Category Archives: Eastern and Central Pacific

TCs between Mexico and Hawaii

Tropical Storm Pali Forms Southwest of Hawaii

A surface circulation organized quickly on Thursday in an area of thunderstorms southwest of Hawaii and the Central Pacific Hurricane Center designated the system as Tropical Storm Pali.  At 4:00 p.m. EDT on Thursday the center of Tropical Storm Pali was located at latitude 4.7°N and longitude 171.2°W which put it about 1450 miles (2335 km) southwest of Honolulu, Hawaii.  Pali was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1000 mb.

Several well formed spiral bands developed within a large area of thunderstorms and the system exhibited sufficient organization to be classified as a tropical storm.  Two of the inner spiral bands appear to be wrapping around the center of circulation and the inner core of Tropical Storm Pali is organizing quickly.  A partial eyewall may be forming around the southern and western sides of the center of circulation.  Thunderstorms near the core of Pali are generating upper level divergence, which is pumping out mass.

The environment surrounding Tropical Storm Pali is favorable for further intensification.  It is moving over water where the Sea Surface Temperatures are near 29°C.  An upper level ridge east of Pali is generating southeasterly winds over the top of the tropical storm, but the vertical wind shear is not too strong.  Pali is likely to intensify further during the next 24 hours.  A period of rapid intensification may be possible, if the inner core consolidates around an eye.

A subtropical ridge east of Pali is steering the tropical storm toward the north-northwest and that general motion is expected to continue.  However, the winds steering the storm are not too strong, and it may not move much during the next several days.

Although the historical record of tropical storms over the Central Pacific is relatively short, it appears that Tropical Storm Pali may have reached tropical storm intensity at a lower latitude than any other tropical storm on record did in that region.

Tropical Depression 09C Forms Near Equator

Sufficient evidence of a surface center of circulation within a broad area of thunderstorms near the Equator prompted the Central Pacific Hurricane Center to classify the system as Tropical Depression 09C.  At 10:00 p.m. EST on Wednesday the center of Tropical Depression 09C (TD09C) was located at latitude 2.8°N and longitude 177.8°W which put it about 1850 miles (2975 km) southwest of Honolulu, Hawaii.  TD09C was moving toward the west-northwest at 8 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 1001 mb.

The circulation of Tropical Depression 09C is not particularly well organized and there may be multiple small centers inside the larger circulation of the system.  One small center of circulation is near a cluster of thunderstorms in the northern half of the circulation and that center is currently being designated as the center of TD09C.  Another circulation center is near latitude 1.0°N and longitude 174.6°W, but there are no thunderstorms near that center.  The main area of thunderstorms is north of the official center of circulation.  There are a few partial spiral bands northeast of the center of the depression.

The environment around TD09C is only marginal for intensification.  The depression is moving over water where the Sea Surface Temperatures are near 30°C.  So, there is plenty of energy in the upper ocean to support intensification.  However, a strong upper level ridge east of TD09C is generating strong southeasterly winds over the top of the depression.  The strong vertical wind shear is contributing to the poor organization of TD09C.  The wind shear is likely to inhibit intensification during the next several days.

A subtropical ridge east of TD09C is expected to steer the depression slowly toward the west-northwest during the next few days.  The actual track of TD09C could be somewhat erratic, especially if some of the small centers of circulation dissipate and additional centers form in clusters of thunderstorms that develop.  On its anticipated track Tropical Depression 09C could approach Tarawa in about three days and it could be approaching the Marshall Islands this weekend.

The most remarkable thing about Tropical Depression 09C is that is developed so close to the Equator.  Conventional wisdom often says that tropical cyclones cannot form near the Equator because the Coriolis effect is too small.  However, although tropical cyclones are rare near the Equator, Tropical Depression 09C is another example that they can form in that region.

Sandra Weakens to a Tropical Storm

Strong vertical wind shear weakened Hurricane Sandra to a tropical storm on Friday.  At 10:00 p.m. EST on Friday the center of Tropical Storm Sandra was located at latitude 21.2°N and longitude 108.8°W which put it about 155 miles (250 km) west of Las Islas Marias and about 205 miles (330 km) southwest of Mazatlan, Mexico.  Sandra was moving toward the north 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 990 mb.  Tropical Storm Warnings are in effect for the portion of the coast from Altata to San Blas, Mexico and for the Las Islas, Marias.

A large upper level trough centered over the southwestern U.S. generated strong southwesterly winds that blew the top half of Hurricane Sandra east of the low level circulation.  The strong wind vertical wind shear will continue, but it will take another day or two for the low level circulation to spin down.  Sandra could weaken to a tropical depression on Saturday and it could be classified as a remnant low by the end of the weekend.

Since the upper portion of the circulation is detached from the lower portion, the surface circulation is being steered by the winds in the lower atmosphere.  A ridge in the lower atmosphere is steering the surface circulation toward the north and that general motion is expected to continue for the next 24 to 48 hours.  On its anticipated track the surface center of Tropical Storm Sandra will pass near the southern tip of Baja California on Saturday.  The surface center could make landfall on the west coast of Mexico on Sunday.

