Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Matthew Becomes a Hurricane Over the Eastern Caribbean Sea

Tropical Storm Matthew strengthened into a hurricane on Thursday as it moved over the eastern Caribbean Sea.  At 8:00 p.m. EDT on Thursday the center of Hurricane Matthew was located at latitude 14.2°N and longitude 68.1°W which put it about 150 miles (240 km) north-northeast of Curacao.  Matthew was moving toward the west at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 987 mb.

Tropical Storm Watches are in effect for Curacao, Bonaire and Aruba.  The government of Columbia has also issued a Tropical Storm Watch for the portion of the coast from the Columbia/Venezuela border to Riohacha.

The structure of Hurricane Matthew became much better organized on Thursday.  A primary rainband wrapped around the center of circulation.  An eye appears to be forming.  A ring of strong thunderstorms surrounds the eye on all sides except to the south.  Additional bands of thunderstorms developed in the northern and eastern parts of the circulation.  The storms near the eye generated upper level divergence which pumped out mass to the north and east of Hurricane Matthew.  The upper level divergence pumped out enough mass to allow the minimum pressure to decrease by 17 mb during the past 24 hours.

Hurricane Matthew will be moving into an environment that will be favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the western Caribbean Sea and an upper level ridge just east of Matthew are producing southwesterly winds which are blowing across the top of the hurricane.  The vertical wind shear made Hurricane Matthew’s structure asymmetrical earlier today, but the shear has been less in recent hours.  The effect of the wind shear will be to slow the rate of intensification, but it will not prevent intensification.  Hurricane Matthew will pass just north of the cost of South America and drier air could also slow the rate of intensification.

A strong subtropical high pressure system to the north of Matthew is steering the hurricane toward the west and that general motion is expected to continue for about another 48 hours.  When Hurricane Matthew reaches the western end of the ridge, it will turn toward the north.  Guidance from the numerical models continues to be quite divergent about when, where and how sharp the turn will be.  If Hurricane Matthew turns sooner and sharper, it could move over Haiti early next week.  On the other hand, if Matthew turns later and more gradually, it could affect Jamaica and eastern Cuba.  It is too early to know which scenario will eventually occur.

Hurricane Matthew could become a major hurricane over the Caribbean Sea and interests in the Greater Antilles should monitor its progress.

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.

Tropical Storm Karl Approaching Bermuda

Tropical Storm Karl continued to move steadily toward Bermuda on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Karl was located at latitude 29.9°N and longitude 65.1°W which put it about 165 miles (270 km) south of Bermuda.  Karl was moving toward the north at 13 m.p.h. (20 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 988 mb.

A Hurricane Watch has been issued for Bermuda.  A Tropical Storm Warning is also in effect for Bemruda.

Tropical Storm Karl strengthened on Friday, but its structure remained asymmetrical.  Almost all of the thunderstorms are in a primary rainband that wraps around the northern and western sides of the center of circulation.  There are few if any thunderstorms south and east of the center.  It appears as it vertical wind shear is tilting the circulation toward the northwest.  The upper level center appears to be located 20 to 30 miles (30 to 50 km) northwest of the low level center.  The thunderstorms in the primary rainband are producing upper level divergence which is pumping out mass to the east of Tropical Storm Karl.  The upper level divergence pumped out enough mass on Friday to allow the surface pressure to decrease by about 10 mb.  However, the vertical wind shear and lack of thunderstorms to the east of the center limited the increase in wind speed at the surface.

Tropical Storm Karl is moving over water where the Sea Surface Temperature is near 29°C.  So, there is enough energy in the upper ocean to support a stronger storm.  However, an upper level trough to the west of Karl is creating significant vertical wind shear, which is likely to limit intensification in the short term.  When Tropical Storm Karl, turns east and moves farther from the upper level trough, the shear could decrease and Karl could strengthen.  In addition Karl will begin a transition to an extratropical cyclone and that transition often produces and increase in the wind speed.  So, Tropical Storm Karl does have a chance to become a hurricane during the weekend.

