will steer the system west-northwest toward the coast of the U.S.  On its anticipated track Invest 91L could move near the southeast coast of the U.S. during the weekend.

If Invest 91L intensifies, the highest probability is that it could become a tropical depression or tropical storm as it approaches the U.S.  It could generate coastal erosion, rip currents and locally heavy rainfall.  The threat for wind damage appears to be minimal at the current time.  People near the coast should monitor trusted sources of weather information.

Possible Development Off Southeast U.S. Coast

Even though the official start to Atlantic hurricane season is not until June 1, the atmosphere doesn’t always wait for the calendar to change to June.  Several numerical models have been predicting that a low pressure system will develop somewhere near the Bahamas later this week.  The models are also predicting that the low pressure system will move toward the southeast coast of the U.S.

A frontal boundary is over the western Atlantic Ocean.  The front runs from east of the Mid-Atlantic States to near the northern Bahamas.  Low pressure systems can develop along the southern end of frontal boundaries.  The low pressure system could start as an extratropical (non-tropical) cyclone or a subtropical (hybrid) cyclone.  The exact type of cyclone will be partly determined by the vertical wind shear later this week.  The structure of a low pressure system can change, if the environment changes and the low can be placed in a different category.

An upper level low over the western Atlantic could cause enough vertical wind shear, so that the low pressure system could be initially classified as extratropical or subtropical.  The Sea Surface Temperatures (SSTs) in the area where the low is most likely to develop are near 26° to 27°C.  There will be enough energy in the upper ocean to support the development of a tropical cyclone.  An upper level ridge could move north of the developing surface low later in the week, which could reduce the vertical wind shear.  If the shear decreases and the low pressure system extracts enough energy from the ocean to develop a warm core, it could eventually be classified as a tropical cyclone.

After the low pressure system forms, a high pressure system over the Atlantic Ocean is expected to steer the low northwest toward southeast coast of the U.S.  The low pressure system could make landfall in Georgia, South Carolina or North Carolina during the weekend or early next week.

The primary threats from the low pressure system will be coastal erosion, rip currents and potentially heavy rainfall.  The wind threat appears to be minimal, since even if the low pressure system becomes tropical, the highest probability is that it would be a tropical depression or tropical storm.

There is a great deal of uncertainty about the future of this system.  The timing of the formation of the low, the type of cyclone, the possible track of the cyclone and its intensity should become clearer later this week.  People near the southeast coast should monitor trusted sources of weather information.

Disturbance Brings Squally Weather to the Northwest Caribbean Sea

A complicated disturbance over the northwestern Caribbean Sea is bringing squally weather to that area.  A tropical wave over the western Caribbean Sea is interacting with an upper level low over eastern Mexico.  The disturbance is causing thunderstorms over a region that extends from the northwestern Caribbean Sea to the southern Gulf of Mexico.  Upper level divergence east of the upper low has led to the formation of a surface low pressure system east of Belize.  At 7:00 p.m. EST on Thursday the center of the surface low was located at latitude 18°N and longitude 86°W which put it about 150 miles (240 km) east-southeast of Chetumal, Mexico.  The surface low was moving toward the west-northwest at 10 m.p.h. (16 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 1011 mb.

The disturbance is not very well organized, which is normally the case when a tropical wave interacts with an upper level low.  There is a broken area of thunderstorms that extends around the east and northern sides of the disturbance.  However, there are not many thunderstorms close to the center of the surface low.  The upper low is causing vertical wind shear over the western half of the surface low.  Some upper level divergence is occurring over the eastern half of the surface low.

A large high pressure system over the western Atlantic Ocean is steering the disturbance toward the west-northwest.  That general steering pattern is expected to continue for the next two days.  On its anticipated track the disturbance will move over the Yucatan peninsula and over the southern Gulf of Mexico during the next several days.

The disturbance is in an environment that is marginally favorable for tropical development.  The Sea Surface Temperature of the northwestern Caribbean is near 29°C.  There is vertical wind shear, but it may be just small enough to allow for slow development.  On the other hand, the disturbance will move over the Yucatan peninsula which will further inhibit development.  There may also be a chance for development after the disturbance moves over the southern Gulf of Mexico.  The National Hurricane Center is giving a 20% probability of tropical cyclone formation out of the disturbance.

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.