Monthly Archives: October 2015

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.

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.

Hurricane Joaquin Passing Northwest of Bermuda

Hurricane Joaquin is bringing tropical storm force winds to Bermuda as the core of the hurricane moves northwest of that island.  Wind gusts to 64 m.p.h. have been reported in recent hours in Bermuda.  At 11:00 p.m. EDT on Sunday the center of Hurricane Joaquin was located at latitude 33.1°N and longitude 65.5°W which put it about 70 miles (110 km) northwest of Bermuda.  Joaquin was moving toward the north-northeast at 13 m.p.h. (20 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 961 mb.  A Hurricane Warning remains in effect for Bermuda.

Hurricane Joaquin is gradually moving over cooler water, but it is still over water where the Sea Surface Temperature is around 28°C.  It appears that a combination of drier air and vertical wind shear caused Joaquin to weaken on Sunday.  Thunderstorms are not rising as far up into the atmosphere and gaps have appeared in the eyewall.  Southwesterly winds in the upper levels are inhibiting upper level divergence in that portion of the hurricane and the pressure rose 17 mb on Sunday.  The wind shear could lessen for a time on Monday and the rate of weakening could slow.

Hurricane Joaquin is moving toward the north-northeast.  When it moves farther north, it will encounter the upper level westerlies in the middle latitudes.  Those westerly winds will carry Joaquin toward the east.  Joaquin could make a transition to a strong extratropical storm and affect western Europe in a few days.

Hurricane Joaquin Heading Toward Bermuda

After intensifying to almost Category 5 on the Saffir-Simpson Scale on Saturday, Hurricane Joaquin headed toward Bermuda.  The Bermuda Weather Service has issued a Hurricane Warning for Bermuda.  At 11:00 p.m. EDT on Saturday the center of Hurricane Joaquin was located at latitude 28.0°N and longitude 68.9°W which put it about 385 miles (620 km) southwest of Bermuda.  Joaquin was moving toward the northeast at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 944 mb.  Joaquin was a Category 4 hurricane on the Saffir-Simpson Scale.  The Hurricane Intensity Index (HII) was 25.1.  The Hurricane Size Index (HSI) was 20.0 and the Hurricane Wind Intensity Size Index (HWISI) was 45.1.

Joaquin is moving over water where the Sea Surface Temperature is near 29°C.  However, a large upper level trough over the southeastern U.S. and an upper level low northwest of Joaquin are combining to generate westerly winds over the hurricane.  The vertical wind shear is causing the circulation to become more asymmetrical and the strongest convection is occurring in the eastern half of the circulation.  The flow of air is also pushing drier air toward the core of Hurricane Joaquin.  If Joaquin can move fast enough to outrun the drier air, it could weaken slowly.  However, if the drier air gets into the core of the circulation, then Joaquin will weaken faster.

The trough and upper level low are steering Hurricane Joaquin quickly toward the northeast and that motion is expected to continue on Sunday.  On its anticipated track Joaquin will pass near Bermuda on Sunday night.  It could bring strong winds and a storm surge as it moves past the island.

Typhoon Mujigae Making Landfall in China

Strong Typhoon Mujigae is making landfall on the coast of China near Zhanjiang.  At 11:00 p.m. EDT on Saturday the center of Typhoon Jiang was located at latitude 20.8°N and longitude 111.1°E which put it about 55 miles (90 km) southeast of Zhanjiang.  Mujigae was moving toward the northwest at 12 m.p.h. (19 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. (215 km/h).  The minimum surface pressure was 949 mb.

The northwestern side of the eyewall is beginning to affect the coast of China.  Mujigae will bring strong winds and heavy rain as it moves inland over southern China.  The typhoon will begin to weaken as soon as the center moves over land and it will gradually spin down over southern China.

Hurricane Joaquin Moving Slowly Away from the Bahamas

Hurricane Joaquin turned northward on Friday and it is starting to move slowly away from the Central Bahamas.  However, it is still producing strong winds, heavy rain and storm surges on San Salvador and nearby islands.  At 5:00 p.m. EDT on Friday the center of Hurricane Joaquin was located at latitude 24.1°N and longitude 74.7°W which put it about 15 miles (25 km) west-northwest of San Salvador in the Central Bahamas and about 745 miles (1200 km) south of Cape Hatteras, North Carolina.  Joaquin was moving toward the north at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h)  which made Joaquin a Category 3 hurricane on the Saffir-Simpson Scale.  There were wind gusts to 155 m.p.h. (250 km/h) and the minimum surface pressure was 942 mb.  The Hurricane Intensity Index (HII) was 23.6.  The Hurricane Size Index (HSI) was 20.3 and the Hurricane Wind Intensity Size Index (HWISI) was 43.9.

A Hurricane Warning is in effect for the Central Bahamas including Cat Island, the Exumas, Rum Cay, Long Island and San Salvador.  A Hurricane Warning is in effect for the Northwestern Bahamas including the Abacos, Berry Island, Eleuthera, Grand Bahama Island and New Providence.  A Hurricane Watch has been issued for Bimini and Andros Island.  A Tropical Storm Warning is in effect for Andros Island and the Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, the Ragged Islands and the Turks and Caicos.  A Tropical Storm Watch has been issued for Bermuda.

Hurricane Joaquin did not change a lot on Friday, although there were some indications that vertical wind shear may be starting to affect it.  Microwave satellite imagery and aerial reconnaissance indicate that there is still and eye, although the eyewall is thinner on the north side.  Most of the stronger thunderstorms are on the southern side of the circulation.  An upper level trough over the eastern U.S. may be creating stronger winds that are hitting Joaquin from the southwest.  Those southwesterly winds may be limiting upper level divergence on that side of the hurricane.  The hurricane is still over water where the Sea Surface Temperature is near 30°C.  So, vertical wind shear is the only factor inhibiting intensification.  The trough is expected to produce more vertical wind shear on Saturday, which could start to weaken Joaquin.