Tropical Storm Karl is moving around the western end of a subtropical ridge which is steering it toward the north.  It is likely to keep moving in that direction for another six to twelve hours.  When Tropical Storm Karl nears Bermuda it will encounter stronger westerly winds which will turn it eastward.  Karl is likely to move quickly toward the east-northeast on Saturday and Sunday.  On its anticipated track Tropical Storm Karl will pass near Bermuda on Saturday morning.  It will bring a period of gusty winds and heavy rain.

Karl Becomes a Tropical Storm Again and Warning Issued for Bermuda

Reconnaissance aircraft investigating Tropical Depression Karl on Thursday afternoon found that it had intensified into a tropical storm again and a Tropical Storm Warning was issued for Bermuda.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Karl was located at latitude 25.5°N and longitude 63.2°W which put it about 480 miles (770 km) south-southeast of Bermuda.  Karl was moving toward the northwest at 16 m.p.h. (26 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 1005 mb.

The structure of Tropical Storm Karl became more organized on Thursday, but the circulation is not well organized.  Most of the thunderstorms are occurring in a primary rainband that spirals around the eastern and northern portions of the circulation.  There are other fragmented rainbands farther to the east of the center of circulation.  There are few thunderstorms or bands south and west of the center and there may be drier air in that part of Tropical Storm Karl.  Thunderstorms in the primary rainband were beginning to generate some upper level divergence.

Tropical Storm Karl is moving into an environment that is more favorable for intensification.  Karl is moving farther away from an upper level low that is west of the the tropical storm.  As the distance between Tropical Storm Karl and the upper low increases, the vertical wind shear will decrease.  Karl is moving over water where the Sea Surface Temperature is near 30°C.  Tropical Storm Karl is likely to intensify slowly until the primary rainband wraps around the center of circulation.  If a tight inner core develops at the center of Karl, then it could intensify more quickly after that happens.

Tropical Storm Karl is moving around the western end of a subtropical high pressure system.  The high is steering Karl in a generally northwesterly direction.  Karl is likely to move more toward the north as it goes around the western end of the high.  When Karl gets northwest of the axis of the high pressure system, the westerly winds in the middle latitudes will start to turn it more toward the northeast.  On its anticipated track, Tropical Storm Karl could be near Bermuda in about 36 hours.  Tropical Storm Karl could bring wind and rain to Bermuda during the weekend.

 

Tropical Storm Lisa Develops West of the Cape Verde Islands

Tropical Depression Thirteen intensified into Tropical Storm Lisa west of the Cape Verde Islands on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Lisa was located at latitude 16.4°N and longitude 31.0°W which put it about 465 miles (750 km) west of the Cape Verde Islands.  Lisa was moving toward the northwest at 12 m.p.h. (19 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 1004 mb.

The degree of organization of the circulation of Tropical Storm Lisa depends on the level of the atmosphere.  The low level circulation is not well organized.  There is a broad center of circulation, but it does not have a tight core of thunderstorms.  Most of the thunderstorms are east of the center of circulation.  There are also several fragmented rainbands in the eastern half of the circulation.  There are only lower clouds and a few showers in the western half of the circulation.  However, the circulation is more well organized in the upper levels.  The thunderstorms in the eastern half of the circulation are generating upper level divergence which is pumping out mass toward the northeast and toward the northwest.  It appears that the circulation could be tilted toward the northeast with height.

The environment around Tropical Storm Lisa is marginal for intensification.  Lisa is moving over water where the Sea Surface Temperature (SST) is near 28°C.  However, an upper level trough north of Lisa is producing southwesterly winds which are blowing across the tropical storm.  The winds are causing moderate vertical wind shear, which probably contributed to the asymmetrical distribution of thunderstorms.  Tropical Storm Lisa could intensify somewhat on Wednesday, if the upper level winds diminish.  When Lisa moves farther north later this week, it will move over cooler SSTs and into a region where the upper level winds are stronger.  Less energy in the upper ocean and more vertical wind shear will cause Tropical Storm Lisa to weaken later this week.

