Category Archives: Atlantic, Caribbean, and Gulf of Mexico

Atlantic TCs

Major Hurricane Harvey Closing in on Texas Coast

Major Hurricane Harvey was closing on the Texas coast on Friday afternoon.  At 4:00 p.m. EDT on Friday the center of Hurricane Harvey was located at latitude 27.4°N and longitude 96.4°W which put it about 70 miles (110 km) east-southeast of Corpus Christi, Texas.  Harvey was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h).  The minimum surface pressure was 943 mb.

A Hurricane Warning was in effect for the portion of the coast from Port Mansfield to Sargent, Texas.  A Tropical Storm Warning was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield and from Sargent to High Island, Texas.  A Tropical Storm Watch was in effect from Boca De Catan, Mexico to the mouth of the Rio Grande River.

Hurricane Harvey has a relatively compact circulation.  Winds to hurricane force extend out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extend out about 140 miles (225 km) from the center.  The current Hurricane Intensity Index (HII) for Harvey is 22.1.  The Hurricane Size Index (HSI) is 10.4 and the Hurricane Wind Intensity Size Index (HWISI) is 32.5.

Hurricane Harvey went through an eyewall replacement cycle earlier today.  A second outer eyewall encircled the original inner eyewall.  The two concentric eyewalls temporarily interrupted the intensification of Harvey.  Most of the air began converging in the outer eyewall and the inner eyewall dissipated.  The eyewall replacement cycle resulted in Harvey becoming a slightly larger hurricane.  After the inner eyewall dissipated, the remaining outer eyewall began to contract and Harvey started to intensify again.

Hurricane Harvey will still be over the warm water of the western Gulf of Mexico for a few more hours.  So, it does have a chance to intensify further.  There is about a 25% chance that Harvey intensifies to Category 4 on the Saffir-Simpson Scale before it makes landfall.

Harvey is being steered toward the northwest by a subtropical ridge located northeast of the hurricane.  On its anticipated track Hurricane Harvey will most likely make landfall on the coast of Texas between Corpus Christi and Freeport in a few hours.  The steering currents are forecast to weaken about the time Harvey makes landfall and it could meander near the coast of Texas during the weekend.  The track forecast becomes very uncertain at that time.  Some models forecast that Harvey will stall inland, while other models predict it will drift back over the Gulf of Mexico.

Based on current projections the forecast Hurricane Intensity Index (HII) for Harvey at landfall is 26.7.  The forecast Hurricane Size Index (HSI) is 11.6 and the forecast Hurricane Wind Intensity Size Index (HWISI) at landfall is 38.3.  Those indices indicate that Harvey could cause regional major damage in Texas.  Harvey will be stronger, but smaller, than Hurricane Ike was when Ike made landfall in Texas in 2008.  The HII for Ike was 19.2, the HSI was 22.5 and the HWISI was 41.7.  Hurricane Harvey is going to be more similar to Hurricane Charley when Charley made landfall in southwest Florida in 2004.  The HII for Charley was 29.9, the HSI was 8.1 and the HWISI was 38.0

Harvey will bring strong damaging winds to Texas.  Harvey will also cause a dangerous storm surge at the coast.  The storm surge could approach 12 feet (4 meters) in some locations.  Harvey will also drop very heavy rain, if it stalls after it moves inland.  Serious fresh water flooding is possible under that scenario.  The strong winds and flooding could also lead to widespread losses of electricity.

Hurricane Harvey Moves Closer to Texas

Hurricane Harvey moved closer to Texas on Thursday night.  At 11:00 p.m. EDT on Thursday the center of Hurricane Harvey was located at latitude 25.2°N and longitude 94.6°W which put it about 250 miles (400 km) southeast of Corpus Christi, Texas.  Harvey was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 973 mb.

A Hurricane Warning was in effect for the portion of the coast from Port Mansfield to Sargent, Texas.  A Hurricane Watch was in effect from the mouth of the Rio Grande River to Port Mansfield.  A Tropical Storm Warning was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield and from Sargent to High Island, Texas.  A Tropical Storm Watch was in effect from Boca De Catan, Mexico to the mouth of the Rio Grande River.

