Category Archives: Eastern and Central Pacific

TCs between Mexico and Hawaii

Tropical Storm Darby Moves Closer to Hawaii and Watches Issued

Tropical Storm Darby moved closed to Hawaii on Thursday and Tropical Storm Watches were issued for some of the islands.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Darby was located at latitude 18.9°N and longitude 147.5°W which put it about 500 miles (800 km) east of Hilo, Hawaii.  Darby was moving toward the west at 13 m.p.h. (20 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 997 mb.

A Tropical Storm Watch has been issued for Hawaii County and Maui County including the islands of Maui, Molokai, Lanai, and Kahoolawe.

Tropical Storm Darby is maintaining its structure.  A primary rainband wraps around the north and west sides of the center of circulation.  Strong thunderstorms continue to develop close to the center of circulation.  Those thunderstorms are producing upper level divergence.  Darby is a small tropical storm.  Winds to tropical storm force extend out about 100 miles (160 km) on the north side of the circulation, but they only extend out about 50 miles (80 km) to south of the center.

Tropical Storm Darby is moving through an environment that is marginal for intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 27°C.  So, there is enough energy in the upper ocean to support a tropical cyclones.  However, an upper level ridge centered west of Hawaii is generating northeasterly winds which are blowing over the western half of the circulation.  The moderate vertical wind shear is inhibiting intensification.  Darby maintained its intensity on Thursday as the positive and negative environmental factors effectively balanced each other out.  Darby could continue to maintain its intensity for several more days until it moves over cooler SSTs and into a region of stronger vertical wind shear.

A subtropical ridge north of Darby is steering the tropical storm toward the west.  That general motion is forecast to continue for another 36 hours.  On its anticipated track Tropical Storm Darby could approach the Big Island of Hawaii in about 36 hours.  It could bring tropical storm force winds to that island.  In addition Darby could cause heavy rain and flash flooding in locations where the wind blows up the slopes on the islands.

Tropical Storm Frank and Tropical Depression 08E Form

The National Hurricane Center designated two new systems over the Eastern North Pacific Ocean as tropical cyclones on Thursday afternoon.  Tropical Storm Frank was the sixth tropical storm to form over the Eastern North Pacific during the month of July.  The record for tropical storms forming in July is seven.  If Tropical Depression 08E intensifies into a tropical storm then 2016 will tie the record for the most tropical storms to form over the Eastern Pacific during July.

At 5:00 p.m. EDT on Thursday the center of Tropical Storm Frank was located at latitude 14.9°N and longitude 104.0°W which put it about 675 miles (1085 km) southeast of the southern tip of Baja California.  Frank was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1005 mb.

At 5:00 p.m. EDT on Thursday the center of Tropical Depression 08E was located at latitude 10.8°N and longitude 114.0°W which put it about 880 miles (1415 km) south-southwest of the southern tip of Baja California.  The depression was moving toward the west-northwest at 12 m.p.h. (19 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 1006 mb.

Tropical Storm Frank is the larger and better organized system.  A primary rainband wraps about three-quarters of way around the western side of the center of circulation.  Additional rainbands are spiraling around the outer portion of Frank.  Thunderstorms near the center of circulation are generating upper level outflow which is pumping out mass in all directions.

The circulation of Tropical Depression 08E is smaller and less well organized.  A primary rainband wraps about half way around the western side of the center of circulation.  Other partial rainbands are evident, but most of the thunderstorms are occurring in the western half of the circulation.  If looks like some of the upper level outflow from Tropical Storm Frank could be causing vertical wind shear over Tropical Depression 08E.

The environment around Tropical Storm Frank is favorable for intensification.  Frank is moving over water where the Sea Surface Temperature is near 29°C.  In addition, Tropical Storm Frank appears to be located beneath an upper level anticyclone, which is enhancing the upper level divergence.  Frank is likely to intensify during the next several days and it could intensify rapidly once an inner core forms around an eye.

The environment around Tropical Depression 08E is not as favorable.  It is over water the Sea Surface Temperature is near 28°C.  Upper level outflow from the anticyclone over Tropical Storm Frank is generating easterly winds and moderate vertical wind shear over the depression.  If Tropical Depression 08E and Tropical Storm Frank move farther apart, then the shear could decrease and the depression could strengthen.

A subtropical ridge is steering both Tropical Storm Frank and Tropical Depression 08E toward the west-northwest.  However, a weaker area in the ridge is forecast to develop northwest of Frank and that could allow the tropical storm to move on a more northwesterly track.  On its anticipated track Tropical Storm Frank could move near the southern tip of Baja California on Sunday.