Tropical Storm Lisa is moving northwest toward a section of the subtropical ridge which is weaker.  Lisa is expected to continue to move in that general direction for the next several days.  Tropical Storm Lisa will move farther into the middle of the Atlantic Ocean and it will not threaten any land areas this week.

Tropical Storm Karl Intensifies a Little

After several days when Tropical Storm Karl was poorly organized and barely maintained tropical storm intensity, Karl intensified a little late on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Karl was located at latitude 19.7°N and longitude 50.5°W which put it about 760 miles (1225 km) east-northeast of the Leeward Islands.  Karl was moving toward the west-northwest at 14 m.p.h. (22 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 1005 mb.

Although the structure of Tropical Storm Karl improved a little during the past few hours, it is still not a well organized storm.  A cluster of thunderstorms (sometimes called a Central Dense Overcast or CDO) formed near the core of Tropical Storm Karl.  Additional thunderstorms developed in fragmented rainbands, which are primarily in the eastern half of the circulation.  The cluster of thunderstorms near the core of the circulation is beginning to generate upper level divergence.

Tropical Storm Karl is moving into a more favorable environment.  It is moving over water where the Sea Surface Temperature (SST) is near 28°C.  An upper level low to the west of Karl has been causing strong vertical wind shear over the top of the tropical storm.  However, the upper low is moving farther west of Karl and the vertical wind shear is lessening.  Warm SSTs and less vertical wind shear allowed Tropical Storm Karl to begin to get a little better organized.  Karl is likely to intensify slowly while the circulation organizes and a more well define structure develops.  Tropical Storm Karl will move over warmer SSTs during the next few days and it is forecast to become a hurricane later this week.

Tropical Storm Karl is moving around the southwestern portion of a subtropical ridge which is steering it toward the west-northwest.  Karl is likely to turn more toward the northwest during the next several days.  On its anticipated track Tropical Storm Karl is likely to move northeast of the Leeward Islands and head in the general direction of Bermuda.

Tropical Storm Karl Develops over the Eastern Atlantic

More thunderstorms developed near the center of Tropical Depression 12 and the National Hurricane Center named it Tropical Storm Karl on Thursday night.  Karl is the third tropical storm to form over the Atlantic Ocean this week.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Karl was located at latitude 17.9°N and longitude 32.5°W which put it about 1930 miles (3150 km) east of the Leeward Islands.  Karl was moving toward the west at 14 m.p.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 1005 mb.

The circulation of Tropical Storm Karl is asymmetrical.  Karl does have a large circular low level wind fields.  However the thunderstorms are northeast of the center of circulation, although some thunderstorms have developed closer to the northeast side of the center in recent hours.  Southwesterly winds in the upper levels are generating moderate vertical wind shear, which has contributed to the asymmetrical distribution of thunderstorms.  In addition, the upper level winds are inhibiting upper level divergence to the west of Tropical Storm Karl.

Tropical Storm Karl is moving through an environment that is not very favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 27°C.  There is moderate vertical wind shear, which will make it hard for thunderstorms to persist near the center of the tropical storm.  Karl could move into an area where the upper level winds are not as strong in a day or two.  The environment could be more favorable for intensification at that time.

A subtropical ridge north of Karl is steering the tropical storm toward the west.  The ridge is expected to get stronger and it should steer Tropical Storm Karl toward the west or west-southwest during the next few days.

Tropical Storm Julia Edges Farther from the Southeast U.S.

Tropical Storm Julia moved slowly eastward on Thursday which took it farther from the Southeastern coast of the U.S.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Julia was located at latitude 32.1°N and longitude 77.1°W which put it about 150 miles (245 km) south-southeast of Wilmington, North Carolina.  Julia was moving toward the east at 8 m.p.h. (13 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 1007 mb.