The upper level trough is starting to steer Joaquin slowly toward the north.  The trough is expected to steer Joaquin toward the northeast at a faster rate during the next several days.  Guidance from all of the numerical models has come into agreement that Joaquin will stay east of the U.S.  Conditions in the Central Bahamas should improve on Saturday as Hurricane Joaquin moves farther away.  The possibility that Joaquin could be near to Bermuda on Sunday prompted the issuance of a Tropical Storm Watch for that island.

Tropical Storms Mujigae and Choi-Wan Form Over NW Pacific

Two new tropical storms with the names of Mujigae and Choi-Wan have formed over the western North Pacific Ocean.  At 11:00 a.m. EDT on Friday the center of Tropical Storm Mujigae was located at latitude 17.4°N and longitude 117.3°E which put it about 275 miles (445 km) northwest of Manila, Philippines.  Mujigae was moving toward the west-northwest at 17 m.p.h.  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

At 11:00 a.m. EDT on Friday the center of Tropical Storm Choi-Wan was located at latitude 19.2°N and longitude 166.4°E which put it about 15 miles (20 km) south-southeast of Wake Island.  Choi-Wan was moving toward the west-northwest 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 996 mb.

Tropical Storm Mujigae organized quickly after the system move west of the Philippines.  A primary curved rainband wrapped around the western and southern sides of the center of circulation.  A possible eye is apparent intermittently on infrared satellite imagery.  Upper level divergence is beginning to occur both north and south of the center.  Mujigae is moving over water where the Sea Surface Temperature is near 28°C and there is not enough vertical wind shear to prevent intensification.  A period of rapid intensification is possible and Mujigae could become a typhoon in 12 to 24 hours.

A subtropical ridge is steering Mujigae toward the west-northwest and that general motion is expected to continue for the next several days.  On its anticipated track, Mujigae could be approaching the southern coast of China in 36 hours.  It could bring strong winds and heavy rain when it makes landfall.

Tropical Storm Choi-Wan is still in the organizational stage.  It has a large broad circulation without a well developed inner core.  Winds to tropical storm force are occurring in clusters of thunderstorms.  Choi-Wan is over Sea Surface Temperatures near 29°C, but there is moderate vertical wind shear over the northern part of the tropical storm.  The wind shear is expected to decrease in a day or two and Choi-Wan is forecast to become a typhoon.

Choi-Wan is between two subtropical ridges and the steering currents are relatively weak.  In a day or two the western ridge is expected to steer Choi-Wan toward the northwest.  Choi-Wan will cause squally weather on Wake Island for 24 to 48 hours.

Category 4 Hurricane Joaquin Bringing Strong Winds and Floods to the Bahamas

Hurricane Joaquin intensified to Category 4 on the Saffir-Simpson Scale on Thursday and it brought strong winds and floods to some of the islands of the Bahamas.  At 11:00 p.m. EDT on Thursday the center of Hurricane Joaquin was located at latitude 22.9°N and longitude 74.6°W which put it about 20 miles (32 km) east-southeast of Clarence Town on Long Island in the Central Bahamas and about 810 miles (1310 km) south of Cape Hatteras, North Carolina.  Joaquin was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 935 mb.  The Hurricane Intensity Index (HII) was 25.1.  The Hurricane Size Index (HSI) was 21.4 and the Hurricane Wind Intensity Size Index (HWISI) was 46.5.

A Hurricane Warning has been issued for the Central Bahamas including Cat Island, Rum Cay, the Exumas, Long Island and San Salvador.   A Hurricane Warning has been issued for the Northwestern Bahamas including the Abacos, Berry Islands, Eleuthera, Grand Bahama Island and New Providence.  A Hurricane Watch has been issued for Bimini and Andros Island.  A Tropical Storm Warning has been issued for Andros Island and the Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Ragged Islands, the Inaguas, Mayaguana and the Turks and Caicos.  A Tropical Storm Warning has been issued for the Cuban provinces of Camaguey, Los Tunas, Holguin and Guantanamo.

The eye in Hurricane Joaquin contracted on Thursday and it has only been visible intermittently on conventional satellite imagery.  The intensity of the hurricane appears to have stabilized in recent hours.  While the intensity of Joaquin has been constant, the circulation has increased in sized and hurricane force winds now extend out about 50 miles (80 km) from the center.  Joaquin is still generating upper level divergence which seems to be pumping out as much mass as is converging in the lower levels of the circulation.  As a result, the pressure has also remained fairly steady during the past few hours.  There is not much vertical wind shear and the overall environment would seems to support further intensification.  However, the slow movement of Joaquin may be causing it to stir cooler water to the surface, which will reduce the energy available to the hurricane.

Hurricane Joaquin has moved little during the past six hours.  An narrow ridge is blocking its motion and the ridge is preventing it from moving toward the north.  A large upper level trough over the eastern U.S. is expected to weaken the ridge on Friday.  The upper level trough is expected to steer Joaquin toward the north on Friday.  Most of the reliable numerical models predict that the trough will carry Joaquin toward the northeast during the weekend and that it will stay east of the U.S.  A couple of other models still suggest a landfall could occur, but they are outliers at the current time.  Until Hurricane Joaquin makes the turn toward the north and northeast, it could still pose a potential risk to the U.S., but that possibility is much less than it was 24 hours ago.  Joaquin will continue to bring high winds and floods to parts of the Bahamas on Friday.