Tropical Storm Rosa Develops Southwest of Mexico

Tropical Storm Rosa developed southwest of Mexico on Tuesday morning.  At 11:00 a.m. EDT on Tuesday the center of Tropical Storm Rosa was located at latitude 14.7°N and longitude 108.0°W which put it about 385 miles (620 km) southwest of Manzanillo, Mexico.  Rosa was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1004 mb.

A distinct center of circulation consolidated in an area of thunderstorms southwest of Mexico on Tuesday morning and the National Hurricane Center designated the system as Tropical Storm Rosa.  An inner rainband wrapped tightly around the center.  Several other bands of showers and thunderstorms were revolving around the core of Tropical Storm Rosa.  The circulation was symmetrical and rainbands were occurring in all parts of the tropical storm.  Storms near the core began to generate upper level divergence which was pumping mass away from Rosa.

Tropical Storm Rosa will move through an environment favorable for intensification during the next several days.  Rosa will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Rosa could intensify into a hurricane by later on Wednesday.

Tropical Storm Rosa will move southwest of a middle level ridge over northern Mexico.  The ridge will steer Rosa in a general west-northwesterly direction during the next several days.  On its anticipated track Tropical Storm Rosa will move southwest of Baja California later this week.

Typhoon Trami Intensifies in Equivalent of Category 5 Hurricane

Typhoon Trami intensified on Monday into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.  At 5:00 p.m. EDT on Monday the center of Typhoon Trami was located at latitude 19.7°N and longitude 129.0°E which put it about 485 miles (780 km) south of Okinawa.  Trami was moving toward the west-northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind sped was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h).  The minimum surface pressure was 912 mb.

Typhoon Trami went through an eyewall replacement cycle on Sunday, which temporarily interrupted its intensification.  When the inner eyewall dissipated on Monday, then Typhoon Trami resumed intensifying.  The eyewall replacement cycle caused Trami’s circulation to get larger.  There is now a large circular eye with a diameter of 40 miles (65 km) at the center of circulation.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds are occurring in that ring of storms.  Several bands of showers and thunderstorms are revolving around the core of Typhoon Trami.  Storms around the core are generating large amounts of upper level divergence which is pumping mass away from the typhoon in all directions.

Typhoon Trami has a large symmetrical circulation.  Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extend out about 235 miles (380 km) from the center of circulation.  The Hurricane Intensity Index (HII) for Typhoon Trami is 35.0.  The Hurricane Size Index (HSI) is 25.3 and the Hurricane Wind Intensity Size Index (HWISI) is 60.3.

Typhoon Trami will move through an environment very favorable for intense typhoons during the next 12 to 24 hours.  Trami will move over water where the Sea Surface Temperature is near 30°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Trami has been through one eyewall replacement cycle.  If another rainband wraps around the existing eye and eyewall and another eyewall replacement cycle starts, then weakening could occur.  An upper level trough near the east coast of China will move north of Typhoon Trami.  Westerly winds at the southern end of the trough could affect the northern portion of Trami’s circulation.  If wind shear increases later this week, then Typhoon Trami will weaken.

Typhoon Trami will move south of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Trami in a west-northwesterly direction during the next 12 to 24 hours.  The upper level trough will weaken the ridge and Trami could turn more toward the north in a day or so.  The winds steering Typhoon Trami could weaken during the middle of the week and it could move slowly toward the north for a day or two.  On its anticipated track Typhoon Trami could approach the southern Rykyu Islands in three or four days.  Trami could still be a powerful typhoon at that time.

Trami Strengthens Into a Typhoon

Former Tropical Storm Trami strengthened into a typhoon on Saturday night.  At 11:00 p.m. EDT on Saturday the center of Typhoon Trami was located at latitude 17.0°N and longitude 134.6°E which put it about 810 miles (1310 km) southeast of Okinawa.  Trami was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 105 m.p.h. (170 km/h).  The minimum surface pressure was 965 mb.

The circulation of Typhoon Trami became more circular and symmetrical on Saturday.   An inner band of thunderstorms wrapped most of the way around the center of circulation and eye was developing at the center of Trami.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Trami.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon in all directions.  Winds to typhoon force extended out about 35 miles (55 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles (320 km) from the center.

