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Disturbance Brings Squally Weather to the Northwest Caribbean Sea

A complicated disturbance over the northwestern Caribbean Sea is bringing squally weather to that area.  A tropical wave over the western Caribbean Sea is interacting with an upper level low over eastern Mexico.  The disturbance is causing thunderstorms over a region that extends from the northwestern Caribbean Sea to the southern Gulf of Mexico.  Upper level divergence east of the upper low has led to the formation of a surface low pressure system east of Belize.  At 7:00 p.m. EST on Thursday the center of the surface low was located at latitude 18°N and longitude 86°W which put it about 150 miles (240 km) east-southeast of Chetumal, Mexico.  The surface low was moving toward the west-northwest at 10 m.p.h. (16 m.p.h.).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1011 mb.

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

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

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

Patricia Is Strongest East Pacific Hurricane on Record

Hurricane Patricia continued to intensify rapidly during the overnight hours and it is now the strongest hurricane on record for the Eastern North Pacific.  At 11:00 a.m. EDT on Friday the center of Hurricane Patricia was located at latitude 17.6°N and longitude 105.5°W which put it about 125 miles (200 km) southwest of Manzanillo, Mexico.  Patricia was moving toward the north at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 200 m.p.h. (320 km) and there were wind gusts to 245 m.p.h. (400 km/h).  The minimum surface pressure was 880 mb.

A Hurricane Warning is in effect for the portion of the coast between Sas Blas and Punta San Telmo, Mexico.  A Tropical Storm Warning and a Hurricane Watch is in effect for the portion of the coast from Punta San Telmo to Lazaro Cardenas, Mexico.

Hurricane Patricia has broken a number of records.  The maximum sustained wind speed increased from 85 m.p.h. to 200 m.p.h. between 5:00 a.m. EDT on Thursday and 5:00 a.m. EDT on Friday.  The rate of increase of 115 m.p.h. in 24 hours is the fastest rate of intensification observed in the Eastern Pacific. It exceeds the 100 m.p.h. in 24 hours that occurred in Hurricane Linda in 1997.  Interestingly, 1997 was also an El Nino year.  The minimum surface pressure of 880 mb is the lowest ever recorded in the National Hurricane Center’s Area of Responsibility which includes the Atlantic and Eastern North Pacific Oceans.  It is lower than the 882 recorded when Hurricane Wilma was over the Caribbean Sea in 2005.

Hurricane Patricia is an extremely dangerous hurricane.  It has a Hurricane Intensity Index (HII) of 50.0, a Hurricane Size Index (HSI) of 11.3 and a Hurricane Wind Intensity Size Index (HWISI) of 61.3.  Those indices mean that Patricia will be capable of causing catastrophic regional damage when it reaches the west coast of Mexico north of Manzanillo later on Friday.  Hurricane Patricia will be capable of causing catastrophic wind damage, generating a potentially destructive storm surge near the coast and producing heavy rain and flooding as it moves inland.

Category 5 Hurricane Patricia Threatens West Coast of Mexico

Hurricane Patricia continued to intensify very rapidly on Thursday night and it reached Category 5 on the Saffir-Simpson Scale.  At 11:00 p.m. EDT on Thursday the center of Hurricane Patricia was located at latitude 16.2°N and longitude 105.1°W which put it about 200 miles (320 km) south-southwest of Manzanillo, Mexico.  Patricia was moving toward the north-northwest at 10 m.p.h.  The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 924 mb.

The government of Mexico has issued a Hurricane Warning for the portion of the coast from San Blas to Punta San Telmo.  A Hurricane Watch and a Tropical Storm Warning is in effect for the portion of the coast from Punta San Telmo to Lazaro Cardenas.

Hurricane Patricia has a Hurricane Intensity Index (HII) of 35.0.  The Hurricane Size Index (HSI) is 12.4 and the Hurricane Wind Intensity Size Index (HWISI) is 47.4.  Those indices mean that Hurricane Patricia is capable of causing catastrophic regional damage.  Hurricane Patricia is currently about the same size that Hurricane Dennis was before Dennis hit the northern coast of the Gulf of Mexico in 2005.  However, Patricia is stronger than Dennis was at that time.

