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Tropical Storm Carlos Stationary South of Acapulco

Tropical Storm Carlos moved very little on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Carlos was located at latitude 14.7°N and longitude 100.6°W which put it about 160 miles (255 km) south-southwest of Acapulco and about 250 miles (405 km) south-southeast of Lazaro Cardenas, Mexico.  Carlos was stationary.  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were gusts to 70 m.p.h. (115 km/h).  The minimum surface pressure was 997 mb.

The intensity of Carlos changed little on Friday and the organization of the circulation fluctuated during the day.  The core of the circulation exhibited greater organization during the afternoon when more thunderstorms developed near the center.  Carlos remains over water where the Sea Surface Temperature (SST) is near 30°C.  At times it appears as though Carlos may be pulling in some sinking drier air from Mexico, because most of the thunderstorms are developing in the southern portion of the circulation.  An upper level ridge north of Carlos is generating some northeasterly winds that are affecting the outflow on the northern side of the tropical storm.  However, an upper level low over the Gulf of Mexico may be enhancing some upper level divergence on the eastern side of the storm.  If Carlos were to remain stationary for several more days, its winds would mix up cooler water.  Carlos should not have as big an effect on the SSTs as Blanca did when it was stationary, because Carlos is weaker than Blanca was.  The intensity forecast is highly uncertain because the SSTs are favorable for intensification, but drier air and vertical wind shear would tend to inhibit strengthening.  The most likely outcome is modest intensification during the weekend.

The interaction of the upper ridge over Mexico and the upper low over the Gulf of Mexico is creating a zone of weak steering winds near Carlos, which is the reason it has been stationary.  Eventually, during the weekend, the upper ridge is expected to move eastward and begin to steer Carlos toward the northwest.  On its anticipated track the center of Carlos is expected to remain off the coast of Mexico, but it is expected to move parallel to the coast.  Any deviation of the track to the east could bring the center very near the coast of Mexico.

TD Three-E Intensifies and Is Now Tropical Storm Carlos

A tight center of circulation consolidated in Tropical Depression Three-E and it intensified on Thursday.  It is now designated as Tropical Storm Carlos.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Carlos was located at latitude 14.5°N and longitude 100.4°W which put it about 170 miles (270 km) south of Acapulco, Mexico and about 235 miles (380 km) south-southeast of Zihuatanejo.  Carlos was moving toward the north-northwest at 2 m.p.h. (4 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were gusts to 70 m.p.h. (115 km/h).  The minimum surface pressure was 997 mb.  The government of Mexico has issued a Tropical Storm Watch for the portion of the coast from Acapulco to Zihuatanejo.

Although a tight circulation developed at the center of Carlos, it is still not fully organized.  Thunderstorms are developing mainly to the south of the core of the circulation.  Some spiral bands are beginning to form in the outer part of Carlos.  However, there are not as many thunderstorms in the northern half of the circulation which may be an indication that some drier air from Mexico could be getting pulled into the circulation.   Carlos is moving over water where the Sea Surface Temperature is near 30°C and there is sufficient energy in the upper ocean to support intensification.  An upper level ridge over Mexico is generating northeasterly winds over the top of Carlos and the vertical wind shear is inhibiting the development of the tropical storm.  An upper level trough moving southward over the Gulf of Mexico could weaken the ridge for a day or two.  That could reduce the wind shear and allow Carlos to intensify into a hurricane.

As the upper level trough weakens the ridge, the steering currents will remain weak and Carlos could move slowly toward the coast of Mexico.  The ridge is forecast to strengthen over the weekend and if that happens it will steer Carlos toward the northwest.  On its anticipated track, Carlos will approach and then move parallel to the coast of Mexico.  Most of the guidance from numerical models keeps Carlos off the coast during the next few days, but it could get close enough to bring some wind to the coast.  That is the reason why the government of Mexico issued a Tropical Storm Watch for a portion of the coast.

Tropical Depression Three-E Forms South of Mexico

A low level circulation in a large area of thunderstorms south of Mexico showed evidence of more organization and the National Hurricane Center classified it as Tropical Depression Three-E on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Three-E (TD3E) was located at latitude 12.9°N and longitude 99.7°W which put it about 275 miles (445 km) south of Acapulco, Mexico.  TD3E was moving toward the northwest at 10 m.p.h. (17 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 1003 mb.

