Monthly Archives: September 2020

Typhoon Haishen Brings Wind and Rain to Northern Ryukyu Islands

Typhoon Haishen brought wind and rain to the northern Ryukyu Islands on Saturday.  At 11:00 p.m. EDT on Saturday the center of Typhoon Haishen was located at latitude 28.3°N and longitude 130.4°E which put it about 170 miles (280 km) east-northeast of Okinawa.  Haishen was moving toward the north-northwest at 15 m.p.h. (24 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 945 mb.

The center of Typhoon Haishen passed west of Minami-Daito Jima on Saturday.  A weather station there measured a wind speed of 72 m.p.h. (116 km/h) and a pressure of 943.6 mb.

The circulation around around Typhoon Haishen developed concentric eyewalls on Saturday.  The smaller original eyewall started to weaken as low level convergence became more concentrated into the much larger outer eyewall.  The strongest winds were originally found in the inner eyewall, but those wind speeds decreased.  The stronger winds were blowing in the larger outer eyewall on Saturday night.

The concentric eyewall structure produced an increase in the size of the circulation around Typhoon Haishen.  Winds to typhoon force extended out 100 miles (160 km) from the center of circulation.  Winds to tropical storm force extended out 325 miles (530 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Haishen was 19.2.  The Hurricane Size Index (HSI) was 37.2 and the Hurricane Wind Intensity Size Index (HWISI) was 56.4.  Typhoon Haishen was capable of causing widespread serious damage.

Typhoon Haishen will move into a less favorable environment during the next 24 hours.  Haishen will move over water where the Sea Surface Temperature is near 28°C.  Drier air over Asia will get pulled into the circulation.  Wind shear will increase when Typhoon Haishen moves farther north because it will get closer to the upper level westerly winds in the middle latitudes.  The effects of the concentric eyewalls, drier air and more wind shear will cause Typhoon Haishen to gradually weaken.

Typhoon Haishen will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Haishen toward the north.  On its anticipated track the center of Typhoon Haishen will pass near the western part of Kyushu in about 12 hours.  Haishen will reach South Korea in about 24 hours.  Typhoon Haishen will bring strong winds and heavy rain to parts of Kyushu and South Korea.  Heavy rain could cause flash floods, especially in places that received heavy rain from Typhoon Maysak a few days ago.

Tropical Storm Julio Develops South of Mexico

Tropical Storm Julio developed south of Mexico on Saturday afternoon.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Julio was located at latitude 16.1°N and longitude 102.7°W which put it about 180 miles (290 km) south-southwest of Zihuatanejo, Mexico.  Julio was moving toward the west-northwest at 20 m.p.h. (32 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 middle and upper portion of the circulation around former Hurricane Nana moved westward from Guatemala over the Gulf of Tehuantepec south of Mexico.  A surface circulation redeveloped over the Eastern North Pacific Ocean.  More thunderstorms formed near the center of the surface circulation and the National Hurricane Center designated the system as Tropical Storm Julio on Saturday afternoon.

The circulation around Tropical Storm Julio was small.  Winds to tropical storm force only extended out 35 miles from the center of Julio.  The stronger winds were occurring north of the center of circulation.  Thunderstorms continued to form near the center.  Short, narrow bands of showers and thunderstorms were revolving around the center of circulation.

Tropical Storm Julio will move through an environment only marginally favorable for intensification.  Julio will move over water where the Sea Surface Temperature is near 30°C.  So, there is sufficient energy in the upper ocean to support intensification.  However, an upper level ridge over Mexico will produce easterly winds which will blow toward the top of Julio.  Those winds will cause moderate vertical wind shear which will inhibit intensification.  In addition, visible satellite images suggest that there is another small low pressure system about 250 miles (400 km) west of Tropical Storm Julio.  Interaction with the small low pressure system could also disrupt the circulation around Julio.

The ridge over Mexico will steer Tropical Storm Julio toward the west-northwest.  However, interaction with the small low pressure system west of Julio could also affect the track.  On its anticipated track Tropical Storm Julio will move toward a position south of Baja California on Sunday night.