Hurricane Patricia remains in an environment with warm Sea Surface Temperatures and little vertical wind shear.  Only an eyewall replacement cycle could cause weakening in the short term.  When Hurricane Patricia moves farther north, it will start to encounter upper level winds blowing from the southwest, which will increase the wind shear.  The wind shear could start to weaken Patricia later on Friday.

Hurricane Patricia is moving around the western end of ridge and the hurricane has turned toward the north.  When Patricia encounters the southwesterly winds in the upper levels, it will turn toward the northeast.  On its anticipated track Hurricane Patricia could make landfall on the west coast of Mexico between San Blas and Boca de Apiza on Friday night.  Even though Hurricane Patricia could weaken somewhat before it makes landfall, it will still be a very dangerous hurricane.  Hurricane Patricia poses a major threat to cause significant regional wind damage and a storm surge at the coast.  Heavy rain could produce serious flooding, especially as Patricia moves inland over steeper terrain.

Hurricane Patricia Intensifies Rapidly to Category 4

Hurricane Patricia intensified rapidly on Thursday and it reached Category 4 on the Saffir-Simpson Scale.  The maximum sustained wind speed in Patricia increased from 60 m.p.h. to 130 m.p.h. in 24 hours, which qualified as very rapid intensification.  At 5:00 p.m. EDT on Thursday the center of Hurricane Patricia was located at latitude 15.4°N and longitude 104.6°W which put it about 250 miles (400 km) south of Manzanillo, Mexico.  Patricia was moving toward the west-northwest at 13 m.p.h. (20 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 953 mb.  The Hurricane Intensity Index (HII) for Patricia was 25.1, the Hurricane Size Index (HSI) was 10.4 and the Hurricane Wind Intensity Size Index was 35.5.  Those indices mean that Patricia is almost as strong and just a little larger than Hurricane Charley was when it hit southwest Florida in 2004.

The government of Mexico has issued a Hurricane Warning for the portion of the coast from San Blas to Punta San Telmo.  It has also issued a Hurricane Watch and a Tropical Storm Warning for the portion of the coast from Punta San Telmo to Lazaro Cardenas.

Patricia is a small hurricane, but it has a very well organized circulation.  A ring of strong thunderstorms surrounds a small, 12 mile (19km), eye (sometimes called a pinhole eye because of the way it looks on satellite images).  Multiple spiral bands are rotating around the core fo the circulation.  Thunderstorms in the core are generating strong upper level divergence in all directions.

Hurricane Patricia remains in a very favorable environment.  It is over water were the Sea Surface Temperature is near 30°C.  An upper level ridge over the top of Patricia is keeping the vertical wind shear to a minimum.  Patricia could intensify further, although if concentric eyewalls develop, then eyewall replacement cycles could produce fluctuations in wind speeds.

Hurricane Patricia is moving around the western end of a ridge that extends from the Gulf of Mexico over Mexico.  When Patricia reaches the end of ridge on Friday, it will turn toward the north.  As the hurricane moves farther north it will encounter westerly winds in the southern end of an upper level trough.  Those winds will turn Hurricane Patricia toward the northeast.

On its anticipated track Hurricane Patricia could approach the west coast of Mexico late on Friday.  It will pose a serious threat to the coast at that time.  Patricia will bring strong winds, heavy rain and a storm surge to the coast.  Very heavy rain could fall as Hurricane Patricia moves inland and serious flooding will be possible, especially in the more mountainous areas of Mexico.  The remnants of Hurricane Patricia could eventually move over parts of Texas and add moisture and rain to that region.

Tropical Depression Bill Crossing Red River Into Oklahoma

Tropical Depression Bill moved northward across north Texas on Wednesday and brought heavy rain to parts of Texas and Oklahoma.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Bill was located at latitude 33.7°N and longitude 97.3°W which put it about 65 miles (105 km) north-northwest of Dallas, Texas.  Bill was moving toward the north at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h).  There were wind gusts to 50 m.p.h. (80 km/h) in some thunderstorms.  The minimum surface pressure was 999 mb.

