Tag Archives: Northern Marianas

Tropical Depression 04W Forms East of the Northern Marianas

Tropical Depression 04W formed east of the Northern Marianas very late on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Depression 04W was located at latitude 18.8°N and longitude 148.5°E which put it about 185 miles (300 km) east of Agrihan.  It was moving toward the northwest at 11 m.p.h. (17 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.

An area of showers and thunderstorms persisted for much of the past week east of the Northern Marianas.  Several smaller centers of circulation formed within the area of showers and storms, but those centers ran into strong upper level winds and weakened because strong vertical wind shear and they dissipated.  Another center formed on Friday, but the upper level winds were a little weaker and the center persisted.  An upper level trough south of Japan was still producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were producing moderate vertical wind shear, but the center of circulation persisted.  Most of the thunderstorms were occurring in bands east of the center of circulation.  The bands west of the center consisted primarily of low clouds and showers.

Tropical Depression will move through an area marginally favorable for intensification during the next 24 hours.  it will move over water where the Sea Surface Temperatures are near 28°C.  So, there will be enough energy in the upper ocean to support some intensification.  The upper level trough south of Japan will continue to cause moderate vertical wind shear, but the upper level winds could be weak enough to allow for further intensification.  Tropical Depression 04W could strengthen into a tropical storm on Saturday.

Tropical Depression 04W is moving near the southwestern part of a ridge over the North Pacific Ocean.  The ridge is steering the depression toward the northwest and that general motion is expected to continue for another day or two.  On its anticipated track Tropical Depression 04W is expected to pass near the northernmost Mariana Islands.  It could pass near Asuncion Island, the Maug Islands, Supply Reef and Farallon de Pajaros.  Tropical Depression 04W could bring gust winds, locally heavy rain and higher waves to those places.

Tropical Storm Jelawat Weakens Rapidly Over the Northern Marianas

Tropical Storm Jelawat weakened rapidly over the Northern Marianas on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Jelawat was located at latitude 19.3°N and longitude 145.5°E which put it about 50 miles (80 km) north-northwest of Agrihan.  Jelawat was moving toward the east-northeast at 14 m.p.h. (22 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 993 mb.

Former Typhoon Jelawat moved into an area where there were upper level westerly winds blowing at 50 m.p.h. (80 km/h).  Those strong upper level winds created enough vertical wind shear to blow the upper two thirds of the circulation east of the lower part of the circulation.  The remaining strong thunderstorms were weakening well to the east of the lower level circulation.  Tropical Storm Jelawat consisted primarily of narrow bands of showers and low clouds that were revolving around the center of circulation.  Jelawat may bring brief gusty winds and showers to the northernmost islands in the Marianas.

Typhoon Jelawat Rapidly Intensifies Into Equivalent of Major Hurricane

Typhoon Jelawat intensified rapidly on Friday into the equivalent of a major hurricane.  At 11:00 a.m. EDT on Friday the center of Typhoon Jelawat was located at latitude 17.1°N and longitude 139.5°E which put it about 440 miles (710 km) northwest of Guam.  Jelawat was moving toward the east-northeast at 13 m.p.h. (21 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 926 mb.

Typhoon Jelawat intensified rapidly on Friday.  There was a small circular eye at the center of circulation.  A ring of very strong storms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several spiral bands were revolving around the core of the circulation.  Storms near the core were generating well developed upper level divergence which was pumping large quantities of mass away to the east of the typhoon.  The removal of mass allowed the surface pressure to decrease rapidly and that produced a a rapid increase in wind speed.

Winds to typhoon force extend out about 45 miles (75 km) from the center of Typhoon Jelawat.  Winds to tropical storm force extend out about 175 miles (280 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Typhoon Jelawat is 31.6.  The Hurricane Size Index (HSI) is 17.7 and the Hurricane Wind Intensity Size Index (HWISI) is 49.3.

