Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Tropical Cyclone Frances Develops North of Western Australia

An area of low pressure northwest of Western Australia developed into Tropical Cyclone Frances on Thursday.  At 10:00 a.m. EDT on Thursday the center of Tropical Cyclone Frances was located at latitude 11.0°S and longitude 128.3°E which put it about 255 miles (410 km) north-northeast of Kalumburu, Australia.  Frances was moving toward the west-southwest at 12 m.p.h. (19 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. (110 km/h).  The minimum surface pressure was 997 mb.

The organization of Tropical Cyclone Frances improved significantly during the past 24 hours.  A well organized center of circulation developed at the surface.  A primary rainband wrapped about two-thirds of the way around the southern and western sides of the center.  Additional bands of showers and thunderstorms formed in the outer portions of the circulation.  Thunderstorms near the core of the circulation generated upper level divergence which was pumping mass away to the south of the tropical cyclone.  Frances is a fairly small tropical cyclone and winds to tropical storm force only extend out about 100 miles (160 km) from the center.

Tropical Cyclone Frances will move through an environment that will be favorable for intensification during the next 24 to 36 hours.  Frances will move over water where the Sea Surface Temperature is near 30°C while is moves across the Timor Sea.  An upper level ridge east of Tropical Cyclone Frances is producing northeasterly winds which are blowing toward the top of the circulation.  Vertical wind shear may be the reason that the primary rainband wrapped around the southern and western sides of the center.  However, the vertical shear does not appear to be strong enough to significantly affect the upper level divergence.  Frances is likely to intensify during the next day or so.  Eventually, Tropical Cyclone Frances will move into an area where there are strong upper level northwesterly winds.  A significant increase in vertical wind shear should weaken Frances when that occurs.

A subtropical ridge to the east of Frances is steering the tropical cyclone toward the west-southwest.  A general motion toward the west-southwest is expected to continue during the next few days.  On its anticipated track the center of Tropical Cyclone Frances is forecast to stay north of the coast of Western Australia.  However, any southward deviation of the track could bring stronger winds closer to the coast.

TD 03W Intensifies Into Tropical Storm Muifa

Tropical Depression 03W intensified into Tropical Storm Muifa on Tuesday as it moved slowly northwest of Yap.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Muifa was located at latitude 13.3°N and longitude 134.6°E which put it about 335 miles (540 km) northwest of Yap.  Muifa was moving toward the west-northwest at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1000 mb.

The circulation of Tropical Cyclone Muifa is not well organized.  There is a well defined low level center.  However, almost all of the showers and thunderstorms are in a cluster east of the low level center.  There are almost no showers and thunderstorms in the western half of the circulation.  Few well defined rainbands are evident in the eastern half of the circulation.  The cluster of thunderstorms east of the center of circulation is generating some upper level divergence which appears to be pumping mass out to the northwest of the tropical storm.

Tropical Storm Muifa will be moving through an environment that will be marginally favorable for intensification.  Muifa will move over water where the Sea Surface Temperature will be near 29.5°C.  A subtropical ridge east of Muifa is producing easterly winds which are blowing toward the tropical storm.  Tropical Storm Muifa is currently south of the upper level westerly winds in the middle latitudes.  Muifa is currently in a region where the upper level winds are weaker and the vertical wind shear is moderate.  Areas of stronger vertical wind shear surround the tropical storm.  Tropical Storm Muifa could intensify a little more during the next 24 hours before it reaches an area where the shear is stronger.

Tropical Storm Muifa is moving around the western end of the subtropical ridge to its east and the steering winds are weak.  As a result Muifa is moving slowly toward the west-northwest.  A gradual turn toward the north is forecast as Tropical Storm Muifa moves around the end of the ridge.  Muifa will reach an area of westerly winds as it moves farther north and the tropical storm is forecast to recurve toward the northeast.

Tropical Depression 03W Forms Northwest of Yap

Tropical Depression 03W formed northwest of Yap on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Depression 03W was located at latitude 12.5°N and longitude 135.2°E which put it about 260 miles (420 km) northwest of Yap.  The depression was moving toward the west at 10 m.p.h. (16 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 1003 mb.

A cluster of thunderstorms developed southeast of the Marianas during the weekend.  The cluster moved slowly toward the west-northwest and the circulation gradually exhibited signs of greater organization.  Satellite imagery indicated that a center of circulation formed in the lower levels of the circulation and the system was designated as Tropical Depression 03W on Monday.

The circulation of Tropical Depression 03W is still organizing.  Although there is a distinct low level center, the distribution of showers and thunderstorms is asymmetrical.  Many of the showers and thunderstorms are forming east of the center of circulation.  There are few showers and thunderstorms in the western half of the circulation.  Thunderstorms just to the east of the center of the circulation are generating some upper level divergence that is pumping out mass to the west and north of the center of circulation.

