Category Archives: Tropical Cyclones

Information about tropical cyclones

Dangerous Typhoon Koppu Making Landfall in Northern Luzon

Typhoon Koppu intensified rapidly during the past 12 hours and it is making landfall near Baler in northern Luzon as the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale.  At 11:00 a.m. EDT on Saturday the center of Typhoon Koppu was located at latitude 16.0°N and longitude 122.9°E which put it about 170 miles (275 km) east-northeast of Manila, Philippines.  Koppu was moving toward the west-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h).  The minimum surface pressure was 918 mb.  Typhoon Koppu has a Hurricane Intensity Index (HII) of 31.6, a Hurricane Size Index (HSI) of 17.5 and a Hurricane Wind Intensity Size Index (HWISI) of 49.1, which means it is capable of producing regional significant wind damage.  In addition the slow movement of Koppu means it will produce very heavy rainfall which will create the potential for serious flooding and landslides.

Koppu will continue to move toward the west-northwest for another 12 to 24 hours.  Then it will reach the western end of the subtropical ridge that has been steering it and start to move toward the north.  Although Typhoon Koppu will weaken as it moves across northern Luzon, it will be over that area for 36 to 48 hours.  Koppu has the potential to cause widespread damage due to winds, floods and landslides.

Typhoon Koppu Continues to Intensify and Threaten Luzon

Typhoon Koppu continued to intensify on Friday and it maintained its steady course toward northern Luzon.  At 5:00 p.m. EDT on Friday the center of Typhoon Koppu was located at latitude 15.8°N and longitude 124.5°E which put it about 270 miles (435 km) east-northeast of Manila, Philippines.  Koppu was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 947 mb.

Typhoon Koppu is evolving into a large well organized typhoon.  An eye has formed at the center of the circulation and multiple rain bands spiral around the core of the typhoon.  Upper level divergence is pumping mass away from the center of circulation.  Koppu is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds are light and there is not much vertical wind shear.  Koppu is likely to continue to intensify until it begins to interact with northern Luzon.

A subtropical ridge is steering Koppu toward the west and that steering pattern is expected to continue for another 24 to 36 hours.  On its anticipated track the center of Typhoon Koppu will be very near the northeastern coast of Luzon in about 24 hours.  Koppu will bring strong winds, heavy rain and a storm surge to northern Luzon.  The large size of Koppu and its relatively slow movement means that it could produce very heavy rainfall.  Serious flooding and numerous mudslides are possible across northern Luzon.

Intensifying Typhoon Koppu Moving Toward Northern Luzon

Typhoon Koppu intensified on Thursday as it continued to move steadily toward Northern Luzon.  At 11:00 p.m. EDT the center of Typhoon Koppu was located at latitude 15.6°N and longitude 126.9°E which put it about 425 miles (685 km) east of Manila, Philippines.  Koppu was moving toward the west at 8 m.p.h. (13 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 969 mb.

Typhoon Koppu is moving over water where the Sea Surface Temperature is near 30°C.  The upper level winds lessened on Thursday which decreased the vertical wind shear and allowed Koppu to intensify more quickly.  The core of the circulation consolidated and there are suggestions that an eyewall may be forming.  Koppu is expected to move through a favorable environment until it reaches northern Luzon and further intensification is very likely.

A subtropical ridge is steering Koppu toward the west and that general steering pattern is expected to continue for another 36 to 48 hours.  On its anticipated track, Typhoon Koppu will approach northern Luzon in 36 to 42 hours.  It could bring strong winds, heavy rain and a storm surge when it reaches that area.  The heavy rain could produce floods and mudslides as Koppu moves over northern Luzon.

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.

Tropical Storm Koppu Forms North of Yap

In spite of significant vertical wind shear a surface circulation has been consolidating inside an area of thunderstorms north of Yap.  The system has been designated Tropical Storm Koppu.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Koppu was located at latitude 15.7°N and longitude 137.1°E which put it about 430 miles (690 km) north of Yap.  Koppu was moving toward the west at 14 m.p.h. (23 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

Significant vertical wind shear is inhibiting the organization of Tropical Storm Koppu.  An upper level ridge north of Koppu is generating strong northeasterly winds over the top of the tropical storm.  The vertical wind shear is causing most of the strong thunderstorms to be located southwest of the center of circulation.  The only other deep convection is occurring in a band that is west of the core of the circulation.

Koppu is over water where the Sea Surface Temperature is near 30°C and so there is plenty of energy in the upper ocean.  The wind shear will inhibit intensification for another 24 to 48 hours before it starts to subside.  Koppu could intensify much more quickly later this week when it moves into an area where the upper level winds are lighter.  Koppu could become a typhoon withing 36 to 48 hours and it could be a strong typhoon by the end of the week.

A subtropical ridge is steering Tropical Storm Koppu quickly to the west.  That general motion is expected to continue for the rest of the week.  On its anticipated track Koppu could be approaching northern Luzon in about three or four days.  It could be a significant typhoon by that time.

Tropical Storm Nora Moves Into the Central Pacific

Tropical Storm Nora moved west of longitude 140°W on Sunday which meant that it officially crossed from the Eastern North Pacific into the Central North Pacific Ocean.  At 11:00 p.m. EDT on Sunday the center of Tropical Storm Nora was located at latitude 13.5°N and longitude 143.8°W which put it about 860 miles (1385 km) east-southeast of Hilo, Hawaii.  Nora was moving toward the west-northwest at 9 m.p.h. (15 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 m.p.h.).  The minimum surface pressure was 993 mb.