Typhoon Jelawat is in an environment favorable for strong typhoons, but it may be near its peak in intensity.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Typhoon Jelwat has moved around the western end of an upper level ridge which is producing easterly winds that are blowing toward the top of the circulation.  The winds are causing some vertical wind shear, but the shear has not inhibited intensification.  When Typhoon Jelawat moves farther to the northeast it will move under stronger easterly and the wind shear will increase.  More shear will cause Jelawat to weaken during the next few days.

A subtropical ridge to the east of Typhoon Jelawat is steering the typhoon toward the east-northeast.  A general motion toward the east-northeast is expected to continue for several more days.  On its anticipated track Typhoon Jelawat could approach the northernmost islands in the Marianas in about 48 hours.

Typhoon Jelawat Strengthens West-Northwest of Guam

Former Tropical Storm Jelawat strengthened into a typhoon as it moved west-northwest of Guam on Thursday.  At 11:00 p.m. EDT on Thursday the center of Typhoon Jelawat was located at latitude 15.9°N and longitude 137.7°E which put it about 520 miles (840 km) west-northwest of Guam.  Jelawat was moving toward the east-northeast at 7 m.p.h. (11 km/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 972 mb.

Typhoon Jelawat strengthened quickly on Thursday night.  A small eye developed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Jelawat.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away to the northeast of the typhoon.  Winds to typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 145 miles (230 km) from the center.

Typhoon Jelawat will move through an area favorable for intensification on Friday.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Typhoon Jelawat has moved around the western end of an upper level ridge which is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds are producing some vertical wind shear, but the wind shear is not strong enough to prevent intensification.   Typhoon Jelwat is likely to intensify further on Friday.

The upper level ridge is steering Typhoon Jelawat toward the east-northeast and that general motion is expected to continue for several more days.  On its anticipated track Typhoon Jelawat is expected to pass northwest of Guam.  Jelawat could approach the northernmost islands in the Marianas in about two or three days.

Tropical Storm Jelawat Strengthens West of Guam

Tropical Storm Jelawat strengthened west of Guam late on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Jelawat was located at latitude 12.3°N and longitude 135.5°E which put it about 230 miles (375 km) northwest of Yap and about 600 miles (970 km) west of Guam.  Jelawat was moving toward the north at 10 m.p.h. (16 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 994 mb.

After being affected by strong vertical wind shear for about 36 hours, Tropical Storm Jelawat began to strengthen late on Tuesday.  Many more thunderstorms formed near the center of circulation.  The circulation became much more symmetrical.  Bands of showers and thunderstorms formed in all parts of the circulation.  The storms near the center of circulation started to generate upper level divergence which pumped mass away from the tropical storm.

Tropical Storm Jelawat will be moving through an environment favorable for intensification during the next several days.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  Tropical Storm Jelawat is moving around the western end of an upper level ridge.  The ridge is producing southerly winds which are blowing toward the tropical storm.  The winds are producing some vertical wind shear, but the shear is not as strong as it has been.  Tropical Storm Jelawat will intensify during the next day or two and it could strengthen into a typhoon.

The ridge is steering Tropical Storm Jelawat toward the north and the northerly motion is expected to continue for another 12 to 24 hours.  Jelawat will move more toward the northeast in a day or so after it rounds the western end of the ridge.  On its anticipated track Tropical Storm Jelawat will move away from Yap and it will remain west of Guam.

Tropical Storm Sanvu Forms Over Northern Marianas

Tropical Storm Sanvu formed over the northern Marianas on Monday.  At 11:00 a.m. EDT on Monday the center of Tropical Storm Sanvu was located at latitude 20.4°N and longitude 146.4°E which put it about 100 miles (160 km) north-northeast of Agrihan.  Sanvu was moving toward the north-northeast at 3 m.p.h.  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 994 mb.

