Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Tropical Depression 07W Forms South of Pohnpei

The active period over the tropical Western North Pacific Ocean continues with the development of another tropical cyclone south of Pohnpei.  At 8:00 p.m. EDT on Wednesday the center of Tropical Depression 07W was located at latitude 4.4°N and longitude 156.8°E which put it about 160 miles south-southeast of Pohnpei.  The tropical depression was stationary.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 1004 mb.

A low level circulation center formed within a broad area of thunderstorms and the system was classified as Tropical Depression 07W.  The strongest thunderstorms are mainly located in the northwestern part of the circulation.  An upper level ridge located east of the depression is generating southeasterly winds over the top of it which is producing modest vertical wind shear.  The wind shear is the probably reason why most of the thunderstorms are northwest of the center of circulation.  The wind shear will also limit the rate of intensification during the next day or two.  Eventually the depression is expected to move farther west into an area with less wind shear and it could intensify more quickly.

Tropical Depression 07W is located near the western end of a subtropical ridge and the steering currents are relatively weak.  It may not move much for the next 12 to 24 hours.  Later this week the ridge is expected to strengthen and steer the depression toward the west-northwest.  On its projected track the depression could approach Pohnpei in two or three days.

Noul Intensified Into a Typhoon As It Passed Over Yap

Tropical Storm Noul intensified slowly on Tuesday and it attained typhoon status as it passed over Yap.  At 10:00 p.m. EDT on Tuesday the center of Typhoon Noul was located at latitude 9.5°N and longitude 137.5°E which put it about 20 miles west-southwest of Yap and about 230 miles east-northeast of Palau.  Noul was moving toward the west at 5 m.p.h.  The maximum sustained wind speed was 75 m.p.h. and there were gusts to 90 m.p.h.  The minimum surface pressure was 976 mb.  Noul brought wind and heavy rain to Yap on Tuesday.  The International Airport reported a wind gust of 68 m.p.h. as the center of Noul passed just south of it.

An upper level ridge located east of the center of circulation is causing light easterly winds to blow over the top of Noul, which is generating some vertical wind shear.  The shear could be the reason why most of the strongest thunderstorms are occurring in the southwestern quadrant of the circulation.  Noul remains over water where the Sea Surface Temperature is around 29°C.  The vertical wind shear is likely to slow the rate of intensification, but Noul is in an environment that favors further strengthening.

Noul is at the western end of a subtropical ridge and the steering pattern is relatively weak.  It is likely to continue to move slowly for another 12 to 24 hours.  Eventually a subtropical ridge is expected to build north of Noul and steering it toward the west-northwest at a faster speed.  On its projected path the center of Noul would pass several hundred miles north of Palau.  Noul could be approaching the northern Philippines by late in the week.

 

Tropical Storm Noul Nearing Yap and Intensifying

Tropical Storm Noul intensified on Monday as it moved closer to Yap.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Noul was located at latitude 9.4°N and longitude 138.8°E which put it about 55 miles east of Yap and about 290 miles east-northeast of Palau.  Noul was moving toward the west-southwest at 5 m.p.h.  The maximum sustained wind speed was 65 m.p.h. and there were gusts 80 m.p.h.  The minimum surface pressure was 982 mb.

A primary rainband appears to be wrapping around the small center of circulation in Tropical Storm Noul.  It continues to move over water where the Sea Surface Temperature in near 29°C.  A subtropical ridge east of Noul is generating light easterly winds over the top the circulation.  The flow is causing modest vertical wind shear and may be the reason why many of the thunderstorms are forming to the west of the center.  If the rainband can wrap completely around the center, then an eye may form.  Noul is likely to remain in an environment that will support further intensification and it could become a typhoon within 24 hours.

Noul is near the western end of a subtropical ridge and it is moving slowly.  The slow motion is likely to continue for another day or so.  After that time, the subtropical ridge is expected to strengthen and extend farther westward.  As the ridge extends westward, it is forecast to steer Noul toward the west-northwest later this week.

On the projected track Noul will move almost directly over Yap on Tuesday.  It could be near typhoon intensity at that time and bring wind and heavy rain.

 

TD 06W Intensifies Into Tropical Storm Noul East of Yap

The center of circulation in Tropical Depression 06W became more well defined on Sunday and the system was upgraded to Tropical Storm Noul.  At 10:00 p.m. EDT on Sunday the center of Tropical Storm Noul was located at latitude 9.7°N and longitude 140.3°E which put it about 150 miles east of Yap and about 360 miles east-northeast of Palau.  Noul was moving toward the northwest at 7 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and there were gusts to 55 m.p.h.  The minimum surface pressure was 996 mb.