Tropical Storm Estelle Forms As Hurricane Darby Nears Peak Intensity

Tropical Storm Estelle developed late Friday over the Eastern North Pacific as Hurricane Darby neared its peak intensity farther west.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Estelle was located at latitude 15.2°N and longitude 108.3°W which put it about 370 miles (600 km) southwest of Manzanillo, Mexico.  Estelle was moving toward the west-northwest at 12 m.p.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 1005 mb.  Estelle is the fifth tropical storm to form over the Eastern North Pacific during the month of July.

Meanwhile, about 950 miles west of Estelle, Hurricane Darby neared its peak intensity.  At 11:00 p.m. EDT on Friday the center of Hurricane Darby was located at latitude 17.3°N and longitude 122.1°W which put it about 880 miles (1415 km) west-southwest of the southern tip of Baja California.  Darby was moving toward the west-northwest at 9 m.p.h.  The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 972 mb.

The large circulation around Tropical Storm Estelle is still organizing.  A primary rainband is wrapping around the western side of the center.  Several spiral bands of thunderstorms are forming farther away from the core of the tropical storm.  Storms near the center are beginning to produce upper level divergence, but it is not currently well developed.

The environment around Estelle is favorable for gradual intensification.  Estelle is moving over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Estelle is generating easterly winds which are blowing over the top of the tropical storm.  There is enough vertical wind shear to slow the rate of intensification, but the shear is probably not strong enough to keep Estelle from intensifying.  Storms like Estelle with large initial circulations can intensify slowly as a tighter core develops within the larger circulation.

Hurricane Darby is a well formed mature hurricane.  It has a well developed eye surrounded by a narrow ring of strong thunderstorms.  Several spiral bands are rotating around the core of Darby.  The thunderstorms near the center of circulation are generating upper level divergence which is pumping out mass in all directions.

Hurricane Darby is probably close to its peak intensity.  It is moving over water where the Sea Surface Temperature is near 27°C and Darby will be moving over cooler water during the next few days.  There is not much vertical wind shear, and Darby may have a chance to intensify during the next 12 to 24 hours.  However, Darby will reach cooler water in about a day and then the hurricane will being to weaken.

A subtropical ridge located north of Hurricane Darby and Tropical Storm Estelle is expected to steer both cyclones toward the west during the next few days.

Tropical Storm Darby Intensifies as Hurricane Celia Weakens

Tropical Storm Darby intensified on Tuesday as it moved in the trail of weakening Hurricane Celia.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Darby was located at latitude 15.4°N and longitude 110.4°W which put it about 520 miles (835 km) south of the southern tip of Baja California.  Darby was moving toward the west 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 1000 mb.

Farther west Hurricane Celia continued to weaken slowly on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Celia was located at latitude 18.0°N and longitude 110.4°W which put it about 1360 miles (2190 km) west of the southern tip of Baja California.  Celia was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 986 mb.

More thunderstorms developed near the center of Tropical Storm Darby on Tuesday.  However, most of the stronger thunderstorms were southwest of the center of circulation.  An upper level ridge near the west coast of Mexico was producing northeasterly winds which are blowing over the top of the tropical storm.  The vertical wind shear caused the asymmetric distribution of convection.  Despite the vertical wind shear the circulation in the lower levels was well developed.

Tropical Storm Darby is over water where the Sea Surface Temperature is near 30°C and Darby is expected to intensify into a hurricane.

Hurricane Celia is moving over water where the Sea Surface Temperature is near 25°C.  Since the hurricane is extracting less energy from the ocean, the thunderstorms are not as tall and Celia is slowly weakening.  The hurricane is in an area where the vertical wind shear is minimal and so the weakening trend is likely to occur at a slower rate than normal.

A subtropical ridge north of the Celia and Darby is steering the two tropical storms toward the west and that general motion is expected to continue for the next few days.

Hurricane Celia Develops West of Mexico

The next in a series of tropical systems over the Eastern North Pacific Ocean developed into Hurricane Celia on Sunday.  At 11:00 p.m. EDT on Sunday the center of Hurricane Celia was located at latitude 15.0°N and longitude 123.5°W which put it about 1040 miles (1675 km) west-southwest of the southern tip of Baja California.  Celia was moving toward the west at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 988 mb.