Hurricane Sandra Turns Toward Mexico

Hurricane Sandra moved around the western end of a subtropical ridge and turned toward Mexico on Thursday.  At 10:00 p.m. EST on Thursday the center of Hurricane Sandra was located at latitude 18.0°N and longitude 109.7°W which put it about 340 miles (545 km) south of the southern tip of Baja California and about 490 miles (790 km) south-southwest of Culiacan, Mexico.  Sandra was moving toward the north at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h).  The minimum surface pressure was 956 mb.  The government of Mexico issued a Tropical Storm Watch for the coast of Baja California from Todos Santos to Los Barriles.

Hurricane Sandra appeared to develop concentric eyewalls on Thursday.  A primary rainband wrapped around the tiny pinhole eye at the center of the hurricane.  Satellite imagery suggests that the tiny inner eye still exists inside the larger outer eye.  Sandra reached Category 4 on the Saffir-Simpson Scale on Thursday morning, but the formation of concentric eyewalls weakened the hurricane back to Category 3 later in the day.  Sandra remains a well organized hurricane.  It has a well defined core surrounded by a ring of strong thunderstorms.  Spiral bands of storms are in the northeastern quadrant of the circulation.

Hurricane Sandra will move into a less favorable environment on Friday.  It will be over water where the Sea Surface Temperature is near 29°C.  However, a large upper level trough along the west coast of North America will generate strong southwesterly winds.  Those winds will cause strong vertical wind shear, which will tilt the circulation toward the northeast.  The upper level winds will also inhibit upper level divergence from the western part of Sandra.  The strong wind shear will weaken Hurricane Sandra on Friday.  Some models are predicting that the shear could be strong enough to blow the middle and upper parts of the circulation northeast of the low level circulation.  If that happens, then Hurricane Sandy could weaken very quickly,

The upper level trough will steer Hurricane Sandra toward the northeast on Friday.  Sandra will likely move faster toward the northeast by Friday night.  On its anticipated track Sandra could be near the southern tip of Baja California by Friday night and it could approach the west coast of Mexico on Saturday.  Sandra could still be a hurricane when it nears Baja California, but it is more likely to be a tropical storm.  It could be a tropical storm or depression by the time it reaches the west coast of Mexico.

Sandra Quickly Intensifies into a Major Hurricane

Hurricane Sandra intensified quickly into a major hurricane on Wednesday.  At 4:00 p.m. EST on Wednesday the center of Hurricane Sandra was located at latitude 13.0°N and longitude 109.9°W which put it about 685 miles (1100 km) south of the southern tip of Baja California.  Sandra was moving toward the northwest at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) which made Sandra a Category 3 hurricane on the Saffir-Simpson Scale and qualified it as a major hurricane.  There were wind gusts to 140 m.p.h. (225 km/h) and the minimum surface pressure was 967 mb.  Sandra is the ninth major hurricane to form over the Eastern North Pacific during 2015, which is a new record for that basin.

Sandra is a small well organized hurricane.  It has a well defined eye surrounded by a ring of thunderstorms, but hurricane force winds only extend out about 25 miles (40 km) from the center.  Thunderstorms in the core of Sandra are producing upper level divergence which is pumping out mass and allowing the surface pressure to decrease.  Sandra is an environment that favors further intensification.  It is over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is not much vertical wind shear.  Sandra could become a Category 4 hurricane on Thursday.

Hurricane Sandra is moving around the western end of a subtropical ridge to the east of it.  Sandra turned toward the northwest on Wednesday and it will gradually start moving more toward the north on Thursday.  A large deepening upper level trough off the west coast of North American will create southwesterly winds that will start to steer Sandra toward the northeast on Friday.  On its anticipated track Hurricane Sandra will approach the southern tip of Baja California on Friday night.

TD 22E Intensifies to Tropical Storm Sandra

A core circulation organized quickly on Tuesday inside Tropical Depression 22E and it intensified into Tropical Storm Sandra.  At 4:00 p.m. EST on Tuesday the center of Tropical Storm Sandra was located at latitude 11.9°N and longitude 107.2°W which put it about 780 miles south-southeast of the southern tip of Baja California.  Sandra was moving toward the west-northwest at 14 m.p.h. (22 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 997 mb.

Eastern upper level winds which were blowing over the top of Tropical Depression 22E diminished on Tuesday and the depression intensified into Tropical Storm Sandra.  A primary rainband wrapped around the center of circulation  and an inner core developed near the interior end of the band.  As the band wrapped around the center of circulation a ring of thunderstorms began to take on the structure of an eyewall.  Those thunderstorms also started to generate some upper level divergence.  The circulation of Sandra is still organizing and other spiral bands are starting to form.

Tropical Storm Sandra is in an environment that is favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.  Although there is still some vertical wind shear, it is much less than it was on Monday.  A combination of very warm water and little vertical wind shear could allow Sandra to intensify very quickly.  It is likely to become a hurricane with 12 to 18 hours and it could become a major hurricane within 24 to 36 hours.  In a couple of days Sandra will start to encounter strong upper level winds from the southwest.  The increased vertical wind shear at that time will cause it to weaken.

