Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Typhoon In-Fa Passes North of Yap

The center of Typhoon In-Fa passed north of Yap on Saturday.  At 10:00 p.m. EST on Saturday the center of Typhoon In-Fa was located at latitude 13.7°N and longitude 136.0°E which put it about 285 miles (465 km) north-northwest of Yap.  In-Fa was moving toward the west-northwest at 19 m.p.h. (31 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 944 mb.

The structure of Typhoon In-Fa deteriorated slightly on Saturday, but it remains the equivalent of a major hurricane.  Fewer thunderstorms formed in the northwestern quadrant of the circulation and there are indications that a gap may have opened on the northwestern side of the eyewall.  It is possible that some drier air could have been pulled into that part of the circulation.  However, an eye may still exist at the center of circulation and there are multiple bands around the eastern and southern sides of the typhoon.

Typhoon In-Fa is moving over water where the Sea Surface Temperature is near 29°C.  The upper level winds over the top of the circulation are light and there is not much vertical wind shear over the core of the typhoon.  Typhoon In-Fa could maintain its intensity or weaken slowly on Sunday.  When it moves farther north, it will encounter stronger southwesterly winds which will increase the vertical wind shear.  When the wind shear increases, the rate of weakening will increase.

A subtropical ridge is steering Typhoon In-Fa toward the west-northwest and that general motion is expected to continue for another day or so.  In-Fa could reach the western end of the ridge and turn northward on Monday.  In 36 to 48 hours the southwesterly upper level winds will start to push the typhoon toward the northeast.  On its anticipated track Typhoon In-Fa could be near Iwo To in about four days.

In-Fa Intensifies Back Into a Typhoon and a Tropical Storm Warning Is Issued for Guam

In-Fa intensified rapidly back into a typhoon on Thursday and a Tropical Storm Warning was issued for Guam.  At 10:00 p.m. EDT on Thursday the center of Typhoon In-Fa was located at latitude 10.1°N and longitude 148.1°E which put it about 365 miles (590 km) southeast of Guam.  In-Fa was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 954 mb.

After weakening slightly on Wednesday, In-Fa intensified rapidly back into a typhoon on Thursday.  Typhoon In-Fa has a compact tightly wound structure with a small inner core and a tiny pinhole eye.  The strongest winds are contained in the ring of thunderstorms around the pinhole eye.  Many of the strongest thunderstorms outside the eyewall are located southwest of the eye, but there are spiral bands in all quadrants of the storm.  The storms around the core of Typhoon In-Fa are generating upper level divergence in all directions.

Typhoon In-Fa is an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 29°C.  The upper level winds around In-Fa are light and there is not much vertical wind shear.  In-Fa is likely to intensify more during the next day or two.

A subtropical ridge north of In-Fa is steering the typhoon to the west-northwest and that general motion is expected to continue for another 48 hours.  On its anticipated track the center of In-Fa is likely to pass about 100 miles (160 km) to 150 miles (240 km) south of Guam in about 18 to 24 hours.  The center of Typhoon In-Fa is likely to pass about 200 miles (320 km) northeast of Yap in about 48 hours.

Tropical Storm In-Fa Near Fananu, Watch Issued for Guam

Tropical Storm In-Fa is near Fananu and it is bringing wind and rain to islands around Chuuk.  At 10:00 p.m. EST on Wednesday the center of Tropical Storm In-Fa was located near latitude 8.6°N and longitude 152.0°E which put it about 25 miles (40 km) southeast of Fananu and about 620 miles (1000 km) southeast of Guam.  In-Fa was moving toward the northwest at 15 m.p.h. (24 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 982 mb.

A Tropical Storm Watch has been issued for Guam.  A Typhoon Warning is in effect for Chuuk lagoon, Losap, Ulul and Fananu.

In-Fa was briefly a typhoon earlier on Wednesday when it had a small, but well formed eye.  However, the core of In-Fa weakened slightly and the eye filled with clouds.  A small, but circular, area of thunderstorms has intensified in the core of the tropical storm during the past few hours.  There are signs that In-Fa may be strengthening again.  The environment surrounding Tropical Storm In-Fa is favorable for intensification.  It is over water where the Sea Surface Temperature is near 29.5°C.  The upper level winds are light and the vertical wind shear is modest.  In-Fa could regain typhoon intensity on Thursday and a period of rapid intensification may be possible once the inner core reorganizes.

A subtropical ridge north of In-Fa is steering the tropical storm toward the northwest and that general motion is expected to continue for another two or three days.  On its anticipated track the center of In-Fa will pass near Fananu during the next few hours.  In-Fa could be south of Guam in about 48 hours.

