Monthly Archives: July 2015

Tropical Storm Claudette Forms Southeast of New England

An area of low pressure off the East Coast of the U.S. rapidly acquired tropical characteristics on Monday and it was classified as Tropical Storm Claudette by the National Hurricane Center.  At 1:00 p.m. EDT on Monday the center of Tropical Storm Claudette was located at latitude 37.4°N and longitude 68.1°W which put it about 290 miles (465 km) south-southeast of Nantucket Island, Massachusetts and about 550 miles (885 km) south-southwest of Halifax, Nova Scotia.  Claudette was moving toward the northeast at 15 m.p.h. (24 km/h).  The maximum sustained wind speed as 50 m.p.h. (85 km/h) and there were gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1004 mb.

Claudette began as a small low pressure system along a nearly stationary frontal boundary off the East Coast of the U.S.  Moderate wind shear kept the system looking non-tropical for much of the weekend.  The wind shear decreased on Monday morning and as the low moved over the warmer water of the Gulf Stream, thunderstorms developed near the center of circulation.  The stationary frontal boundary dissipated and the system took on a more tropical appearance.  Latent energy released in thunderstorms near the center produced the development of a warm core and some banding developed in the eastern portion of the circulation.  As a result of those changes, the system was classified as Tropical Storm Claudette.

Claudette could strengthen in the short term.  It is still over the Gulf Stream and the upper level winds are not too strong.  However, once the tropical storm moves north of latitude 40°N, it will move over cooler Sea Surface Temperatures.  In addition, stronger upper level winds will increase the vertical wind shear in a day or two.  Claudette could make a transition to an extratropical cyclone within 48 hours.

A combination of a trough approaching the eastern U.S, and a ridge over the Atlantic are expected to steer Claudette toward the northeast.  On its anticipated track, Claudette could approach eastern Nova Scotia in about 24 hours and Labrador in 30 hours.

Tropical Storm Dolores Forms South of Mexico

A low level circulation organized in a large area of thunderstorms south of Acapulco, Mexico on Sunday and the system was classified as Tropical Storm Dolores.  At 2:00 p.m. EDT on Sunday the center of Tropical Storm Dolores was located at latitude 15.6°N and longitude 102.1°W which put it about 145 miles (230 km) south-southwest of Zihuatanejo, Mexico and about 295 miles (475 km) southeast of Manzanillo, Mexico.  Dolores was moving toward the northwest 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 55 m.p.h. (90 km/h).  The minimum surface pressure was 1002 mb.  The government of Mexico has issued a Tropical Storm Watch for the portion of the coast from Lazaro Cardenas to Cabo Corrientes.

The circulation around Dolores is not particularly well organized.  Most of the strong thunderstorms are occurring in the eastern half of the circulation.  There are few thunderstorms in the southwestern part of the tropical storm.  Upper level winds are light over Dolores and the tropical storm is producing strong upper level divergence which is pumping out mass.  Dolores is over water where the Sea Surface Temperatures are near 30°C and there is plenty of energy in the upper ocean to support intensification.  Dolores is close enough to Mexico that it could be pulling in some drier air from land, which may be inhibiting intensification at this time.  The environmental factors would support intensification and rapid intensification may be possible if Dolores moves farther away from the coast of Mexico.

A strong mid-level ridge over Texas and Mexico is steering Dolores toward the west-northwest.  That general steering pattern is expected to continue for the next few days.  On its anticipated track the center of Dolores is forecast to stay west of the coast of Mexico.  However, the proximity of Dolores to the coast prompted the issuance of a Tropical Storm Watch for a portion of the coast.

Typhoon Chan-hom Approaching Shanghai

Large Typhoon Chan-hom is moving northward toward Shanghai, China.  At 5:00 p.m. EDT on Friday the center of Typhoon Chan-hom was located at latitude 28.2°N and longitude 123.1°E which put it about 300 miles (500 km) south-southeast of Shanghai, China.  Chan-hom was moving to the northwest at 10 m.p.h. (16 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. (200 km/h).  The minimum surface pressure was 956 mb.

Chan-hom still has a very symmetrical circulation, but the intensity of the thunderstorms appears to have weakened in recent hours.  The typhoon is moving over water where the Sea Surface Temperatures (SSTs) are cooler and that is the most likely cause for the decreased intensity of the thunderstorms.  As it nears the coast of China, more of the western half of the circulation will be over land and increased friction will further reduce the wind speeds.  Vertical wind shear may also increase as Chan-hom moves farther north.

