Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Tropical Storm Franklin Makes Landfall on Yucatan

The center of Tropical Storm Franklin made landfall on the southeast coast of the Yucatan peninsula on Monday night.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Franklin was located at latitude 19.1°N and longitude 87.3°W which put it about 75 miles (120 km) east-northeast of Chetumal, Mexico.  Franklin was moving toward the west-northwest at 14 m.p.h. (22 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 995 mb.

A Hurricane Watch is in effect for the portion of the coast from Puerto de Veracruz to Rio Panuco, Mexico.  A Tropical Storm Warning is in effect for the portion of the coast from Chetumal to Sabancuy, Mexico and from Belize City northward to the Belize/Mexico border.  A Tropical Storm Watch is in effect for the portion of the coast from Sabancuy to Puerto de Veracruz, Mexico.

The circulation of Tropical Storm Franklin became better organized on Monday, but thunderstorms were unable to consolidate around the core of the circulation.  A ring of showers and weaker thunderstorms surrounds the center of circulation.  A band of stronger thunderstorms curls around the eastern side of the circulation.  The are weaker bands of showers and thunderstorms in the western half of the circulation.  The thunderstorms in the eastern side of Franklin were generating upper level divergence which was pumping mass away to the east of the tropical storm.

Tropical Storm Franklin will weaken as it moves over the Yucatan peninsula.  Franklin will spend approximately 18 hours over land and it will be a weaker tropical storm or tropical depression by the time it reaches the southern Gulf of Mexico.  The Sea Surface Temperature of the southern Gulf of Mexico is near 30°C.  The upper level winds should be weak and there is likely to be little vertical wind shear when Franklin moves over the southern Gulf.  Franklin is likely to intensify when it moves over the Gulf of Mexico and it could strengthen into a hurricane.

A subtropical high pressure system is steering Tropical Storm Franklin toward the west-northwest and that general motion is expected to continue for another day or two.  On its anticipated track Franklin will move across the Yucatan peninsula on Tuesday.  Franklin will produce gusty winds and locally heavy rainfall.  Floods could occur in some locations.

Tropical Storm Franklin Develops Over Northwest Caribbean Sea

A center of circulation developed in a system previously designated as Potential Tropical Cyclone Seven and the National Hurricane Center named the system Tropical Storm Franklin on Sunday night.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Franklin was located at latitude 16.4°N and longitude 83.0°W which put it about 380 miles (610 km) east-southeast of Chetumal, Mexico.  Franklin was moving toward the west-northwest at 13 m.p.h. (20 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.

A Tropical Storm Warning is in effect for the portion of the coast from Chetumal to Campeche, Mexico.  A Tropical Storm Watch is in effect for the portion of the coast from Belize City, Belize northward to the Belize/Mexico border.

Visible satellite images just before sunset suggested that a center of circulation had formed in the tropical wave previously designated Potential Tropical Cyclone Seven and the National Hurricane Center named it Tropical Storm Franklin.  The circulation of Tropical Storm Franklin is still not well organized.  The apparent center is located near the western edge of an area of thunderstorms.  Most of the thunderstorms are still forming east of the system, which indicates that vertical wind shear is probably still affecting the circulation.  The thunderstorms are producing some upper level divergence which is pumping mass away to the east of the tropical storm.

The environment ahead of Tropical Storm Franklin will become more favorable for intensification.  Franklin will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough west of Franklin is producing westerly winds which are causing the vertical wind shear.  The trough is expected to weaken on Monday and when that happens the shear will diminish.  Warm water and less shear should allow Tropical Storm Franklin to strengthen before it reaches the Yucatan peninsula.  Franklin will weaken when it moves over land, but it is likely to re-intensify when it moves over the southern Gulf of Mexico.

Tropical Storm Franklin is being steered toward the west-northwest by a subtropical high centered over the Atlantic Ocean.  A general west-northwesterly motion is expected to continue.  On its anticipated track Tropical Storm Franklin could approach the Yucatan peninsula in about 24 hours.  Franklin will bring gusty winds and locally heavy rain to that area.  The heavy rain could cause flooding in some locations.

Tropical Storm Warning Issued for Mexico Due to Potential Tropical Cyclone Seven

The National Hurricane Center changed the designation of Invest 90L to Potential Tropical Cyclone Seven because of the need to issue a Tropical Storm Warning for portions of Mexico.  At 5: 00 p.m. EDT on Sunday the center of Potential Tropical Cyclone Seven was located at latitude 15.6°N and longitude 82.0°W which put it about 90 miles (145 km) east-northeast of Cabo Gracias a Dios.  It was moving toward the west-northwest at 12 m.p.h. (19 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.

