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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.

Hurricane Joaquin Passing Northwest of Bermuda

Hurricane Joaquin is bringing tropical storm force winds to Bermuda as the core of the hurricane moves northwest of that island.  Wind gusts to 64 m.p.h. have been reported in recent hours in Bermuda.  At 11:00 p.m. EDT on Sunday the center of Hurricane Joaquin was located at latitude 33.1°N and longitude 65.5°W which put it about 70 miles (110 km) northwest of Bermuda.  Joaquin was moving toward the north-northeast at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 961 mb.  A Hurricane Warning remains in effect for Bermuda.

Hurricane Joaquin is gradually moving over cooler water, but it is still over water where the Sea Surface Temperature is around 28°C.  It appears that a combination of drier air and vertical wind shear caused Joaquin to weaken on Sunday.  Thunderstorms are not rising as far up into the atmosphere and gaps have appeared in the eyewall.  Southwesterly winds in the upper levels are inhibiting upper level divergence in that portion of the hurricane and the pressure rose 17 mb on Sunday.  The wind shear could lessen for a time on Monday and the rate of weakening could slow.

Hurricane Joaquin is moving toward the north-northeast.  When it moves farther north, it will encounter the upper level westerlies in the middle latitudes.  Those westerly winds will carry Joaquin toward the east.  Joaquin could make a transition to a strong extratropical storm and affect western Europe in a few days.

Hurricane Joaquin Heading Toward Bermuda

After intensifying to almost Category 5 on the Saffir-Simpson Scale on Saturday, Hurricane Joaquin headed toward Bermuda.  The Bermuda Weather Service has issued a Hurricane Warning for Bermuda.  At 11:00 p.m. EDT on Saturday the center of Hurricane Joaquin was located at latitude 28.0°N and longitude 68.9°W which put it about 385 miles (620 km) southwest of Bermuda.  Joaquin was moving toward the northeast at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 944 mb.  Joaquin was a Category 4 hurricane on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) was 25.1.  The Hurricane Size Index (HSI) was 20.0 and the Hurricane Wind Intensity Size Index (HWISI) was 45.1.

Joaquin is moving over water where the Sea Surface Temperature is near 29°C.  However, a large upper level trough over the southeastern U.S. and an upper level low northwest of Joaquin are combining to generate westerly winds over the hurricane.  The vertical wind shear is causing the circulation to become more asymmetrical and the strongest convection is occurring in the eastern half of the circulation.  The flow of air is also pushing drier air toward the core of Hurricane Joaquin.  If Joaquin can move fast enough to outrun the drier air, it could weaken slowly.  However, if the drier air gets into the core of the circulation, then Joaquin will weaken faster.

The trough and upper level low are steering Hurricane Joaquin quickly toward the northeast and that motion is expected to continue on Sunday.  On its anticipated track Joaquin will pass near Bermuda on Sunday night.  It could bring strong winds and a storm surge as it moves past the island.

Hurricane Joaquin Moving Slowly Away from the Bahamas

Hurricane Joaquin turned northward on Friday and it is starting to move slowly away from the Central Bahamas.  However, it is still producing strong winds, heavy rain and storm surges on San Salvador and nearby islands.  At 5:00 p.m. EDT on Friday the center of Hurricane Joaquin was located at latitude 24.1°N and longitude 74.7°W which put it about 15 miles (25 km) west-northwest of San Salvador in the Central Bahamas and about 745 miles (1200 km) south of Cape Hatteras, North Carolina.  Joaquin was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h)  which made Joaquin a Category 3 hurricane on the Saffir-Simpson Scale.  There were wind gusts to 155 m.p.h. (250 km/h) and the minimum surface pressure was 942 mb.  The Hurricane Intensity Index (HII) was 23.6.  The Hurricane Size Index (HSI) was 20.3 and the Hurricane Wind Intensity Size Index (HWISI) was 43.9.

A Hurricane Warning is in effect for the Central Bahamas including Cat Island, the Exumas, Rum Cay, Long Island and San Salvador.  A Hurricane Warning is in effect for the Northwestern Bahamas including the Abacos, Berry Island, Eleuthera, Grand Bahama Island and New Providence.  A Hurricane Watch has been issued for Bimini and Andros Island.  A Tropical Storm Warning is in effect for Andros Island and the Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands and the Turks and Caicos.  A Tropical Storm Watch has been issued for Bermuda.

