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.

Joaquin Becomes a Major Hurricane Near the Bahamas

Hurricane Joaquin intensified very rapidly on Wednesday and it reached Major Hurricane intensity.  At 11:00 p.m. EDT on Wednesday night the center of Hurricane Joaquin was located at latitude 23.8°N and longitude 73.1°W which put it about 90 miles (145 km) east of San Salvador and about 750 miles (1215 km) south-southeast of Cape Hatteras, North Carolina.  Joaquin was moving toward the southwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 140 m.p.h. (220 km/h).  The wind speed made Joaquin a Category 3 hurricane on the Saffir-Simpson Scale and a Major Hurricane.  The minimum surface pressure was 951 mb.  The Hurricane Intensity Index (HII) was 20.6, the Hurricane Size Index (HSI) was 11.6, and the Hurricane Wind Intensity Size Index (HWISI) was 32.2.

A Hurricane Warning has been issued for the Central Bahamas including Cat Island, the Exumas, Long Island, Rum Cay 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 Inaguas, Mayguana and the Ragged Islands.

Joaquin has a well formed structure.  The circulation is fairly symmetrical, although there are more spiral bands of thunderstorms south and east of the center.  The hurricane is over water where the Sea Surface Temperature is near 30°C.  A narrow upper level ridge west of Joaquin is causing light northerly winds over the circulation, but those winds did not inhibit rapid intensification on Wednesday.  The convection generated upper level divergence which pumped out mass and caused the pressure to decrease quickly.  Further intensification is possible during the next 24 hours, although if an eyewall replacement occurs, it would interrupt that process.  An upper level trough over the eastern U.S. will generate more vertical wind shear in a day or two and Joaquin will start to weaken.

A ridge north of Joaquin is blocking the hurricane and forcing it to move toward the southwest.  The ridge will weaken in a day or so and the upper level trough will start to steer Joaquin toward the north.  When the hurricane starts moving northward, it will also begin to move faster.  It could be approaching the Mid-Atlantic Coast by later on Saturday.

 

Joaquin Almost a Hurricane, Watch Issued for Central Bahamas

Tropical Storm Joaquin is on the verge of reaching hurricane intensity.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Joaquin was located at latitude 25.8°N and longitude 71.7°W which put it about 360 miles (580 km) east of the Northwestern Bahamas and about 680 miles (1100 km) south-southeast of Cape Hatteras, North Carolina.  Joaquin was moving toward the west-southwest at 5 m.p.h. (8 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 988 mb.  The government of the Bahamas has issued a Hurricane Watch for the Central Bahamas.

The organization of the circulation of Tropical Storm Joaquin increased on Tuesday in spite of moderate amounts of vertical wind shear.  More thunderstorms developed near the core of circulation and a partial eyewall formed around the southern and eastern parts of the center.  Although it is more organized, the circulation is still asymmetrical and the stronger winds were found in the eastern side of the tropical storm.

A thin upper level ridge is east of Florida and clockwise flow around the ridge is producing northerly winds over the top of Joaquin.  Those winds produced moderate vertical wind shear on Tuesday but the shear appears to be decreasing with time.  Joaquin is over water where the Sea Surface Temperature is near 30°C.  As the upper level winds diminish, the environment favors intensification and Joaquin is likely to become a hurricane on Wednesday.  Joaquin will continue to be in an environment that favors intensification during the next several days.

A ridge of high pressure north of Joaquin is blocking it from moving north and the ridge is forcing the tropical storm to move toward the west-southwest.  That general motion is expected to continue for another 24 to 48 hours and it could bring Joaquin near the Central and Northwestern Bahamas.  When Joaquin reaches the western end of the ridge it will turn toward the north.  An upper level trough over the eastern U.S. will cause Joaquin to move more quickly toward the north at the end of the week.  On its anticipated track, Joaquin could be approaching the Mid-Atlantic Coast of the U.S. by the weekend.

TD11 Becomes Tropical Storm Joaquin

The circulation in Tropical Depression 11 exhibited more organization on Monday night and the National Hurricane Center upgraded it to Tropical Storm Joaquin.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Joaquin was located at latitude 26.7°N and longitude 70.4°W which put it about 400 miles (640 km) northeast of the Central Bahamas and about 670 miles (1080 km) south-southeast of Cape Hatteras, North Carolina.  Joaquin was moving toward the southwest at 5 m.p.h. (8 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 1002 mb.