The circulation of Tropical Storm Julia is not well organized.  All of the stronger thunderstorms are well to the east of the center of circulation.  The broad low level circulation is elongated from the west-southwest of the east-northeast.  There are no thunderstorms close to the center of circulation.

Tropical Storm Julia is in an environment that is unfavorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, upper level westerly winds are causing strong vertical wind shear.  The upper level winds have at least temporarily blown the upper part of the circulation east of the lower third of the circulation.  As long as the upper level winds are as strong as they are now, Tropical Storm Julia will slowly weaken.  If the upper level winds slow down, then more thunderstorms could develop near the center and Julia could get a little stronger.  With the current strong vertical wind shear Tropical Storm Julia should slowly weaken during the next few hours.

The vertical structure of Tropical Storm Julia maintained enough integrity that the westerly winds pushed the thunderstorms toward the east and they dragged the low level center with them.  However, it now appears that the vertical parts of the circulation have separated.  The low level circulation is being steered slowly back toward the southwest by a surface high pressure system to the north of Julia.  Tropical Storm Julia could move erratically during the next several days.  As long as no thunderstorms form near the center, it will drift slowly toward the southwest.  Any time thunderstorms form near the center of circulation, the taller storm will be pushed toward the east.

Tropical Storm Julia Forms over Northeast Florida

Although tropical storms normally form over an ocean, Tropical Storm Julia formed over northeast Florida on Tuesday.  The National Hurricane Center (NHC) had tracked a tropical disturbance from Africa across the Atlantic Ocean to Florida.  NHC had designated the system as Invest 93L for tracking purposes.  Although the disturbance moved over the Florida peninsula on Monday, a distinct center of circulation developed at the surface on Tuesday while the disturbance moved north over the northeastern part of Florida.  An area of stronger thunderstorms formed over the Atlantic Ocean east of the center of circulation on Tuesday afternoon and persisted into Tuesday evening.  Because the system had a distinct surface center, persistent thunderstorms and winds to tropical storm force, the National Hurricane Center named it Tropical Storm Julia at 11:00 p.m. EDT on Tuesday and initiated advisories on the Julia.

At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Julia was located at latitude 30.3°N and longitude 81.6°W which put it about 5 miles (10 km) west of Jacksonville, Florida.  Julia was moving toward the north-northwest at 9 m.p.h. (15 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 issued for the portion of the coast from Ponte Vedra Beach, Florida to Altamaha Sound, Georgia.

The circulation of Tropical Storm Julia is very asymmetrical.  Most of the thunderstorms and rain are north and east of the of circulation.  There are few storms or rain west and south of the center.  One primary rainband extends part of the way around the southeastern portion of the circulation.  The thunderstorms to the east of the center are generating upper level divergence which is pumping out mass to the northeast of the circulation.

Since the center of Tropical Storm Julia is over land, intensification would normally be unlikely.  However, about half of the circulation is over water where the Sea Surface Temperature is near 28.5°C.  In addition, the atmospheric environment is favorable for strengthening.  The upper level winds are not too strong and the vertical wind shear is moderate.  It is possible that the wind speeds could increase in the thunderstorms in the part of the circulation that is over the Atlantic Ocean on Wednesday.

The steering currents around Tropical Storm Julia are quite complicated.  There is an upper low over the Gulf of Mexico, a ridge over the western Atlantic Ocean and an upper level trough moving toward the Great Lakes and East Coast of the U.S.  The upper low and ridge over the western Atlantic combined to steer Julia mainly toward the north-northwest on Tuesday.  At times the asymmetric circulation and the upper level divergence to the east of the circulation caused the center to move east as well.  It is likely that this motion will continue on Wednesday.  The center of Julia could move very close to the coast of Georgia.  If the center remains inland, then Tropical Storm Julia will start to weaken slowly.  If the center moves over the water, then it could intensify and persist longer.

The primary risk posed by Tropical Storm Julia will be locally heavy rain and the potential for flash flooding.  Winds and waves along the coast will cause rip currents and some beach erosion.  Water rises of several feet (one meter) will be possible.