Chan-hom is moving around the western end of the subtropical ridge which has been steering it toward the northwest.  As it moves around the end of the ridge, Chan-hom will first turn toward the north and then it could accelerate toward the northeast when it begins to be affected by the mid-latitude westerlies.  On its anticipated track the center of Chan-hom will be near Shanghai in about 24 hours.  Given the large size of Chan-hom, the typhoon could bring strong winds and locally heavy rain to the region near Shanghai.

Large Powerful Typhoon Chan-hom Heading for Northeastern China

Large and powerful Typhoon Chan-hom passed south of Okinawa and headed for northeastern China on Thursday.  At 11:00 p.m. EDT on Thursday the center of Typhoon Chan-hom was located at latitude 25.9°N and longitude 125.0°E which put it about 155 miles (250 km) west-southwest of Okinawa and about 400 miles (640 km) south-southeast of Shanghai, China.  Chan-hom was moving toward the west-northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were gusts to 165 m.p.h. (265 km/h).  The minimum surface pressure was 933 mb.

Typhoon Chan-hom has a very symmetrical structure with a well formed eye and numerous rainbands.  Hurricane force winds extend out 75 miles (120 km) in all directions from the center.  Upper level divergence is well developed and it is pumping out mass in all directions.  Chan-hom is moving over water where the Sea Surface Temperature is near 28°C.  Given the favorable environment, Chan-hom is likely to remain a powerful typhoon as it approaches the coast of northeastern China.

A subtropical ridge is steering Chan-hom toward the northwest and that steering motion is expected to continue on Friday.  On its anticipated track Chan-hom will approach the coast of China in about 24 hours.  It could make landfall south of Shanghai near Taizhou.  Chan-hom is likely to bring strong winds and heavy rain to parts of northeastern China when it makes landfall.

Powerful Typhoon Nangka Moving Through Northern Marianas

Powerful Typhoon Nangka is moving through the northern Mariana Islands.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Nangka was located at latitude 17.2°N and longitude 146.5°E which put it about 145 miles (240 km) north-northeast of Saipan and about 45 miles (75 km) southeast of Alamagan.  Nangka was moving toward the west-northwest at 12 m.p.h.  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 170 m.p.h. (275 km/h).  Nangka is the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  The minimum surface pressure was 929 mb.

Nangka has a very symmetrical structure and strong convection surrounds the eye.  It is over warm Sea Surface Temperatures and it could intensify further.  Upper level outflow from the eastern side of large Typhoon Chan-hom which is about 1200 miles (1940 km) west-northwest of Nangka could begin to create wind shear over the western side of Nangka.  Eyewall replacement cycles could also produce fluctuations in intensity.

A subtropical ridge is steering Nangka toward the west-northwest and that steering pattern is expected to continue for another two or three days.  On its anticipated track the core of Nangka will pass close to the islands of Guguan, Alamagan, Pagan and Agrihan.  It could bring very strong winds and heavy rain to those locations on Thursday.

Large Typhoon Chan-hom South-Southeast of Okinawa

Large Typhoon Chan-hom is approaching the far southern islands of Japan.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Chan-hom was located at latitude 22.8°N and longitude 129.2°E which put it about 300 miles (480 km) south-southeast of Okinawa.  Chan-hom was moving toward the northwest at 14 m.p.h.  The maximum sustained wind speed was 105 m.p.h. (120 km/h) and there were wind gusts to 125 m.p.h. (200 km/h).  The minimum surface pressure was 956 mb.

Typhoon Chan-hom has a very large circulation.  It has a 32 mile (50 km) wide eye and hurricane force winds extend out 40 miles (65 km) in all directions from the center.  The circulation is very symmetrical and upper level divergence is well developed in all directions.  Chan-hom is still over warm Sea Surface Temperatures and there is little wind shear.  Further intensification is possible, although the size of the circulation could limit the rate of intensification.

A subtropical ridge is steering Chan-hom toward the northwest and that steering pattern is expected to continue during the next several days.  On its anticipated track the center of Chan-hom could pass south of Okinawa on Thursday.  Given the large circulation it could bring winds and rain to that island.  The center could come close to Miyako-Jima and that location and other nearby islands could experience typhoon force winds and heavy rain.

