Monthly Archives: September 2021

Typhoon Mindulle Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Mindulle rapidly intensified to the equivalent of a major hurricane on Saturday. At 11:00 a.m. EDT on Saturday the center of Typhoon Mindulle was located at latitude 18.3°N and longitude 137.3°E which put it about 525 miles (850 km) south-southwest of Iwo To. Mindulle moving toward the north-northwest at 16 m.p.h. (26 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 942 mb.

Typhoon Mindulle rapidly intensified to the equivalent of a major hurricane over the Western North Pacific Ocean on Saturday. A circular eye was present at the center of Mindulle. 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 Typhoon Mindulle. Storms near the core generated upper level divergence that pumped large quantities of mass away from the typhoon. The removal of large amounts of mass allowed the surface pressure to decrease rapidly.

The circulation around Typhoon Mindulle was about twice as large as the circulation of Hurricane Sam which was over the Atlantic Ocean. Winds to typhoon force extended out 45 miles (75 km) from the center of Mindulle. Winds to tropical storm force extended out 160 miles (260 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 25.1. The Hurricane Size Index (HSI) was 16.0 and the Hurricane Wind Intensity Size Index (HWISI) was 41.1.

Typhoon Mindulle will move through an environment favorable for intensification during the next 24 hours. Mindulle will move over water where the Sea Surface Temperatures are near 30˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Mindulle will continue to intensify during the next 24 hours. If the inner end of a rainband wraps around the existing eye and eyewall, then concentric eyewalls could form. That structure would start an eyewall replacement cycle that could cause Typhoon Mindulle to weaken.

Typhoon Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next several days. The high will steer Mindulle slowly toward the northwest during the next several days. On its anticipated track Typhoon Mindulle could be west of Iwo To in three or four days.

Sam Intensifies to a Major Hurricane

Hurricane Sam intensified to a major hurricane on Saturday morning. At 11:00 a.m. EDT on Saturday the center of Hurricane Sam was located at latitude 12.9°N and longitude 47.6°W which put it about 1095 miles (1760 km) east-southeast of the Northern Leeward Islands. Sam moving toward the west-northwest at 10 m.p.h. (16 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 140 m.p.h. (225 km/h). The minimum surface pressure was 960 mb.

Hurricane Sam intensified to a major hurricane over the tropical Atlantic Ocean on Saturday morning. A well formed circular eye was present at the center of Hurricane Sam. 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 Hurricane Sam. Storms near the core generated strong upper level divergence that pumped mass away from the hurricane in all directions.

The circulation around Hurricane Sam was relatively small. Winds to hurricane force extended out 25 miles (40 km) from the center of Sam. Winds to tropical storm force extended out 80 miles (130 km) from the center of circulation. The Hurricane Intensity Index (HII) for Hurricane Sam was 22.1. The Hurricane Size Index (HSI) was 7.4 and the Hurricane Wind Intensity Size Index (HWISI) was 29.5.

Hurricane Sam will move through an environment favorable for intensification during the next 24 hours. Sam will move over water where the Sea Surface Temperatures are near 28˚C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Hurricane Sam will continue to intensify during the next 24 hours. Sam could strengthen to Category 5 on the Saffir-Simpson Scale.

Hurricane Sam will move around the southern side of a subtropical high pressure system over the Atlantic Ocean. The high will steer Sam toward the west-northwest during the next few days. On its anticipated track Hurricane Sam could be east of the Northern Leeward Islands by the middle of next week.

Elsewhere over the Atlantic Ocean, former Subtropical Storm Teresa weakened north of Bermuda. At 11:00 a.m. EDT on Saturday the center of Subtropical Depression Teresa was located at latitude 34.3°N and longitude 65.0°W which put it about 140 miles (225 km) north of Bermuda. Teresa was stationary. 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 1009 mb.

Mindulle Strengthens to a Typhoon

Former Tropical Storm Mindulle strengthened to a typhoon south-southwest of Iwo To on Friday night. At 11:00 p.m. EDT on Friday the center of Typhoon Mindulle was located at latitude 17.1°N and longitude 138.1°E which put it about 565 miles (910 km) south-southwest of Iwo To. Mindulle moving toward the northwest at 4 m.p.h. (6 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. (150 km/h). The minimum surface pressure was 978 mb.