The circulation of TD3E is still organizing and there could be multiple smaller centers of circulation rotating around inside a larger, broader center of low pressure.  The tropical depression is moving over water where the Sea Surface Temperature is near 30°C, which means there is plenty of energy in the upper ocean to support intensification.  An upper level high ridge over Mexico is generating modest amounts of vertical wind shear over TD3E.  The wind shear could slow the organization and intensification of the depression, but it should not prevent it.  The rate of intensification could quicken after the circulation becomes more well organized.

The ridge over Mexico is currently steering TD3E toward the northwest.  Guidance from numerical models is inconsistent about the future track of the depression.  Some models predict the ridge over Mexico will weaken and that TD3E will move northward toward the coast.  Other models maintain the ridge and forecast the depression will move northwest and stay west of the coast of Mexico.  The current motion of TD3E may suggest that the latter scenario has a higher probability of being correct, but there is still significant uncertainty about its future track.

Tropical Cyclone Ashobaa Moving Slowly Toward Oman

Tropical Cyclone Ashobaa moved slowly westward toward Oman on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Ashobaa was located at latitude 20.6°N and longitude 61.1°E which put it about 160 miles (260 km) east of Masirah Island, Oman.  Ashobaa was moving toward the west at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 992 mb.

Most of the strong thunderstorms are occurring south and west of the center Ashobaa.  An upper level ridge located over southern Asia is generating easterly winds over the top of the tropical cyclone.  Those easterly winds are producing moderate amounts of vertical wind shear and account for the asymmetric distribution of thunderstorms.  Ashobaa is moving over warm Sea Surface Temperatures and there is enough energy in the upper ocean to support intensification.  However, the vertical shear is strong enough to inhibit intensification.  Once Ashobaa moves closer to the coast of Oman, the circulation will begin to pull in drier air from land.  The tropical cyclone could start to weaken before the center moves on land.

The ridge over southern Asia strengthened on Wednesday and it pushed Ashobaa a little south of due west.  The ridge is expected to remain in place and to continue steering the tropical cyclone westward for the next several days.  On its anticipated track, Ashobaa would make landfall in Oman in about 24 to 36 hours.

Tropical Cyclone Ashobaa Moves Toward Oman

Tropical Cyclone Ashobaa turned toward the west on Tuesday and it now appears on track to make a landfall in Oman.  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone Ashobaa was located at latitude 21.2°N and longitude 61.6°E which put it about 200 miles (325 km) east-northeast of Masirah Island, Oman.  Ashobaa was moving toward the west-northwest at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 985 mb.

The circulation around Tropical Cyclone Ashobaa is showing signs of greater organization.  A band of thunderstorms has wrapped around the southern portion of the center of circulation and it could represent the formation of a partial eyewall.  Ashobaa is moving over water where the Sea Surface Temperature is warm, but an upper level ridge north of the tropical cyclone is generating easterly winds.  Those winds are producing some vertical wind shear which is inhibiting intensification.  The shear decreased somewhat on Tuesday and there was a modest increase in the wind speed.  The strong thunderstorms near the center of Ashobaa are generating some upper level divergence, mainly on the western side of the circulation and the tropical cyclone could intensify further during the next 24 hours.  As the circulation nears the coast of Oman, the circulation will start to pull in drier air from land and Ashobaa will start to weaken.

An upper level ridge north Ashobaa has strengthened and it appears the ridge will steer the tropical cyclone westward to the coast of Oman.  On its anticipated track the center of Tropical Cyclone Ashobaa will approach the coast of Oman near As Suwayh in about 24 hours.