Bill still has a well organized circulation at the surface and throughout the troposphere.  There is still a warm core in the middle troposphere and divergence in the upper levels.  The upper level divergence pumped out the same amount of mass as converged in the lower levels and the surface pressure remained constant on Wednesday.  Some drier air is wrapping around the southern part of the circulation and most of the rain is falling north and east of the center.  The slow movement of Bill has generated significant amounts of rain and flooding is occurring in some parts of Texas and Oklahoma.  A few thunderstorms have also produced damaging wind gusts.

Bill is expected to turn toward the northeast as is moves around the western end of a high pressure system centered off the southeast coast of the U.S.  It will move slowly across Oklahoma on Thursday and across Arkansas on Friday before moving up the Ohio River Valley during the weekend.

 

Tropical Storm Bill Moving Farther Into Texas

Tropical Storm Bill continued to move farther into Texas after making landfall near Matagorda Island on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Bill was located at latitude 29.5°N and longitude 97.0°W which put it about 45 miles (70 km) north of Victoria, Texas.  Bill was moving toward the north at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were winds gusts to 50 m.p.h. (85 km/h).  The minimum surface pressure was 1000 mb.  The strongest winds were occurring primarily in a rainband over the Gulf of Mexico.  A Tropical Storm Warning was in effect for the portion of the coast from Port Oconnor to San Luis Pass, Texas.

The circulation around Bill remains well organized and most of the rain is falling north and east of the center.  The circulation will slowly spin down as it moves farther away from the Gulf of Mexico and its supply of moist air is reduced.  Bill is expected to move north and then turn northeast as it moves around the western end of a high pressure system centered off the coast of the southeastern U.S.  The greatest risk will be from locally heavy rain falling on saturated ground in north Texas and Oklahoma.  Flooding may occur in some locations as a result of the heavy rain.  Some of the moisture associated with the tropical storm could be transported over the Ohio River Valley later this week.

Tropical Storm Bills Forms Near Texas

The National Hurricane Center (NHC) classified a low pressure system over the western Gulf of Mexico as Tropical Storm Bill.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Bill was located at latitude 27.1°N and longitude 94.2°W which put it about 160 miles (260 km) east-southeast of Port OConnor, Texas and about 155 miles (250 km) south-southeast of Galveston, Texas.  Bill was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 50 m.p.h. (85 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1005 mb.  A Tropical Storm Warning has been issued for the portion of the coast from Baffin Bay to High Island, Texas.

Bill formed as a result of the interaction between a broad surface low pressure system and an upper level low over the Gulf of Mexico.  Thunderstorms began to form near the center of circulation on Monday afternoon and the structure of the system changed to a more tropical cyclone like pattern.  The thunderstorms near the center began to warm the middle and upper troposphere and create a warm core.  The thunderstorms became substantial enough to generate upper level divergence from the core of the circulation and NHC classified it as Tropical Storm Bill.  Bill is moving over water where the Sea Surface Temperature (SST) is near 29°C.  The vertical wind shear over the system decreased on Monday and Bill has a few hours during which it could intensify before it makes landfall in Texas.

An upper level ridge over the southeastern U.S. is steering Bill northwestward toward the coast of Texas and that motion is expected to continue.  Bill is expected to make landfall in Texas on Tuesday.  Although Bill will bring some wind when it makes landfall, heavy rainfall will be the biggest hazard.  Heavy rain on top of wet soils will create the potential for new flooding in some locations, especially in Texas and Oklahoma.  Winds blowing toward the coast will also create some water level rises and Coastal Flood Warnings and Advisories have been issued for portions of the coast of Texas and Louisiana.