A Tropical Storm Warning has been issued for the portion of the coast from Chetumal to Campeche, Mexico.  A Tropical Storm Watch has been issued for the portion of the coast from Belize City to the Belize/Mexico border.

A broad area of low pressure formed in a strong tropical wave over the northwestern Caribbean Sea.  There is not a well defined center of circulation within the broad area of low pressure.  Most of the thunderstorms are developing in the eastern half of the circulation.  There are few thunderstorms in the western half of the system.  The thunderstorms in the eastern half of the low are generating some upper level divergence which is pumping out mass to the east of the low.

Potential Tropical Cyclone Seven will move through a relatively favorable environment over the northwestern Caribbean Sea.  It will move over water where the Sea Surface Temperature is 30°C.  A small upper level trough to the west of the low is producing westerly winds which are causing moderate vertical wind shear.  The wind shear is probably the reason why most of the thunderstorms are in the eastern side of the circulation.  The upper trough is forecast to weaken and the shear is expected to diminish.  Potential Tropical Cyclone Seven could become a tropical storm over the northwestern Caribbean Sea, which is why the Tropical Storm Warning was issued.

Potential Tropical Cyclone Seven is being steered to the west-northwest by a subtropical high pressure system centered over the Atlantic Ocean.  That general motion is expected to continue for the next several days.  On its anticipated track Potential Tropical Cyclone Seven could reach the Yucatan Peninsula within 36 hours.  It could bring gusty winds and heavy rain when it moves over the Yucatan.  The system could restrengthen when it moves over the southern Gulf of Mexico.

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.

Tropical Storm Emily Makes Landfall on West Coast of Florida

Tropical Storm Emily made landfall on the west coast of Florida at Anna Maria Island late Monday morning.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Emily was located at latitude 27.5°N and longitude 82.7°W which put it about 10 miles (15 km) northwest of Bradenton, Florida.  Emily was moving toward the east at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1005 mb.  A Tropical Storm Warning was in effect for the portion of the coast from Anclote River to Bonita Beach, Florida.

Thunderstorms developed near the center of the non-tropical low pressure system over the eastern Gulf of Mexico.  Latent energy released higher in the atmosphere by condensation in those storms created a warm core and the low pressure system made a transition to Tropical Storm Emily.  Thunderstorms near the core of Emily were generating a small area of upper level divergence.  Thunderstorms near the core, a warm core and upper level divergence are part of the typical structure of a tropical cyclone, which is why the National Hurricane Center classified the system as Tropical Storm Emily.  Emily has a well developed circulation, but most of the bands of showers and thunderstorms are in the eastern half of the tropical storm.  Drier air northwest of Emily and vertical wind shear are the probable causes of the asymmetrical distribution of precipitation.

Tropical Storm Emily is bringing gusty winds and heavy rain to parts of Central Florida.  A surface weather station in Sarasota (KSRQ) reported a sustained wind of 39 m.p.h. (63 km/h) and a wind gust of 49 m.p.h. (80 km/h).  The Skyway Bridge over Tampa Bay was closed due to strong winds.

Tropical Storm Emily is likely to weaken as it moves eastward across Central Florida.  When Emily moves over the Atlantic Ocean, it will move over water where the Sea Surface Temperature is near 29°C.  Emily could strengthen back into a tropical storm at that time.

Emily is being steered toward the east by a high pressure system north of the tropical storm.  An upper level trough over the Midwestern U.S. is forecast to move southeastward.  When Emily reaches the Atlantic Ocean southwesterly winds ahead of the trough will turn the tropical storm toward the northeast.

Non-Tropical Low Forms Over Northeast Gulf of Mexico

A non-tropical low pressure system formed over the northeastern Gulf of Mexico on Sunday.  The low pressure system is currently designated as Invest 98L.  At 2:00 p.m. EDT on Sunday the center of Invest 98L was located at latitude 28.4°N and longitude 85.5°W which put it about 100 miles (160 km) south-southwest of Apalachicola, Florida.  It was moving toward the east at 8 m.p.h. (13 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 low pressure system formed along a frontal boundary that stalled over the northeastern Gulf of Mexico.  It is not usual for low pressure systems to form along stationary fronts.  A source of positive vorticity to provide counterclockwise rotation and upper level divergence to pump away mass and allow the surface pressure to decrease will generate a surface low.  The low pressure system does not have a warm core in the middle and upper levels and it is still associated with a frontal system.  So, it is classified as a non-tropical low pressure system.

