Category Archives: Tropical Cyclones

Information about tropical cyclones

Tropical Storm Linfa Nearing Northern Luzon

Tropical Storm Linfa is moving steadily toward the coast of northern Luzon.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Linfa was located at latitude 16.1°N and longitude 123.9°E which put it about 230 miles (370 km) east-northeast of Manila, Philippines.  Linfa was moving toward the northwest at 9 m.p.h. (15 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 989 mb.

Tropical Storm Linfa has a small circulation, but it appears to be intensifying quickly.  A circular area of strong thunderstorms has developed around the center of circulation and it is producing strong upper level outflow.  Linfa is over water where the Sea Surface Temperature is near 30°C.  An upper level ridge northwest of the tropical storm is producing some vertical wind shear, but the shear does not seem to be enough to prevent intensification.  Linfa has about 18 hours to intensify before it reaches the coast of Luzon and it could attain typhoon intensity before it gets there.  Mountains in northern Luzon will disrupt the lowers levels of the circulation and Linfa will weaken after if makes landfall.

A subtropical ridge is steering Linfa toward the northwest and that steering pattern is expected to continue until the tropical storm makes landfall in northern Luzon.   Linfa will reach the western end of the subtropical ridge while it is over Luzon and if the circulation remains intact vertically, it will turn toward the north.  On its anticipated track Linfa will make landfall in northern Luzon in about 18 hours.  It is expected to eventually turn north toward Taiwan and the southern islands of Japan.  Linfa cold bring strong winds and locally heavy rainfall for parts of northern Luzon.  Heavy rainfall could contribute to flooding and mudslides in some locations.

Tropical Storm Chan-hom Moving Toward Marianas

Tropical Storm Chan-hom has resumed a northwesterly motion and it is moving toward the Mariana Islands.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Chan-hom was located at latitude 12.7°N and longitude 148.2°E which put it about 250 miles (400 km) east-southeast of Guam.  Chan-hom was moving toward the northwest at 11 m.p.h. (18 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 989 mb.  A Typhoon Watch is in effect for Guam, Rota, Tinian and Saipan.

The upper level low that produced the vertical wind shear which blew the top off Chan-hom on Thursday moved northeast and the upper level winds decreased on Friday.  A reduction in vertical wind shear allowed new thunderstorms to develop around the center of circulation and the circulation became better organized.  The thunderstorms near the center are beginning to generate upper level divergence and more spiral bands appear to be forming.  Chan-hom is over water where the Sea Surface Temperature is near 29°C.  The environment is favorable for intensification and rapid intensification is possible, if the wind shear remains modest.  Chan-hom could attain typhoon intensity before it reaches the Mariana Islands.

A subtropical ridge is steering Chan-hom toward the northwest and that ridge is expected to continue to steer it in the same general direction during the next few days.  On its anticipated track, Chan-hom could approach the Mariana Islands in about 24 hours.  The center could pass north of Guam, but it may pass near to Rota, Tinian or Saipan.  Chan-hom will bring wind and heavy rain to any islands it crosses.

Tropical Storm Nangka Forms East of Kwajalein

Another tropical storm formed over the western North Pacific when a circulation developed west of the International Dateline and was designated as Tropical Storm Nangka (11W).  At 11:00 p.m. EDT on Friday the center of Tropical Storm Nangka was located at latitude 9.9°N and longitude 169.2°E which put it about 150 miles east-northeast of Kwajalein.  Nangka was moving toward the west-northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 992 mb.

Tropical Storm Nangka is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and upper level divergence is increasing.  However, there is sinking drier air north of the tropical storm and the circulation appears to be pulling some of the drier air into it.  As a result many of the stronger thunderstorms are occurring in the western half of the circulation.  The drier air could inhibit intensification in the short term.  The other favorable environmental factors are likely to produce intensification in the longer term once Nangka moves west of the drier air.

A subtropical ridge north of Nangka is expected to steer it in a west-northwesterly direction during the next few days.  On its expected track Nangka will bring wind and rain to a number of atolls in the Marshall Islands.  Nangka could approach the Mariana Islands in a few days.

Wind Shear Affecting Tropical Storm Chan-hom

Although Tropical Storm Chan-hom briefly reached typhoon intensity on Thursday, strong upper vertical wind shear quickly weakened it back to a tropical storm.  At 11:00 p.m. EDT on Thursday the center of Tropical Storm Chan-hom was located at latitude 10.3°N and longitude 148.0°E which put it about 325 miles (525 km) southeast of Guam.  Chan-hom was moving toward the west at 6 m.p.h. (10 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 981 mb.  A Typhoon Watch has been issued for Guam, Rota, Tinian and Saipan.