Tropical Storm Joaquin formed when an upper level low sat in place over warm Sea Surface Temperatures for a few days.  Transfers of momentum slowly increased the rotation in the lower atmosphere until a distinct center of circulation developed.  However, northwesterly winds in the upper levels created vertical wind shear that inhibited the development of the system.  Eventually, the wind shear decreased enough to allow more thunderstorms to develop near the center of circulation.  Condensation in those storms created a warm core in the middle and upper atmosphere and Joaquin began to intensify.  Now, upper level divergence is beginning to develop and the environment is becoming more favorable for intensification.

A ridge north of Joaquin is steering it slowly toward the west and that steering pattern is expected to continue for the next day or two.  An upper level trough approaching from the west is expected to turn Joaquin toward the north.  Guidance from numerical models is divergent.  Some models bring Joaquin to the Mid-Atlantic Coast while other models forecast Joaquin to move toward Long Island.  The future track of Joaquin will depend on how far west it moves before it turns northward and how strong it gets.

Typhoon Dujan Making Landfall in China

Typhoon Dujuan moved across Taiwan on Monday and it is currently making another landfall on the east coast of China.  At 11:00 p.m. EDT the center of Typhoon Dujuan was located at latitude 25.3°N and longitude 118.6°E which put it near Putian, China.  Dujuan was moving toward the northwest at 13 m.p.h.  The maximum sustained wind speed was 85 m.p.h. (135 m.p.h.) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 976 mb.

Dujuan brought strong winds and heavy rain when it moved across Taiwan.  It weakened as the center moved over the mountains on Taiwan, but its large size and intensity allow Dujuan to survive.  Dujuan was still a typhoon as it moved into the coast of eastern China near Putian.  It could produce heavy rainfall and flooding as it moves inland.  Dujuan should spin down gradually during the next few days as it moves farther into eastern China.

Recon Finds Marty a Hurricane, Mexico Issues Warnings

A reconnaissance plane investigated Marty on Monday afternoon and the data showed that Marty was a hurricane.  At 5:00 p.m. EDT on Monday the center of Hurricane Marty was located at latitude 16.7°N and longitude 102.1°W which put it about 75 miles (125 km) south-southwest of Zihuatanejo, Mexico.  Marty was moving toward the northeast at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 95 m.p.h. (155 km/h).  The minimum surface pressure was 986 mb.

The government of Mexico has issued a Hurricane Warning for the portion of the coast from Tecpan de Galeana to Lazaro Cardenas.  A Tropical Storm Warning has been issued for the coast from Tecpan de Galeana to Acapulco.  A Tropical Storm Watch has been issued for the portion of the coast from Lazaro Cardenas to Punta San Telmo.

Although an upper level trough over Mexico has been producing southwesterly flow and causing moderate vertical wind shear over Marty, the vertical integrity of the circulation has been maintained.  So, instead of blowing the top off the circulation, the southwesterly winds have pushed the entire circulation toward the northeast.  As Marty moved over water where the Sea Surface Temperature was near 30°C, it extracted enough energy from the water to intensify into a hurricane.  The southwesterly winds inhibited upper level divergence on the western side of the circulation, but the upper level divergence east of Marty pumped out mass and the pressure decreased.

The environment is not favorable for much more intensification.  The upper level trough is expected to continue to cause vertical wind shear.  In addition, Marty is close enough to the coast of Mexico that the hurricane will begin to pull in some drier air from land.  Marty could intensify a little more, but it is likely to weaken on Tuesday.  If Marty makes landfall, it will weaken quickly.

The upper level trough is pushing Marty northeastward toward the coast of Mexico.  Unless the shear blows the upper part of the circulation away from the lower portion, it will continue to move toward the coast.  Marty could make landfall in 12 to 24 hours, which is why the government of Mexico issued warnings for the coast.  Hurricane Marty could bring strong winds and locally heavy rainfall when it moves inland.

Large Dangerous Typhoon Dujuan Nearing Taiwan

Large and dangerous Typhoon Dujuan is nearing Taiwan.  At 11:00 p.m. EDT on Sunday the center of Typhoon Dujuan was located at latitude 23.5°N and longitude 123.2°W which put it about 185 miles (300 km) southeast of Taipei, Taiwan.  Dujuan was moving toward the west-northwest at 13 m.p.h. (21 km/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).  The minimum surface pressure was 912 mb.