Typhoon Haishen Intensifies to Equivalent of Major Hurricane

Typhoon Haishen intensified to the equivalent of a major hurricane over the Western North Pacific Ocean on Thursday.  At 5:00 p.m. EDT on Thursday the center of Typhoon Haishen was located at latitude 21.4°N and longitude 135.4°E which put it about 405 miles (650 km) southeast of Minamidaitojima, Japan.  Haishen was moving toward the west-northwest at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 175 m.p.h. (280 km/h).  The minimum surface pressure was 938 mb.

Typhoon Haishen intensified rapidly on Thursday.  A circular eye became more visible on conventional satellite images.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Haishen.  Storms near the core generated strong upper level divergence which pumped mass away from the typhoon.

The circulation around Typhoon Haishen increased in size on Thursday.  Winds to typhoon force extended out 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extended out 215 miles (315 km) from the center.  The Hurricane Intensity Index (HII) was 29.9.  The Hurricane Size Index (HSI) was 23.5 and the Hurricane Wind Intensity Size Index (HWISI) was 53.4.  Typhoon Haishen was capable of causing widespread significant damage.

Typhoon Haishen will move through an environment favorable for intensification during the next 24 hours.  Haishen 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 Haishen could strengthen to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.

Typhoon Haishen will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Typhoon Haishen toward the northwest during the next 36 hours.  Haishen will move more toward the north when it reaches the western end of the high pressure system.  On its anticipated track Typhoon Haishen could reach Minamidaitojima in about 36 hours.  Haishen could approach the northern Ryukyu Islands in about 48 hours.  Typhoon Haishen could hit South Korea in a little over three days.

Tropical Storm Nana Moves Over Guatemala

Tropical Storm Nana moved over Guatemala on Thursday.  At 2:00 p.m. EDT on Thursday the center of Tropical Storm Nana was located at latitude 16.3°N and longitude 90.6°W which put it about 120 miles (195 km) north of Guatemala City, Guatemala.  Nana was moving toward the west t 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.

After making landfall in southern Belize as a hurricane on Wednesday night, Tropical Storm Nana moved westward over northern Guatemala.  The small circulation around Nana weakened steadily on Thursday.  Tropical Storm Nana was dropping locally heavy rain over Guatemala on Thursday afternoon.  The heavy rain could cause flash floods in some locations.

Tropical Storm Nana will weaken to a tropical depression within a few hours.  Nana will continue to move toward the west.  It could emerge over the Gulf of Tehuantepec on Friday.

Elsewhere over the Atlantic Ocean, Tropical Depression Omar moved away from Bermuda.  At 11:00 a.m. EDT on Thursday the center of Tropical Depression Omar was located at latitude 35.9°N and longitude 61.1°W which put it about 335 miles (540 km) northeast of Bermuda.  Omar was moving toward the east at 13 m.p.h. (20 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 1005 mb.

Nana Strengthens to a Hurricane Near Belize

Former Tropical Storm Nana strengthened into a hurricane as it neared a landfall in Belize.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Nana was located at latitude 17.0°N and longitude 87.5°W which put it about 60 miles (95 km) southeast of Belize City, Belize.  Nana was moving toward the west at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 994 mb.

A Hurricane Warning was in effect for the portion of the coast from Belize City to the Belize/Guatemala border.  A Hurricane Watch was in effect for the portion of the coast from Belize City to the Belize/Mexico border.  A Tropical Storm Warning was in effect for the portion of the coast from Belize City to Belize/Mexico border.  A Hurricane Warning was also in effect for the portion of the coast from Puerto Costa Maya to Chetumal, Mexico.  Tropical Storm Warnings were in effect for the Caribbean Sea coast of Guatemala, Isla Roatan and the Bay Islands.  A Tropical Storm Watch was in effect for the north coast of Honduras from Punta Patuca to the border with Guatemala.

Former Tropical Storm Nana moved into a more favorable environment on Wednesday night and strengthened to a hurricane.  More thunderstorms formed near the center of circulation and those thunderstorms helped to spin up the circulation.  Since the circulation around Hurricane Nana was relatively small, it was able to spin up into a hurricane in a few hours.  Winds to hurricane force extended out 15 miles (25 km) on the northern side of Nana.  Winds to tropical storm force only extended out 70 miles (110 km) from the center of circulation.

