Tag Archives: Alaska

Typhoon Bolaven Passes East of Iwo To

Typhoon Bolaven passed east of Iwo To on Thursday evening. At 11:00 p.m. EDT on Thursday the center of Typhoon Bolaven was located at latitude 26.2°N and longitude 147.8°E which put it about 350 miles (570 km) east of Iwo To. Bolaven was moving toward the northeast at 23 m.p.h. (37 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. (285 km/h). The minimum surface pressure was 928 mb.

Concentric eyewalls developed at the center of Typhoon Bolaven on Thursday. The inner end of a rainband wrapped around the existing small eye and eyewall. The larger outer eyewall surrounded the inner eye and eyewall. Bands of showers and thunderstorms revolved around the concentric eyewalls. Storms near the eyewalls generated upper level divergence that pumped mass away to the northeast of the typhoon.

The size of Typhoon Bolaven increased when the concentric eyewalls developed. Winds to typhoon force extended out 60 miles (95 km) from the center of Bolaven’s circulation. Winds to tropical storm force extended out 265 miles (425 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Bolaven was 29.9. The Hurricane Size Index (HSI) was 21.3 and the Hurricane Wind Intensity Size Index (HWISI) was 51.2.

Typhoon Bolaven will move through an environment that will become more unfavorable for a powerful typhoon during the next 24 hours. Bolaven will move over water where the Sea Surface Temperatures are near 27°C. It will move under the eastern side of an upper level trough near Japan. The upper level trough will produce southwesterly winds that will blow toward the top of Bolaven’s circulation. Those winds will cause the vertical wind shear to increase. Typhoon Bolaven is likely to weaken during the next 24 hours as it goes through an eyewall replacement cycle and the vertical wind shear increases. Bolaven could make a transition to a strong extratropical cyclone when it moves over cooler water south of Alaska.

The upper level trough near Japan will steer Typhoon Bolaven quickly toward the northeast during the next 24 hours. On its anticipated track, Typhoon Bolaven will pass far to the east of Japan on Friday. Bolaven could move south of the Aleutian Islands during the weekend.

Nanmadol Strengthens to a Typhoon South of Japan

Former Tropical Storm Nanmadol strengthened to a typhoon south of Japan on Thursday morning. At 5:00 a.m. EDT on Thursday the center of Typhoon Nanmadol was located at latitude 23.6°N and longitude 137.5°E which put it about 660 miles (1065 km) east-southeast of Okinawa. Nanmadol was moving toward the west-northwest at 9 m.p.h. (15 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 981 mb.

Former Tropical Storm Nanmadol intensified to a typhoon over the Western North Pacific Ocean south of Japan on Thursday morning. A circular eye formed at the center of Nanmadol’s circulation. The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Nanmadol. Storms near the core generated upper level divergence that pumped mass away from the typhoon. Winds to typhoon force extended out 30 miles (50 km) from the center of circulation in the northern side of Nanmadol. Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation.

Typhoon Nanmadol will move through an environment favorable for intensification during the next 36 hours. Nanmadol will move over water where the Sea Surface Temperatures are 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 Nanmadol will intensify during the next 36 hours. It is likely to strengthen to the equivalent of a major hurricane.

Typhoon Nanmadol will move around the southwestern part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Nanmadol toward then northwest during the next 36 hours. On its anticipated track Typhoon Nanmadol could approach the northern Ryukyu Islands in 48 hours. Nanmadol is likely to be a large, dangerous typhoon when it moves near the north Ryukyu Islands.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Muifa weakened over the Yellow Sea and Typhoon Merbok was transitioning to a powerful extratropical cyclone south of the western Aleutian Islands. At 5:00 a.m. EDT on Thursday the center of Tropical Storm Muifa was located at latitude 34.6°N and longitude 120.3°E which put it about 100 miles (160 km) south-southwest of Qingdao, China. Muifa was moving toward the north-northwest at 16 m.p.h. (26 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 994 mb.

