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Strengthening Tropical Storm Maria Brings Wind and Rain to Guam

Tropical Storm Maria strengthened quickly on Wednesday and it brought gusty winds and heavy rain to Guam.  The weather station at Andersen Air Force Base on Guam reported sustained winds to 44 m.p.h. (71 km/h) and wind gusts to 72 m.p.h. (116 km/h).  At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Maria was located at latitude 13.9°N and longitude 144.7°E which put it about 5 miles (10 km/h) south of Andersen Air Force Base.  Maria was moving toward the north-northwest at 11 m.p.h. (17 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 987 mb.  Tropical Storm Warnings remained in effect for Guam and Rota.  Tropical Storm Watches were in effect for Saipan and Tinian.

The circulation of Tropical Storm Maria organized quickly on Wednesday.  A tight center of circulation contracted at the center of Maria.  A partial ring of thunderstorms formed on the east side of the center.  Numerous bands of showers and thunderstorms were revolving around the core of the circulation.  Storms around the core generated well developed upper level divergence which pumped mass away in all directions from the tropical storm.  Winds to tropical storm force extended out about 95 miles (155 km) from the center of circulation.

Tropical Storm Maria will move through an environment very favorable for intensification.  Maria will move over water where the Sea Surface Temperature is near 30°C.  Tropical Storm Maria will move under the western portion of an upper level ridge where the upper level winds are weak.  There will little vertical wind shear.  Upper level lows east and west of the ridge will enhance the upper level divergence.  Tropical Storm Maria will strengthen into a typhoon on Thursday.  Maria could intensify rapidly and it is likely to become the equivalent of a major hurricane.

Tropical Storm Maria was moving around the western end of a subtropical ridge which was steering Maria toward the north-northwest.  The ridge is forecast to steer Maria toward the northwest during the next few days.  On its anticipated track Tropical Storm Maria will move away from the Marianas and toward the Ryukyu Islands.  Tropical Storm Maria will continue to cause gusty winds and drop locally heavy rain on the southern Marianas for a few more hours.  Conditions will improve on Thursday when Maria moves away the Marianas.

Typhoon Prapiroon Brings Winds and Rain to Okinawa

Typhoon Prapiroon brought wind and rain to Okinawa on Sunday.  At 5:00 p.m. EDT on Sunday the center of Typhoon Prapiroon was located at latitude 26.8°N and longitude 126.8°E which put it about 65 miles (100 km) west-southwest of Okinawa.  Prapiroon was moving toward the north 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 978 mb.

The circulation of former Tropical Storm Prapiroon became much more well organized on Sunday.  A circular eye formed at the center of circulation and Prapiroon strengthened into a typhoon.  A ring of thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of showers and thunderstorms in the eastern half of the typhoon were revolving around the center of circulation.  Bands northwest of the center consisted mostly of showers and low clouds.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away to the east of the typhoon.

Typhoon Prapiroon will move through an environment favorable for intensification during the next 12 to 24 hours.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Prapiroon could intensify during the next 12 to 24 hours.  Prapiroon will move over cooler water in a day or so.  It will also reach a location where an upper level trough west of South Korea will cause more vertical wind shear.  An environment of cooler water and more wind shear will cause Typhoon Prapiroon to weaken at that time.

Typhoon Prapiroon is moving around the western end of a subtropical ridge which is steering it toward the north.  On its anticipated track the center of Typhoon Prapiroon will pass west of Okinawa and the northern Ryukyu Islands.  Winds to typhoon force extend out about 30 miles (50 km) east of the center of circulation.  Winds to tropical storm force extend out about 150 miles (240 km) east of the center.  So, even though the center of Typhoon Prapiroon will pass west of the northern Ryukyu Islands, it will bring gusty winds and heavy rain.  Typhoon Prapiroon could approach western Kyushu in 24 hours.  When Prapiroon moves farther north the trough west of South Korea will start to steer the typhoon more toward the northeast.