Low Pressure Organizing Over the Southern Gulf of Mexico

A complex low pressure system over the southern Gulf of Mexico is showing signs of greater organization.  A reconnaissance aircraft investigated the system on Sunday afternoon and found evidence of a broad area of low pressure at the surface and winds to tropical storm force northeast of the low.  The official designation for this system is Invest 91L.  At 11:00 p.m. EDT on Sunday night the approximate center of the broad low was located at latitude 22.7°N and longitude 90.2°W which put it about 540 miles (870 km) south-southeast of Galveston, Texas and about 540 miles (870 km) east-southeast of Brownsville, Texas.  The low was moving toward the northwest at 14 m.p.h. (23 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 1007 mb.

Invest 91L is a complex system which includes an upper level low over the southern Gulf of Mexico and a broad area of low pressure at the surface.  Clusters of thunderstorms are forming intermittently east and north of the center of circulation.  The pressure gradient between a strong high pressure system centered over the Atlantic Ocean and the developing surface low is causing the strongest winds to be found in the northeastern part of Invest 91L.  The upper level low is causing the system is to exhibit a more subtropical mode of formation rather a typical tropical genesis.  However, more thunderstorms are beginning to develop closer to the center of circulation and the National Hurricane Center is giving Invest 91L an 80% chance of becoming a tropical cyclone.  The low is moving over water where the Sea Surface Temperature (SST) is around 27°C to 28°C, which is warm enough to support the development of a tropical cyclone.  The upper level low was generating vertical wind shear, but if the surface low develops under the center of the upper low, then the wind shear will have less of an effect.  If more thunderstorms form near the center of circulation and a warm core develops, then the low could be classified as a tropical storm on Monday.  Some intensification is possible because of the warm SSTs.

An upper level ridge centered over the southeastern U.S. is expected to steer the system toward the northwest and it could make landfall on the coast of Texas in 24 to 48 hours.  The primary risk will be locally heavy rainfall, although a minor storm surge could occur in some coastal locations.

Possible Tropical Development in Western Gulf of Mexico

An area of showers and thunderstorms near the Yucatan Peninsula has shown signs of a cyclonic circulation, although the rotation may be in the middle troposphere and not at the surface.  The formal designation of this system is Invest 91L.  At 2:00 p.m EDT on Saturday the center of Invest 91L was located at latitude 20.0°N and longitude 88.4°W which put it about 100 miles (165 km) southeast of Merida, Mexico and about 760 miles (1220 km) south-southeast of Galveston, Texas.  Invest 91L was moving toward the northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1009 mb.  The National Hurricane Center is now giving Invest 91L a 50% chance of developing into a tropical depression or tropical storm in the next five days.  An additional reconnaissance plane has been scheduled to investigate it on Sunday afternoon.

The circulation of Invest 91L is not very well organized.  Almost all of the showers and thunderstorms are occurring in the eastern half of the circulation.  Visible satellite images indicate a possible center of cyclonic rotation over the Yucatan peninsula, but it is not clear if the rotation extends all of the way down to the surface.  Counterclockwise winds around an upper level low over the Gulf of Mexico are generating significant vertical wind shear over Invest 91L.  However, the upper level winds east of the upper low are diverging, which is enhancing rising motion and is supporting the development of the showers and thunderstorms in that area.  The upper level divergence is also causing the surface pressure to decrease slowly, which could lead to the formation of a surface center of low pressure.

When Invest 91L moves into the southern Gulf of Mexico, it will move over water where the Sea Surface Temperature is near 27°C to 28°C.  So, there is sufficient energy in the upper ocean to support the development of a tropical cyclone.  The key factor will be the interaction between the upper low and any surface center that forms.  If the surface center forms too close to the upper low, then vertical wind shear will likely inhibit development and the system will remain fairly weak.  If the surface low develops a little farther southeast of the upper low, then there will be less shear and more upper level divergence.  That could allow for more intensification.

Invest 91L is expected to move with the upper low as the upper low moves northward.  Most guidance from numerical models moves the system toward the north-northwest toward the Upper Texas Coast.  However, there will be above normal uncertainty in the track until a well defined center of circulation forms at the surface.

Interests in the western Gulf of Mexico should monitor the progress of Invest 91L.