Tropical Storm In-Fa Intensifying, Typhoon Watch for Fananu

Tropical Storm In-Fa intensified quickly on Tuesday and it caused watches and warnings to be issued for the area around Chuuk.  At 10:00 p.m. EST on Tuesday the center of Tropical Storm In-Fa was located at latitude 6.0°N and longitude 156.3°E which put it about 385 miles (620 km) east-southeast of Fananu and about 985 miles (1590 km) east-southeast of Guam.  In-Fa was moving toward the west-northwest 18 m.p.h. (29 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 983 mb.  A Typhoon Watch has been issued for Fananu.

The circulation of Tropical Storm In-Fa organized rapidly on Tuesday.  A tight core formed in the center of circulation and an eyelike feature appeared on satellite images.  A small ring of thunderstorms formed around the eye and a large primary rainband wrapped around the circulation.  The circulation became more symmetrical and upper level outflow began to create divergence in most directions.

Tropical Storm In-Fa remains in an environment favorable for intensification.  It is over water where the Sea Surface Temperature is near 30°C.   The upper level winds are light and the vertical wind shear is modest.  In-Fa is likely to continue to intensify and now that an inner core has developed, it could intensify rapidly.  In-Fa could become a typhoon on Wednesday and it could become the equivalent of a major hurricane later this week.

A subtropical ridge north of In-Fa is steering the tropical storm toward the west-northwest and that general motion is expected to continue for the rest of the week.  On its anticipated track In-Fa will approach Fananu in about 24 hours and it could be a typhoon at that time.  In-Fa could be approaching Guam in about three days as a typhoon.

Tropical Depression 27W Forms Southeast of Pohnpei

A center of circulation formed in an area of thunderstorms southeast of Pohnpei and the system was designated Tropical Depression 27W (TD 27W).  At 10:00 p.m. EST on Monday the center of Tropical Depression 27W was located at latitude 4.7°N and longitude 162.3°E which put it about 360 miles (585 km) east-southeast of Pohnpei.  TD 27W was moving to the west at 17 m.p.h. (27 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 1001 mb.

The circulation of TD 27W is still organizing.  A clearly defined low level center of circulation formed near the northern edge of an area of thunderstorms.  However, most of the stronger thunderstorms are southwest of the center.  Those storms are generating upper level divergence that is expanding south and west of the center.

Tropical Depression 27W is in an environment that favors further intensification.  It is over water where the Sea Surface Temperature is near 30°C.  An upper level ridge north of TD 27W is producing light easterly winds over the top of the depression.  The vertical wind shear is modest, and it should only slow the rate of intensification.  Intensification could be slow initially as a stronger inner core forms around the center of circulation.  Once the core of the circulation consolidates, then intensification could occur more quickly.  TD 27W could become a tropical storm within 24 to 36 hours and it could be a typhoon in three or four days.

A subtropical ridge north of TD 27W is steering the depression toward the west.  A gradual turn toward the west-northwest is expected and that general motion is expected to continue for much of the week.  On its anticipated track TD 27W could be near Pohnpei in about 24 hours and it could bring tropical storm force winds and heavy rain.  The tropical cyclone could be approaching Guam by the end of the week and it could be a typhoon by that time.

Typhoon Champi Bringing Wind and Rain to Iwo To

A portion of the northern eyewall of Typhoon Champi is over Iwo To and it is bringing wind and rain to the island.  A weather station on Iwo To is reporting east-northeasterly winds at 47 m.p.h. (75 km/h) with gusts to 73 m.p.h. (118 km/h).  At 11:00 p.m. EDT on Wednesday the center of Typhoon Champi was located at latitude 23.8°N and longitude 141.6°E which put it about 75 miles (120 km) south of Iwo To.  Champi was moving toward the northeast at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h).  The minimum surface pressure was 945 mb.

The inner core of Typhoon Champi became much more well organized during the past 12 hours and it now has a clear circular eye that is approximately 30 miles (48 km) across.  The eye is surrounded by a ring of strong convection which contains the strongest winds.  The core is also generating upper level divergence which is pumping out mass.

Typhoon Champi will be in a favorable environment for another 12 hours.  It is moving over water where the Sea Surface Temperature is near 28.5°C.  The upper level winds are light and there is not much upper level divergence.  Champi could intensify further on Thursday, but it will move into a less favorable environment when it moves farther north.  Once Champi gets north of latitude 27°N, it will move over cooler SSTs.  Typhoon Champi will start to encounter strong upper level westerly winds at about the same time.  The combination of cooler water and more vertical wind shear will steadily weaken Champi.

Typhoon Champi is moving northward around the western end of a subtropical ridge.  When it reaches the upper level westerly winds, those winds will accelerated Champi toward the east-northeast until it transforms into an extratropical cyclone over cooler waters.  On its anticipated track the center of Champi will pass southeast of Iwo To, but it will bring strong winds and rain to that island for another 12 hours or so.