Tropical Storm Sanvu developed when a distinct center of circulation formed within a much larger area of low pressure over the northern Marianas.  The circulation of Sanvu is still in the early stages of consolidation around the center.  Most of the showers and thunderstorms were forming in bands in the southern half of the circulation.  The bands in the northern half of the circulation were weaker.  The showers and thunderstorms south of the center were beginning to generate some upper level divergence which was pumping mass away to the south of the tropical storm.

Tropical Storm Sanvu will be moving through an environment that is somewhat favorable for intensification.  Sanvu will move over water where the Sea Surface Temperature is near 30.5°C.  Sanvu is under the axis of a narrow upper level ridge and the winds over the southern half of the circulation are fairly weak.  There is little vertical wind shear over that part of the tropical storm.  An upper level trough north of the ridge is producing stronger winds over that half of the circulation.  The stronger winds may be responsible for the lack of strong rainbands in the northern half of Sanvu.  The trough is forecast to move east and the shear in that region should decrease.  When the shear decreases Sanvu could intensify at a faster rate and it is forecast to become a typhoon in two or three days.

The trough is currently steering Tropical Storm Sanvu slowly toward the north-northeast.  When the trough moves away to the east a ridge if forecast to steer Sanvu more toward the north.  On its anticipated track Tropical Storm Sanvu will gradually move away from the northern Marianas and the weather should improve in that region.

Tropical Storm Ma-On Forms East of the Northern Marianas

Tropical Depression 27W intensified into Tropical Storm Ma-On east of the Northern Marianas on Thursday.  At 10:00 a.m. EDT on Thursday the center of Tropical Storm Ma-On was located at latitude 17.7°N and longitude 153.7°E which put it about 405 miles (655 km) south-southeast of Minami Tori Shima.  Ma-On was moving toward the west at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1003 mb.

More thunderstorms developed near the center of a system originally designated Tropical Depression 27W and the Japan Meteorological Agency named it Tropical Storm Ma-On on Thursday.  Although many of the thunderstorms are still developing east of the center of circulation, a few stronger thunderstorms are forming around the center.  The thunderstorms around the center are beginning to generate upper level divergence which is pumping out mass.  Some additional rainbands appear to be forming in the eastern half of the circulation.

Tropical Storm Ma-On is moving through an environment that is favorable for intensification.  Ma-On is moving over water where the Sea Surface Temperature is near 30°C.  Ma-On is moving under the western end of an upper level ridge.  The upper level winds in that part of the ridge are not too strong and the ridge may be enhancing upper level divergence.  Tropical Storm Ma-On could intensify during the next day or so.  When Ma-On gets farther west, it will approach an upper level trough moving off of Asia.  There are stronger southwesterly winds on the eastern side of the trough and the vertical wind shear will increase at that time.

Tropical Storm Ma-On is moving along the southwestern end of a subtropical high pressure system.  The subtropical high is expected to steer Ma-On in a general west-northwesterly direction during the next two or three days.  On its anticipated track Tropical Storm Ma-On could approach the northernmost Marianas in about 36 hours.  It could bring gusty winds and locally heavy rain.

Typhoon Meari Passing Northwest of the Marianas

Typhoon Meari moved northwest of the Marianas on Saturday.  At 11:00 p.m. EDT on Saturday the center of Typhoon Meari was located at latitude 20.2°N and longitude 143.2°E which put it about 240 miles (390 km) west-northwest of Agrihan.  Meari was moving toward the northeast at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 963 mb.

Typhoon Meari strengthened on Saturday.  An eye appeared on visible satellite imagery.  The eyewall is thicker on the southwestern side and thinner on the northeastern side.  There are also more rainbands in the southwestern part of the circulation.  Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Thunderstorms around the core of Typhoon Meari are generating upper level divergence which is pumping out mass.

Typhoon Meari will be moving through a favorable environment for another 12 to 24 hours.  Meari is moving over water where the Sea Surface Temperature is near 30°C.  The typhoon is moving along the transition zone between an upper level trough to its west and an upper level ridge to its east.  There are southwesterly winds blowing across the western side of Typhoon Meari, but those winds are actually enhancing the upper level divergence.  Vertical wind shear will increase when the upper level trough moves closer to the typhoon and Meari will start to weaken early next week.