The combination of a upper level ridge and an upper level low produced strong northeasterly winds that blew the middle and upper portions of the circulation of Chan-hom west of the low level circulation.  The middle and upper parts of the circulation are about 100 miles (160 km) southwest of the surface center.  There are no thunderstorms currently near the surface center.  The upper level winds and the vertical wind shear they are producing are likely to continue to weaken Chan-hom on Friday.  The upper low is expected to move eastward during the next several days, which would result in a decrease in the wind shear.  If the surface circulation is still intact, it will be over warm Sea Surface Temperatures and reintensification would be possible.

Chan-hom is likely to be steered toward the west on Friday by the winds in the lower levels.  If new thunderstorms develop near the center and the height of the circulation increases, then a subtropical ridge in the middle levels could cause the tropical storm to turn toward the northwest.  If that turn occurs on Friday, it could put Chan-hom on a track toward Guam, Saipan or Tiniana.  If the turn occurs later in the weekend, then Chan-hom could pass to the south of those islands before it turns toward the northwest.

Tropical Storm Linfa Forms East of the Philippines

A well defined low level circulation developed in an area of thunderstorms east of the Philippines on Thursday and the system was designated as Tropical Storm Linfa (10W).  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Linfa was located at latitude 16.3°N and longitude 127.6°E which put it about 470 miles (760 km) east-northeast of Manila, Philippines.  Linfa was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

Linfa developed over water where the Sea Surface Temperature (SST) is near 30°C,  There is sufficient energy in the upper ocean to support intensification.  An upper level ridge centered northwest of Linfa is producing northeasterly winds over the top of the circulation and most of the thunderstorms are occurring west of the center.  The vertical wind shear is modest and some upper level divergence is present, especially over the western half of the circulation.  The vertical wind shear is expected to remain moderate and Linfa could intensify during the next several days.  If the upper level winds weaken, then a period of more rapid intensification is possible.

Linfa is being steered by a subtropical ridge located to the east of the tropical storm.  The ridge is expected to steer it toward the northwest in the short term.  As Linfa reaches the western end of the ridge it is expected to be steered more toward the north.  The timing of the turn toward the north will be important because it will determine if Linfa moves over the northern Philippines or moves northeast of that area.  The timing on the turn to the north will also determine the potential risk for Taiwan.  Another factor that could complicated the track forecast is a potential interaction with Typhoon Chan-hom which is abut 1500 miles (2400 km) east-southeast of Linfa.

Tropical Cyclone Raquel Reorganizing Near Solomon Islands

Strong upper level winds blew away the upper potion of Tropical Cyclone Raquel on Wednesday.  However, the upper level winds lessened on Thursday and thunderstorms began to reform on the western side of the circulation.  At 5:00 p.m. EDT on Thursday the center of Tropical Cyclone Raquel was located at latitude 6.4°S and longitude 160.5°E which put it about 220 miles (360 km) north of Honiara in the Solomon Islands.  Raquel was moving toward the south-southeast at 3 m.p.h. (5 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 994 mb.

Tropical Cyclone Raquel is over water where the Sea Surface Temperatures are very warm.  However, an upper level ridge east of Raquel generated strong winds over the top of the tropical cyclone on Wednesday and blew away the upper parts of the circulation.  The upper level winds weakened on Thursday and new thunderstorms began to develop west of the center of circulation.  Upper level divergence is also occurring in the western half of the circulation and Raquel looks like a tropical cyclone again.  The upper level winds are still strong enough to inhibit intensification, but Raquel could strengthen further in the short term.

When the top parts of the circulation were blown away on Wednesday, the lower level circulation was steered by winds in the lower troposphere and it moved toward the northeast.  As the thunderstorms redevelop, the height of the circulation is increasing and Raquel is more likely to be steered by winds in the middle troposphere.  Those winds are expected to steer Raquel back toward the southwest.  On its anticipated track Raquel could again approach Santa Isabel Island on Friday.  It could bring winds and locally heavy rain to portions of the Central Solomon Islands.