Typhoon Linfa Making Landfall East of Hong Kong

The center of Typhoon Linfa is very near the coast of China.  At 11:00 p.m. EDT on Wednesday the center of Typhoon Linfa was located at latitude 22.6°N and longitude 116.4°E which put it about 165 miles east of Hong Kong.  Linfa was moving toward the west 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 974 mb.

A mid-level ridge north of Typhoon Linfa is steering it toward the west and that steering pattern is expected to continue in the short term.  On its anticipated track Linfa will move along the coast of China and it could approach Hong Kong in 12 to 18 hours.  Since half of the circulation will be over land and half of the circulation will be over water, Linfa is expected to weaken slowly on Thursday.  It could bring tropical storm force winds and heavy rain to areas near the coast.  Linfa could still be a tropical storm when it moves across Hong Kong.

Nangka Intensifies Rapidly Into a Strong Typhoon

Typhoon Nangka intensified rapidly into a strong typhoon on Monday.  At 11:00 p.m. EDT on Monday the center of Typhoon Nanga was located at latitude 13.2°N and longitude 155.0°E which put it about 670 miles (1080 km) east-southeast of Saipan.  Nangka was moving toward the west-northwest at 13 m.p.h. (21 km/h).  The maximum sustained wind speed was 110 m.p.h. (180 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 952 mb.

The circulation of Typhoon Nangka is very well organized with a strong ring of thunderstorms surrounding a circular eye.  The typhoon is over an area where the Sea Surface Temperature is around 28°C to 29°C.  The upper level winds are relatively light and there appear to outflow channels to the northeast and southwest which are transporting mass away from the center of circulation.  The surface pressure is decreasing rapidly and the wind speeds are increasing quickly.  Nangka is in an environment that is very favorable for further intensification and it could become a very powerful typhoon.

A subtropical ridge is steering Nangka toward the west-northwest and that general motion is expected to continue during the next few days.  On its anticipated track Typhoon Nangka could approach the northern Mariana Islands in about 48 to 72 hours.

Chan-hom Intensifies Into a Typhoon

The circulation around Chan-hom organized rapidly on Monday and it intensified into a typhoon.  At 11:00 p.m. EDT on Monday the center of Typhoon Chan-hom was located at latitude 18.1°N and longitude 136.8°E which put it about 850 miles (1370 km) southeast of Okinawa.  Chan-hom was moving toward the west at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 967 mb.

A primary rainband wrapped completely around the center of circulation of Typhoon Chan-hom and a large eye is apparent on satellite images.  Strong thunderstorms around the eye are generating upper level divergence which is pumping out mass and allowing the surface pressure to decrease.  The typhoon is over water where the Sea Surface Temperature is around 28°C and there is plenty of energy in the upper ocean.  Upper level winds are relatively light and there is not much vertical wind shear.  The environment is very favorable for further intensification and rapid intensification is possible.  Chan-hom is expected to continue to intensify and it could become the equivalent of a major hurricane later this week.

A subtropical ridge north of Chan-hom is steering the typhoon toward the west.  The ridge is expected to steer Chan-hom toward the northwest during the next few days.  On its anticipated track Typhoon Chan-hom could approach the southern islands of Japan in about three days.  It could be a large and powerful typhoon at that time.

Tropical Storm Chan-hom Moving Away From the Marianas

Tropical Storm Chan-hom continued to move farther west of the Mariana Islands on Sunday.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Chan-hom was located at latitude 16.6°N and longitude 142.0°E which put it about 1170 miles (1890 km) southeast of Okinawa.  Chan-hom was moving toward the north-northwest at 10 m.p.h. (16 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 982 mb.

The circulation around Tropical Storm Chan-hom became a little better organized on Sunday.  A primary band of thunderstorms wrapped around the southern half of the circulation.  There also appears to be some drier air wrapping into the circulation as well.  The upper level winds have decreased and some upper level divergence appears to be developing.  Chan-hom is over water there the Sea Surface Temperature is near 28°C.  With the exception of the drier air the environment is favorable for intensification Chan-hom is expected to become a typhoon.

A subtropical ridge is steering Chan-hom in a generally northwesterly direction and that steering pattern is expected to continue for the next few days.  On its anticipated track Chan-hom could approach Okinawa in three or four days.