The low pressure system will be moving through an environment that will be only marginally favorable for a transition to a tropical or subtropical cyclone.  The Sea Surface Temperature in the northeastern Gulf of Mexico is near 30°C.  So, there is plenty of energy to support the formation of a tropical cyclone.  However, an upper level ridge over the central U.S. and a trough over the northeastern U.S. are combining to produce northerly winds of 40 m.p.h. (65 km/h) over the northeastern Gulf of Mexico.  Those winds are generating significant vertical wind shear.  The shear has limited the development of thunderstorms in the northern half of the low and it may be tilting the vertical structure of the low toward the south.  The strong upper level winds will also inhibit divergence on the northern side of the low and they could make it difficult for a warm core to develop in the middle and upper levels.  The air north of the frontal boundary is drier continental air, which is another a negative factor for transition to a tropical cyclone.  Based on all of the environmental factors the National Hurricane Center is indicating that there is a 30% chance the low could make a transition to a tropical or subtropical cyclone.

The low pressure system is moving a little to the south of due east.  A strong surface high pressure system over the eastern U.S. is now pushing the front toward the south as a cold front.  The low is moving slowly eastward along the front.  Combination of the southward motion of the front and eastward motion of the low produces a forecast motion of a little south of due east.  On its anticipated track the low pressure system could reach the west coast of Florida in 24 to 36 hours.  So, the low has about a day, if it is going to transition to a tropical cyclone over the Gulf of Mexico.

Tropical Storm Don Forms East of Windward Islands

Tropical Storm Don formed east of the Windward Islands on Monday.  An Air Force Reserve Hurricane Hunter reconnaissance aircraft found a small, but well defined center of circulation in a cluster of thunderstorms formerly designated Invest 91L.  Based on information from the recon plane, the National Hurricane Center classified the system at Tropical Storm Don.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Don was located at latitude 11.2°N and longitude 52.6°W which put it about 595 miles (955 km) east of Trinidad.  Don was moving toward the west at 17 m.p.h. (28 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.

A Tropical Storm Warning has been issue for Grenada.  Tropical Storm Watches are in effect for Barbados, St. Vincent, the Grenadines and St. Lucia.

The reconnaissance plane found a small, tight center of circulation near the surface.  A thin band of showers and thunderstorms wrapped partially around the western side of the center.  Other thin bands of showers and thunderstorms were occurring north and west of the center.  There were fewer showers and thunderstorms in the eastern half of Tropical Storm Don.  The circulation of Tropical Storm Don is small and winds to tropical storm force only extend out about 25 miles (40 km) from the center of circulation.  Thunderstorms in the band west of the center of circulation were generating some upper level divergence but it was not well developed.

Tropical Storm Don will move through an environment that will be somewhat favorable for intensification during the next several days.  Don will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge east of Don is generating easterly winds which are blowing over the top of the tropical storm.  Those easterly winds are generating some vertical wind shear and the shear may partly explain why there are fewer showers and thunderstorms in the eastern half of the circulation.  The shear will also inhibit intensification, but Tropical Storm Don could strengthen during the next 24 to 48 hours.

A strong subtropical high over the Atlantic Ocean is steering Tropical Storm Don toward the west and a generally westward motion is expected to continue during the next several days.  On its anticipated track the center of Tropical Storm Don could pass south of Barbados on Tuesday.  Tropical Storm Don could move over the southern Windward Islands on Tuesday night.  Tropical Storm Don could bring gusty winds and locally heavy rain to the southern Windward Islands.  Flash floods could occur in areas of steep terrain, if they receive locally heavy rainfall.

Tropical Depression Four Develops East of the Lesser Antilles

Tropical Depression Four developed east of the Lesser Antilles on Wednesday night.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Four was located at latitude 12.8°N and longitude 38.4°W which put it about 1545 (2485 km) east of the Lesser Antilles.  The depression was moving toward the west-northwest at 14 m.p.h. (22 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 1009 mb.

A larger area of thunderstorms formed and persisted on the western side of a tropical disturbance formerly designated as Invest 94L on Wednesday and the National Hurricane Center classified the system as Tropical Depression Four.  The distribution of thunderstorms is still asymmetrical.  Most of the stronger storms are developing in the western half of the circulation.  The thunderstorms in the western part of the circulation were beginning to generate upper level divergence.  There were few thunderstorms in the eastern half of the depression and the vertical structure of the circulation could be tilted to the west with height.

