Monthly Archives: July 2016

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.

Weakened Tropical Storm Nepartak Still Bringing Rain to Parts of China and Taiwan

Although Tropical Storm Nepartak was weakened significantly during its passage over the mountains on Taiwan, it is still producing heavy rain over portions of eastern China and Taiwan.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Nepartak was located at latitude 24.0°N and longitude 119.0°E which put it about 100 miles (160 km) east-southeast of Xiamen, China.  Nepartak was moving toward the northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 70 m.p.h. (115 km/h) and there were wind gusts to 85 m.p.h. (140 km/h).  The minimum surface pressure was 978 mb.

Typhoon Nepartak brought damaging winds and heavy rainfall to Taiwan when the core of the tropical cyclone passed over that area.  The mountains on Taiwan significantly disrupted the lower levels of the circulation.  There are some indications on satellite imagery that the upper portion of the circulation is located northwest of the surface center.  When a typhoon crosses Taiwan, the mountains can cause the original center of circulation to weaken and a new center can sometimes form over the water on the downstream side of the island.

In any case, crossing over Taiwan caused Nepartak to weaken to a tropical storm and the circulation no longer exhibits a tight inner core.  However, there are still rainbands that are producing heavy rain and wind speeds to almost typhoon force.   Because Nepartak no longer has a tight inner core, it is unlikely to intensify significantly before the centers moves into eastern China.

A ridge northeast of Nepartak is steering the tropical storm toward the northwest and that general motion is expected to continue for the next 12 to 24 hours.  After that time Nepartak is expected to turn toward the north.  On its anticipated track Tropical Storm Nepartak will make landfall in China between Xiamen and Fuqing on Saturday.

Tropical Storm Nepartak could produce locally heavy rainfall over portions of eastern China.  Some of that region has already received a lot of rain from other weather systems.  So, the potential for additional flooding is high in some areas.

Typhoon Nepartak Pounding Taiwan

Typhoon Nepartak is pounding Taiwan with strong winds and heavy rain.  The eye will make landfall during the next few hours near T’aitung.  At 5:00 p.m. EDT on Thursday the center of Typhoon Nepartak was located at latitude 22.7°N and longitude 121.4°E which put it about 185 miles (305 km) south of Taipei, Taiwan.  Nepartak was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 926 mb.

Typhoon Nepartak is the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) for Nepartak is 31.5.  The Hurricane Size Index (HSI) is 20.5, and the Hurricane Wind Intensity Size Index (HWISI) is 52.0.  These indices mean that Typhoon Nepartak is capable of causing widespread significant damage as it crosses Taiwan.

In addition to the strong winds locally heavy rain could cause flash floods, especially in the mountains of Taiwan.

The circulation of Typhoon Nepartak is very well organized.  It has a well formed eye which is surrounded by a ring of strong thunderstorms.  Numerous rainbands are rotating around the typhoon.

The atmospheric environment is favorable for strong tropical cyclones.  The winds in the upper levels are weak and there is little vertical wind shear.  However, the mountains on Taiwan will disrupt the lower part of the circulation and Typhoon Nepartak will weaken significantly when it crosses the island.  It will take about 12 hours for the typhoon to move across Taiwan.  Nepartak could still be a typhoon when the center emerges over the Taiwan Strait on Friday.

Typhoon Nepartak is expected to also make landfall on the east coast of China between Xiamen and Fuzhou.  Although it will be much weaker, Nepartak could cause some wind damage when it reaches China.  However, heavy rain will be a greater risk because it cause significant flooding in parts of eastern China.

Dangerous Super Typhoon Nepartak Closing In On Taiwan

Dangerous Super Typhoon Nepartak closed in on Taiwan on Wednesday.  At 11:00 a.m. EDT on Wednesday the center of Typhoon Nepartak was located at latitude 20.5°N and longitude 126.3°E which put it about 480 miles (775 km) southeast of Taipei, Taiwan. Nepartak was moving toward the west-northwest at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 210 m.p.h. (335 km/h).  The minimum surface pressure was 911 mb.

Typhoon Nepartak is the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) for Nepartak was 40.3.  The Hurricane Size Index (HSI) was 18.8 and the Hurricane Wind Intensity Size Index (HWISI) was 59.1.  These indices mean that Typhoon Nepartak is capable of producing regional catastrophic damage.  As a point of comparison, Typhoon Nepartak is almost as strong as and slightly smaller than Hurricane Rita was when Rita was a Category 5 hurricane over the Gulf of Mexico in 2005.

The circulation of Typhoon Nepartak is very well organized.  It is symmetrical and winds to typhoon force extend out about 45 miles (75 km) from the center.  There is a very small eye at the center of Nepartak and the eye is surrounded by a ring of very strong thunderstorms.  The thunderstorms around the eye are generating strong upper level divergence which is offsetting the flow of mass into the typhoon near the surface.  The upper level divergence is allowing the pressure to stay low and strong winds to persist.  Spiral bands of thunderstorms are rotating around the core of the typhoon.