Hurricane Joaquin did not change a lot on Friday, although there were some indications that vertical wind shear may be starting to affect it.  Microwave satellite imagery and aerial reconnaissance indicate that there is still and eye, although the eyewall is thinner on the north side.  Most of the stronger thunderstorms are on the southern side of the circulation.  An upper level trough over the eastern U.S. may be creating stronger winds that are hitting Joaquin from the southwest.  Those southwesterly winds may be limiting upper level divergence on that side of the hurricane.  The hurricane is still over water where the Sea Surface Temperature is near 30°C.  So, vertical wind shear is the only factor inhibiting intensification.  The trough is expected to produce more vertical wind shear on Saturday, which could start to weaken Joaquin.

The upper level trough is starting to steer Joaquin slowly toward the north.  The trough is expected to steer Joaquin toward the northeast at a faster rate during the next several days.  Guidance from all of the numerical models has come into agreement that Joaquin will stay east of the U.S.  Conditions in the Central Bahamas should improve on Saturday as Hurricane Joaquin moves farther away.  The possibility that Joaquin could be near to Bermuda on Sunday prompted the issuance of a Tropical Storm Watch for that island.

Category 4 Hurricane Joaquin Bringing Strong Winds and Floods to the Bahamas

Hurricane Joaquin intensified to Category 4 on the Saffir-Simpson Scale on Thursday and it brought strong winds and floods to some of the islands of the Bahamas.  At 11:00 p.m. EDT on Thursday the center of Hurricane Joaquin was located at latitude 22.9°N and longitude 74.6°W which put it about 20 miles (32 km) east-southeast of Clarence Town on Long Island in the Central Bahamas and about 810 miles (1310 km) south of Cape Hatteras, North Carolina.  Joaquin was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 935 mb.  The Hurricane Intensity Index (HII) was 25.1.  The Hurricane Size Index (HSI) was 21.4 and the Hurricane Wind Intensity Size Index (HWISI) was 46.5.

A Hurricane Warning has been issued for the Central Bahamas including Cat Island, Rum Cay, the Exumas, Long Island and San Salvador.   A Hurricane Warning has been issued for the Northwestern Bahamas including the Abacos, Berry Islands, Eleuthera, Grand Bahama Island and New Providence.  A Hurricane Watch has been issued for Bimini and Andros Island.  A Tropical Storm Warning has been issued for Andros Island and the Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Ragged Islands, the Inaguas, Mayaguana and the Turks and Caicos.  A Tropical Storm Warning has been issued for the Cuban provinces of Camaguey, Los Tunas, Holguin and Guantanamo.

The eye in Hurricane Joaquin contracted on Thursday and it has only been visible intermittently on conventional satellite imagery.  The intensity of the hurricane appears to have stabilized in recent hours.  While the intensity of Joaquin has been constant, the circulation has increased in sized and hurricane force winds now extend out about 50 miles (80 km) from the center.  Joaquin is still generating upper level divergence which seems to be pumping out as much mass as is converging in the lower levels of the circulation.  As a result, the pressure has also remained fairly steady during the past few hours.  There is not much vertical wind shear and the overall environment would seems to support further intensification.  However, the slow movement of Joaquin may be causing it to stir cooler water to the surface, which will reduce the energy available to the hurricane.

Hurricane Joaquin has moved little during the past six hours.  An narrow ridge is blocking its motion and the ridge is preventing it from moving toward the north.  A large upper level trough over the eastern U.S. is expected to weaken the ridge on Friday.  The upper level trough is expected to steer Joaquin toward the north on Friday.  Most of the reliable numerical models predict that the trough will carry Joaquin toward the northeast during the weekend and that it will stay east of the U.S.  A couple of other models still suggest a landfall could occur, but they are outliers at the current time.  Until Hurricane Joaquin makes the turn toward the north and northeast, it could still pose a potential risk to the U.S., but that possibility is much less than it was 24 hours ago.  Joaquin will continue to bring high winds and floods to parts of the Bahamas on Friday.