Tropical Depression Four will be moving through an environment that contains both positive and negative factors for intensification.  The depression will move over water where the Sea Surface Temperature is near 27°C.  So, there is sufficient energy in the upper ocean to support intensification.  An upper level ridge is producing easterly winds which are blowing toward the top of the circulation.  Those winds could be causing the circulation to tilt toward the west with height.  Moderate vertical wind shear could inhibit intensification.  Drier air is north of the tropical depression.  If the depression remains south of the drier air and if the vertical wind shear does not become too strong, then the depression could strengthen.  Alternatively, if the depression pulls in drier air and/or the vertical shear increases, then the depression could weaken back to a tropical wave.

The subtropical ridge over the Atlantic Ocean is steering Tropical Depression Four toward the west-northwest.  A general west-northwesterly motion is expected for the next several days.  The actual track will also have a significant effect on the future intensity of Tropical Depression Four. If the depression moves on a more southerly track, it will stay south of the drier air and it would have a greater opportunity to intensify.  If the depression moves farther to the north, it will move into the drier air and will be more likely to weaken,

Invest 94L Likely to Develop East of Lesser Antilles

A tropical disturbance currently designated as Invest 94L is likely to develop into a tropical cyclone east of the Lesser Antilles.  The National Hurricane Center’s probability of formation of a tropical cyclone from this system during the next five days is 70%.  At 2:00 p.m. EDT on Monday the center of Invest 94L was located at latitude 8.7°N and longitude 32.7°W which put it about 1830 miles (2950 km) east of the Lesser Antilles.  It was moving toward the west at 4 m.p.h. (6 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 1011 mb.

Invest 94L consists of a broad area of low pressure, but it has not developed a well organized inner core.  The initial area of low pressure consisted of a counterclockwise rotation associated with a tropical wave that moved over the eastern Atlantic Ocean.  The initial low slowed down as it was moving westward and a second tropical wave caught up to it.  The thunderstorms from the two waves appear to be merging into a single system.  An area of showers and thunderstorms on the northern and western sides of the surface low was part of the first tropical wave.  Other bands of showers and thunderstorms south and east of the low are associated with the second tropical wave.  If the broad low pressure system can collect the rotation from the two tropical waves, it could strengthen the surface low.

Invest 94L will move through an environment that will be favorable for the development of a tropical cyclone.  It will move over water where the Sea Surface Temperature (SST) is near 28°C.  There are easterly winds blowing at multiple levels in the atmosphere and there is little vertical winds shear.  The existence of a surface low pressure system, warm SSTs and little vertical wind shear are the primary ingredients for the development of a tropical cyclone.  That is the reason why there is strong probability that Invest 94L will develop into a tropical depression or a tropical storm.

Invest 94L will be steered by the subtropical high pressure system over the Atlantic Ocean.  A general westerly or west-northwesterly track is forecast during the next few days.  There is still significant uncertainty about the ultimate track and intensity of this system beyond that time frame.  It will need to be monitored closely as it moves west.

Tropical Depression Cindy Brings Stormy Weather to Southern U.S.

Tropical Depression Cindy brought stormy weather to parts of the southern U.S. on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Depression Cindy was located at latitude 33.1°N and 93.5°W which put it about 70 miles (115 km) southwest of Little Rock, Arkansas.  Cindy was moving toward the north-northeast at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 20 m.p.h. (30 km/h) and there were wind gusts to 30 m.p.h. (50 km/h).  The minimum surface pressure was 1000 mb.

Tropical Storm Cindy made landfall early on Thursday morning near the border between Texas and Louisiana.  Cindy moved steadily northward during the day and it was centered over southwestern Arkansas by Thursday night.  Broad counterclockwise rotation around Cindy transported warm and very humid air over the southern U.S.  Bands of showers and thunderstorms dropped locally heavy rain in some places.  Rivers and streams were above flood stage in several southern states.  Flash Flood Warnings and Flash Flood Watches were issued for portions of the southern U.S. and Ohio River Valley.  Several tornadoes formed in the bands of thunderstorms.  A tornado in Alabama caused property damage.  Southerly winds blowing toward the shore were still causing storm surges along the northern coast of the Gulf of Mexico.

Tropical Depression Cindy is forecast to move northeast toward the Ohio River Valley on Friday.  It will continue to produce locally heavy rain.  A slow moving cold front will approach the region from the west.  A band of stronger convergence could develop where the counterclockwise flow around Cindy interacts with the flow along the cold front.  Higher rainfall totals may occur where this interaction happens.  Wind shear created by the interacting weather systems could also create the potential for some tornadoes.  Tropical Depression Cindy could merge with the cold front during Friday night or Saturday.