Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

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.

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.

Tropical Storm Nepartak Develops South of Guam

A center of circulation organized within an area of thunderstorms south of Guam and the system was designated Tropical Storm Nepartak.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Nepartak was located at latitude 12.2°N and longitude 141.4°E which put it about 215 miles (345 km) west-southwest of Guam.  Nepartak was moving northwest at 16 m.p.h. (26 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 989 mb.

The circulation of Tropical Storm Nepartak is still organizing.  A primary rainband wrapped around the center and a circular area of thunderstorms formed at the core of the circulation.  The area of thunderstorms is generating upper level divergence which is pumping out mass and allowing the surface pressure to decrease.  Winds to tropical storm force extend our about 100 miles (160 km) from the center of circulation.

An upper level low located north of Nepartak is producing southwesterly winds which area blowing over the top of the tropical storm.  Those winds are creating some vertical wind shear, which is slowing the intensification of Nepartak.  However, the upper low is also enhancing upper level divergence to the northeast of the tropical storm.  Nepartak is moving over water where the Sea Surface Temperature is near 30°C.  The environment is favorable for intensification and Nepartak could become a hurricane during the next several days.

A subtropical ridge located northeast of Nepartak is steering the tropical storm toward the northwest.  That general motion is expected to continue during the next few days.  On its anticipated track, Nepartak could be approaching the southernmost islands of Japan in three or four days.  It is likely to be a typhoon at that time.

Typhoon Melor Making Landfall on Mindoro as Equivalent of Cat. 4 Hurricane

Typhoon Melor intensified on Monday and it is making landfall on Mindoro in the Philippines as the equivalent of a Category 4 Hurricane on the Saffir-Simpson Scale.  At 10:00 p.m. EST on Monday the center of Typhoon Melor was located at latitude 13.0°N and longitude 121.5°E which put it about 20 miles (32 km) southeast of Calapan and about 125 miles (205 km) south-southeast of Manila, Philippines.  Melor was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 140 m.p.h. (230 km/h) and there were wind gusts to 170 m.p.h. (270 km/h).  The minimum surface pressure was 939 mb.

The core of Typhoon Melor passed just north of Samar and it quickly moved over the southeastern tip of Luzon.  Since the core stayed mainly over water, the circulation was not seriously disrupted by the increased friction that would have occurred if it had moved over land.  As a result, the core Typhoon Melor was intact when it moved over the Sibuyan Sea.  The circulation was able to extract energy from the warm water of Sibuyan Sea.  Melor was in an area where the upper level winds were light and there was little vertical wind shear.  The favorable environment allowed the typhoon to intensify further on Monday and Melor reached the equivalent of a Category 4 hurricane.

The center of Typhoon Melor is making a landfall on the northeast coast of Mindoro.  Since the core of Melor will be moving over the island of Mindoro during the next few hours, the typhoon should start to weaken.  Melor will likely still be a typhoon when the center emerges over the South China Sea.  A strong surge of cold, dry air from the north will increase vertical wind shear around Typhoon Melor in 24 to 36 hours.  The dry air and increased wind shear will weaken Melor more rapidly after that occurs.

A subtropical ridge is steering Typhoon Melor toward the west and that general motion is expected to continue for another 24 to 36 hours.  After that time a weakening Melor will be steered by the flow closer to the surface, which should start to push it toward the southwest.

Typhoon Melor will bring very strong winds and heavy rain to Mindoro and southern Luzon.  The core of Melor should stay south of Manila, but locally heavy rain may be possible.  Heavy rain could also cause flooding and mudslides in areas of steep terrain.

Strong Typhoon Melor Along Coast of Samar Heading for SE Luzon

Typhoon Melor reached the Philippines on Sunday and it was moving along the north coast of Samar toward southeastern Luzon.  At 10:00 p.m. EST on Sunday the center of Typhoon Melor was located at latitude 12.6°N and longitude 125.3°E which put it about 20 miles (32 km) north of Laoang, Philippines and about 100 miles (160 km) east-southeast of Legaspi in southeastern Luzon.  Melor was moving toward the west at 13 m.p.h. (21 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 949 mb.

Typhoon Melor has been moving through an environment favorable for intensification.  The Sea Surface Temperatures were near 28°C and there has been little vertical wind shear.  However, the circulation is starting to interact with the Philippines.  The southwestern quarter of the circulation is over Samar.  However, since the core of the circulation is north of the coast of Samar, Melor has remained a strong typhoon.  The circulation of Typhoon Melor is likely to retain much of its integrity until the center makes landfall in southeastern Luzon near Sorsogon.  Melor could remain at typhoon intensity for another 24 hours.  However, eventually the increased friction will slow the portions of the circulation that move over land and Melor will weaken to a tropical storm.

A subtropical ridge is steering Typhoon Melor slightly north of due west and that general motion is expected to continue for several more days.  On its anticipated track the core of Typhoon Melor will pass north of Samar.  It will make landfall on extreme southeastern Luzon near Sorsogon in a few hours.  The center of Melor should pass south of Legaspi before moving over the Sibuyan Sea.  It could move south of Manila in about 36 hours as a tropical storm.

Melor is a strong typhoon and it could bring strong winds and heavy rain to northern Samar, southeastern Luzon, the islands around the Sibuyan Sea and Mindoro.  Heavy rain could cause flooding and trigger mudslides, especially in areas of steep terrain.