Hurricane Nana has a few more hours when it could strengthen before it makes landfall in southern Belize.  Nana 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 less vertical wind shear.  Hurricane Nana could get a little stronger.

Hurricane Nana will move south of a subtropical high pressure system over the western Atlantic Ocean.  The high will steer Nana a little to the south of due west.  On its anticipated track Hurricane Nana will make landfall on the coast of Belize south of Belize City early on Wednesday morning.  Nana will be capable of causing localized wind damage.  It could cause a storm surge of up to eight feet (2.6 meters) along the south coast of Belize.  Hurricane Nana will drop heavy rain over parts of southern Belize and northern Guatemala.  Flash floods could occur in some locations.

Elsewhere over the North Atlantic Ocean, former Tropical Storm Omar weakened to a tropical depression north of Bermuda.  At 11:00 p.m. EDT on Wednesday the center of Tropical Depression Omar was located at latitude 36.1°N and longitude 64.1°W which put it about 265 miles (425 km) north of Bermuda.  Omar was moving toward the east at 13 m.p.h. (20 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 1005 mb.

Typhoon Maysak Brings Wind and Rain to South Korea

Typhoon Maysak brought wind and rain to South Korea on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Maysak was located at latitude 36.9°N and longitude 128.9°E which put it about 30 miles (50 km) north-northwest of Busan, South Korea.  Maysak was moving toward the north-northeast at 30 m.p.h. (50 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. (165 km/h).  The minimum surface pressure was 950 mb.

The center of Typhoon Maysak made landfall on the south coast of South Korea west of Busan on Wednesday.  The large circulation around Maysak brought gusty winds and heavy rain to much of the Korean Peninsula.  Winds to typhoon force extended out 60 miles (95 km) from the center of circulation.  Winds to tropical storm force extended out 200 miles (320 km) from the center.  The heavy rain was falling on ground that was saturated by previous tropical cyclones and other weather systems.  The rain will likely cause widespread flash flooding.

Typhoon Maysak was being steered quickly toward the north by an upper level trough over eastern Asia.  On its anticipated track the center of Maysak will move along the east coast of the Korean Peninsula.  Typhoon Maysak will weaken and it will made a transition to an extratropical cyclone during the next 24 hours.

Elsewhere over the Western North Pacific Ocean, Typhoon Haishen strengthened south of Iwo To.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Haishen was located at latitude 20.3°N and longitude 138.8°E which put it about 350 miles (560 km) south-southwest of Iwo To.  Haishen was moving toward the west-northwest at 13 m.p.h. (20 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. (165 km/h).  The minimum surface pressure was 979 mb.

Typhoon Haishen will move through an environment favorable for intensification during the next 36 to 48 hours.  Haishen 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 Haishen will continue to intensify and it is likely to strengthen into the equivalent of a major hurricane.

Typhoon Haishen will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Haishen toward the northwest during the next several days.  On its anticipated track Typhoon Haishen could approach the northern Ryukyu Islands in about 72 hours.  Haishen could eventually bring wind and rain to the same areas in Kyushu and South Korea affected by Typhoon Maysak.

Tropical Storm Nana Strengthens, Hurricane Watch Issued for Belize

Tropical Storm Nana strengthened on Tuesday night and a Hurricane Watch was issued for Belize.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Nana was located at latitude 17.0°N and longitude 80.9°W which put it about 485 miles (775 km) east of Belize City, Belize.  Nana was moving toward the west at 18 m.p.h. (30 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 999 mb.

A Hurricane Watch was issued for the entire coast of Belize.  A Tropical Storm Warning was also in effect for Belize.  A Tropical Storm Warning was in effect for the portion of the coast from Puerto Costa Maya to Chetumal, Mexico.  Tropical Storm Watches were in effect for the Caribbean Sea coast of Guatemala and for the north coast of Honduras from Punta Patuca to the border with Guatemala including Roatan Island and the Bay Islands.

