Monthly Archives: July 2018

Tropical Storm Son-tinh Moves Across Hainan Island

Tropical Storm Son-tinh moved across Hainan Island on Tuesday.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Son-tinh was located at latitude 18.9°N and longitude 108.5°E which put it about 15 miles (25 km) southwest of Dongfang, China.  Son-tinh was moving toward the west at 21 m.p.h. (34 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.

The center of Tropical Storm Son-tinh moved east to west across the southern half of Hainan Island on Tuesday.  In spite of moving over the island, the circulation of Tropical Storm Son-tinh retained its organization.  There was still a distinct low level center of circulation.  A primary rainband wrapped around the southern and eastern portions of the center.  Additional bands of showers and thunderstorms were revolving around the core of Son-tinh.  The strongest rainbands were in the western half of the tropical storm.  The circulation of Tropical Storm Son-tinh remains small.  Winds to tropical storm force only extend out about 70 miles (110 km) from the center of circulation.

Tropical Storm Son-tinh will move through an environment somewhat favorable for intensification during the next 12 hours.  Son-tinh will move over water where the Sea Surface Temperature is near 30°C.  It will move south of an upper level ridge.  The ridge will produce northeasterly winds which will blow toward the top of the circulation.  Those winds will create moderate vertical wind shear, but the shear will not be strong enough to prevent intensification.  Tropical Storm Son-tinh could strengthen after it moves west of Hainan Island and the center of circulation moves back over water.  Son-tinh is likely to reach the coast of Vietnam in 12 to 18 hours and it will weaken after landfall.

The ridge north of Son-tinh steered the tropical storm quickly toward the west on Tuesday.  It will continue to steer Tropical Storm Son-tinh in a general westerly direction on Wednesday.  On its anticipated track Tropical Storm Son-tinh will move steadily west of Hainan Island.  Locally heavy rain and gusty winds should gradually diminish there on Wednesday.  Son-tinh is likely to make landfall on the coast of Vietnam near Vinh in 12 to 18 hours and then move across Vietnam toward Laos.  Tropical Storm Son-tinh will bring gusty winds and locally heavy rain, but its impact will be lessened because of the small size of the circulation.  The heavy rain could cause flooding in isolated locations.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 12W formed east of Luzon.  At 11:00 p.m. EDT on Tuesday the center of Tropical Depression 12W was located at latitude 18.9°N and longitude 126.1°E which put it about 545 miles (875 km) south of Okinawa.  It was moving toward the west at 12 m.p.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 999 mb.

Tropical Storm Son-tinh Develops East of Hainan Island

Tropical Storm Son-tinh developed east of Hainan Island on Monday night.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Son-tinh was located at latitude 19.4°N and longitude 116.9°E which put it about 430 miles east of Hainan Island.  Son-tinh was moving toward the west at 24 m.p.h. (35 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.

A small circulation began west of Guam last week and then it moved north of the Philippines on Monday.  Thunderstorms would form near the circulation and then wind shear would blow the tops of the storms away.  A small area of thunderstorms eventually persisted near the center of circulation on Monday and the Japan Meteorological Agency designated the system as Tropical Storm Son-tinh.  There was a small tight center of circulation in Son-tinh, but strong upper level winds were causing the distribution of thunderstorms to be asymmetrical.  More of the thunderstorms were occurring west of the center.  The circulation of Son-tinh was relatively small.  Winds to tropical storm force only extended out 80 miles (130 km) from the center of circulation.

Tropical Storm Son-tinh will move through an environment marginally favorable for intensification.  Son-tinh will move over water where the Sea Surface Temperature is near 30°C.  Tropical Storm Son-tinh is moving south of an upper level ridge.  The ridge is producing strong easterly winds which are blowing toward the top of the circulation.  Those winds will cause strong vertical wind shear and the shear will limit intensification.  Tropical Storm Son-tinh could intensify a little before it reaches Hainan Island, but it will weaken when it moves over the island.

The ridge north of Son-tinh is steering the tropical storm rapidly toward the west and that general motion is forecast to continue on Tuesday.  On its anticipated track Tropical Storm Son-tinh will reach Hainan Island in about 18 hours.  Son-tinh will bring gusty winds and locally heavy rain.  Isolated flash floods could occur,but the overall impacts are likely to be minor.