Typhoon Trami will move through an environment favorable for intensification during the next several days.  Trami will move over water where the Sea Surface Temperature is near 30°C.  it will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Trami could intensify into the equivalent of a major hurricane during the next day or two.

Typhoon Trami will move south of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Trami toward the west-northwest during the next few days.  On its anticipated track Typhoon Trami could be east of Taiwan and southeast of the Ryukyu Islands in four or five days.  It could be a powerful typhoon at that time.

Tropical Storm Kirk Forms South of the Cabo Verde Islands

Tropical Storm Kirk formed south of the Cabo Verde Islands on Saturday.  At 11:00 a.m. EDT on Saturday the center of Tropical Storm Kirk was located at latitude 8.3°N and longitude 23.6°W which put it about 450 miles (730 km) south of the Cabo Verde Islands.  Kirk was moving toward the west at 14 m.p.h. (22 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 1005 mb.

The circulation around Tropical Storm Kirk is large and not well organized.  There is a low level center of circulation, but there are not many thunderstorms near the center.  There were thunderstorms in a cluster west of the center and more thunderstorms were in another cluster east of the center.  Some of the thunderstorms appeared to be organizing into bands, but the bands were not well developed.

Tropical Storm Kirk will move through an environment during the next day or two that should be favorable for intensification.  Kirk will move over water where the Sea Surface Temperature is near 27°C.  It will move through an area where the upper level winds are weak and the wind shear will not be strong enough to prevent intensification.  Tropical Storm Kirk is likely to become more organized during the next 24 to 48 hours.  It will move into a region in a couple of days where the lower level easterly winds will be stronger vertical wind shear could increase.

Tropical Storm Kirk will move south of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Kirk toward the west at a fairly quick pace.  On its anticipated track Tropical Storm Kirk could approach the Lesser Antilles by late next week.

Elsewhere over the tropical Atlantic, Tropical Depression Eleven moved slowly toward the Windward Islands.  At 11:00 a.m. EDT on Saturday the center of Tropical Depression Eleven was located at latitude 13.2°N and longitude 53.8°W which put it about 485 miles (780 km) east of the Windward Islands.  It was moving toward the west at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1008 mb.

Tropical Depression Eleven Forms East of the Windward Islands

Tropical Depression Eleven formed east of the Windward Islands on Friday night.  At 11:00 p.m. EDT on Friday the center of Tropical Depression Eleven was located at latitude 13.1°N and longitude 53.4°W which put it about 510 miles (825 km) east of the Windward Islands.  It was moving toward the west-northwest at 6 m.p.h. (10 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1007 mb.

A small circular low pressure system within a tropical wave has been moving westward toward the Windward Islands.  An upper level trough near the eastern Caribbean Sea has been producing southwesterly winds which blowing across the top of the low.  Those winds were producing significant vertical wind shear and they were preventing taller thunderstorms from persisting near the center of circulation.  The National Hurricane Center decided that the low pressure system possessed sufficient convection to be classified as a Tropical Depression at 11:00 p.m.. EDT on Friday night.

The distribution of thunderstorms around Tropical Depression Eleven was still asymmetrical because of the wind shear caused by the upper level trough.  There was a well defined, but small, low level circulation with a distinct center.  Most of the bands around the center of circulation consisted of showers and lower clouds.  There were stronger thunderstorms in some of the bands east of the center of circulation.

Tropical Depression Eleven will move through an environment somewhat favorable for intensification.  It will move over water where the Sea Surface Temperature is near 29°C.  The upper level trough will continue to cause significant vertical wind shear.  The wind shear will limit the potential for intensification.  Tropical Depression Eleven could strengthen into a tropical storm, but rapid intensification is not likely.  However, small tropical cyclones can strengthen or weaken very rapidly if the environment around them changes.

Tropical Depression Eleven will move south of the subtropical high pressure system over the Atlantic Ocean.  The high will steer the depression in a west-northwesterly direction.  On its anticipated track the center of Tropical Depression Eleven could be east of the Lesser Antilles on Sunday night.