Tropical Storm Nana continued to strengthen on Tuesday night.  There were signs that a small eye might be starting to form in the lower levels of the atmosphere.  More thunderstorms formed near the center of circulation.  Storms near the center generated upper level divergence which pumped mass away from the tropical storm.  Winds to tropical storm force extended out 80 miles (130 km) from the center of circulation.

Tropical Storm Nana will move through an environment favorable for intensification during the next 24 hours.  Nana will move over water where the Sea Surface Temperature is near 29.5°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Nana is likely to intensify into a hurricane on Wednesday.

Tropical Storm Nana will move south of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Nana toward the west during the next 24 to 36 hours.  On its anticipated track the center of Tropical Storm Nana will pass north of Honduras.  Nana could approach Belize on Wednesday night.

Elsewhere over the Atlantic Ocean, Tropical Storm Omar continued to move away from North Carolina.  At 11:00 p.m. EDT on Tuesday the center of Tropical Storm Omar was located at latitude 35.8°N and longitude 70.0°W which put it about 310 miles (500 km) east of Cape Hatteras, North Carolina.  Omar was moving toward the east-northeast 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 1003 mb.

Large Typhoon Maysak Churns Toward South Korea

Large, powerful Typhoon Maysak churned toward South Korea on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Maysak was located at latitude 30.1°N and longitude 126.9°E which put it about 405 miles (655 km) south-southwest of Busan, South Korea.  Maysak was moving toward the north-northeast at 13 m.p.h. (20 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 932 mb.

Typhoon Maysak neared the completion of an eyewall replacement cycle on Tuesday which resulted in an increase in the size of the circulation.  The original inner eyewall had not quite dissipated, but low level convergence was focused on the much larger outer eyewall.  Winds to typhoon force extended out 90 miles (145 km) from the center of circulation.  Winds to tropical storm force extended out 240 miles (390 km) from the center of Maysak.

Typhoon Maysak was a large, dangerous tropical cyclone.  The Hurricane Intensity Index (HII) was 25.1.  The Hurricane Size Index (HSI) was 27.5 and the Hurricane Wind Intensity Size Index (HWISI) was 52.6.  Typhoon Maysak was capable of causing widespread major damage.

Since Typhoon Maysak was near the end of an eyewall replacement cycle, it will likely weaken slowly during the next 18 hours.  Maysak will move over water where the Sea Surface Temperature is near 28°C.  An upper level trough over eastern Asia will approach Typhoon Maysak on Wednesday.  The trough will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will cause more vertical wind shear and the shear will cause Typhoon Maysak to weaken more quickly.

Typhoon Maysak will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Maysak toward the north during the next 24 hours.  On its anticipated track the core of Typhoon Maysak is likely to pass west of Kyushu.  Maysak could reach South Korea in about 18 hours.  Typhoon Maysak could be the equivalent of a large, major hurricane when it gets to South Korea.  Maysak will produce very strong winds over South Korea.  It will also drop heavy rain and flash floods could occur.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Haishen strengthened south of Iwo To.  At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Haishen was located at latitude 20.1°N and longitude 142.8°E which put it about 340 miles (545 km) south-southeast of Iwo To.  Haishen was moving toward the west-southwest at 8 m.p.h. (13 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 1000 mb.  Tropical Storm Haishen is forecast to strengthen into a typhoon and it could move toward western Japan later this week.

Tropical Storm Nana Forms South of Jamaica

Tropical Storm Nana formed over the Caribbean Sea south of Jamaica on Tuesday.  At 2:00 p.m. EDT on Tuesday the center of Tropical Storm Nana was located at latitude 16.7°N and longitude 78.4°W which put it about 110 miles (175 km) south of Negril, Jamaica.  Nana was moving toward the west at 18 m.p.h. (30 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 1002 mb.

A Tropical Storm Watch was issued for the entire coast of Belize.  A Tropical Storm Watch was also issued for the north coast of Honduras from Punta Patuca to the border with Guatemala including Roatan Island and the Bay Islands.