Beryl Reorganizes as a Subtropical Storm North of Bermuda

A low pressure system associated with former Tropical Storm Beryl reorganized north of Bermuda on Saturday and the National Hurricane Center designated the system as Subtropical Storm Beryl.  At 2:00 p.m. EDT on Saturday the center of Subtropical Storm Beryl was located at latitude 36.4°N and longitude 65.7°W which put it about 575 miles (930 km) south-southwest of Halifax, Nova Scotia.  Beryl was moving toward the northeast at 12 m.p.h. (19 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 1010 mb.

The remnants of former Tropical Storm Beryl moved slowly across the northern Caribbean Sea and then over the southeastern Bahamas to a position northwest of Bermuda.  A low pressure system formed at the surface.  Bands of showers and thunderstorms developed and began to revolve around the the low pressure system.  The low pressure system moved under the eastern side of an upper level trough.  The trough contains colder air in the upper levels and it was also producing southwesterly winds which were blowing toward the top of the surface low pressure system.  The southwesterly winds were generating moderate vertical wind shear and the strongest rainbands were occurring on the eastern side of the surface low.  Some drier air was moving around the western and southern part of the upper level trough, which may have contributed to the weaker bands on the western side of the circulation.  The presence of the upper level trough and the asymmetrical distribution of thunderstorms around the surface low prompted the National Hurricane Center to designate the system as a subtropical storm.

Subtropical Storm Beryl will move through an environment marginally favorable for intensification during the next 24 hours.  Beryl will move over water where the Sea Surface Temperature is near 26°C.  The upper level trough will continue to produce moderate vertical wind shear.  The wind shear and the drier air will inhibit intensification.  Subtropical Storm Beryl could intensify a little more during the next 24 hours.  Beryl will move over colder water later on Sunday and it will start to weaken when that occurs.

The upper level trough was steering Subtropical Storm Beryl toward the northeast and a general motion in that direction is forecast to continue for several more days.  On its anticipated track Subtropical Storm Beryl will pass south of Nova Scotia on Sunday.  Beryl could be near Newfoundland by Tuesday.

Hurricane Chris Weakens South of Nova Scotia

Hurricane Chris weakened slowly on Wednesday as it passed well south of Nova Scotia.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Chris was located at latitude 39.6°N and longitude 63.0°W.  Chris was moving toward the northeast at 29 m.p.h. (46 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 980 mb.

Hurricane Chris exhibited the structure of a hurricane on Thursday, but the clouds did not rise quite as high because it was over slightly cooler water.  There was still an eye at the center of circulation.  Several bands of showers and thunderstorms were revolving around the core of the circulation.  The rainbands were weaker in the southwestern part of the hurricane because some drier air was entering that part of the circulation.  Storms in the core of the circulation were generating upper level divergence.

Hurricane Chris is likely to weaken again on Thursday.  It will start to move over much cooler water where there is less energy in the upper ocean.  In addition an upper level trough over the eastern U.S. will produce southwesterly winds which will blow toward the upper part of the hurricane.  Those winds will cause strong vertical wind shear.  The shear will undercut the upper level divergence and tilt the circulation toward the northeast with height.  Hurricane Chris will start to make a transition to an extratropical cyclone when the effects of the cooler water and stronger shear begin to alter the structure of the hurricane.

The upper level trough was steering Hurricane Chris rapidly toward the northeast and that motion is expected to continue for several more days.  On its anticipated track Hurricane Chris will be near Labrador on Thursday night.  The extratropical cyclone that results from the transition of Hurricane Chris will be near Iceland during the weekend.

Typhoon Maria Makes Landfall in China

The center of Typhoon Maria made landfall Lianjiang, China on Tuesday night.  At 11:00 p.m. EDT on Tuesday the center of Typhoon Maria was located at latitude 26.7°N and longitude 119.3°E which put it near Ningde, China.  Maria was moving toward the west-northwest at 22 m.p.h. (35 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 135 m.p.h. (215 km/h).  The minimum surface pressure was 952 mb.

Two concentric eyewalls formed at the center of Typhoon Maria before it made landfall on the coast of China.  The inner eyewall was dissipating, but it still existed at the time of landfall.  The outer eyewall started to contract prior to landfall.  Winds to typhoon force extended out about 65 miles (105 km) from the center of circulation in the part of the circulation over water.  Winds to tropical storm force extended out about 235 miles (380 km) from the center in the part of the circulation over water.