Tropical Storm Prapiroon Moves Toward Okinawa

Tropical Storm Prapiroon moved closer to Okinawa on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Prapiroon was located at latitude 22.4°N and longitude 128.3°E which put it about 315 miles (510 km) south of Okinawa.  Prapiroon was moving toward the northwest at 8 m.p.h. (13 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. (105 km/h).  The minimum surface pressure was 992 mb.

There was a distinct center of circulation in the middle of Tropical Storm Prapiroon, but the distribution of thunderstorms was asymmetrical.  The stronger thunderstorms were occurring in bands south and east of the center of circulation.  The bands north and west of the center consisted primarily of showers and low clouds.  A large upper level ridge over Asia was producing northerly winds which were blowing toward the top of Tropical Storm Prapiroon.  Those winds were causing moderate vertical wind shear and they were probably the reason for the asymmetric distribution of thunderstorms.  Those winds were also blocking upper level divergence to the north and west of Prapiroon.

Tropical Storm Prapiroon will move through an area marginally favorable for intensification during the next 24 to 36 hours.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  So, there will be enough energy in the upper ocean to support intensification.  The upper level ridge will continue to cause some vertical wind shear, but Tropical Storm Prapiroon could move into an area where the upper level winds are a little weaker on Sunday.  If the wind shear decreases, then Tropical Storm Prapiroon will intensify.  There is still a chance that Prapiroon could strengthen into a typhoon when it passes near Okinawa.

Tropical Storm Prapiroon is moving around the western end of a subtropical ridge over the Pacific Ocean which is steering the tropical storm toward the northwest.  Prapiroon is forecast to move more toward the north when it reaches the western end of the ridge in 12 to 24 hours.  On its anticipated track the center of Tropical Storm Prapiroon could approach Okinawa in 12 to 18 hours.  The center of Prapiroon will likely pass west of Okinawa which would bring the strongest winds and heaviest rain over Okinawa.

Tropical Storm Prapiroon Forms South-Southeast of Okinawa

A distinct center of circulation formed within an area of thunderstorms south-southeast of Okinawa on Thursday night and the Japan Meteorological Agency designated the system as Tropical Storm Prapiroon.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Prapiroon was located at latitude 20.0°N and longitude 130.2°E which put it about 500 miles (800 km) south-southeast of Okinawa.  Prapiroon was moving toward the west at 7 m.p.h. (11 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 998 mb.

The circulation of Tropical Storm Prapiroon was still organizing.  More thunderstorms were forming close to the center of circulation.  There were more thunderstorms west of the center than there were east of the center.  Several bands of showers and thunderstorms in the outer part of the circulation were revolving around the core of Tropical Storm Prapiroon.  The storms in the core were generating upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Prapiroon formed beneath an upper level ridge that developed between an upper level low northwest of the Philippines and a much larger upper low east of the Marianas.  The winds in the upper ridge will be weak and there will be little vertical wind shear.  Prapiroon will move over water where the Sea Surface Temperature is near 29°C.  Tropical Storm Prapiroon will move through an environment very favorable for intensification.  Prapiroon will strengthen and it could intensify rapidly once the inner core organizes.  Tropical Storm Prapiroon could strengthen into a typhoon in 24 to 48 hours.

Tropical Storm Prapiroon was moving around the southwestern part of a subtropical ridge which was steering the tropical storm toward the west.  Prapiroon will turn toward the north in 12 to 24 hours when it reaches the western end of the ridge.  On its anticipated track Tropical Storm Prapiroon could approach Okinawa in about 36 hours.  Prapiroon could be a typhoon when it nears Okinawa.

Tropical Storm Gaemi Brings Wind and Rain to Okinawa

Tropical Storm Gaemi brought wind and rain to Okinawa late on Friday.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Gaemi was located at latitude 26.7°N and longitude 127.9°E which put it near Okinawa.  Gaemi was moving toward the east-northeast at 19 m.p.h (30 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 990 mb.

Tropical Storm Gaemi became better organized after it moved across southern Taiwan early on Friday.  The center of circulation was more evident on microwave satellite images.  A primary band of showers and thunderstorms formed in the eastern side of circulation.  Other showers and thunderstorms were located farther to the northeast of the center of Tropical Storm Gaemi.  An upper level trough west of Gaemi was producing string southwesterly winds which were blowing toward the top of the tropical storm.  Those winds were causing moderate vertical wind shear and they were likely the reason why most of the heavier rain was occurring northeast of the center of circulation.