Noul is moving over water where the Sea Surface Temperatures are near 29°C.  An upper level ridge northeast of the tropical storm is producing some southeasterly winds over the top of Noul.  However, the vertical wind shear appears to be decreasing.  More thunderstorms developed close to the center of circulation in recent hours and a primary rainband appears to be wrapping around the northern side of the storm.  These are indications of a tropical cyclone that is becoming more well organized.  The increased convection near the center is contributing to well developed upper level divergence on the western and northern portions of the circulation.  Noul will be moving through an environment favorable for intensification.  Wind speeds are likely to increase and a period of rapid intensification is possible once the circulation is more well organized.  Noul could become a typhoon in a day or two and it could become the equivalent of a major hurricane later this week.

Noul is at the western end of a subtropical ridge which is steering it slowly toward the northwest.  It could continue to move slowly for another 24 hours or so.  After that time the subtropical ridge is forecast to extend farther west and begin to steer Noul on a west-northwesterly track.  The projected track would take Noul in the general direction of the northern Philippines.  The center of Noul is forecast to pass just north of Yap and it could bring wind and heavy rain when it does.

 

Tropical Depression 06W Forms Southeast of Yap

A low level circulation with a primary spiral band developed within a broad area of thunderstorms and the system was classified as Tropical Depression 06W on Saturday night.  At 10:00 p.m. EDT on Saturday night the center of Tropical Depression 06W was located at latitude 7.5°N and longitude 141.2°E which put it about 240 miles southeast of Yap and about 430 miles east of Palau.  06W was moving toward the west at 7 m.p.h.  The maximum sustained wind speed was 35 m.p.h. and there were gusts to 50 m.p.h.  The minimum surface pressure was 1004 mb.

Tropical Depression 06W is an environment favorable for further intensification.  It is over Sea Surface Temperatures that are warmer than 28°C and it will be able to extract plenty of energy from the ocean along its path.  An upper level ridge northeast of the circulation is generating some easterly winds over the top of it, but the vertical wind shear is only likely to slow the rate of intensification.  Tropical Depression 06W is likely to become a tropical storm on Sunday and it could become a typhoon in several days.

A subtropical ridge is steering 06W toward the west and it is expected to continue to steer it in a generally west-northwesterly motion during the next day or so.  The movement could slow as 06W nears the western end of the subtropical ridge.  The eastern end of a second subtropical ridge located farther west could take over as the primary steering mechanism in two or three days.  In that scenario Tropical Depression 06W would continue to move toward the northern Philippines.

Tropical Depression 06W could be nearing Yap in 24 to 30 hours.  It is likely to be a tropical storm at that time and it could bring some wind and rain to Yap.

 

Tropical Cyclone Solo Passing Near New Caledonia

The center of Tropical Cyclone Solo is passing near New Caledonia.  At 10:00 p.m. EDT on Saturday the center of Tropical Cyclone Solo was located at latitude 19.7°S and longitude 164.6°E which put it about 200 miles northwest of Noumea, New Caledonia.  Solo was moving toward the southeast at 11 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and there were gusts to 65 m.p.h.  The minimum surface pressure was 989 mb.

Strong northwesterly winds in the upper levels are generating significant vertical wind shear over the top of Solo.  The strong upper level winds are blowing the tops of thunderstorms to the southeast side of the circulation.  The wind shear is disrupting the circulation and the low level center is exposed on visible satellite images.  Solo is weakening and that trend is likely to continue as it moves farther southeast.

Tropical Storm Maysak Making Landfall in Luzon

Typhoon Maysak moved into an area of drier air and weakened to a tropical storm on Saturday before making landfall in Luzon.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Maysak was located at latitude 16.7°N and longitude 122.0°E which put it about 20 miles southeast of Cauayan and about 160 miles northeast of Manila, Philippines.  Maysak was moving toward the northwest at 12 m.p.h.  The maximum sustained wind speed was 50 m.p.h. and there were gusts to 65 m.p.h.  The minimum surface pressure was 989 mb.

Maysak is moving inland over Luzon.  The combination of the mountains in northern Luzon and drier air will cause Maysak to continue to weaken.  Even as the wind speeds decrease, air flowing up the sides of mountains will enhance the rainfall and create the potential for localized flooding and mudslides.  If a closed circulation still exists, it will be much weaker when it emerges over the South China Sea on Sunday.