Tropical Storm Sandra is starting to move around the western end of a subtropical ridge that has been steering toward the north.  Sandra should gradually turn toward the north during the next 24 hours.  It is likely to move mainly toward the north until Thursday when southwesterly winds will turn it toward the northeast.  Sandra could be approaching the southern tip of Baja California by Friday night.

Tropical Depression 22E Forms Southwest of Mexico

A small center of circulation formed within a larger area of thunderstorms southwest of Mexico on Monday and the National Hurricane Center designated the system as Tropical Depression 22E.  At 4:00 p.m. EST on Monday the center of Tropical Depression 22E (TD22E) was located at latitude 10.8°N and longitude 102.9°W which put it about 465 miles (750 km) south-southwest of Acapulco, Mexico.  TD22E was moving toward the west at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were gusts to 45 m.p.h. (70 km/h).  The minimum surface pressure was 1005 mb.

TD22E is still in the early stages of an organizational process.  The small center of circulation is located near the western end of a long band of thunderstorms.  There are not many thunderstorms south and west of the center and there is not much evidence of spiral bands.  A subtropical ridge northeast of TD22E is pushing the depression quickly toward the west and its rapid movement is retarding the organizational process.

TD22E is currently in an environment that is marginal for intensification.  It is over water where the Sea Surface Temperature (SST) is near 30°C, which is very favorable for intensification.  However, the ridge northeast of TD22E is causing strong easterly winds to blow over the top of the depression.  The strong vertical wind shear and the rapid motion of the depression are negative factors for intensification.

As TD22E moves farther west, the vertical wind shear is expected to decrease and the depression is expected to move more slowly.  When that happens, TD22E will be able to more efficiently use the energy it is getting from the warm water and it will intensify.  A period of rapid intensification may occur once the core of the circulation is better organized.  TD22E could become a tropical storm on Tuesday and it could become a hurricane later this week.

The subtropical ridge is steering TD22E quickly toward the west.  In another 24 to 36 hours TD22E is likely to reach the western end of the ridge.  At that time it will slow down and turn toward the north.  TD22E will encounter southwesterly winds when it moves farther north.  Those winds will push TD22E toward the northeast later this week.  On its anticipated track TD22E could be near the southern tip of Baja California by the end of the week.

TD 21E Intensifies into Tropical Storm Rick

The organization of Tropical Depression 21E improved slightly on Thursday and the National Hurricane Center upgraded it to Tropical Storm Rick.  At 10:00 p.m. EST on Thursday the center of Tropical Storm Rick was located at latitude 15.2°N and longitude 108.1°W which put it about 365 miles (585 km) southwest of Manzanillo, Mexico.  Rick was moving toward the west-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 wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1002 mb.

More thunderstorms formed near the center of Tropical Depression 21E for a few hours on Thursday and the improved organization prompted the National Hurricane Center to upgrade the system to Tropical Storm Rick.  The organization of Rick has diminished in recent hours. The stronger thunderstorms are located northwest of the center of circulation and there are few thunderstorms in the rest of the Rick.  An upper level ridge located east of the tropical storm is producing southerly winds over the top of Rick.  The vertical wind shear is causing the stronger thunderstorms to be northwest of the center.

Rick is over water where the Sea Surface Temperature is near 29°C.  So, there is enough energy in the ocean to support intensification.  However, the strong vertical wind shear is likely to limit intensification and it could weaken Rick if it the shear gets stronger.

The ridge east of Rick is expected to strengthen and to continue to steer the tropical storm toward the west-northwest for another day or two.  After that time Rick will reach the western end of the ridge, and the tropical storm will turn more toward the north.

Poorly Organized Tropical Depression 21E Forms West of Mexico

A low level circulation center formed in a cluster of thunderstorms west of Mexico and the National Hurricane Center decided it had enough organization to be classified as a tropical depression.  At 10:00 p.m. EDT on Wednesday the center of Tropical Depression 21E (TD21E) was located at latitude 13.2°N and longitude 106.1°W which put it about 420 miles (675 km) south-southwest of Manzanillo, Mexico.  TD21E was moving toward the north at 2 m.p.h. (3 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 1004 mb.

TD21E looked more well organized earlier today when the low level center of circulation was located within the area of thunderstorms.  The low level center is now southeast of an area of weakening thunderstorms, which is an indication that the tropical depression is poorly organized.  Most of the remaining thunderstorms are located north of the low level center.

The tropical depression is over water where the Sea Surface Temperature is near 30°C.  However, the environment is not really favorable for intensification.  An upper level ridge east of the depression is causing southerly winds over the top of TD21E.  Those winds are generating vertical wind shear over the top of the depression.  The wind shear has blown the thunderstorms north of circulation center.  Some slight intensification may be possible if the wind shear decreases, but the poor organization of the depression will limit any potential strengthening.

If the tropical depression retains its vertical integrity, the southerly winds in the upper levels should push it toward the north.  However, if the wind shear blows the thunderstorms farther north of the low level center of circulation, then the low level center could remain stationary while it spins down.

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.