Tropical Depression 03W will be moving through an environment that will be somewhat favorable for intensification.  It will move over water where the Sea Surface Temperature will be near 30°C.  A ridge of high pressure east of the depression is producing easterly flow that is blowing toward the depression.  The flow may be pushing the lower part of the circulation to the west of the middle and upper portions.  Vertical wind shear could be an inhibiting factor.  Some intensification is forecast during the next day or two and the depression could intensify into a tropical storm.

The ridge of the depression is steering it toward the west.  The depression is expected to turn toward the northwest when it reaches the western end of the depression in a day or so.

Tropical Depression 02W Forms East of the Philippines

Tropical Depression 02W formed east of the Philippines on Friday.  At 11:00 a.m. EDT on Friday the center of Tropical Depression 02W was located at latitude 10.7°N and longitude 128.1°E which put it about 190 miles (305 km) east-southeast of Dolores, Philippines.  Tropical Depression 02W was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1004 mb.

The circulation of Tropical Depression 02W is organizing around a low level center east of Samar and Leyte.  Thunderstorms were developing near the center of circulation and several spiral bands were developing farther away from the center.  The thunderstorms near the center of circulation were just beginning to generate upper level divergence.

Tropical Depression 02W will move through an environment that will be favorable for intensification during the next 18 to 24 hours.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge located east of Tropical Depression 02W is producing easterly winds that are blowing toward the depression, but the vertical wind shear is minimal.  The combination of warm SSTs and little vertical wind shear could allow Tropical Depression 02W to organize quickly and it could become a tropical storm before it reaches the Philippines.

A subtropical ridge is steering Tropical Depression 02W toward the west-northwest and that general motion is expected to continue for the next several days.  On its anticipated track Tropical Depression 02W will move across the Central Philippines during the weekend.  Tropical Depression 02W could bring gusty winds and heavy rain to portions of Samar, Leyte, Cebu, Panay, Mindoro and southern Luzon.  Heavy rain could create a risk for mudslides in some areas.

Tropical Depression 01W Redevelops East of Vietnam

More thunderstorms developed on Saturday around the circulation previously designated Tropical Depression 01W earlier this week when it moved through the southern Philippines.  At 10:00 p.m. EST the center of Tropical Depression 01W was located at latitude 9.4°N and longitude 109.1°E which put it about 220 miles (355 km) east-southeast of Ho Chi Minh City, Vietnam.  The depression was moving toward the west at 6 m.p.h. (10 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 1002 mb.

After persisting mainly as a low level circulation during the past few days as it moved westward across the South China Sea, more thunderstorms developed in the depression on Saturday.  Most of the thunderstorms developed in bands north and west of the center of circulation.  There were bands of low clouds and showers in the southeastern portion of the circulation. The depression has a well defined low level center of circulation.  Thunderstorms were starting to generate some upper level divergence which was pumping mass away to the northwest of the depression.

The depression will be moving through an environment that is marginal for intensification.  It will be moving over water where the Sea Surface Temperature is near 26°C to 27°C.  So, there will be enough energy in the upper ocean to support intensification.  An upper level ridge to the east of the depression is generating southeasterly winds which are blowing across the top of the circulation.  The moderate vertical wind shear will inhibit intensification.  If the shear does not increase, the depression could maintain its intensity or strengthen slightly during the next 24 hours.

A ridge north of the depression is steering it toward the west and that general motion is expected to continue for another day or two.  On its anticipated track the depression will move toward the southernmost part of Vietnam.  The depression could bring locally heavy rain to southern Vietnam.  The rain could be heavy enough to cause flooding in some areas.

Tropical Depression 01W Forms Near Mindanao

A center of circulation formed within a cluster of thunderstorms east of Mindanao on Saturday and the system was designated Tropical Depression 01W.  At 10:00 p.m. EST on Saturday the center of Tropical Depression 01W was located at latitude 9.2°N and longitude 126.5°E which put it about 200 miles (320 km) east-southeast of Cebu, Philippines.  The depression was moving toward the northwest at 10 m.p.h.  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1000 mb.

Although there is a distinct center of circulation in Tropical Depression 01W, the distribution of thunderstorms is asymmetrical.  Most of the stronger thunderstorms are forming in the northern half of the circulation and there are few thunderstorms in the southern half of the circulation.  The thunderstorms in the northern half of the circulation are generating upper level divergence that is pumping out mass toward the northeast and northwest of the tropical depression.