Tropical Storm Trami Develops West of the Marianas

Tropical Storm Trami developed west of the Marianas on Friday.  At 5:00 p.m. EDT on Friday the center of Tropical Storm Trami was located at latitude 16.2°N and longitude 140.8°E which put it about 285 miles (460 km) northwest of Guam.  Trami was moving toward the west-northwest at 14 m.p.h. (22 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 993 mb.

The circulation around former Tropical Depression 28W strengthened on Friday and the Japan Meteorological Agency designated the system as Tropical Storm Trami.  An inner band of thunderstorms wrapped tightly around the northern and western sides of the center of circulation.  Several other bands of showers and thunderstorms in the eastern half of the circulation were revolving around the core of Tropical Storm Trami.  Bands in the western half of the circulation consisted primarily of showers and lower clouds.  Storms near the core of Trami were generating upper level divergence which was pumping mass away from the tropical storm.

Tropical Storm Trami will be moving through an environment favorable for intensification.  Trami will move over water where the Sea Surface Temperature is near 30°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Trami will continue to intensify and it could become a typhoon during the next 24 hours.  A period of rapid intensification is possible once the inner core is fully developed.  Tropical Storm Trami could become the equivalent of a major hurricane during the next few days.

Tropical Storm Trami will continue to move south of a subtropical ridge over the Western North Pacific Ocean.  The ridge will steer Trami in a general west-northwesterly direction.  On its anticipated track Trami could be southeast of Okinawa and the Ryukyu Islands in four or five days.  It could be a powerful typhoon at that time.

Tropical Depression 28W Forms Over the Marianas

Tropical Depression 28W formed over the Mariana Islands on Thursday.  At 5:00 p.m. EDT on Thursday the center of Tropical Depression 28W was located at latitude 14.1°N and longitude 144.8°E which put it about 15 miles (25 km) east-northeast of Guam.  It was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1002 mb.  Tropical Storm Watches were issued for Rota, Saipan and Tinian.

Tropical Depression 28W was still organizing on Thursday.  A distinct center of circulation formed in an area of thunderstorms near the Marianas.  Bands of showers and thunderstorms developed around the circulation.  The strongest rainbands were forming in the eastern half of the circulation.  Bands of showers and thunderstorms were also forming in the western half of the circulation but there were fewer strong thunderstorms in that half of the tropical depression.  Storm closer to the center of circulation were starting to generate upper level divergence which was pumping mass away from the depression.

Tropical Depression 28W will move through an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  The tropical depression will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Tropical Depression 28W will intensify during the next few days.  It is likely to strengthen into a tropical storm on Friday and it could intensify into a typhoon during the weekend.

Tropical Depression 28W will move around the southern side of a subtropical ridge over the Western North Pacific Ocean during the next several days.  The ridge will steer the depression in a general west-northwesterly direction.  On its anticipated track the depression could be southeast of Okinawa in four or five days and it is likely to be a typhoon at that time.

Tropical Depression Forms Over Gulf of California

Tropical Depression Nineteen-E formed over the Gulf of California on Wednesday morning.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Nineteen-E was located at latitude 26.3°N and longitude 110.9°W which put it about 35 miles (55 km) northeast of Loreto, Mexico.  It was moving toward the north at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1004 mb.

The circulation of Tropical Depression Nineteen-E was still organizing .  There was a cluster of thunderstorms near the center of circulation.  Most of the stronger storms were east of the center.  Several short bands of showers and thunderstorms were beginning to develop north and south of the center of circulation.  Storms near the center were generating some upper level divergence which was pumping mass away to the northeast of the depression.

Tropical Depression Nineteen-E will move through an environment somewhat favorable for intensification during the next 12 hours.  The water in the Gulf of California is very warm and the depression will move over water where the Sea Surface Temperature is near 31°C.  An upper level trough west of California will produce southwesterly winds which will cause moderate vertical wind shear.  Tropical Depression Nineteen-E could intensify during the next 12 hours and it has a chance to become a tropical storm.