The circulation of Hurricane Celia is well developed.  A primary spiral band loops around the center of circulation and a small eye is apparent intermittently on satellite imagery.  The strongest winds are occurring within 20 miles (30 km) of the center of circulation.  Although there are numerous thunderstorms in the core of Hurricane Celia, they are not as tall as one might expect.  It could be that slightly cooler water was mixed to the surface by Hurricane Blas and the cooler water is causing the thunderstorms to reach their Equilibrium Level at a lower height.  In spite of the shorter thunderstorms, the circulation is generating upper level divergence in all directions.

The environment is favorable for intensification.  Hurricane Celia is moving over water where the Sea Surface Temperature (SST) is near 28°C.  The winds in the upper levels are weak and there is not much vertical wind shear.  Celia could intensify while is remains over warmer SSTs.  The hurricane will start to move over cooler SSTs in about another 24 hours, which will contribute to a less favorable environment.

A subtropical high pressure system north of Celia is steering the hurricane toward the west and that general motion is expected to continue during the next few days.  On its anticipated track Hurricane Celia will continue to move farther away from Mexico.

Blas Strengthens to Cat. 4 Hurricane

Hurricane Blas strengthened rapidly Tuesday to a Category 4 hurricane on the Saffir-Simpson Scale.  At 11:00 p.m. EDT on Thursday the center of Hurricane Blas was located at latitude 14.4°N and longitude 121.7°W which put it about 970 miles (1560 km) west-southwest of the southern tip of Baja California.  Blas was moving toward the west at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 140 m.p.h. (220 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  The minimum surface pressure was 947 mb.

The Hurricane Intensity Index (HII) for Blas was 28.2.  The Hurricane Size Index (HSI) was 12.2 and the Hurricane Wind Intensity Size Index (HWISI) was 40.4.

The circulation of Hurricane Blas is fairly symmetrical and well organized, although many of the stronger thunderstorms are occurring in the southeastern quadrant.  Blas has a clear eye which is surrounded by a ring of strong thunderstorms.  Those storms generated upper level divergence which pumped out a lot of mass in all directions and allowed the pressure to decrease rapidly on Tuesday.

Hurricane Blas is in an environment that is favorable for strong hurricanes.  It is moving over water where the Sea Surface Temperature is near 29°C.  The winds in the upper levels are light and there is not much vertical wind shear.  Hurricane Blas could get stronger on Wednesday.  However, eyewall replacement cycles sometimes occur in strong hurricanes.  When an eyewall replacement cycle occurs, it can bring an end to a period of intensification.

A ridge of high pressure located north of Blas is steering the hurricane toward the west and that motion is expected to continue for several more days.  Hurricane Blas continues to move farther away from Mexico.

Blas Intensifies Into a Hurricane

Tropical Storm Blas intensified into the first Eastern North Pacific hurricane of 2016 on Monday.  At 5:00 p.m. EDT on Monday the center of Hurricane Blas was located at latitude 13.7°N and longitude 115.7°W which put it about 740 miles (1190 km) southwest of the southern tip of Baja California.  Blas was moving toward the west-northwest at 14 m.p.h. (22 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 994 mb.

The Hurricane Intensity Index (HII) for Blas was 10.4.  The Hurricane Size Index (HSI) was 6.1.  The Hurricane Wind Intensity Size Index (HWISI) was 16.5.

The large circulation of Hurricane Blas is still organizing.  A primary rainband wrapped around the center of circulation and an eye may be forming in the center of Blas.  Additional bands of thunderstorms are spiraling around the core of Hurricane Blas.  The thunderstorms near the center of circulation are generating upper level divergence which is pumping out mass.  Despite the improved organization the wind field around Hurricane Blas is asymmetrical.  Winds to hurricane force are occurring primarily in the eastern half of the circulation.  The strongest winds extend out about 25 miles (40 km) east of the center of Hurricane Blas.  Winds to tropical storm force extend out about 150 miles (240 km) east of the center, but only about 80 miles (130 km) west of the center.

Hurricane Blas is in an environment that is favorable for further intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  An upper level ridge north of Blas is generating some northeasterly winds which are blowing over the top of the circulation.  The vertical wind shear is moderate.  It is slowing the rate of intensification, but the shear is unlikely to prevent Hurricane Blas from intensifying during the next several days.  Blas does have a chance to become a major hurricane later this week.

A ridge of high pressure is steering Hurricane Blas toward the west-northwest and that general motion is expect to continue for several more days.  Hurricane Blas is moving farther away from Mexico.

