Category Archives: Western North Pacific

Western Pacific Typhoons and Tropical Storms

Tropical Storm Dolphin Moving West and Organizing Slowly

Tropical Storm Dolphin turned toward the west on Monday and showed signs of more organization.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Dolphin was located at latitude 10.3°N and longitude 158.0°E which put it about 490 miles east-northeast of Chuuk and about 950 miles east-southeast of Guam.  Dolphin was moving toward the west at 8 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.

Dolphin is moving over water where the Sea Surface Temperature (SST) is near 29°C.  Satellite imagery suggests that the circulation became more symmetrical although many of the stronger thunderstorms are west of the center of circulation.  A strong upper level ridge is located northwest of Dolphin and it is generating easterly winds winds over the top of the circulation.  The vertical wind shear may be the reason why the stronger thunderstorms are west of the center.  The upper level ridge is also contributing to an outflow channel to the southwest of Dolphin which cold pump out more mass.  The vertical wind shear is inhibiting the intensification of Dolphin.  However, as the tropical storm moves farther west, it could move into an area where the upper level winds are lighter.  Given the warm SSTs, a decrease in shear would lead to more intensification.

A subtropical ridge is expected to steer Dolphin toward the west during the next two or three days.  A turn toward the west-northwest will be possible later in the week if a weakness develops in the ridge.  On the anticipated track Dolphin could approach Guam in 48 to 60 hours and it could be a typhoon by that time.

Typhoon Noul Expected to Head Toward Okinawa

Typhoon Noul is expected to pass east of Taiwan and move toward Okinawa on Monday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Noul was located at latitude 21.2°N and longitude 122.4°E which put it about 260 miles south-southeast of Taipei, Taiwan, about 240 miles south-southwest of Ishigaki and about 550 miles southwest of Naha, Okinawa.  Noul was moving toward the north at 11 m.p.h.  The maximum sustained wind speed was 120 m.p.h. and there were gusts to 150 m.p.h.  The minimum surface pressure was 944 mb.

Noul will be moving over increasingly cooler Sea Surface Temperatures (SSTs) as it moves northeastward on Monday.  In addition, it will move into an area where stronger westerly winds are blowing in the upper levels of the atmosphere.  Cooler SSTs and increasing vertical wind shear will cause Noul to weaken steadily.  However, it could still be a typhoon when it passes near Okinawa.

Noul is moving around the western end of the subtropical ridge that has been steering it.  As it moves farther to the north, it will be steered by the mid-latitude westerly winds and Noul will accelerate toward the northeast.  Noul is like to make a transition to an extratropical cyclone when it passes south of Japan.

Tropical Storm Dolphin Expected to Turn West and Head Toward Guam

Tropical Storm Dolphin (07W) has been meandering around within a much larger region of low pressure west of the International Dateline, but it is expected to take a turn toward the west on Monday.  At 10:00 p.m. EDT on Sunday the center of Tropical Storm Dolphin was located at latitude 9.3°N and longitude 159.4°E which put it about 180 miles north-northeast of Pohnpei and about 1040 miles east-southeast of Guam.  Dolphin was moving toward the north-northwest at 10 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 60 m.p.h.  The minimum surface pressure was 993 mb.

An upper level ridge northeast of Dolphin is producing easterly winds over the top of the circulation and is creating moderate vertical wind shear.  The wind shear is contributing to an asymmetrical circulation where most of the thunderstorms are on the western side.  The shear is inhibiting further organization of the circulation and has kept Dolphin as a minimal tropical storm.  Dolphin is over warm Sea Surface Temperatures and it has the potential to intensify if the wind shear decreases.

A subtropical ridge is expected to build north of Dolphin and to steer it mainly toward the west for much of the coming week.  On its expected track Dolphin could approach Guam in about four days.