Tropical Cyclone Ashobaa Moving South of Pakistan

Tropical Cyclone Ashobaa moved northwestward across the Arabian Sea south of Pakistan on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Ashobaa was located at latitude 20.4° and longitude 64.8°W which put it about 340 miles (550 km) south-southwest of Karachi, Pakistan.  Ashobaa was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

More thunderstorms developed near the center of Ashobaa on Monday, but vertical wind shear is still inhibiting intensification.  Ashobaa is moving over water where the Sea Surface Temperature (SST) is warm and there is sufficient energy in the upper ocean to promote intensification.  The circulation is extracting energy from the ocean and it is generating vigorous convection west of the center of circulation.  However, an upper level ridge over southern Asia is creating moderate easterly winds over the top of Ashobaa.  The resulting vertical wind shear is the reason why the strongest storms are west of the center.  Ashobaa will spend several more days in a thermodynamic environment that favors intensification and if the upper level winds lessen, it will intensify.  Eventually, when Ashobaa gets closer to land, the circulation will start to pull in drier air, which will weaken the tropical cyclone.

A ridge over India is steering Ashobaa toward the northwest.  A trough passing north of the Arabian Sea is expected to weaken the western end of the ridge and cause the tropical cyclone to turn more toward the north for a time.  Eventually, most models are forecasting that the ridge will rebuild and steer Ashobaa toward the west-northwest.   However, some models are still predicting that Ashobaa could move northward and make landfall on the northern coast of the Arabian Sea.  The spread in the guidance from the models makes the long-term track more uncertain.

Tropical Cyclone 01A Forms Over the Arabian Sea

A low level circulation formed within a larger area of thunderstorms over the Arabian Sea and the system was classified as Tropical Cyclone 01A.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone 01A was located at latitude 18.0°N and longitude 67.5°E which put it about 490 miles (790 km) south of Karachi, Pakistan.  It was moving toward the north-northwest at 10 m.p.h. (17 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were gusts to 60 m.p.h. (75 km/h).  The minimum surface pressure was 994 mb.

Tropical Cyclone 01A is over warm Sea Surface Temperatures and there is sufficient energy in the upper ocean to support further intensification.  An upper level ridge over India is creating some easterly wind over the cyclone.  The strongest thunderstorms are occurring in the western half of the core of the cyclone.  The shear will inhibit intensification, but Tropical Cyclone 01A is likely to intensify during the next day or two.  Uncertainty about the future track of the cyclone also creates uncertainty about the longer term intensity forecast.

Tropical Cyclone 01A is moving northward around the western end of the ridge over India.  A trough farther to the north over Asia is expected to weaken the ridge and at that point the steering pattern will weaken.  Model guidance is inconsistent about the future track of the cyclone.  Some models forecast that Tropical Cyclone 01A will continue to move northward into Pakistan.  Other models predict that the cyclone could curve westward before it reaches Pakistan.  Thus, there is a high degree of uncertainty about the future track of Tropical Cyclone 01A.

Tropical Storm Blanca Passing West of Cabo San Lucas and Weakening

The center of Tropical Storm Blanca is passing west of Cabo San Lucas and it is weakening as it moves over cooler Sea Surface Temperatures.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Blanca was located at latitude 22.3°N and longitude 111.2°W which put it about 95 miles (150 km) west-southwest of Cabo San Lucas, Mexico and about 185 miles (300 km) south-southeast of Cabo San Lazaro.  Blanca was moving toward the north-northwest at 10 mp.h. (17 km/h).  The maximum sustained wind speed was 65 m.p.h. (100 km/h) and there were gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 988 mb.

Blanca will continue to weaken as it moves toward the southwestern part of Baja California.  However, it could still produce locally heavy rainfall and a potential for flooding exists.  It is possible that the upper portion of the circulation will detach from the lower portion of the circulation.  If that happens, then the upper part of the circulation will be pulled northward toward the southwestern U.S., while the lower portions moves slowly toward Baja California.  The upper portion could bring some additional moisture to the southwestern U.S. during the early part of next week.