Typhoon Koppu Still Affecting Northern Luzon

The center of Typhoon Koppu moved across northern Luzon on Sunday and it is still affecting that region.  At 11:00 p.m. EDT on Sunday the center of Typhoon Koppu was located at latitude 17.5°N and longitude 120.3°E which put it about 200 miles (320 km) north-northwest of Manila, Philippines and just west of the coast of northwestern Luzon.  Koppu was moving toward the north-northeast at 5 m.p.h. (8 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 968 mb.

Passage over northern Luzon weakened Typhoon Koppu and its structure is asymmetrical.  Most of the stronger thunderstorms are located in the western half of the circulation.  Much of the eastern half of the circulation is still over Luzon and there are few thunderstorms there.  The center of circulation is just west of Luzon.  Since it is back over water, the core of the typhoon could start to reorganize.  Intensification will be limited because of the large proportion of the circulation which is over land.

Koppu is near the western end of a subtropical ridge, which is causing the typhoon to move slowly northward.  That motion could continue for another 24 to 36 hours.  Eventually the ridge is expected to strengthen and push Typhoon Koppu northward at a faster speed.  Typhoon Koppu will continue to bring heavy rain to parts of northern Luzon for another day or two.

Strong Typhoon Champi Intensifies South of Iwo To

Typhoon Champi intensified rapidly on Sunday and it reached the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. EDT on Sunday the center of Typhoon Champi was located at latitude 20.3°N and longitude 140.3°E which put it about 325 miles (525 km) south-southwest of Iwo To.  Champi was moving toward the north-northeast at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 175 m.p.h. (280 km/h).  The minimum surface pressure was 924 mb.

The circulation of Typhoon Champi is very well organized.  It has a well defined eye and there could be a rainband wrapping around the center to create concentric eyewalls.  Multiple spiral bands are revolving around the center of circulation.  Winds to typhoon force extend out 40 miles (65 km) from the center.  Well developed upper level divergence is pumping out mass in all directions.

Typhoon Champi is moving over water where the Sea Surface Temperature is near 29°C.  The winds in the upper levels are relatively light and there is not much vertical wind shear.  Champi will remain in a favorable environment for another 24 to 48 hours.  Eyewall replacement cycles could cause fluctuations in intensity during that period.  When it moves north of latitude 25°N, Champi will encounter the upper level westerly winds in the middle latitudes which will cause significant vertical wind shear.  Champi will weaken as the wind shear increases.

Champi is moving slowly northward as it curves around the western end of a subtropical ridge.  It will continue to move northward for another day or two.  When it begins to be affected by the upper level westerly winds, Champi will accelerate toward the northeast.  On its anticipated track Typhoon Champi will approach Iwo To in 48 to 60 hours.  Champi will be a large, strong typhoon at that time.

Dangerous Typhoon Koppu Making Landfall in Northern Luzon

Typhoon Koppu intensified rapidly during the past 12 hours and it is making landfall near Baler in northern Luzon as the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 11:00 a.m. EDT on Saturday the center of Typhoon Koppu was located at latitude 16.0°N and longitude 122.9°E which put it about 170 miles (275 km) east-northeast of Manila, Philippines.  Koppu was moving toward the west-northwest at 7 m.p.h. (11 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 918 mb.  Typhoon Koppu has a Hurricane Intensity Index (HII) of 31.6, a Hurricane Size Index (HSI) of 17.5 and a Hurricane Wind Intensity Size Index (HWISI) of 49.1, which means it is capable of producing regional significant wind damage.  In addition the slow movement of Koppu means it will produce very heavy rainfall which will create the potential for serious flooding and landslides.

Koppu will continue to move toward the west-northwest for another 12 to 24 hours.  Then it will reach the western end of the subtropical ridge that has been steering it and start to move toward the north.  Although Typhoon Koppu will weaken as it moves across northern Luzon, it will be over that area for 36 to 48 hours.  Koppu has the potential to cause widespread damage due to winds, floods and landslides.

Typhoon Koppu Continues to Intensify and Threaten Luzon

Typhoon Koppu continued to intensify on Friday and it maintained its steady course toward northern Luzon.  At 5:00 p.m. EDT on Friday the center of Typhoon Koppu was located at latitude 15.8°N and longitude 124.5°E which put it about 270 miles (435 km) east-northeast of Manila, Philippines.  Koppu was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 947 mb.

Typhoon Koppu is evolving into a large well organized typhoon.  An eye has formed at the center of the circulation and multiple rain bands spiral around the core of the typhoon.  Upper level divergence is pumping mass away from the center of circulation.  Koppu is moving 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.  Koppu is likely to continue to intensify until it begins to interact with northern Luzon.

A subtropical ridge is steering Koppu toward the west and that steering pattern is expected to continue for another 24 to 36 hours.  On its anticipated track the center of Typhoon Koppu will be very near the northeastern coast of Luzon in about 24 hours.  Koppu will bring strong winds, heavy rain and a storm surge to northern Luzon.  The large size of Koppu and its relatively slow movement means that it could produce very heavy rainfall.  Serious flooding and numerous mudslides are possible across northern Luzon.