An Air Force Reserve Hurricane Hunter flight into a low pressure system south of Jamaica found a defined low level center of circulation and winds to tropical storm force on Tuesday.  Based on data from the reconnaissance aircraft the National Hurricane Center designated the system Tropical Storm Nana.  The circulation around Tropical Storm Nana was organizing quickly.  Thunderstorms were developing near the center of circulation.  Bands of showers and thunderstorms were revolving around the center.  Storms near the center began to generate upper level divergence which was pumping mass away from the tropical storm.  The strongest winds were occurring in the northern half of the circulation.  Winds to tropical storm force extended out 80 miles (130 km) from the center of Nana.

Tropical Storm Nana will move through an environment favorable for intensification during the next 36 hours.  Nana will move over water where the Sea Surface Temperature is near 29.5°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Nana will continue to intensify and it is likely to strengthen to a hurricane within 36 hours.

Tropical Storm Nana will move south of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Nana toward the west during the next day or two.  On its anticipated track the center of Tropical Storm Nana will pass north of Honduras on Wednesday.  Nana could reach Belize on Thursday and it is likely to be a hurricane by that time.

Elsewhere over the Atlantic Ocean, Tropical Depression Fifteen moved away from the East Coast of the U.S.  At 11:00 a.m. EDT on Tuesday the center of Tropical Depression Fifteen was located at latitude 34.7°N and longitude 73.1°W which put it about 140 miles (225 km) east-southeast of Cape Hatteras, North Carolina.  The depression was moving toward the east-northeast 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 1008 mb.

Typhoon Maysak Brings Wind and Rain to the Ryukyu Islands

Typhoon Maysak brought winds and rain to the Ryukyu Islands on Monday.  At 11:00 p.m. EDT on Monday the center of Typhoon Maysak was located at latitude 27.5°N and longitude 126.5°E which put it about 110 miles (175 km) west-northwest of Kadena AFB, Okinawa.  Maysak was moving toward the north-northwest at 13 m.p.h. (20 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 932 mb.

The eye and eyewall of Typhoon Maysak passed west of Okinawa on Monday.  Rainbands on the eastern side of Maysak passed over Okinawa and some of the other southern Ryukyu Islands.  A weather station at Naha reported a sustained wind speed of 58 m.p.h. (93 km/h).  A station at Kitahari (Kumejima Airport), which was closer to the center of Typhoon Maysak reported a sustained wind speed of 89 m.p.h. (144 km/h).

Satellite and radar images suggest that concentric eyewalls may have formed at the core of Typhoon Maysak.  The inner eye had a diameter of 8 miles (13 km).  A much larger outer eye with a diameter of approximately 100 miles (160 km) surrounded the inner eye.  Bands of showers and thunderstorms were revolving around the large core of Maysak.  Storms near the core were generating upper level divergence which was pumping mass away from the typhoon.

The circulation around Typhoon Maysak was large.  Winds to typhoon force extended out 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extended out 200 miles (320 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Maysak was 25.1.  The Hurricane Size Index (HSI) was 25.5 and the Hurricane Wind Intensity Size Index (HWISI).  Maysak was capable of causing widespread major damage.

Typhoon Maysak will move through an environment capable of supporting a strong typhoon during the next 24 hours, but it has likely reached its peak intensity.  The formation of concentric eyewalls normally results in a weaker, but larger tropical cyclone.  The wind speed will decrease when the inner eyewall dissipates.  When that occurs, the maximum wind speeds will occur in the larger outer eyewall.  Since Maysak will move over water where the Sea Surface Temperature is near 29°C, it will remain a typhoon for another 24 to 36 hours.

Typhoon Maysak will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean.  The high will steer Maysak toward the north during the next 36 hours.  On its anticipated track the center of Typhoon Maysak will pass west of Kyushu.  Typhoon Maysak could reach South Korea in 36 hours

Elsewhere over the Western North Pacific Ocean, Tropical Depression 11W was passing southeast of Iwo To.  At 11:00 p.m. EDT on Monday the center of Tropical Depression 11W was located at latitude 21.7°N and longitude 144.2°E which put it about 290 miles (470 km) southeast of Iwo To.  The depression was moving toward the west-southwest at 8 m.p.h. (13 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.