The upper level trough was also steering Tropical Storm Gaemi quickly toward the east-northeast.  On its anticipated track Gaemi will move over the middle Ryukyu Islands including Amami-O-Shima during the next 12 hours.  Tropical Storm Gaemi will continue to produce gusty winds and locally heavy rain.  Most of the rain will fall before the center of circulation reaches a location.  Gaemi is likely to make a transition to an extratropical cyclone when it moves south of the larger islands of Japan during the weekend.

Tropical Storm Gaemi Forms Near Southwest Taiwan

Tropical Storm Gaemi formed near Kaohsiung on the southwest coast of Taiwan late on Thursday.  At 8:00 p.m. EDT on Thursday the center of Tropical Storm Gaemi was located at latitude 22.8°N and longitude 120.2°E which put it near Kaohsiung, Taiwan.  Gaemi was moving toward the northeast at 5 m.p.h. (8 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 992 mb.

A distinct low level center of circulation developed in an area of showers and thunderstorms southwest of Taiwan on Thursday and the Japan Meteorological Agency designated the system as Tropical Storm Gaemi.  Thunderstorms developed near the core of the circulation.  Several short bands of showers and thunderstorms were revolving around the core.  Mountains in eastern Taiwan may have deflected the flow in the lower levels and contributed to the organization of a center of circulation.  Storms around the center were generating some upper level divergence which was pumping mass away to the east of the tropical storm.

Tropical Storm Gaemi is likely to weaken during the next few hours while the center of circulation moves across southern Taiwan.  Mountains in eastern Taiwan could disrupt the lower portions of the circulation when it moves over them.  If the circulation still exists when it moves east of Taiwan in a few hours, then Tropical Storm Gaemi will move into a more favorable environment for intensification.  Gaemi will move over water where the Sea Surface Temperature is near 29°C.  An upper level trough over eastern Asia is producing southwesterly winds which are blowing toward the top of the circulation.  Those winds will cause some vertical wind shear, but the shear will probably not be strong enough to tear the circulation apart.  Gaemi could remain a tropical storm for another 24 to 36 hours.  When Tropical Storm Gaemi moves farther north in a day or two, it will move over colder water and into an area with stronger vertical wind shear.  Gaemi will likely make a transition to an extratropical cyclone at that time.

The upper level trough is forecast to steer Tropical Storm Gaemi toward the northeast.  Gaemi will move across southern Taiwan during the next few hours.  It will cause gusty winds, but the greater risks will be heavy rain and flash floods.  On its anticipated track Tropical Storm Gaemi will move near the southern Ryukyu Islands of Japan.  It could pass near Ishigaki Jima and Miyako Jima in the next 12 to 18 hours.  Gaemi could be near Okinawa later on Friday.

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 Jelawat Forms Near Yap

Tropical Storm Jelawat formed near Yap on Sunday.  At 2:00 p.m. EDT on Sunday the center of Tropical Storm Jelawat was located at latitude 7.6°N and longitude 138.4°E which put it about 120 miles (195 km) south of Yap.  Jelawat was moving toward the northwest at 14 m.p.h. (22 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 998 mb.

A low level center of circulation formed near the eastern edge of a cluster of thunderstorms near Yap on Sunday and the Japan Meteorological Agency designated the system as Tropical Storm Jelawat.  Tropical Storm Jelawat does not have a well organized circulation.  There is a distinct low level center of circulation, but most of the stronger thunderstorms are occurring west of the center of circulation.  The bands in the eastern half of the circulation consist mainly of showers and low clouds.  An upper level ridge over the Central North Pacific Ocean is producing strong easterly winds which are blowing across the top of the circulation.  Those winds are generating strong vertical wind shear and the shear is the main reason for the asymmetrical distribution of storms.