Joaquin Becomes a Major Hurricane Near the Bahamas

Hurricane Joaquin intensified very rapidly on Wednesday and it reached Major Hurricane intensity.  At 11:00 p.m. EDT on Wednesday night the center of Hurricane Joaquin was located at latitude 23.8°N and longitude 73.1°W which put it about 90 miles (145 km) east of San Salvador and about 750 miles (1215 km) south-southeast of Cape Hatteras, North Carolina.  Joaquin was moving toward the southwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 140 m.p.h. (220 km/h).  The wind speed made Joaquin a Category 3 hurricane on the Saffir-Simpson Scale and a Major Hurricane.  The minimum surface pressure was 951 mb.  The Hurricane Intensity Index (HII) was 20.6, the Hurricane Size Index (HSI) was 11.6, and the Hurricane Wind Intensity Size Index (HWISI) was 32.2.

A Hurricane Warning has been issued for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay and San Salvador.  A Hurricane Warning has been issued for the Northwestern Bahamas including the Abacos, Berry Islands, Eleuthera, Grand Bahama Island and New Providence.  A Hurricane Watch has been issued for Bimini and Andros Island.  A Tropical Storm Warning has been issued for Andros Island and the Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayguana and the Ragged Islands.

Joaquin has a well formed structure.  The circulation is fairly symmetrical, although there are more spiral bands of thunderstorms south and east of the center.  The hurricane is over water where the Sea Surface Temperature is near 30°C.  A narrow upper level ridge west of Joaquin is causing light northerly winds over the circulation, but those winds did not inhibit rapid intensification on Wednesday.  The convection generated upper level divergence which pumped out mass and caused the pressure to decrease quickly.  Further intensification is possible during the next 24 hours, although if an eyewall replacement occurs, it would interrupt that process.  An upper level trough over the eastern U.S. will generate more vertical wind shear in a day or two and Joaquin will start to weaken.

A ridge north of Joaquin is blocking the hurricane and forcing it to move toward the southwest.  The ridge will weaken in a day or so and the upper level trough will start to steer Joaquin toward the north.  When the hurricane starts moving northward, it will also begin to move faster.  It could be approaching the Mid-Atlantic Coast by later on Saturday.

 

Joaquin Almost a Hurricane, Watch Issued for Central Bahamas

Tropical Storm Joaquin is on the verge of reaching hurricane intensity.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Joaquin was located at latitude 25.8°N and longitude 71.7°W which put it about 360 miles (580 km) east of the Northwestern Bahamas and about 680 miles (1100 km) south-southeast of Cape Hatteras, North Carolina.  Joaquin was moving toward the west-southwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 988 mb.  The government of the Bahamas has issued a Hurricane Watch for the Central Bahamas.

The organization of the circulation of Tropical Storm Joaquin increased on Tuesday in spite of moderate amounts of vertical wind shear.  More thunderstorms developed near the core of circulation and a partial eyewall formed around the southern and eastern parts of the center.  Although it is more organized, the circulation is still asymmetrical and the stronger winds were found in the eastern side of the tropical storm.

A thin upper level ridge is east of Florida and clockwise flow around the ridge is producing northerly winds over the top of Joaquin.  Those winds produced moderate vertical wind shear on Tuesday but the shear appears to be decreasing with time.  Joaquin is over water where the Sea Surface Temperature is near 30°C.  As the upper level winds diminish, the environment favors intensification and Joaquin is likely to become a hurricane on Wednesday.  Joaquin will continue to be in an environment that favors intensification during the next several days.

A ridge of high pressure north of Joaquin is blocking it from moving north and the ridge is forcing the tropical storm to move toward the west-southwest.  That general motion is expected to continue for another 24 to 48 hours and it could bring Joaquin near the Central and Northwestern Bahamas.  When Joaquin reaches the western end of the ridge it will turn toward the north.  An upper level trough over the eastern U.S. will cause Joaquin to move more quickly toward the north at the end of the week.  On its anticipated track, Joaquin could be approaching the Mid-Atlantic Coast of the U.S. by the weekend.