Nora is a small tropical storm.  Wind to tropical storm force only extend out about 70 miles (110 km) from the center of circulation.  Most of the stronger thunderstorms are located northwest of the center of circulation and there is not much deep convection in the other parts of Nora.  Although Nora is over water where the Sea Surface Temperature is near 29°C, southerly winds in the upper levels appear to be causing vertical wind shear.  The wind shear is likely to increase as an upper level trough north of Hawaii gets closer to Nora.

Tropical Storm Nora is nearing the western end of a subtropical ridge which has been steering it toward the west.  If the vertical structure of Nora remains intact, the tropical storm should turn toward the north during the next day or two.  After that time the upper level trough north of Hawaii could sweep Nora toward the northeast.  An alternate and possibly more likely scenario, given the small size of Tropical Storm Nora, is that the vertical wind shear blows the upper portion of the circulation north of the surface circulation.  If that happens, then the surface circulation will be steered westward until it dissipates by the winds in the lower atmosphere.

Tropical Storm Nora Form Far East of Hawaii

Another Tropical Cyclone has formed over the Eastern North Pacific Ocean well east of Hawaii and the National Hurricane Center has upgraded Tropical Depression 18-E to Tropical Storm Nora.  At 11:00 p.m. EDT on Friday the center of Tropical Storm Nora was located at latitude 11.3°N and longitude 135.1°W which put it about 1470 miles (2365 km) east-southeast of South Point Hawaii.  Nora was moving toward the west at 16 m.p.h. (26 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 1006 mb.

The circulation inside Tropical Storm Nora is still in the process of organizing.  There is one primary rainband that wraps around the western and southern side of the tropical storm.  More thunderstorms are forming near the center, but a clearly defined core of convection has not yet developed.  The storms close to the center of circulation are producing more upper level divergence which is pumping out mass.

Tropical Storm Nora is in an environment that favors intensification,   The Sea Surface Temperature is warmer than 29°C,  The upper level winds are light and there is not much upper level divergence.  Nora is expected to intensify gradually into a hurricane.  Once a tight, well organized inner core develops, it could intensify more quickly.

A subtropical ridge north of Nora is steering the tropical storm westward.  That general steering pattern is expected to continue for another day or two.  When Nora reaches the western end of the subtropical ridge, it is expected to turn toward the north.

Oho Becomes a Hurricane Southeast of Hawaii

The circulation around Tropical Storm Oho became much more organized on Tuesday and it intensified into a hurricane.  At 5:00 p.m. EDT on Tuesday the center of Hurricane Oho was located at latitude 16.6°N and longitude 150.2°W which put it about 385 miles (620 km) east-southeast of Hilo, Hawaii.  Oho was moving toward the northeast at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 85 m.p.h. (140 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 975 mb.

A primary rainband wrapped tightly around the center of circulation and created a banded eye feature.  In addition other rainbands developed around the core of the circulation and Oho looks much more like a tropical cyclone today.  Thunderstorms near the center of circulation are generating upper level divergence, especially northeast of the center.  The upper level divergence caused the surface pressure to decrease and the wind speeds to increase.

Hurricane Oho is moving over water where the Sea Surface Temperature (SST) is near 28°C.  The upper level winds are currently fairly light and there is not much vertical wind shear.  The conditions are favorable for intensification and Oho could get stronger during the next 24 hours.  After that time Oho will move over cooler SSTs and the vertical wind shear will increase.  Oho should start to weaken and begin a transition to an an extratropical cyclone.

A large upper level trough north of Hawaii will steer Hurricane Oho toward the northeast during the next few days.  On its anticipated track Oho will pass about 400 miles east of Hawaii.  The extratropical stage of Hurricane Oho could approach the Pacific Northwest in three or four days.

Tropical Storm Oho Passing Southeast of Hawaii

Tropical Storm Oho moved slowly southeast of Hawaii on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Oho was located at latitude 15.0°N and longitude 153.6°W which put it about 340 miles (545 km) south-southeast of Hilo, Hawaii.  Oho was moving toward the northeast 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 984 mb.

Tropical Storm Oho is only partially organized.  A partial eyewall wrapped around the western and southern sides of the center of circulation.  However, most of the stronger thunderstorms are located southwest of the center.  A weak upper level ridge south of Hawaii appears to be generating some northeasterly winds over the top of Oho, which is causing some vertical wind shear.  The wind shear is inhibiting the organization of the circulation of the tropical storm.

Tropical Storm Oho is over water where the Sea Surface Temperature (SST) is near 28.5°C.  The wind shear could decrease on Tuesday and that could allow Oho to increase to hurricane intensity.  Oho will move northward over cooler SSTs later this week.  A combination of cooler water and more vertical wind shear will cause Oho to weaken and make a transition to an extratropical cyclone.

A large upper level trough northwest of Hawaii is expected to move eastward and begin to steer Oho toward the northeast.  On its expected track, Oho will pass southeast of Hawaii.  The extratropical cyclone that is currently Tropical Storm Oho could be approaching the west coast of the U.S. by the weekend.