Former Tropical Storm Mindulle strengthened to a typhoon over the Western North Pacific Ocean on Friday night. A circular eye developed at the center of Typhoon Mindulle. A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Mindulle. Storms near the core generated upper level divergence that pumped mass away from the typhoon. Winds to typhoon force extended out 30 miles (50 km) from the center of Mindulle. Winds to tropical storm force extended out 145 miles (230 km) from the center of circulation.

Typhoon Mindulle will move through an environment favorable for intensification during the next 48 hours. Mindulle will move over water where the Sea Surface Temperatures are near 30˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Mindulle will continue to intensify during the next 48 hours. Mindulle could strengthen to the equivalent of a major hurricane.

Typhoon Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next several days. The high will steer Mindulle slowly toward the northwest during the next several days. On its anticipated track Typhoon Mindulle could be southwest of Iwo To by the end of the weekend.

Subtropical Storm Teresa Develops North of Bermuda

Subtropical Storm Teresa developed north of Bermuda on Friday afternoon. At 5:00 p.m. EDT on Friday the center of Subtropical Storm Teresa was located at latitude 34.5°N and longitude 64.5°W which put it about 155 miles (245 km) north of Bermuda. Teresa moving toward the northwest at 14 m.p.h. (22 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 1008 mb.

A distinct low level of circulation was evident under an upper level low pressure system north of Bermuda and the National Hurricane Center designated the system as Subtropical Storm Teresa. The structure of Subtropical Storm Teresa was complex. There was a distinct low level center of circulation under the western side of the upper level low. A long band of showers and thunderstorms arced around the eastern and northern side of the larger circulation. Winds to tropical storm force extended out 70 miles (110 km) in the northeastern quadrant of Subtropical Storm Teresa. Winds in the other parts of Teresa were blowing at less than tropical storm force.

Subtropical Storm Teresa will move through an environment that is only marginally favorable for intensification during the next 24 hours. Teresa will move over water where the Sea Surface Temperatures are near 27˚C. However, the circulation around the upper level low will cause vertical wind shear over the low level center of Teresa. The wind shear will inhibit intensification. Subtropical Storm Teresa could get a little stronger during the next 24 hours. Teresa is forecast to be absorbed by a larger extratropical cyclone by the end of the weekend.

An upper level trough over the eastern U.S. will steer Subtropical Storm Teresa toward the northeast during the weekend. On its anticipated track, Teresa will move farther away from Bermuda. Subtropical Storm Teresa is forecast to be absorbed by an extratropical cyclone south of Nova Scotia on Sunday.

Elsewhere, Hurricane Same strengthened over the tropical Atlantic Ocean. At 5:00 p.m. EDT on Friday the center of Hurricane Sam was located at latitude 12.1°N and longitude 44.8°W which put it about 1290 miles (2075 km) east-southeast of the Northern Leeward Islands. Sam 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 100 m.p.h. (160 km/h). The minimum surface pressure was 986 mb. Hurricane Sam is forecast to strengthen to a major hurricane during the weekend.

Sam Strengthens to a Hurricane

Former Tropical Storm Sam strengthened to a hurricane over the Tropical Atlantic Ocean early on Friday. At 5:00 a.m. EDT on Friday the center of Hurricane Sam was located at latitude 11.5°N and longitude 42.2°W which put it about 1470 miles (2365 km) east-southeast of the Northern Leeward Islands. Sam moving toward the west at 15 m.p.h. (24 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 993 mb.

Former Tropical Storm Sam strengthened to a hurricane early on Friday. The inner end of a rainband wrapped around the eastern side of the center of Hurricane Sam. Bands of showers and thunderstorms were revolving around the center of circulation. Storms near the center generated upper level divergence that pumped mass away from the hurricane in all directions. The circulation around Hurricane Sam was relatively small. Winds to hurricane force extended out 20 miles (30 km) from the center of Sam. Winds to tropical storm force extended out 60 miles (95 km) from the center of circulation.

Hurricane Sam will move through an environment very favorable for intensification during the next 48 hours. Sam will move over water where the Sea Surface Temperatures are near 28˚C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Hurricane Sam will continue to intensify during the next 48 hours. Sam could intensify rapidly after an inner core with an eye and an eyewall fully form. Hurricane Sam could intensify to a major hurricane during the weekend.

Hurricane Sam will move around the southern side of a subtropical high pressure system over the Atlantic Ocean. The high will steer Sam toward the west-northwest during the next few days. On its anticipated track Hurricane Sam could approach the Northern Leeward Islands by the middle of next week. Sam could be a major hurricane at that time.