Hurricane Blanca Heading for West Coast of Baja California

Hurricane Blanca turned toward the north-northwest on Saturday and it appears headed toward the west coast of Baja California.  At 11:00 p.m. EDT on Saturday the center of Hurricane Blanca was located at latitude 19.2°N and longitude 110.4°W which put it about 255 miles (415 km) south of Cabo San Lucas, Mexico.  Blanca was moving toward the north-northwest at 10 m.p.h. (17 km/h).  The maximum sustained wind speed was 120 m.p.h. (185 km/h) and there were gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 952 mb.  The Hurricane Intensity Index (HII) was 22.1, the Hurricane Size Index (HSI) was 20.2 and the Hurricane Wind Intensity Size Index (HWISI) was 42.3.  The government of Mexico has issued a Hurricane Watch for the portion of the coast from Cabo San Lucas to Santa Fe.  A Tropical Storm Warning has been issued for the portion of the coast from Loreto to Puerto San Andresito including Cabo San Lucas.  Tropical Storm Watches have been issued for the portions of the coast from Puerto San Andresito to Punta Abreojos and from Loreto to Mulege.

Hurricane Blanca intensified early on Saturday as it was moving over water where the Sea Surface Temperature (SST) was near 28°C.  It is currently over water where the SST is closer to 27°C and it will move over cooler water when it gets north of latitude 20°N.  As a result it will be unable to extract enough energy from the upper ocean to maintain its current intensity.  An upper level ridge over Mexico also seems to be generating some easterly winds near Blanca and those winds are responsible for vertical wind shear on the eastern half of the circulation.  The combination of shear and cooler SSTs should steadily weaken the hurricane on Sunday.  However, it has a well organized circulation and it will spin down relatively slowly.  The rate of weakening will increase once it moves over SSTs that are cooler than 26°C.  Blanca could still have hurricane force winds when it nears the southern tip of Baja California.

A mid-level ridge over Texas and northern Mexico and a trough over the southwestern U.S. are combining to steer Blanca toward the north-northwest.  That track should continue as long as the vertical structure of the hurricane remains intact.  As Blanca weakens over cooler water, the vertical integrity of the circulation will not be as strong.  Some storms that move just west of Baja California, as Blanca is forecast to do, have the upper portion of their circulation decouple from the lower level circulation.  In those cases the middle and upper level portions of the circulation continue to move northward across Baja California and into the southwestern U.S., while the low level circulation stalls and spins down west of Baja California.  On its anticipated track Blanca could bring some strong winds to portions of southern Baja California, but the greater risks are high waves and locally heavy rainfall that could produce flooding.

 

Tropical Storm Watch Issued for Southern Part of Baja California

The government of Mexico issued a Tropical Storm Watch for the southern portion of Baja California.  At 5:00 p.m. EDT on Friday the center of Hurricane Blanca was located at latitude 15.3°N and longitude 107.5°W which put it about 550 miles (880 km) south-southeast of Cabo San Lucas, Mexico and about 330 miles (535 km) southwest of Manzanillo, Mexico.  Blanca was moving toward the northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 90 m.p.h. (150 km/h) and there were gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 976 mb.  The Hurricane Intensity Index (HII) was 13.9, the Hurricane Size Index (HSI) was 17.7 and the Hurricane Wind Intensity Size Index (HWISI) was 31.6.  A reconnaissance aircraft investigated Blanca on Friday afternoon and so there is high confidence in the data about its strength and position.  The government of Mexico issued a Tropical Storm Watch for the portion of the coast from La Paz to Santa Fe including Cabo San Lucas.

Satellite imagery and data from the reconnaissance plane indicate that the structure of Blanca is more well organized.  A ring of thunderstorms surrounds a circular eye with a diameter of about 60 miles (65 km).  However, the better organization has not produced an increase in the wind speed as yet.  However, the aircraft did find winds to 105 m.p.h. (170 km/h) in the northwestern portion of the eyewall.  If downdrafts in thunderstorms in the eyewall bring those winds to the surface, then there could be some intensification.

Blanca is moving over water where the Sea Surface Temperature (SST) is about 29°C and there is sufficient energy in the upper ocean to support some increase in wind speed.  As the hurricane moves farther north it will move over cooler SSTs and when it gets near latitude 20°N in about 36 hours, it will start to move over much cooler water.  So, there is a potential for some intensification on Saturday, but Blanca will start to weaken as it approaches the southern tip of Baja California on Sunday.

A ridge northeast of Blanca and a trough west of Baja California are combining to steer Blanca toward the northwest.  As it moves farther north, it is likely to turn a little more toward the north.  Blanca is likely to approach the southern tip of Baja California on Sunday which is the reason for the Tropical Storm Watch.