Tag Archives: Northern Marianas

Tropical Storm Chanthu Forms South of Japan

A center of circulation consolidated near a cluster of thunderstorms south of Japan on Saturday and the system was designated as Tropical Storm Chanthu.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Chanthu was located at latitude 21.2°N and longitude 143.1°E which put it about 295 miles (475 km) south-southeast of Iwo To.  Chanthu was moving toward the northeast at 14 m.p.h. (23 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.

Although a distinct center of circulation exists in the lower levels of Tropical Storm Chanthu, the storm is not well organized.  Southwesterly winds in the upper levels are causing vertical wind shear which is tilting the upper portion of the circulation toward the northeast.  Most of the thunderstorms associated with Tropical Storm Chanthu are occurring in the northeastern quadrant of the circulation.  Several broken rainbands extend into the southern portion of the circulation, but there are few thunderstorms in the western half of Chanthu.

Tropical Storm Chanthu is moving through an environment that is marginally favorable for intensification.  Chanthu is moving over water where the Sea Surface Temperature is near 30°C.  However, an upper level trough west of Chanthu is causing the southwesterly winds which are blowing across the top of the tropical storm.  Moderate vertical wind shear will inhibit intensification in the short term.  As Tropical Storm Chanthu moves farther north, it could move into a region where the upper level winds are not as strong.  If the vertical wind shear decreases, then Chanthu could intensify.

Winds from the upper level trough are steering Tropical Storm Chanthu toward the northeast.  As the tropical storm moves farther north, a subtropical ridge located east of Chanthu will steer it more toward the north.  On its anticipated track, the center of Tropical Storm Chanthu is expected to pass east of Iwo To in about 24 hours.  Tropical Storm Chanthu could be approaching the coast of Japan near Tokyo in about three or four days.

Tropical Storm Champi Passing Through the Northern Marianas

Tropical Storm Champi is bringing gusty winds and heavy rain as it moves through the Northern Marianas.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Champi was centered near latitude 15.9°N and longitude 146.3°E which put it about 80 miles (135 km) east-northeast of Saipan.  Champi was moving toward the west at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 70 m.p.h. (115 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 980 mb.  A Tropical Storm Warning remains in effect for Rota, Tinian, Saipan, Alamagan, Pagan and Agrihan.  The weather station at the airport on Saipan was reporting southwesterly winds at 46 m.p.h. (74 km/h) with gusts to 78 m.p.h. (126 km/h).

Although an upper level ridge north of Champi continued to cause vertical wind shear over the tropical storm, it slowly intensified on Thursday.  More thunderstorms formed near the center of circulation and those storms are generating more upper level divergence.  The core of the circulation is consolidating and more spiral bands are forming outside the core.  Champi is on the threshold of becoming a typhoon.  It is moving over water where the Sea Surface Temperature is near 29°C.  Champi is likely to move into an area where the upper level winds are lighter during the weekend and it will continue to intensify during the next several days.

A subtropical ridge is steering Champi toward the west and that motion is expected to continue for the next 12 to 24 hours.  After that time Champi will reach the western end of the ridge and turn toward the north.  Champi could be a strong typhoon south of Iwo To in about three days.

Tropical Storm Champi Intensifies, Warnings Issued for Northern Marianas

Tropical Storm Champi intensified on Wednesday and the National Weather Service issued watches and warnings for the northern Marianas.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Champi was located at latitude 15.5°N and longitude 151.9°E which put it about 450 miles (730 km) east of Saipan.  Champi was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 60 m.p.h. (95 km/h) and there were wind gusts to 75 m.p.h. (120 km/h).  The minimum surface pressure was 984 mb.  Tropical Storm Warnings have been issued for Rota, Tinian, Saipan, Alamagan, Pagan and Agrihan.  A Typhoon Watch has been issued for Alamagan, Pagan and Agrihan.

The circulation of Tropical Storm Champi is still organizing.  An upper level ridge north of the tropical storm is causing easterly winds to blow over the top of Champi.  The resulting vertical wind shear is causing most of the stronger thunderstorms to form in the western half of the circulation.  Champi is over water where the Sea Surface Temperature is near 29°C.  The vertical wind shear will inhibit intensification on Thursday, but Champi could reach typhoon intensity within 24 hours.  It is expected to move into an area where the upper level winds are lighter on Friday and the rate of intensification could increase.

A subtropical ridge is steering Champi on a track that is a little north of due west.  That general motion is expected to continue for the next several days.  Champi will reach the western end of the subtropical ridge and turn toward the north later in the weekend.  On its anticipated track Champi will approach the northern Marianas in 24 to 30 hours.  It could bring strong winds and heavy rain to those islands.  Since the strongest thunderstorms are west of the center of circulation, conditions could start to deteriorate on some of the islands in less than 24 hours.

Krovanh Becomes a Typhoon Southeast of Iwo To

Krovanh continued to intensify rapidly on Wednesday and it reached typhoon status.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Krovanh was located at latitude 21.5°N and longitude 144.5°E which put it about 330 miles (530 km) southeast of Iwo To.  Krovanh was moving toward the northwest at 13 m.p.h. (21 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 961 mb.

Typhoon Krovanh remains in a very favorable environment.  It is over water with warm Sea Surface Temperatures and the upper level winds are light.  The absence of significant vertical wind shear has allowed upper level divergence to continue to pump away mass in all directions.  The structure of the inner core of Krovanh improved as it intensified and the typhoon now has a well developed eye surrounded by a nearly complete eyewall.  The favorable environment could allow Krovanh to intensify for another 24 to 36 hours.  When the typhoon begins to approach latitude 30°N, it will begin to be affected by the upper level westerly winds in the middle latitudes.  The increased vertical wind shear will begin to weaken Krovanh.

Typhoon Krovanh is moving around the western end of a subtropical ridge.  The ridge should steer Krovanh toward the northwest for another 24 hours.  When it reaches the western end of the ridge, the typhoon will start moving toward the north.  As the upper level westerly winds start to affect Krovanh, those winds will accelerate it toward the northeast.  On its anticipated track Krovanh could be approaching Iwo To in about 24 hours and it could be near Chichi Jima in about 36 hours.  Krovanh could be a strong typhoon when it passes those islands.