Tropical Depression 01W will be moving through an oceanic and atmospheric environment that is somewhat favorable for intensification.  It will move over water where the Sea Surface Temperature is near 28°C.  An upper level ridge is generating southeasterly winds which are blowing across the top of the depression, but the vertical wind shear is not too strong.  However, the center of Tropical Depression 01W will move over some of the islands of the southern Philippines.  Increases friction and high topography will disrupt the circulation each time the center moves over land.  The intermittent passages overland will cause weakening and the intensity of Tropical Depression 01W is likely to fluctuate during the next several days.

A subtropical ridge north of the depression is steering it toward the northwest.  The ridge is forecast to strengthen and it is predicted to steer Tropical Depression 01W in a general westerly direction during the next several days.  On its anticipated track the center of Tropical Depression 01W will pass near northern Mindanao, Siargao Island, Dinogat Island, Leyte, Bohol Island, Cebu, Negros, and Panay Island.

Heavy rain associated will be the greatest threat with Tropical Depression 01W.  The heaviest rain will fall north of where the center moves.  The heavy rain could cause flooding and mudslides,

Typhoon Nock-ten Moves South of Manila

Typhoon Nock-ten moved across southern Luzon and weakened on Sunday.  At 10:00 p.m. EST on Sunday the center of Typhoon Nock-ten was located at latitude 13.8°N and longitude 120.9°E which put it near Batangas and about 75 miles (120 km/h) south-southeast of Manila, Philippines.  Nock-ten was moving toward the west at 18 m.p.h.  The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  The minimum surface pressure was 956 mb.

Typhoon Nock-ten weakened when the center moved over parts of southern Luzon.  Increased friction slowed the wind and areas of higher terrain temporarily disrupted the lower level circulation.  In addition easterly winds in the upper levels appeared to increase.  The increased vertical wind shear contributed to making the circulation more asymmetrical.  More of the thunderstorms formed in the western half of the circulation and there were fewer storms east of the center of circulation.

Typhoon Nock-ten will remain in a favorable environment for another day or so.  When Nock-ten moves west of Luzon into the South China Sea, it will move over water where the Sea Surface Temperature is near 29°C.  Typhoon Nock-ten could maintain its intensity or weaken slowly during the next 24 hours.  After that time Typhoon Nock-ten will move into an environment where the upper level winds are stronger.  Increased vertical wind shear will weaken the circulation.

A subtropical ridge to the north of Nock-ten is steering the typhoon toward the west and that general motion is expected to continue for another day or two.  The center of Typhoon Nock-ten passed near Catanduanes Island.  The center then moved near Tabaco, Ligao, Burias Island, San Francisco, and Marinduque Island.  The center is near Batangas.  It will move across Lake Taal and Lubang Island before it passes into the South China Sea.  Typhoon Nock-ten will continue to produce gusty winds and locally heavy rain as the center passes south of Manila.

Strong Typhoon Nock-ten Makes Landfall in Luzon

Strong Typhoon Nock-ten made landfall in Luzon on Sunday after passing very close to Catanduanes Island.  At 10:00 a.m. EST on Sunday the center of Typhoon Nock-ten was located at latitude 13.5°N and longitude 123.5°E which put it near Tabaco and about 215 miles (345 km) east-southeast of Manila, Philippines.  Nock-ten was moving toward the west at 12 m.p.h. (19 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. (290 km/h).  The minimum surface pressure was 924 mb.

The circulation of Typhoon Nock-ten is very well organized.  There is a circular eye with a diameter of 14 miles (23 km) at the center of circulation.  A ring of very strong thunderstorms surrounds the eye and the strongest winds are occurring in those thunderstorms.  A second ring of thunderstorms nearly surrounds the inner eye and eyewall.  Nock-ten may have a double eyewall structure.  Additional bands of thunderstorms are occurring outside the core of the circulation.  Winds to typhoon force extend out about 50 miles (80 km) from the center.  The core of Typhoon Nock-ten is generating strong upper level divergence which is pumping out mass in all directions.

The Hurricane Intensity Index (HII) is 31.6.  The Hurricane Size Index (HSI) is 15.5 and the Hurricane Wind Intensity Size Index (HWISI) is 47.1.  The indices indicate that Typhoon Nock-ten is capable of causing regional significant wind damage.

Typhoon Nock-ten will be moving through an atmospheric and oceanic environment that is supportive of tropical cyclones.  When the center of Typhoon Nock-ten is over water, it will move across areas where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  At times the center of Typhoon Nock-ten will move over portions of southern Luzon.  Nock-ten will weaken each time the center moves over land.  In addition, if an eyewall replacement cycle occurs, the strongest winds will slow as the inner eyewall decays.  However, the broader outer eyewall will cause Nock-ten to retain typhoon intensity for a longer period of time.