Tropical Storm Chan-hom Forms East of Guam

A center of circulation developed in an area of thunderstorms on the opposite side of the Equator from Tropical Cyclone Raquel and it was designated as Tropical Storm Chan-hom on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Chan-hom was located at latitude 11.0°N and longitude 156.5°E which put it about 250 miles (400 km) north-northeast of Oroluk atoll and about 800 miles (1290 km) east of Guam.  Chan-hom was moving toward the west at 22 m.p.h. (35 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

Tropical Storm Chan-hom formed over water where the Sea Surface Temperatures (SSTs) are around 29°C to 30°C and there is plenty of energy in the upper ocean to support intensification.  An upper level ridge located north of the tropical storm is generating easterly winds over the top of the circulation.  The easterly winds are generating moderate amounts of vertical wind shear and many of the stronger thunderstorms are occurring in the western half of the circulation.  Those thunderstorms are producing strong rising motion and upper level divergence is well developed on the western side of Chan-hom.  However the upper level easterly winds are interfering with upper level divergence on the eastern side of the tropical storm.  As a result, a modest rate of intensification is expected in the short term.  If the upper level winds were to lessen, then a more rapid rate of intensification would be possible.

The upper level ridge is expected to steer Chan-hom toward the west during the next several days.  On its anticipated track Chan-hom could approach Guam in about three days.  It could be a typhoon by that time.  However, there is some divergence in the track guidance from numerical models at the end of this week and that is producing uncertainty about the future track of Chan during that time period.

Tropical Cyclone Raquel Forms Near the Solomon Islands

A distinct low level center of circulation was detected inside a large area of thunderstorms north of the Solomon Islands and the system was designated as Tropical Cyclone Raquel (25P).  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone Raquel was located at latitude 6.5°S and longitude 158.9°E which put it about 210 miles (335 km) north of Honiara in the Solomon Islands.  Raquel was moving toward the southwest at 11 m.p.h. (18 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 989 mb.

Raquel is over water where the Sea Surface Temperature is quite warm and there is plenty of energy in the upper ocean to support intensification.  However, and upper level ridge east of Raquel is northeasterly winds over the top of the circulation and it is creating moderate amounts of vertical wind shear.  The wind shear is causing many of the stronger thunderstorms to occur on the western side of the circulation.  The wind shear may be tilting the vertical structure of the circulation toward the southwest and it is limiting the potential for intensification.

As Raquel moves around the western end of the upper level ridge, it is expected to be steered toward the south on Wednesday.  On its anticipated track Raquel is expected to move across Santa Isabel on Wednesday.  It could be near Guadacanal in 36 to 48 hours.  Raquel is likely to bring some wind and locally heavy rain to parts of the central Solomon Islands during the next two days.

Tropical Storm Kujira Makes Landfall on Hainan Island

Tropical Storm Kujira made landfall on the east coast of Hainan Island on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Kujira was located at latitude 19.9°N and longitude 109.1°E which put it about 100 miles (160 km) south of Beihai, China.  Kujira was moving toward the northwest at 10 m.p.h. (16 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.

Passing across Hainan Island weakened Tropical Storm Kujira on Monday.  In addition, an upper level ridge over southern Asia continues to generate vertical wind shear over the tropical storm.  However, it will move over warm water when the center moves northwest of Hainan Island.  So, Kujira could maintain tropical storm intensity until it makes another landfall in China in about 18 to 24 hours.  The primary risk will be locally heavy rainfall.

Tropical Storm Kujira Nearing Hainan Island

Tropical Storm Kujira moved slowly northward on Sunday.  At 11:00 p.m. EDT on Sunday night the center of Tropical Storm Kujira was located at latitude 18.0°N and longitude 111.2°E which put it about 150 miles (240 km) south-southeast of Xuwen, China.  Kujira was moving toward the north-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 994 mb.

Although Kujira is moving over water where the Sea Surface Temperature is near 30°C, vertical wind shear is inhibiting intensification.  An upper level ridge over southern Asia is producing northeasterly winds over the top of Kujira.  As a result of the vertical shear, most of the stronger thunderstorms are occurring southwest of the center of circulation.  As Kujira moves farther north, some of the circulation will move over Hainan Island, which will further limit the potential for intensification.

Kujira is moving around the western end of a subtropical ridge which is steering the tropical storm toward the north.  The steering pattern is expected to remain in place for the early part of the week.  Kujira could be very close to the east coast of Hainan Island in about 12 hours.  It will move near or just east of Hainan and Kujira could make landfall in China in 24 to 36 hours.  Although it will bring some wind, the primary risk will be locally heavy rainfall.