Typhoon Dujuan is a very symmetrical storm with a large eye.  Winds to hurricane force extend out 60 miles from the center.  A weather station on Ishigaki Jima, Japan has reported winds over 54 m.p.h. (87 km/h) for the past five hours even though the center is passing south of that island.  The upper level winds around the typhoon are light and upper level divergence is pumping out mass in all directions  Typhoon Dujuan is likely to maintain its intensify until it makes landfall in Taiwan.  When the core of the typhoon moves over the mountains on Taiwan it will weaken.  However, given Dujuan’s size and intensity, it is likely to still be a typhoon when it moves west of Taiwan.

A subtropical ridge north of Dujuan is steering the typhoon toward the west-northwest and that general steering pattern is expected to continue.  On its anticipated track Dujuan will make landfall in northeastern Taiwan in less than 12 hours.  It will move across Taiwan and the center could reform northwest of that island.  Dujuan could make a landfall in China between Xiamen and Fuzhou in less than 24 hours.

Dujuan has the potential to be a very destructive typhoon.  It has a Hurricane Intensity Index of 29.9 and a Hurricane Size Index of 21.3.  Those numbers produce a Hurricane Wind Intensity Size Index of 51.2.  Those Indices suggest it is capable of producing widespread significant damage.  In addition to wind damage, Dujuan is capable of producing very heavy rainfall and floods.

Marty Intensifies and Mexico Issues a Tropical Storm Watch

Tropical Storm Marty intensified on Sunday and the government of Mexico issued a Tropical Storm Watch for a portion of the west coast.  At 2:00 p.m. EDT on Sunday the center of Tropical Storm Marty was located at latitude 15.0°N and longitude 102.8°W which put it about 235 miles (380 km) southwest of Acapulco, Mexico.  Marty was moving toward the north-northeast at 6 m.p.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 997 mb.  A Tropical Storm Watch has been issued for the portion of the coast from Acapulco to Lazaro Cardenas, Mexico.

The structure of Tropical Storm Marty improved on Sunday morning.  A long rainband stretched around the southern and eastern sides of the circulation and more thunderstorms developed near the center or circulation.  Marty is over water where the Sea Surface Temperature (SST) is near 30°C, which means there is a lot of energy in the upper ocean.  However, an upper level trough extends from the western Gulf of Mexico across northern Mexico.  The upper level trough is causing westerly winds, which could already be producing vertical wind shear over the northern half of the circulation of Tropical Storm Marty.  Very warm SSTs mean that the potential for intensification exists, but the vertical wind shear will limit how much intensification actually occurs.  If the upper level winds get stronger, they could shear the top half of the circulation away from the bottom half and cause Marty to dissipate.

The upper level trough is beginning to steer Marty toward the north-northeast and the tropical storm is likely to move in that direction over the short term.  The ultimate track of Marty will be determined by the vertical integrity of the circulation and the strength of the vertical wind shear.  If the wind shear is not too strong and the upper and lower portions of the circulation remain together, then the trough will steer all of Marty toward the northeast.  In that case it could make landfall on the Mexican coast in several days.  However, if the vertical wind shear blows then top off of the circulation, then the upper level portion will move northeast toward Mexico, while the lower part of the tropical storm is left behind.  The upper half of the circulation could still bring heavy rain and the potential for floods to parts of Mexico, even if the surface circulation does not make landfall.

Shear Hits Tropical Storm Niala and It Turns West

After intensifying earlier on Saturday, vertical wind shear began to affect Tropical Storm Niala and it turned westward.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Niala was located near latitude 16.9°N and longitude 152.8°W which put it about 245 miles (395 km) southeast of Hilo, Hawaii.  Niala was moving toward the west at 8 m.p.h. (13 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 992 mb.  A Tropical Storm Watch remains in effect for Hawaii County.

A large upper level trough centered northeast of Hawaii is causing southwesterly winds that are blowing over Tropical Storm Niala.  The wind shear is blowing the tops off the thunderstorms that try to form near the center of circulation.  As a result the low level circulation is exposed on satellite imagery.  The effect of the wind shear will be to weaken Niala even though it is over warm Sea Surface Temperatures.

Since there are not tall thunderstorms near the center of circulation, it is being steered toward the west by winds lower in the atmosphere.  A general westerly motion is expected for the next several days and Tropical Storm Niala is likely to pass south of Hawaii.