Typhoon Maria brought strong winds and a storm surge to the coast of Zhejiang province when it made landfall.  Maria was also dropping heavy rain and flash flooding could occur.  Typhoon Maria was moving around the western end of a subtropical ridge over the Western North Pacific Ocean.  The ridge was steering Maria toward the west-northwest, but the typhoon is likely to turn more toward the northwest when it moves farther inland.  Typhoon Maria will weaken as it moves inland over eastern China, but it will still drop heavy rain and flooding will be a significant risk.

Typhoon Maria Drops Heavy Rain on Taiwan

Typhoon Maria dropped heavy rain on Taiwan on Tuesday after it brought wind and rain to the southern Ryukyu Islands.  At 5:00 p.m. EDT the center of Typhoon Maria was located at latitude 26.5°N and longitude 121.4°E which put it about 85 miles (135 km) north-northeast of Taipei, Taiwan.  Maria was moving toward the west-northwest at 22 m.p.h. (35 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h).  The minimum surface pressure was 949 mb.

A primary rainband wrapped around the existing eye and eyewall in Typhoon Maria and the structure exhibited concentric eyewalls.  The inner eyewall started to weaken as more air converged and rose in the much larger outer eyewall.  The wind speeds decreased slowly as the inner eyewall weakened.  The concentric eyewalls altered the structure of Typhoon Maria and the size of the circulation increased.  Winds to typhoon force extended out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extended out about 235 miles (380 km) from the center.

Typhoon Maria was moving around the southern side of a subtropical ridge over the Western North Pacific Ocean.  The ridge was steering Maria toward the west-northwest and a general motion in that direction is expected to continue for another 12 to 24 hours.  On its anticipated track the center of Typhoon Maria will pass north of Taiwan, but Maria will continue to drop heavy rain over Taiwan.  Maria will make landfall on the east coast of China near Fuding during the next 6 to 12 hours.  The typhoon will bring gusty winds, a storm surge and heavy rain to Zhejiang province in eastern China.  The heavy rain could cause flash floods.

Chris Strengthens to a Hurricane Southeast of Cape Hatteras

Former Tropical Storm Chris strengthened to a hurricane southeast of Cape Hatteras on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Hurricane Chris was located at latitude 33.7°N and longitude 72.4°W which put it about 205 miles (330 km) east-southeast of Cape Hatteras, North Carolina.  Chris was moving toward the northeast at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 85 m.p.h. (135 km/h) and there were wind gusts to 100 m.p.h. (160 km/h).  The minimum surface pressure was 980 mb.

Hurricane Chris strengthened on Tuesday when it moved northeast of cooler water Chris had mixed to the surface while it was meandering off the coast of the Carolinas.  An eye with a diameter of 30 miles (50 km) formed at the center of circulation.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in the eastern side of that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Hurricane Chris.  The strongest rainbands were in the eastern half of the circulation.  Drier air near the western half of the circulation was contributing to the weaker bands in that part of the hurricane.  Storms in the core of the circulation were generating upper level divergence which was pumping mass away to the north and east of the hurricane.  Winds to hurricane force extended out about 20 miles (30 km) from the center of circulation.  Winds to tropical storm force extended out about 95 miles (155 km) from the center.

Hurricane Chris will move through an environment favorable for intensification on Wednesday.  Chris will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over the northeastern U.S. will produce southwesterly winds that will blow toward the top of the hurricane.  The winds speeds are similar at most levels and they will not generate a lot of vertical wind shear during the next 24 hours.  Hurricane Chris will strengthen on Wednesday and it could intensify rapidly.  Chris will move over cooler water when it gets north of the Gulf Stream and it will start to weaken when that occurs.

The trough over the northeastern U.S. will steer Hurricane Chris toward the northeast.  On its anticipated track Chris will move away from the coast of North Carolina.  Chris could be south of Nova Scotia in about 36 hours and it could be near Newfoundland in several days.