Hurricane Harvey intensified rapidly for much of Thursday, but the wind speed stopped increasing Thursday evening.  The interruption of the intensification is probably only temporary.  The minimum surface pressure has continued to decrease slowly, but steadily throughout the evening.  An eye with a diameter of 18 miles (29 km) has appeared intermittently.  Although there was a continuous ring of strong thunderstorms around the eye earlier this afternoon, there has been a break in that ring this evening.  It seems as if there are strong thunderstorms at the leading edge of the primary rainband and downdrafts from those storms may be interfering with the eyewall.  The interference with the eyewall may have temporarily paused the intensification of Hurricane Harvey.

Hurricane Harvey is a small hurricane.  Winds to hurricane force extend out about 25 miles from the center, primarily in the northeastern quadrant of the circulation.  Winds to tropical storm force extend out about 105 miles (170 km) from the center.  The current Hurricane Intensity Index (HII) for Harvey is 12.7.  The Hurricane Size Index (HSI) is 6.6 and the Hurricane Wind Intensity Size Index (HWISI) is 19.3.

Hurricane Harvey will move through a very favorable environment on Friday.  Harvey will move over water where the Sea Surface Temperature is near 31°C.  The upper level winds are weak and there is little vertical wind shear.  Hurricane Harvey is likely to strengthen on Friday and it could intensify rapidly again.  Harvey is likely to be a major hurricane by the time it makes landfall on the Texas coast and it has a chance to get to Category 4 on the Saffir-Simpson Scale.

Harvey is being steered toward the northwest by a subtropical ridge located northeast of the hurricane.  A general northwesterly motion is expected to continue on Friday.  On its anticipated track Hurricane Harvey would make landfall on the coast of Texas near Corpus Christi in about 36 hours.  The steering currents are forecast to weaken about the time Harvey makes landfall and it could meander near the coast of Texas during the weekend.  The track forecast becomes very uncertain at that time.

Based on current projections the forecast Hurricane Intensity Index (HII) for Harvey at landfall is 25.5.  The forecast Hurricane Size Index (HSI) is 16.0 and the forecast Hurricane Wind Intensity Size Index (HWISI) at landfall is 41.5.  Those indices indicate that Harvey could cause regional major damage in Texas.  Harvey would be stronger, but smaller, than Hurricane Ike was when Ike made landfall in Texas in 2008.  The HII for Ike was 19.2, the HSI was 22.5 and the HWISI was 41.7.

Harvey will bring strong damaging winds to Texas.  Harvey will also cause a dangerous storm surge at the coast.  The storm surge could approach 12 feet (4 meters) in some locations.  Harvey will also drop very heavy rain, if it stalls after it moves inland.  Serious fresh water flooding is possible under that scenario.  The strong winds and flooding could also lead to widespread losses of electricity.

Tropical Storm Harvey Intensifying Rapidly, Hurricane Warning for Texas

Tropical Storm Harvey was intensifying rapidly on Thursday morning and a Hurricane Warning was issued portions of the coast of Texas.  At 11:00 a.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 24.0°N and longitude 93.3°W which put it about 365 miles southeast of Corpus Christi, Texas.  Harvey was moving toward the north-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 982 mb.

A Hurricane Warning was in effect for the portion of the coast from Port Mansfield to Matagorda, Texas.  A Hurricane Watch was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield.  A Tropical Storm Warning was in effect for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield and from Matagorda to High Island, Texas.  A Tropical Storm Watch was in effect for the portion of the coast from Boca De Catan, Mexico to the mouth of the Rio Grande River.

Tropical Storm Harvey intensified very rapidly on Thursday morning.  An eye with a diameter of 18 miles (29 km) formed at the center of circulation.  The eye was surrounded by a ring of very strong thunderstorms.  Additional bands of strong thunderstorms were revolving around the core of Tropical Storm Harvey.  The thunderstorms were generating very strong upper level divergence which was pumping away large amounts of mass in all directions from the tropical storm.  The strong upper level divergence was causing the surface pressure to decrease rapidly.  The minimum surface pressure decreased from 1002 mb to 982 mb in 12 hours.  The rapid decrease in pressure was increasing the pressure gradient force and the winds speeds were increasing accordingly.