Typhoon Nepartak is in an ideal environment for a tropical cyclone.  It is moving over water where the Sea Surface Temperature (SST) is near 31°C.  The upper level winds are weak and there is almost no vertical wind shear.  Typhoon Nepartak is likely to maintain its intensity as it approaches the coast of Taiwan.

A subtropical ridge northeast of Nepartak is steering the typhoon toward the west-northwest and that general motion is expected to continue for another 24 to 36 hours.  On its anticipated track Typhoon Nepartak will make landfall along the central portion of the east coast of Taiwan in 12 to 18 hours.  After it moves across Taiwan, Nepartak is expected to make another landfall on the east coast of China.

Nepartak is a strong and dangerous typhoon.  It is capable of causing catastrophic damage over portions of Taiwan.  Nepartak will also produce very rainfall which is likely to cause flash floods and mudslides.  Nepartak will weaken when it moves over Taiwan, but it could still be a typhoon when it reaches the east coast of China.  Nepartak could also bring heavy rain and floods to parts of eastern China.

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.

Typhoon Nepartak Rapidly Intensifies As It Moves Toward Taiwan

Typhoon Nepartak intensified rapidly on Tuesday and it is now the equivalent of a major hurricane.  At 11:00 a.m. EDT on Tuesday the center of Typhoon Nepartak was located at latitude 17.6°N and longitude 132.7°E which put it about 945 miles (1525 km) east-southeast of Taipei, Taiwan.  Nepartak was moving toward west-northwest at 21 m.p.h. (34 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (270 km/h).  The minimum surface pressure was 933 mb.

Tyyphoon Nepartak is the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) for Nepartak is 28.3.  The Hurricane Size Index (HSI) is 16.6 and the Hurricane Wind Intensity Size Index (HWISI) is 44.9.  These indices mean that Nepartak is capable of causing regionalized significant damage.

Typhoon Nepartak is very well organized.  It has a well formed eye, which is surround by a ring of strong thunderstorms.  Additional spiral bands of thunderstorms are rotating around the core of the circulation.  Nepartak is generating strong upper level divergence which is pumping out a lot of mass and is allowing the surface pressure to decrease rapidly.

Typhoon Nepartak is in an environment that is favorable for further intensification.  It is moving over water where the Sea Surface Temperature (SST) is near 31°C.  The upper level winds are weak and there is very little vertical wind shear.  Nepartak could intensify into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale during the next 24 to 36 hours.  If one of the rainbands wraps around the existing eye, then concentric eyewalls could form.  If concentric eyewalls develop, then an ensuing eyewall replacement cycle could cause fluctuations in the intensity of Typhoon Nepartak.

A subtropical ridge northeast of Nepartak is steering the typhoon toward the west-northwest and that general motion is expected to continue for another day or two.  On its anticipated track Typhoon Nepartak could be very near the southernmost islands of Japan and the coast of Taiwan in 36 to 48 hours.  It is likely to be a strong typhoon at that time.  Nepartak could cause significant wind damage.  It could also produce heavy rain that could lead to flash floods and mudslides.

Nepartak Intensifies Into a Typhoon

Tropical Storm Nepartak intensified into a typhoon on Monday as it moved west of Guam.  At 11:00 p.m. EDT on Monday the center of Typhoon Nepartak was located at latitude 15.8°N and longitude 136.0°E which put it about 870 miles (1400 km) southeast of Okinawa.  Nepartak was moving toward the west-northwest at 20 m.p.h. (32 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 974 mb.

The Hurricane Intensity Index (HII) for Typhoon Nepartak was 10.4.  The Hurricane Size Index (HSI) was 3.7 and the Hurricane Wind Intensity Size Index (HWISI) was 14.1.

The structure of Typhoon Nepartak improved on Monday.  A circular area of strong thunderstorms developed at the center of circulation.  Those thunderstorms generated upper level divergence that pumped out mass in all directions, which allowed the surface pressure to decrease.  Several other bands of thunderstorms spiraled around the core of Nepartak.

Typhoon Nepartak is moving over water where the Sea Surface Temperature (SST) is near 31°C.  Nepartak moved into an area where the upper level winds were weaker and the vertical wind shear was reduced.  The combination of very warm water and reduced shear allowed Nepartak to organize and strengthen into a typhoon.  It is expected to remain in an environment favorable for intensification, and Nepartak will grow into a stronger typhoon during the next several days.

A ridge of high pressure northeast of Nepartak is steering the typhoon toward the west-northwest and that general motion is expected to continue for the next several days.  On its anticipated track Typhoon Nepartak could be approaching the southernmost islands of Japan and Taiwan in 48 to 60 hours.  It could be a very strong typhoon at that time.

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.