The upper level trough is steering Typhoon Meari toward the northeast and that general motion is expected to continue for the next several days.  On its anticipated track the center of Typhoon Meari will pass northwest of the northernmost Marianas.  Meari will pass southeast of Iwo To as it moves toward the northern Pacific.

Tropical Storm Meari Intensifies Into a Typhoon

A well organized core developed at the center of Tropical Storm Meari on Friday and it intensified into a typhoon.  At 5:00 p.m. EDT on Friday the center of Typhoon Meari was located at latitude 17.0°N and longitude 140.0°E which put it about 425 miles (685 km) west-northwest of Saipan.  Meari was moving toward the north-northeast at 10 m.p.h. (16 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 979 mb.

A strong center of circulation finally developed within a broader area of low pressure that contained Tropical Storm Meari.  An inner rainband wrapped around the center and an eye appeared on microwave satellite imagery.  The formation of a tight inner core allowed Meari to strengthen into a typhoon.  There are some rainbands east of the center of Typhoon Meari, but most of the stronger thunderstorms are occurring in bands south and west of the center.  Thunderstorms in the core of Typhoon Meari are now generating upper level divergence which is pumping out mass.  Typhoon Meari is now a well organized tropical cyclone.

Typhoon Meari is moving through an environment that is favorable for intensification.  It is moving over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is over Meari which is resulting in light winds in the upper levels and little vertical wind shear.  In fact the upper level ridge is enhancing the divergence generated by the typhoon.  Typhoon Meari should continue to strengthen during the next 24 hours.  Since a well formed core now exists at the center, a period of rapid intensification is quite possible.

Typhoon Meari is moving around the western end of a subtropical ridge which is steering it toward the north-northeast.  That general motion is expected to continue for another day or so.  When Typhoon Meari gets farther north, westerly winds from the middle latitudes will push it toward the northeast more quickly.  On its anticipated track, Typhoon Meari could be near the northernmost Marianas in about 36 hours.  Meari could be a strong typhoon at that time.  Although no warnings are currently in effect, people on Alamagan, Pagan and Agrihan need to monitor the movement of Typhoon Meari.

Tropical Storm Meari Reorganizes West of Guam

The circulation designated as Tropical Storm Meari reorganized west of Guam on Thursday.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Meari was located at latitude 15.0°N and longitude 139.0°E which put it about 415 miles (670 km) west of Guam.  Meari was moving toward the north-northeast at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

Tropical Storm Meari initially formed as a smaller counterclockwise circulation within a much broader cyclonic circulation that stretched from the Northern Mariana Islands toward the Philippines.  The initial surface center weakened on Thursday and a new center of circulation organized northeast of the original center.  A primary rainband began to wrap around the southern and east side of the low level center.  Numerous other bands of showers and thunderstorms were forming within the broader cyclonic circulation.  More bands of showers and thunderstorms were developing southwest of the new center and fewer bands were northeast of the center.  The new center of circulation is still consolidating and Tropical Storm Meari still does not have a well developed core.

Although Meari is still not well organized, the tropical storm is moving through an environment that is favorable for intensification.  Tropical Storm Meari is moving over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is located over Tropical Storm Meari and the upper level winds are weak.  So, there is little vertical wind shear.  Warm water and little shear should allow Tropical Storm Meari to continue to intensify.  The lack of a well formed inner core and the large broad cyclonic circulation will slow the rate of strengthening.

The reformation of the center of circulation farther toward the northeast caused the forecast track guidance from numerical models to shift to a more northeasterly track.  If the current center of Tropical Storm Meari persists, it is located near the western end of a subtropical ridge.  Meari is expected to move toward the northeast around the western end of the ridge.  When Meari moves farther north, westerly winds in the middle latitudes will accelerate the tropical storm toward the northeast.