Tropical Storm Harvey is in an almost perfect environment for rapid intensification.  Harvey is moving over water where the Sea Surface Temperature is near 31°C.  The upper level winds are very weak and there is almost no vertical wind shear.  Tropical Storm Harvey should continue to intensify rapidly for another 24 to 36 hours.  Harvey will become a hurricane later today and it will likely become a major hurricane before it makes landfall.  Tropical Storm Harvey has the potential to intensify to a Category 4 hurricane on the Saffir-Simpson Scale.

Harvey is being steered toward the north-northwest by a subtropical ridge to the east of the tropical storm.  A general northwesterly motion is forecast continue for another 36 to 48 hours.  On its anticipated track the center of Harvey will approach the coast of Texas on Friday night.  The steering currents are forecast to weaken as Harvey nears the coast.  Some models are forecasting that Harvey drifts slowly toward the west.  Other models stall Harvey and then turn it northeastward.  There is a large degree of uncertainty about the future track of Harvey after it nears the coast.

Based on current projections the forecast Hurricane Intensity Index (HII) for Harvey at landfall is 22.1.  The forecast Hurricane Size Index (HSI) is 18.0 and the forecast Hurricane Wind Intensity Size Index (HWISI) at landfall is 40.1  Those indices indicate that Harvey could cause regional major damage in Texas.  The indices may be conservative if Harvey continues to intensify rapidly up until it makes landfall.  Harvey would be stronger, but a little smaller, than Hurricane Ike was when Ike made landfall in Texas in 2008.  The HII for Ike was 19.2, the HSI was 22.5 and the HWISI was 41.7.

Harvey will bring strong damaging winds to Texas.  Harvey will also cause a dangerous storm surge at the coast.  The storm surge could approach 12 feet (4 meters) in some locations.  Harvey will also drop very heavy rain, if it stalls after it moves inland.  Serious fresh water flooding is possible under that scenario.

Tropical Depression Harvey Redevelops Southeast of Texas

A tropical depression redeveloped southeast of Texas from the remnants of former Tropical Storm Harvey on Wednesday morning.  The National Hurricane Center (NHC) began issuing advisories on Tropical Depression Harvey again.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Harvey was located at latitude 21.5°N and longitude 92.5°W which put it about 535 miles (860 km) southeast of Port O’Connor, Texas.  Harvey was moving toward the northwest at 9 m.p.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 1006 mb.

A Hurricane Watch was issued for the portion of the coast from Port Mansfield to San Luis Pass, Texas.  A Tropical Storm Watch was issued for the portion of the coast from the mouth of the Rio Grande River to Port Mansfield and from San Luis Pass to High Island, Texas.  NHC also issued a Storm Surge Watch for the portion of the coast from Port Mansfield to High Island.

A reconnaissance aircraft found that a distinct low level center had formed in the remnants of Tropical Storm Harvey on Wednesday morning.  The circulation in Tropical Depression Harvey was still in the process of organizing.  Stronger thunderstorms were forming near the center of circulation.  Additional bands of showers and thunderstorms were forming outside the core of the circulation.  The distribution of showers and thunderstorms was somewhat asymmetrical.  There were more showers and thunderstorms in the eastern half of the circulation.  Although there were fewer showers and thunderstorms in the western half of the circulation, more storms were developing in that part of Tropical Depression Harvey.  The thunderstorms near the core were beginning to generate upper level divergence which was pumping away mass to the northeast of the tropical depression.

Tropical Depression Harvey will move through an environment that will become increasing favorable for intensification.  Harvey will move over water where the Sea Surface Temperature is near 30°C.  An upper level low near the coast of Louisiana is causing some vertical wind shear.  However, the low is forecast to move north and weaken and the shear is forecast to decrease.  Tropical Depression Harvey may strengthen slowly at first while the circulation is organizing.  The rate of intensification will likely increase on Thursday and there could be a period of rapid intensification when the Harvey near hurricane intensity.

Tropical Depression Harvey is moving around the western end of a subtropical high pressure system which is steering Harvey toward the northwest.  Harvey is forecast to continue to move toward the northwest and it will approach Texas in about 48 hours.  The winds are the steering level are forecast to weaken when Harvey approaches Texas and it could move more slowly as it nears the coast.

Tropical Depression Harvey could evolve into a very dangerous storm.  The coast along the western Gulf of Mexico is very susceptible to storm surges.  An intensifying, slow moving hurricane could generate dangerous storm surges along the coast.  If Harvey stalls after it moves inland, it could drop very heavy rain and there is also the potential for dangerous fresh water flooding.