A subtropical ridge to the north of Nock-ten is steering the typhoon toward the west and that general motion is expected to continue.  On its anticipated track the center of Typhoon Nock-ten will pass near Naga, Calauag, Lucena, San Pablo,  and Manila in southern Luzon.

Typhoon Nock-ten is capable of doing significant wind damage.  Wind blowing water toward the coast will also create significant storm surges in east facing bays and inlets as the center of Nock-ten approaches.  When the center of circulation moves past parts of southern Luzon, the wind will shift to a southwesterly direction and there will be storms surges in in westerly facing bays and inlets.  Typhoon Nock-ten will produce very heavy rain over parts of southern Luzon.  Serious flooding and mudslides could occur in areas with steeper slopes.

Dangerous Typhoon Nock-ten Threatens the Philippines

Dangerous Typhoon Nock-ten intensified to super typhoon status on Saturday and it posed a significant threat to the northern Philippines.  At 10:00 a.m. EST on Saturday the center of Typhoon Nock-ten was located at latitude 13.5°N and longitude 127.1°E which put it about 440 miles (715 km) east of Manila, Philippines.  Nock-ten was moving toward the west at 8 m.p.h. (13 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. (290 km/h).  The minimum surface pressure was 928 mb.

Typhoon Nock-ten is a very strong, well organized typhoon.  Nock-ten has a small eye surrounded by a ring of strong thunderstorms.  A rainband is wrapping around the eye and concentric eyewalls could be forming.  Additional rainbands are rotating around the core of the circulation.  Winds to typhoon force extend out about 40 miles (65 km) from the center.  Thunderstorms in the core of the typhoon are generating strong upper level divergence which is pumping out mass in all directions.

Typhoon Nock-ten is moving through an environment that is favorable for tropical cyclones.  It is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  If concentric eyewalls forms, then there could be a period of weakening as the inner eyewall dissipates and the inflow becomes concentrated in the outer eyewall.  Wind speeds could increase again if the outer eyewall starts to contract.  In either case Typhoon Nock-ten will be a dangerous typhoon when it reaches the Philippines

A subtropical ridge to the north of Nock-ten is steering the typhoon toward the west and that general motion is expected to continue.  On its anticipated track Typhoon Nock-ten will reach Catanduanes Island within 24 hours.  Nock-ten is expected to move across southern Luzon.

The Hurricane Intensity Index (HII) is 31.6 and the Hurricane Size Index (HSI) is 15.5.  The Hurricane Wind Intensity Size Index (HWISI) is 47.1.  Those indices indicate that Nock-ten is capable of producing regional significant wind damage.

Typhoon Nock-ten will cause significant wind damage when it moves across the Philippines.  It will also generate a significant storm surge in portions of the coast near the path of the center.  Nock-ten will cause heavy rain and create the potential for floods and mudslides over parts of Catanduanes Island and southern Luzon.

Typhoon Nock-ten Rapidly Intensifies Into Equivalent of a Major Hurricane

Typhoon Nock-ten intensified rapidly into the equivalent of a major hurricane on Friday.  At 10:00 p.m. EST on Friday the center of Typhoon Nock-ten was located at latitude 13.2°N and longitude 128.6°E which put it about 545 miles (880 km) east of Manila, Philippines.  Nock-ten was moving toward the west at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 935 mb.

Nock-ten is a very well organized typhoon.  There is an eye with a diameter of 14 miles (23 km) at the center of Typhoon Nock-ten.  The eye is surrounded by a ring of strong thunderstorms.  Additional bands of thunderstorms surround the core of the circulation.  Winds to typhoon force extend out about 40 miles (65 km) from the center.  Thunderstorms around the center are generating strong upper level divergence in all directions.  The divergence is pumping out large amounts of mass which allowed the surface pressure to decrease rapidly.

The Hurricane Intensity Index (HII) is 23.6 and the Hurricane Size Index (HSI) is 15.5.  The Hurricane Wind Intensity Size Index (HWISI) is 39.1.  Those indices indicate that Typhoon Nock-ten is capable of causing major regional wind damage.

Typhoon Nock-ten will continue to move through an environment that is very favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds are weak and there is little vertical wind shear.  Nock-ten could intensify more during the next 24 hours and it could become a super typhoon before it reaches the Philippines.

A subtropical ridge to the north of Nock-ten is steering the typhoon toward the west and that general motion is expected to continue.  On its anticipated track Typhoon Nock-ten could be near Catanduanes Island within 36 hours.  Nock-ten is likely to pass across southern Luzon and the center could move close to Manila.  Typhoon Nock-ten will be capable of causing major wind damage.  It will also bring heavy rain and create the potential for floods and mudslides.