Tropical Storm Jelawat will be moving through an environment that is somewhat favorable for intensification.  Jelawat will move over water where the Sea Surface Temperature is near 28°C.  However, the upper level ridge will continue to cause vertical wind shear.  If the shear is not too strong and the circulation remains vertically coherent, then Tropical Storm Jelawat could strengthen during the next several days.   Some models predict this scenario and forecast that Jelawat will intensify into a typhoon.  Alternatively, if the wind shear increases further, strong upper level winds could blow the upper half of the circulation away from the lower level circulation.  If that occurs, Tropical Storm Jelawat will weaken.

The ridge over the Central North Pacific is steering Tropical Storm Jelawat toward the northwest.  Jelawat will reach the western end of the ridge in 12 to 24 hours.  The tropical storm will turn more toward the north when it reaches the end of the ridge.  On its anticipated track the center of Tropical Storm Jelawat is forecast to pass between Yap and Palau.

Tropical Storm Saola Develops West of Guam

Tropical Storm Saola developed west of Guam on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Saola was located at latitude 14.8°N and longitude 134.8°E which put it about 375 miles (605 km) northwest of Yap.  Saola was moving toward the west-northwest at 24 m.p.h. (39 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 997 mb.

The core of the circulation of Tropical Storm Saola became more well organized on Tuesday.  The center of circulation strengthened and more thunderstorms developed close to the center  Bands of showers and thunderstorms formed outside the core of Tropical Storm Saola.  Many of the showers and storms formed southwest of the center.  There were fewer showers and storms northeast of the center.  The storms near the core of Saola began to produce upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Saola will move through an environment that will be somewhat favorable for intensification.  Saola will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge north of Tropical Storm Saola is producing easterly winds which are blowing toward the top of the circulation.  Those winds are causing moderate vertical wind shear which is inhibiting the intensification of Tropical Storm Saola.  The upper level winds are forecast to weaken which would cause the wind shear to decrease.  The decreased wind shear should allow Tropical Storm Saola to intensify during the next several days and it could eventually strengthen into a typhoon.

The upper level ridge has been steering Tropical Storm Saola toward the west-northwest.  An upper level trough east of Asia is forecast to weaken the ridge.  When the ridge weakens,Tropical Storm Saola will turn more the north.  On its anticipated track Tropical Storm Saola will remain east of the Philippines and Taiwan.  Tropical Storm Saola could approach Okinawa in about 72 hours.  Saola could be a typhoon when it approaches Okinawa.

Lan Strengthens to a Typhoon East of the Philippines

Tropical Storm Lan strengthened east of the Philippines on Tuesday and the Japan Meteorological Agency designated it a typhoon.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Lan was located at latitude 11.2°N and longitude 132.4°E which put it about 515 miles (830 km) east of the Philippines.  Lan was moving toward the north-northeast at 5 m.p.h. (8 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. (150 km/h).  The minimum surface pressure was 976 mb.

The circulation of Typhoon Lan became much more well organized on Tuesday.  Several long rainbands developed in the circulation and other smaller bands formed in the periphery of the typhoon.  The circulation of Typhoon Lan was circular and symmetrical.  Thunderstorms near the core of Lan began to generate strong upper level divergence which was pumping mass away from the typhoon in all directions.  The upper level divergence allowed the surface pressure to decrease and the wind speed to increase.  Lan is a large typhoon.  Winds to tropical storm force extend out about 230 miles (370 km) from the center of circulation.

Typhoon Lan will move through an environment favorable for intensification.  Lan will move over water where the Sea Surface Temperature is near 30°C.  Typhoon Lan will move through an area where the upper level winds will be weak and there will be little vertical wind shear during the next several days.  Typhoon Lan will continue to strengthen and there could be a period of rapid intensification after a well formed eye develops at the center of circulation.

Typhoon Lan was in an area where the steering currents were weak and it moved little on Tuesday.  An upper level ridge north of Lan blocked the typhoon from moving northward.  A weakness is forecast to develop in the ridge and the models are forecasting that Typhoon Lan will move northward during the rest of this week.  On its anticipated track Typhoon Lan will remain east of the Philippines.  Lan could be southeast of Okinawa in three or four days.