Remnants of Tropical Storm Harvey About to Move Over Gulf of Mexico

The remnants of former Tropical Storm Harvey are about to move over the southern Gulf of Mexico.  At 2:00 p.m. EDT on Tuesday the center of the remnants of Tropical Storm Harvey was located at latitude 20.3°N and longitude 89.8°W which put it about 45 miles (75 km) south-southwest of Merida, Mexico.  It was moving toward the northwest at 15 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 1010 mb.

A broad area of low pressure that contained the remnants of former Tropical Storm Harvey moved across the Yucatan peninsula on Tuesday.  Thin bands of showers were rotating around the broad area of low pressure over land.  Several broken bands of thunderstorms were evident on the northern and northeastern periphery of the low pressure system.  There were several smaller centers rotating around inside the larger area of low pressure, but the circulation appeared to consolidating around a center near Merida.  A few thunderstorms were forming near that center as it neared the coast.

The National Hurricane Center indicated that there is a nearly 100% chance that the low pressure system will strengthen into a tropical cyclone again once it moves over the Gulf of Mexico.  The Sea Surface Temperature (SST) in the southern Gulf of Mexico is near 31°C.  An upper level low over the northwestern Gulf of Mexico was producing some vertical shear over the top of the surface low.  The upper low is forecast to move north and weaken.  An upper level ridge over the northwestern Caribbean Sea is forecast to move over the western Gulf of Mexico.  The upper ridge will produce southerly winds which will cause some vertical wind shear.  However, those winds are expected to be weak enough to allow for intensification.  The southerly winds could actually enhance upper level divergence to the north of the low pressure system in a day or two.

Given the large size of the low pressure system and the lack of a well defined center of circulation, the system will likely start to intensify slowly.  The rate of intensification will increase once a well defined center forms.  A period of very rapid intensification could occur later this week because of very warm SSTs and little vertical wind shear.  The area of low pressure could become a tropical depression within 12 hours.  It is likely to be a tropical storm on Wednesday.  The system has a good chance of becoming a hurricane over the western Gulf of Mexico.  If the system moves slowly and rapid intensification occurs, it could become a major hurricane.

A ridge in the middle troposphere near Florida is steering the low pressure system toward the northwest and a general northwesterly motion is forecast for the next several days.  There will be more uncertainty about the future track until a well developed center of circulation forms.  However, it seems likely that this system will move toward the coast of Texas.  The system could slow and/or turn more toward the north when it nears the coast.  It has the potential to become a significant hurricane by the time it reaches the coast.  It could bring strong gusty winds, which could cause a significant storm surge at the coast.  If the system moves slowly, it could also drop very heavy rain, which would create flash floods.

Tropical Storm Harvey Weakens to a Tropical Wave

Tropical Storm Harvey weakened to a tropical wave on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Wave Harvey was located at latitude 14.3°N and longitude 71.8°W which put it about 765 miles (1230 km) east of Cape Gracias a Dios.  The wave was moving toward the west at 22 m.p.h. (35 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 1007 mb.

An upper level ridge east of Harvey produced northerly winds that blew toward the top of the former tropical storm.  A subtropical high over the Atlantic Ocean produced strong easterly winds in the lower levels of the atmosphere.  The combination of northerly winds in the upper levels and easterly winds in the lower levels produced strong vertical wind shear which disrupted the vertical structure of Harvey.  A reconnaissance plane was unable to locate a low level center of low pressure on Saturday evening and the National Hurricane Center reclassified the system as a tropical wave.

Tropical Wave Harvey will continue to move west across the Caribbean Sea during the next several days.  It will move over water where the Sea Surface Temperature is near 30°C.  So, there will be sufficient energy in the ocean to support a tropical cyclone. When the tropical wave moves under the core of the upper level ridge, the wind shear will decrease.  If the tropical wave moves into a more favorable environment and slows down, a new center of circulation could redevelop.  Models are not forecasting significant redevelopment of the tropical wave at the current time, but the National Hurricane Center will continue to monitor the wave for possible redevelopment.