Typhoon Noul Equivalent of Category 5 Hurricane

Typhoon Noul moved into an area with very little vertical wind shear and intensified into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Saturday.  At 11:00 p.m. EDT on Saturday Typhoon Noul was located at latitude 17.4°N and longitude 123.1°E which put it about 130 miles east of Tuguegarao and about 85 miles southeast of Escarpada Point on the northeastern tip of Luzon.  Noul was moving toward the north-northwest at 12 m.p.h.  The maximum sustained wind speed was 160 m.p.h. and there were gusts to 195 m.p.h.  The minimum surface pressure was 918 mb.

Noul is at the western end of the subtropical ridge that has been steering it toward the northwest.  It should gradually turn more toward the north on Sunday.  The anticipated track will take the center of Noul very close to the northeastern tip of Luzon in a few hours.  As it moves northward, it will start to be affected by westerly winds in a day or so.  Those winds will turn it more toward the northeast and it could affect some of the southern islands of Japan early next week.

As Noul moves toward the north it will move over cooler Sea Surface Temperatures  (SSTs).  In addition the upper level westerly winds will create more vertical wind shear over Noul.  The combination of cooler SSTs and more vertical wind shear will cause Noul to weaken throughout the next few days.  However, if could still be a typhoon when it passes by Okinawa in about 48 hours.

Noul could bring strong winds and heavy rain to the northeastern tip of Luzon on Sunday.  Mudslides could be a possibility in locations that receive heavy rain.

 

Typhoon Noul Approaching the Philippines

Typhoon Noul continued to move steadily toward the west-northwest on Friday and it is approaching the northeastern Philippines.  At 3:00 pm. EDT on Friday the center of Typhoon Noul was located near latitude 13.9°N and longitude 127.0°E which put it about 300 miles east of Labo and about 480 miles east-southeast of Tuguegarao in the Philippines.  Noul was moving toward the west-northwest at 14 m.p.h.  The maximum sustained wind speed was 120 m.p.h. and there were gusts to 150 m.p.h.  The minimum surface pressure was 944 mb.  Noul is the equivalent of a Category 3 hurricane on the Saffir-Simpson Scale.

Noul is being steered to the west-northwest by a subtropical ridge located northeast of it.  As Noul nears the western end of the ridge, it is expected to begin to move more toward the northwest.  As Noul approaches the northeastern coast of Luzon, an upper level trough to the west is expected to turn it more toward the north.  The timing of the turn is still uncertain which makes the track forecast more difficult.  On its projected track Noul would approach northeastern Luzon in about 30 hours.

Noul is over Sea Surface Temperatures near 29°C and there is not much vertical wind shear.  However, there are fewer thunderstorms in the northwestern portion of the circulation and the could be some drier air in that region.  The environment is favorable for intensification but large changes in Noul’s intensity are not expected.  Noul is expected to be a significant typhoon when it approaches Luzon and it could bring strong winds and locally heavy rain to that region.  The heavy rain could lead to mudslides in areas where the slopes are steeper.

Typhoon Noul Intensfying North of Palau

Typhoon Noul continued to intensify on Wednesday as it passed north of Palau.  At 10:00 p.m. EDT on Wednesday the center of Typhoon Noul was located at latitude 10.7°N and longitude 133.7°E which put it about 270 miles north of Palau and about 550 miles east of the Philippines.  Noul was moving toward the west-northwest at 14 m.p.h.  The maximum sustained wind speed was 105 m.p.h. and there were gusts to 125 m.p.h.  The minimum surface pressure was 955 mb.

Noul is moving over water where the Sea Surface Temperatures are near 29°C.  It is moving close to the axis of an upper level ridge and so the vertical wind shear is low.  The environment is favorable for further intensification and Noul could eventually reach the equivalent of a major hurricane.

A subtropical ridge north of Noul is steering it toward the west-northwest and that motion is expected to continue for several days.   On its projected track Noul could approach the Philippines in two days and it could be near Luzon in three days.  As Noul nears Luzon it is expected to turn more toward the north.  If the circulation is intact after it crosses Luzon, it could head toward Taiwan.

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.