Melor Intensifies into a Typhoon and Threatens the Philippines

Tropical Storm Melor continued to intensify on Saturday and it reached typhoon status.  At 10:00 p.m. EST on Saturday the center of Typhoon Melor was located at latitude 12.0°N and longitude 129.7°E which put it about 320 miles (520 km) east of Laoang, Philippines.  Melor was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 973 mb.

The structure of Typhoon Melor is well organized and an eye has appeared intermittently on satellite imagery.  Melor has a small, well developed inner core surrounded by multiple spiral rainbands.  Thunderstorms near the core are generating upper level divergence, especially to the northeast of the center of circulation.  The upper level divergence is pumping out mass and causing the surface pressure to decrease.

Typhoon Melor is in an environment that is favorable for further intensification.  It is moving over water where the Sea Surface Temperature is around 28°C.  An upper level ridge east of Melor is producing light southerly winds over the top of the typhoon, but the vertical wind shear is modest.  Melor is likely to continue to intensify on Sunday and it could become the equivalent of a major hurricane.

A subtropical ridge is steering Typhoon Melor toward the west-northwest and that general motion is expected to continue for another two or three days.  On its anticipated track Typhoon Melor could be near the northeast coast of Samar in about 24 hours.  The center of Melor could make landfall over southeast Luzon in about 36 hours.  Melor could bring strong winds and heavy rain.  The heavy rain could cause flooding and mudslides, especially in areas of steep terrain.

Tropical Storm Melor Forms West of Yap

A well defined center of circulation developed within an area of thunderstorms on Friday and the system was designated Tropical Storm Melor (28W).  At 4:00 p.m. EST on Friday the center of Tropical Storm Melor was located at latitude 10.4°N and longitude 134.9°E which put it about 210 miles (335 km) north-northeast of Koror, Palau.  Melor was moving toward the west-northwest at 17 m.p.h. (27 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 997 mb.

Tropical Storm Melor organized quickly on Friday.  A rainband wrapped about three quarters of the way around the center of circulation and an eyewall may be forming.  Outer rainbands are also rotating around the center of circulation.  Thunderstorms around the center of circulation are producing upper level divergence.

The environment around Tropical Storm Melor is favorable for further intensification.  It is over water where the Sea Surface Temperatures are warm.  An upper level ridge is producing light southerly winds over the top of Melor, but there is only modest vertical wind shear.  Once a fully developed eye forms at the center of Melor, the tropical storm could intensify rapidly.  Melor could become a typhoon on Saturday and it could become the equivalent of a major hurricane in 48 to 73 hours.

A subtropical ridge north of Melor is steering the tropical storm toward the west-northwest and that general motion is expected to continue during the next two or three days.  On its anticipated track, Melor could reach the Central Philippines within 72 hours.  It could be a strong typhoon at that time.

In-Fa Weakens to a Tropical Storm on Its Way to Iwo To

In-Fa weakened below typhoon intensity on Tuesday as it moved toward Iwo To.  At 10:00 p.m. EST on Tuesday the center of Tropical Storm In-Fa was located at latitude 20.1°N and longitude 135.3°E which put it about 540 miles (870 km) southwest of Iwo To.  In-Fa was moving toward the northeast at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 994 mb.

A large upper level trough that extends south of Japan is producing strong southwesterly winds over the top of Tropical Storm In-Fa.  Those winds are causing strong vertical wind shear which is tilting the upper portion of the circulation of the tropical storm toward the northeast.  The stronger thunderstorms are all located northeast of the center of In-Fa.  It also appears drier air is wrapping around the southwestern part of the circulation.  The strong vertical wind shear will continue to weaken Tropical Storm In-Fa.  As it moves into a cooler environment In-Fa will gradually make a transition to an extratropical cyclone during the next 48 hours.

The upper level trough will continue to steer Tropical Storm In-Fa toward the northeast while it makes the transition to an extratropical cyclone.  On its anticipated track In-Fa could bring tropical storm force winds to Iwo To in 24 to 36 hours.

Typhoon In-Fa Turns Toward Iwo To

Typhoon In-fa turned northeast and started to move toward Iwo To late on Monday.  At 10:00 p.m. EST on Monday the center of Typhoon In-Fa was located at latitude 19.0°N and longitude 132.6°E which put it about 695 miles (1120 km) southwest of Iwo To.  In-Fa was moving toward the northeast at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 956 mb.

Although In-Fa may be beginning to respond to increased vertical wind shear, it remains a well organized typhoon.  There are signs that a cloud filled eye still exists at the core of In-Fa.  The eye is surround by a ring of strong thunderstorms.  The outer portion of In-Fa’s circulation is becoming more asymmetrical, which is probably the result of increased wind shear.  Most of the thunderstorms outside the core are north and east of the center of circulation.  There are few thunderstorms in the southwestern part of In-Fa.

Typhoon In-Fa is currently over water where the Sea Surface Temperature (SST) is near 28°C.  In-Fa will move over increasingly cooler SSTs as it moves northeast.  The strength of the upper level southwesterly winds will increase as In-Fa moves northeast.  The combination of cooler SSTs and more vertical wind shear will cause Typhoon In-Fa to weaken during the next several days.  It could weaken to a tropical storm by Wednesday.

An upper level trough is steering Typhoon In-Fa toward the northeast and that general motion is expected to continue during the next 48 hours.  In-Fa could start to move faster as the upper level winds increase.  In-Fa could be near Iwo To in about 48 hours.