Tropical Storm Harvey Develops East of Barbados

A reconnaissance plane found that a center of circulation and winds to tropical storm force had developed in a tropical wave previously designated as Invest 91L and Potential Tropical Cyclone Nine.  Based on data collected by the recon plane the National Hurricane Center named the system Tropical Storm Harvey on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Harvey was located at latitude 13.0°N and longitude 55.8°W which put it about 250 miles (400 km) east of Barbados.  Harvey was moving toward the west at 18 m.p.h. (30 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 1004 mb.

A Tropical Storm Warning is in effect for Martinique, Barbados, St. Vincent and the Grenadines, and St. Lucia.  A Tropical Storm Watch is in effect for Dominica.

The circulation of Tropical Storm Harvey became better organized on Thursday.  A low level center of circulation developed and bands of showers and thunderstorms began to revolve around the center.  Intermittent bursts of thunderstorms occurred near and to the west of the center of circulation.  The circulation of Tropical Storm Harvey is asymmetrical.  Most of the stronger thunderstorms are occurring in the western half of the circulation.  The bands in the eastern half of the circulation consist primarily of showers and low clouds.  Thunderstorms near the core of Harvey were generating some upper level divergence which was pumping mass away to the south and west of the tropical storm.

Tropical Storm Harvey will be moving through an environment that will be somewhat favorable for intensification.  Harvey will move over water where the Sea Surface Temperature is near 29°C.  An upper level ridge northeast of Puerto Rico is producing northeasterly winds which are blowing toward the top of Tropical Storm Harvey.  Those winds are producing moderate vertical wind shear which is probably the cause of the asymmetrical distribution of thunderstorms.  Tropical Storm Harvey is likely to get better organized on Friday and it could strengthen.  The intensity guidance is mixed.  Some guidance forecasts that Harvey will become a hurricane as it moves over the Caribbean Sea, while other guidance weaken the tropical storm back to a tropical wave.  So far, the guidance has underpredicted the strength of Tropical Storm Harvey and so strengthen would seem more likely.

Tropical Storm Harvey is being steered quickly toward the west by the subtropical high over the Atlantic Ocean.  A general westerly or west-northwesterly track is forecast for the next few days.  On its anticipate track Tropical Storm Harvey could reach Barbados in about 12 hours.  Harvey could also reach Martinique, St. Lucia, St. Vincent and the Grenadines on Friday.  Tropical Storm Harvey will bring gusty winds and locally heavy rain to those islands when it moves over them.

Hurricane Gert Intensifies to Cat. 2 South of Nova Scotia

Hurricane Gert intensified to Category 2 on the Saffir-Simpson Scale as it sped over the Gulf Stream south of Nova Scotia on Wednesday afternoon.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Gert was located at latitude 38.7°N and longitude 62.4°W which put it about 410 miles (665 km) south of Halifax, Nova Scotia.  Gert was moving toward the northeast at 31 m.p.h. (50 km/h).  The maximum sustained wind speed was 100 mp.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 970 mb.

Although Hurricane Gert is at a fairly high latitude, it has the classic structure of a Hurricane.  There is a fairly small eye at the center of circulation.  The eye is surround by a ring of strong thunderstorm and the strongest winds are occurring in this ring of thunderstorms.  There are additional bands of showers and thunderstorms revolving around the core of the hurricane.  The circulation is symmetrical and thunderstorms in the core are producing upper level divergence which is pumping away mass to the northeast of the hurricane.  Winds to hurricane force extend out about 40 miles (65 km) primarily to the east of the center of circulation.  Winds to tropical storm force extend out about 140 miles (225 km) from the center.

Hurricane Gert is moving over the Gulf Stream which means it is moving over water where the Sea Surface Temperature (SST) is near 28.5°C.  An upper level trough west of Gert is producing southwesterly winds which are blowing toward the top of the hurricane.  However, there is not much change of wind speed with height, which means that there is little vertical wind shear.  The combination of the warm water of the Gulf Stream and little vertical shear, allowed Hurricane Gert to strengthen on Wednesday.

Hurricane Gert could intensify during the next few hours, but it will soon move into a much less favorable environment.  Gert will soon move north of the Gulf Stream where the SSTs are much cooler.  The upper level trough is moving closer to Hurricane Gert and the winds are the upper level are forecast to get stronger.  When those winds increase, there will be much more vertical wind shear.  Colder water and more wind shear will cause Hurricane Gert to weaken on Thursday.  Gert could make a transition to an extratropical cyclone in colder environment of the North Atlantic.