At 5:00 a.m. EDT on Thursday the center of Typhoon Merbok was located at latitude 41.0°N and longitude 166.0°E which put it about 890 miles (1435 km) south-southwest of Kiska, Alaska. Merbok was moving toward the north-northeast at 45 m.p.h. (75 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 960 mb.

Typhoon Sanvu Brings Wind and Rain to Chichi Jima

Typhoon Sanvu is bringing a prolonged period of gusty winds and heavy rain to Chichi JIma, Japan.  Sanvu strengthened during the past several days while it meandered around Chichi Jima.  At 11:00 a.m. EDT on Thursday the center to Typhoon Sanvu was located at latitude 28.1°N and longitude 142.0°E which put it about 60 miles (95 km) north-northwest of Chichi Jima, Japan.  Sanvu was moving toward the north at 8 m.p.h. (13 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 967 mb.

The organization of Typhoon Sanvu has been slowly improving.  An eye developed at the center of Sanvu as the typhoon moved slowly over Chichi Jima.  A broken ring of thunderstorms surrounds the eye.  The strongest winds are occurring in the ring of storms.  A primary band of thunderstorms wraps around the western and southern sides of the center of circulation.  Other bands of showers and thunderstorms are developing outside the core of Typhoon Sanvu.  Most of the bands are developing in the southern half of the circulation.  Thunderstorms in the core of Sanvu are producing upper level divergence which is pumping mass away to the north of the typhoon.

Typhoon Sanvu will move through an environment favorable for intensification for several more days.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge east of Sanvu is producing southerly winds which are blowing toward the top of the circulation, but there is not much vertical wind shear.  Typhoon Sanvu is likely to continue to strengthen for another 24 to 48 hours.  Eventually, Sanvu will move over colder water and the wind shear will increase.  It will start to weaken when that happens.

Sanvu is moving around the western end of a subtropical ridge which steering the typhoon toward the north.  When Typhoon Sanvu moves farther north, it will be steered by an upper level trough over Japan.  Southwesterly winds will steer Sanvu toward the northeast at a faster speed in a day or two.  On its anticipated track Typhoon Sanvu would stay east of Tokyo, but it could affect the northernmost islands of Japan in four or five days.  Conditions in Chichi Jima should improve slowly as Typhoon Sanvu moves farther away.

Tropical Storm Choi-Wan Organizing Southeast of Japan

Tropical Storm Choi-Wan exhibited better organization on Monday as it moved southeast of Japan.  At 5:00 p.m. EDT on Monday the center of Tropical Storm Choi-Wan was located at latitude 23.4°N and longitude 151.4°W which put it about 615 miles (990 km) east of Iwo To.  Choi-Wan was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 981 mb.

Tropical Storm Choi-Wan has a broad center of circulation without a tight inner core.  A rainband appears to be trying to wrap entirely around the broad center and other rainbands are forming outside the center.  Satellite images seem to indicate that Choi-Wan is slowly organizing.  Thunderstorms near the center of circulation are producing upper level divergence.

The environment favors intensification.  Choi-Wan is over water where the Sea Surface Temperature (SST) is near 29°C.  The upper level winds are light and there is little vertical wind shear.  Upper level outflow channels appear to be developing northeast and southwest of Choi-Wan.  If the tropical storm had a tight core, rapid intensification would be likely.  With a broader center of circulation, intensification will be more gradual.  Choi-Wan could become a typhoon on Tuesday.  When Choi-Wan moves farther north it will move over cooler SSTs and the wind shear will increase, which will weaken it.

Tropical Storm Choi-Wan is moving around the western end of a subtropical ridge.  The ridge is expected to steer Choi-Wan mainly toward the north during the next several days.  On its anticipated track, Choi-Wan could approach some of the northern islands of Japan in about three days.  Choi-Wan could be a tropical storm or a strong extratropical low pressure system at that time.