The upper level trough west of California will steer Tropical Depression Nineteen-E toward the north-northeast.  On its anticipated track the depression will reach the west coast of Mexico near Guaymas in about 12 hours.  It could be a tropical storm when it reaches the coast.  It will bring some gusty winds, but locally heavy rain is the greatest risk.  There is the potential for flash floods in parts of Sinaloa, Sonora and Chihuahua.  The lower portion of Tropical Depression Nineteen will weaken quickly after it makes landfall and moves over mountains in western Mexico.  The upper portion of the circulation and some of the moist air will be transported farther northeast and the remnants of the circulation could enhance rainfall farther inland.

Florence Still Producing Heavy Rain and Floods in Carolinas

Although former Hurricane Florence weakened to a tropical depression on Sunday, it was still producing heavy rain and causing floods in portions of the Carolinas.  At 5:00 p.m. EDT on Sunday the center of Tropical Depression Florence was located at latitude 34.6°N and longitude 82.2°W which put it about 25 miles (40 km) south-southeast of Greenville, South Carolina.  Florence was moving toward the north at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 35 m.p.h. (55 km/h) and there were wind gusts to 45 m.p.h. (75 km/h).  The minimum surface pressure was 1006 mb.

Slow movement of Tropical Depression Florence resulted in persistent heavy rain over portions of North Carolina and South Carolina.  The National Weather Service Office in Newport/Morehead City, North Carolina measured 25.20 inches (64.0 cm) of rain with Florence.  The airport in Wilmington, North Carolina measured 23.59 inches (59.9 cm) of rain.  A Remotely operated Automated Weather Station (RAWS) in Marion, South Carolina measured 18.13 inches (46.0 cm) of rain.  There were reports of up to ten inches (25.4 cm) at some locations around Charlotte, North Carolina.  Runoff of the persistent heavy rain has caused floods in many locations.  The Cape Fear River near Chinquapin, North Carolina has risen above the previous record flood level.  Parts of the Cape Fear River, Neuse River, Trent River and Lumber River are at major flood levels.  Minor and moderate flooding is occurring in numerous other places around North Carolina and South Carolina.

Tropical Depression Florence has started to move toward the north.  Florence will move into western Carolina on Sunday night.  It will move over eastern Tennessee, western Virginia, eastern Kentucky, and West Virginia on its way toward Ohio on Monday.  One primary rainband on the eastern side of the circulation will continue to drop heavy rain over parts of eastern South Carolina for a few more hours.  Convergence into the low will produce heavy rain that could move into western Virginia and West Virginia on Monday.  Flash Flood Watches have been issued for South Carolina, North Carolina, western Virginia and southern West Virginia.

Typhoon Mangkhut Makes Landfall West of Hong Kong

Typhoon Mangkhut made landfall west of Hong Kong on Sunday.  At 11:00 a.m. EDT on Sunday the center of Typhoon Mangkhut was located at latitude 22.3°N and longitude 111.0°E which put it about 65 miles (105 km) east-southeast of Yulin, China.  Mangkhut was moving toward the west-northwest at 20 m.p.h. (32 km/h).  The maximum sustained wind speed was 80 m.p.h. (130 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 979 mb.

Typhoon Mangkhut made landfall on the coast of China near Yangjiang on Sunday.  The maximum sustained wind speed was near 90 m.p.h. (145 km/h) and there were wind gusts to 115 m.p.h. (185 km/h).  There were reports that strong winds blew out windows in high rise buildings in Hong Kong.  There were strong gusty winds along the coast between Hong Kong and Yangjiang.  Strong winds blowing water toward the coast also produced a storm surge along that section of the coast.  The highest surge occurred just to the east of where the center made landfall.

Typhoon Mangkhut will drop heavy rain over Zizhiqu, Zhaungzu and Guangxi provinces while it moves farther inland.  Mangkhut will weaken slowly as it moves slowly across southern China.  The locally heavy rain could cause flash floods, especially in regions of steeper terrain.  Reports of damage and casualties caused when Typhoon Mangkhut move across northern Luzon were still coming in.