Tropical Storm Blas Forms West of Mexico

After having no tropical storms during the first month and a half of the Eastern North Pacific hurricane season, Blas became the second tropical storm to form in the past two days.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Blas was located at latitude 12.4°N and longitude 112.2°W which put it about 740 miles (1190 km) south-southwest of the southern tip of Baja California.  Blas was moving toward the west-northwest at 12 m.p.h. (19 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 1001 mb.

The circulation of Tropical Storm Blas organized quickly on Sunday.  A primary rainband wrapped around the western and southern portions of the center of circulation.  Additional rainbands spiraled around the core of the storm.  The intensity of the thunderstorms weakened for a few hours, but storms east of the center of the circulation are intensifying again.  Winds to tropical storm force extend out about 70 miles (115 km) from the center of circulation.

An upper level ridge northeast of Blas is causing some northeasterly winds to blow over the top of the tropical storm.  The winds are responsible for vertical wind shear and they are inhibiting upper level divergence to the east of the circulation.  Tropical Storm Blas is moving over water where the Sea Surface Temperature is near 29°C.  In spite of the vertical wind shear the environment is favorable for intensification and Blas could become a hurricane on Monday.

A ridge of high pressure north of Blas is steering the tropical storm toward the west-northwest and that general motion is expected to continue for the next several days.  Tropical Storm Blas is moving away from Mexico.

Tropical Depression 2E Intensifies Into Tropical Storm Agatha

Tropical Depression 2E intensified into Tropical Storm Agatha on Saturday morning.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Agatha was located at latitude 15.6°N and longitude 118.9°W which put it about 775 miles (1245 km) southwest of the southern tip of Baja California.  Agatha was moving toward the west-northwest at 12 m.p.h. (19 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 1005 mb.

The upper level winds blowing over the top to Tropical Depression 2E weakened and the vertical wind shear decreased.  Less vertical wind shear allowed thunderstorms on the northwestern side of the circulation to wrap around the southern side of the center.  With the center of circulation embedded near the main area of thunderstorms the National Hurricane Center named the system Tropical Storm Agatha.  Agatha is a small system and tropical storm force winds only extend out about 45 miles (75 km) from the center.

Agatha has a limited period in which to intensify further.  It is currently moving over water where the Sea Surface Temperature (SST) is near 28°C.  However, Agatha is moving toward cooler SSTs where there will be less energy to drive the circulation.  In addition, there is much drier air north and west of the tropical storm.  Since there is little vertical wind shear, Agatha could intensify during the next 12 to 24 hours.  It will start to weaken when it moves over the cooler SSTs.

A ridge of high pressure north of Agatha is steering the tropical storm toward the east-northwest and that general motion is expected to continue for another day or two.  Agatha currently poses no threat to land.

Agatha was named on July 2.  This is the latest date for the naming of the first tropical storm over the Eastern North Pacific since Ava was named in 1969.

Tropical Depression 2E Forms Southwest of Baja California

After a prolonged period of relatively quiet weather over the Eastern North Pacific Ocean, a tropical depression formed southwest of Baja California.  At 11:00 p.m. EDT on Friday the center of Tropical Depression 2E (TD2E) was located at latitude 14.7°N and longitude 116.7°W which put it about 730 miles (1170 km) southwest of the southern tip of Baja California.  TD2E was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1007 mb.

A tropical wave over the Eastern North Pacific Ocean developed a well defined low level circulation and the National Hurricane Center classified the system as Tropical Depression 2E on Friday night.  Although the structure of the low level wind field is symmetrical, most of the thunderstorms are located northwest of the center of circulation.  An upper level ridge north of the depression is generating easterly winds over the top of the circulation.  The vertical wind shear is causing the asymmetrical distribution of the thunderstorms.

The environment around Tropical Depression 2E is marginal for intensification because there are both positive and negative factors.  TD2E is moving over water where the Sea Surface Temperature is near 29°C.  So, there is plenty of energy in the upper ocean to support intensification.  However, the air to the west of the tropical depression is very dry, which will limit the growth of thunderstorms and the formation of rain bands in that part of the system.  In addition moderate vertical wind shear will also inhibit intensification.  Tropical Depression 2E could intensify during the weekend and it has a chance to become the first named storm of the 2016 Eastern Pacific hurricane season.  However, the potential for intensification is limited.

The ridge to the north of TD2E is expected to continue to steer it toward the west-northwest during the next several days.  Tropical Depression 2E poses no threat to land during the next five days.