Elsewhere, the remnants of former Tropical Storm Beryl crossed Hispaniola and they were moving toward the southeastern Bahamas.  At 2:00 p.m. EDT on Tuesday the center of Former Tropical Storm Chris was located at latitude 20.1°N and longitude 72.6°W which put it about 40 miles (65 km) northeast of Port de Paix, Haiti.  It was moving toward the northwest at 17 m.p.h. (28 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 1013 mb.  A reconnaissance aircraft is scheduled to investigate the system on Wednesday if there are signs that it could be reorganizing into a tropical cyclone.

Typhoon Maria Nears Southern Ryukyu Islands

Typhoon Maria neared the southern Ryukyu Islands on Monday night.  At 11:00 p.m. EDT on Monday night the center of Typhoon Maria was located at latitude 24.3°N and longitude 126.4°E which put it about 130 miles (210 km) east of Ishigaki, Japan.  Maria was moving toward the west-northwest at 18 m.p.h. (29 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 155 m.p.h. (250 km/h).  The minimum surface pressure was 949 mb.

Typhoon Maria weakened slowly on Monday, but it remained a powerful typhoon.  Maria moved over some slightly cooler water mixed to the surface by recent Typhoon Prapiroon when it passed near the Ryukyu Islands.  Maria was unable to extract enough energy from the upper ocean to maintain the intense wind speeds it produced during the weekend.  However, Typhoon Maria was still the equivalent of a major hurricane.  There was a circular eye with a diameter of 35 miles (55 km).  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Several bands of thunderstorms were revolving around the core of Typhoon Maria.   Storms in the core were generating strong upper level divergence which was pumping mass away from the center of circulation.

Winds to typhoon force extended out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles from the center.  The Hurricane Intensity Index (HII) for Typhoon Maria was 23.6.  The Hurricane Size Index (HSI) was 23.8 and the Hurricane Wind Intensity Size Index (HWISI) was 47.4.  Those indices indicated that Typhoon Maria was capable of causing widespread major damage.

Typhoon Maria will move through an environment capable of sustaining a strong typhoon on Tuesday.  Maria will move west of the cooler water mixed to the surface by previous Typhoon Prapiroon and it will move over water where the Sea Surface Temperature is near 29°C.  Typhoon Maria will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Maria could weaken slowly on Tuesday if it is unable to extract enough energy from the upper ocean to sustain its circulation.  It could strengthen a little when it moves over slightly warmer water if it has time to extract more energy from the ocean.

Typhoon Maria was moving south of a subtropical ridge over the Western North Pacific Ocean.  The ridge was steering Maria toward the west-northwest and that general motion is expected to continue during the 36 hours.  On its anticipated track Typhoon Maria will reach the southern Ryukyu Islands in six to twelve hours.  Maria will bring destructive winds, heavy rain and a storm surge.  It will be capable of causing major damage to Miyako Jima, Ishigaki Jima, Iriomote Jima and the other islands in the southern Ryukyus.  The strongest part of Typhoon Maria will pass south of Okinawa, which could experience rainbands in the outer portion of the circulation.  Typhoon Maria will pass near northern Taiwan in about 18 hours.  It will bring strong winds and locally heavy rain to that area and flash floods could occur.  Maria could be near Fuding on the coast of China in about 24 hours.

Dangerous Typhoon Maria Churns Toward the Ryukyu Islands

Dangerous Typhoon Maria churned closer to the Ryukyu Islands on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Maria was located at latitude 22.1°N and longitude 132.7°E which put it about 485 miles (780 km) southeast of Okinawa.  Maria was moving toward the west-northwest at 19 m.p.h. (31 km/h).  The maximum sustained wind speed was 155 m.p.h. (250 km/h) and there were wind gusts to 190 m.p.h. (305 km/h).  The minimum surface pressure was 922 mb.

Typhoon Maria has a large symmetrical circulation.  There is a circular eye with a diameter of 32 miles (52 km) at the center of Maria.  The eye is surrounded by a ring of strong thunderstorms and the strongest winds are occurring in that ring of storms.  Multiple bands of showers and thunderstorms are revolving around the core of Typhoon Maria.  Storms around the core are generating well developed upper level divergence which is pumping away large amounts of mass from the typhoon.

Winds to typhoon force extend out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extend out about 230 miles (370 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Maria is 33.3.  The Hurricane Size Index (HSI) is 23.7 and the Hurricane Wind Intensity Size Index (HWISI) is 57.0.