Typhoon Maysak Nearing Luzon

Typhoon Maysak maintained its heading toward Luzon on Friday and it is about 24 hours away from making landfall.  At 5:00 p.m. EDT on Friday the center of Typhoon Maysak was located at latitude 14.6°N and longitude 127.2°E which put it about 200 miles east-northeast of Catanduanes Island and about east-southeast of Luzon.  Maysak was moving toward the west at 15 m.p.h.  The maximum sustained wind speed was 95 m.p.h. and there were gusts to 115 m.p.h.  The minimum surface pressure was 963 mb.

An upper level trough that was causing vertical wind shear over Maysak moved eastward on Friday and the wind shear over the typhoon decreased.  Infrared satellite imagery indicates that more convection developed near the core of Maysak and the upper level divergence has increased in recent hours.  The additional convection appears to have slowed the weakening of the circulation.  Maysak will remain over warm Sea Surface Temperatures as it approaches Luzon and so it will likely still be a typhoon when it makes landfall there.  If new thunderstorms continue to develop near the center of circulation, then some intensification may be possible before landfall.

A subtropical ridge is steering Maysak toward the west-northwest and that motion is expected to continue.  On the projected track Maysak would make landfall in Luzon in 24 to 36 hours.  It has the potential to bring strong winds and locally heavy rain to parts of Luzon.  The locally heavy rain will also create the conditions that could produce mudslides in some areas.

Typhoon Maysak Weakening As It Moves Toward Luzon

Typhoon Maysak weakened slowly on Thursday as it moved in the direction of Luzon.  At 11:00 p.m. EDT on Thursday the center of Typhoon Maysak was located at latitude 14.3°N and longitude 130.6°E which put it about 420 miles east of Catanduanes Island and about 580 miles east-southeast of Luzon.  Maysak was moving toward the west-northwest at 11 m.p.h.  The maximum sustained wind speed was 110 m.p.h. and there were wind gusts to 130 m.p.h.  The minimum surface pressure was 948 mb.

An upper level trough passing north of Maysak is generating vertical wind shear which is causing the typhoon to weaken slowly.  The western side of the trough contains some drier air which is also getting into the circulation of Maysak.  The drier air is reducing the amount of latent energy available to maintain the circulation.  So, even though Maysak is still over warm Sea Surface Temperatures it is slowly weakening.  The wind shear may decrease after the upper level trough moves east of Maysak, but as the typhoon moves further west, it will still encounter drier air.  As a result, Maysak it expected to continue to slowly weaken.

A subtropical ridge is steering Maysak in a west-northwesterly direction.  The upper level trough has temporarily weakened the ridge and Maysak is moving a bit more toward the northwest.  After the upper level trough moves east of the typhoon, it is expected to resume a west-northwesterly motion.  The expected track would bring Maysak close to Luzon in 36 to 42 hours.  Maysak is expected to be a low end typhoon or strong tropical storm when it nears Luzon.  It will be capable of producing some stronger winds and locally heavy rainfall as it moves across Luzon.

Typhoon Maysak Weakens As It Moves Away from Yap

Typhoon Maysak weakened below Super Typhoon intensity on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Typoon Maysak was located at latitude 12.6°N and longitude 133.5°E which put it about 300 miles northwest of Yap and about 780 miles east-southwest of Luzon.  Maysak was moving toward the west-northwest at 10 m.p.h.  The maximum sustained wind speed was 135 m.p.h. and there were wind gusts to 160 m.p.h.  The minimum surface pressure was 937 mb.

Maysak appears to have gone through an eyewall replacement cycle on Wednesday.  A rainband wrapped around the existing eyewall to create to concentric eyewalls.  As more air started to converge and rise in the outer eyewall, the inner eyewall which had the stronger winds weakened.  As the inner eyewall dissipated, the core of Maysak became enlarged and it now has an eye with a diameter of 32 miles.  The maximum wind speed decreased as part of the eyewall replacement process.  If the current eye were to shrink, the wind speed could increase again because it is still over warm Sea Surface Temperatures.  However, as Maysak moves toward the west-northwest it is moving toward an area where the upper level winds are stronger.  An upper level trough located northwest of Maysak is generating stronger upper level winds, which will increase the vertical wind shear.  Maysak could intensify on Thursday, but the wind shear is expected to weaken it during the next several days.

A subtropical ridge is steering Maysak toward the west-northwest.  The upper level trough is expected to make it move a little more toward the north during the next 24 to 48 hours.  On its expected track, Maysak could be approaching Luzon in about 60 hours.  Maysak is expected to still be a typhoon when it approaches Luzon.  It could bring strong winds and locally heavy rains.