Southwesterly winds in the upper level trough are steering Hurricane  Gert quickly toward the northeast and that general motion is expected to continue.  On its anticipated track, Hurricane Gert will move south of Labrador and Greenland.

Even as Hurricane Gert speeds away over the North Atlantic three new tropical waves over the tropical Atlantic have the potential to develop into tropical cyclones.  A tropical wave about 800 miles (1290 km) east of the Lesser Antilles designated as Invest 91L showed signs of organization on Wednesday.  A few more thunderstorms developed closed to the center of circulation.  A reconnaissance plane is scheduled to investigate this system on Thursday.  A little farther to the east another tropical wave designated Invest 92L was also showing evidence or more organization.  A third tropical wave just west of Africa also has the potential to develop during the next few days.

Gert Intensifies to a Hurricane West of Bermuda

Gert intensified to a hurricane west of Bermuda on Monday.  Gert became the second Atlantic hurricane of 2017 and it is the second hurricane to form during the past six days.  Hurricane Franklin developed over the southern Gulf of Mexico last week.  At 11:00 p.m. EDT on Monday the center of Hurricane Gert was located at latitude 31.2°N and longitude 72.3°W which put it about 445 miles (720 km) west of Bermuda.  Gert was moving toward the north at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 986 mb.

An eye appeared on satellite images of Hurricane Gert at various times on Monday and it looked more like a hurricane.  There was a somewhat elliptical eye at the center of Hurricane Gert on Monday night.  The ring of thunderstorms around the eye did not completely surround the eye.  There was a large break on the northwest side of the eye.  Additional bands of showers and thunderstorms were occurring in the southeastern half of Gert.  There were fewer showers and thunderstorms in the northwestern half of the hurricane.  Thunderstorms near the core of Gert were generating upper level divergence which was pumping out mass to the south of the hurricane.

Hurricane Gert will be an environment that will be favorable for intensification for another 24 to 48 hours.  Gert will move over water where the Sea Surface Temperature is near 28.5°C.  An upper level ridge centered northwest of Gert is producing northerly winds which are blowing toward the top of the circulation.  Those winds are producing some vertical wind shear and they may be responsible for the asymmetrical distribution of showers and thunderstorms.  However, the vertical wind shear should not be strong enough to prevent Hurricane Gert from intensifying further.  An upper level trough will approach Gert from the west, but before the trough reaches the hurricane, the wind shear will decrease and a period of rapid intensification could occur.

Hurricane Gert is moving around the western end of a subtropical high over the Atlantic Ocean.  The high is steering Gert slowly toward the north.  When the upper level trough approaches Gert, southwesterly winds will start to steer the hurricane toward the northeast.  On its anticipated track Hurricane Gert should pass northwest of Bermuda.

TD 8 Strengthens to Tropical Storm Gert

Tropical Depression Eight strengthened to Tropical Storm Gert on Sunday afternoon.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Gert was located at latitude 28.1°N and longitude 71.7°W which put it about 505 miles (810 km) west-southwest of Bermuda.  Gert was moving toward the north-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 gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1011 mb.

The structure of Tropical Storm Gert improved on Sunday.  Numerous bands of showers and thunderstorms developed and began to rotate around the center of circulation.  The thunderstorms began to produce upper level divergence which was pumping out mass in all directions.  The circulation of Tropical Storm Gert became more circular and symmetrical.

Tropical Storm Gert will move through an environment that will be favorable for intensification during the next 24 hours.  Gert will move over water where the Sea Surface Temperature is near 29°C.  The upper level winds over Tropical Storm Gert are weak and there is not much vertical wind shear.  There is an upper level ridge northwest of Tropical Storm Gert and the ridge is producing northeasterly winds west of Bermuda.  So, the vertical wind shear could increase when Gert moves farther north.  Tropical Storm Gert will continue to intensify during the next 24 hours.

Tropical Storm Gert is moving around the western end of the subtropical high pressure system over the Atlantic Ocean.  The high is steering Gert toward the north-northwest and a northerly motion is  expected to continue for another 24 hours.  When Gert moves west of Bermuda, it will start to encounter the westerly winds in the middle latitudes.  Those winds should turn Tropical Storm Gert toward the northeast in a day or so.  On its anticipated track Tropical Storm Gert is expected to move east of the U.S. and west of Bermuda.