Typhoon Maria will remain in an environment favorable for strong typhoons for another 24 to 36 hours.  Maria will move over water where the Sea Surface Temperature is near 29°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Maria will remain a large and dangerous typhoon for another day or two.

Typhoon Maria was moving south of a subtropical ridge over the Western North Pacific Ocean.  The ridge was steering Maria toward the west-northwest and a general motion toward the west-northwest is likely to continue for another day or two.  On its anticipated track Typhoon Maria will approach the southern Ryukyu Islands in about 24 hours.  Maria could be near northern Taiwan in about 36 hours and it could approach the coast of China in about 48 hours.

Typhoon Maria will bring strong winds, locally heavy rain and a significant storm surge.  Maria will be capable of causing major damage over a widespread area.

Tropical Storm Chris Develops South of Cape Hatteras, Beryl Nears Lesser Antilles

Tropical Storm Chris developed south of Cape Hatteras on Sunday morning, while Tropical Storm Beryl neared the Lesser Antilles.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Chris was located at latitude 32.9°N and longitude 75.0°W which put it about 160 miles (260 km) south of Cape Hatteras, North Carolina.  Chris was nearly stationary.  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 1006 mb.

Thunderstorms developed closer to the center of circulation on Sunday morning and the National Hurricane Center designated former Tropical Depression Three as Tropical Storm Chris.  The circulation of Chris was organizing quickly.  A band of showers and thunderstorms was wrapping around the center of circulation.  Several other rainbands were revolving around the core of the tropical storm.  The bands northwest of the center were weaker because there was drier air in that part of Chris.  The storms near the center of circulation were beginning to generate upper level divergence.

Tropical Storm Chris will remain in an environment favorable for intensification for the next two or three days.  The water in the upper portion of the Atlantic Ocean east of the Carolinas is warmer than normal.  Tropical Storm Chris will be over water where the Sea Surface Temperature is near 28°C.  Chris will be southeast of an upper level trough over the northeastern quarter of the U.S. and it will be under a small upper level ridge.  The upper level winds will be weak and there will be little vertical wind shear.  Tropical Storm Chris will continue to intensify and it could strengthen to a hurricane in the next day or two.

Since Tropical Storm Chris is under the small upper level ridge, the steering winds are weak.  Chris may not move much during the next 24 to 48 hours.  Tropical Storm Chris is forecast to linger of the coast of the Carolinas for several days.  Eventually an upper level trough will approach from the west and start to push Chris toward the northeast.

Elsewhere, Tropical Storm Beryl was nearing the Lesser Antilles on Sunday morning.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Beryl was located at latitude 14.4°N and longitude 57.9°W which put it about 210 miles (335 km) east of Martinique.  Beryl was moving toward the west-northwest at 23 m.p.h. (37 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 1007 mb.

Tropical Storm Warnings were in effect for Dominica and Guadeloupe.  Tropical Storm Watches were in effect for Saba, St. Eustatius, St. Maarten, St. Martin, Martinique, St. Lucia, and St. Barthelemy.

Thunderstorms continued to develop near the center of Tropical Storm Beryl on Sunday morning and the weakening trend halted at least temporarily.  Beryl remained a small tropical storm.  Winds to tropical storm force only extended out about 45 miles (75 km) from the center of circulation.  There were several bands of showers and thunderstorms in the eastern half of Tropical Storm Beryl.  The bands in the western half of the circulation consisted primarily of showers and low clouds.

Tropical Storm Beryl is forecast to into a region where the easterly winds in the lower levels are stronger.  That would increase the vertical wind shear and make it difficult for the circulation to stay vertically coherent.  Beryl will move over water where the Sea Surface Temperature is near 27°C.  So, there will be enough energy in the upper ocean to support a tropical storm if the wind shear is not too strong.  Tropical Storm Beryl is forecast to weaken when it moves over the eastern Caribbean Sea, but that will depend on how strong the vertical shear gets.

Tropical Storm Beryl is moving south of the subtropical high over the Atlantic Ocean which is steering Beryl toward the west-northwest.  A general motion toward the west-northwest is forecast to continue for several more days.  On its anticipated track Tropical Storm Beryl will bring gusty winds and locally heavy rain to St. Lucia, Martinique, Dominica and Guadeloupe during the next few hours,