Tropical Storm Sam Strengthens over Eastern Atlantic

Tropical Storm Sam strengthened over the eastern Atlantic Ocean on Thursday morning. At 11:00 a.m. EDT on Thursday the center of Tropical Storm Sam was located at latitude 10.9°N and longitude 38.1°W which put it about 1745 miles (2805 km) east-southeast of the Northern Leeward Islands. Sam moving toward the west at 16 m.p.h. (26 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 1003 mb.

Former Tropical Depression Eighteen strengthened to Tropical Storm Sam on Thursday morning. Tropical Storm Sam was organizing quickly. The inner end of a rainband wrapped around the center of Sam . An eye appeared to be forming at the center of circulation. Bands of showers and thunderstorms were revolving around the center of Tropical Storm Sam. Storms near the center generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 45 miles (75 km) from the center of Sam.

Tropical Storm Sam will move through an environment very favorable for intensification during the next 48 hours. Sam will move over water where the Sea Surface Temperatures are near 28˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Storm Sam will continue to intensify during the next 36 hours. Sam could strengthen to a hurricane by Friday. Sam could intensify rapidly after an inner core with an eye and an eyewall forms. Sam could intensify to a major hurricane during the weekend.

Tropical Storm Sam will move around the southern side of a subtropical high pressure system over the Atlantic Ocean. The high will steer Sam toward the west-northwest during the next few days. On its anticipated track Tropical Storm Sam could approach the Northern Leeward Islands next week. Sam could be a major hurricane by that time.

Tropical Storm Mindulle Brings Wind and Rain to Marianas, Dianmu Hits Vietnam

Tropical Storm Mindulle brought wind and rain to the Marianas on Thursday and Tropical Storm Dianmu hit Vietnam. At 11:00 a.m. EDT on Thursday the center of Tropical Storm Mindulle was located at latitude 14.1°N and longitude 142.3°E which put it about 175 miles (280 km) west-northwest of Guam. Mindulle 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 997 mb.

Tropical Storm Mindulle brought wind and rain to the Marianas including Guam on Thursday. Tropical Storm Warnings were in effect for Guam, Rota, Tinian and Saipan. Mindulle was intensifying as it moved across the Marianas. More thunderstorms developed about the center of circulation. Bands of showers and thunderstorms were revolving the center of Tropical Storm Mindulle. Storms near the center generated upper level divergence that pumped mass away from the tropical storm. The strongest winds were occurring in the northeastern part of Mindulle. Winds to tropical storm force extended out 150 miles (240 km) in the northeastern quadrant to Mindulle.

Tropical Storm Mindulle will move through an environment favorable for intensification during the next few days. Mindulle will move over water where the Sea Surface Temperatures are near 30˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Storm Mindulle will continue to intensify during the next 36 hours. Mindulle could strengthen to a typhoon in 24 hours. Mindulle could intensify more rapidly after an inner core becomes more well developed. It could intensify to the equivalent of a major hurricane during the weekend.

Tropical Storm Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next several days. The high will steer Mindulle toward the northwest during the next 48 hours. On its anticipated track Tropical Storm Mindulle will move quickly away from the Marianas. Mindulle could approach the Ryukyu Islands in a few days.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Dianmu bought wind and rain to central Vietnam. At 11:00 a.m. EDT on Thursday the center of Tropical Storm Dianmu was located at latitude 15.4°N and longitude 108.3°E which put it about 15 miles (25 km) southeast of Tam Ky, Vietnam. Dianmu was moving toward the northwest at 17 m.p.h. (28 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 1000 mb. Tropical Storm Dianmu will weaken as it moves inlands over Southeast Asia. Dianmu will bring gusty winds and locally heavy rain to central Vietnam, southern Laos and northern Cambodia. Heavy rain could cause flash floods in some locations.

Tropical Depression 20W Forms Southeast of Guam

Tropical Depression Twenty-W formed southeast of Guam on Wednesday. At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Twenty-W was located at latitude 11.5°N and longitude 148.1°E which put it about 305 miles (490 km) east-southeast of Guam. The tropical depression moving toward the west-northwest at 10 m.p.h. (16 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). T he minimum surface pressure was 1005 mb.

Tropical Depression Twenty-W developed over the Western North Pacific Ocean southeast of Guam on Wednesday. The circulation around the tropical depression was organizing quickly. Thunderstorms formed near the center of the tropical depression. Other thunderstorms developed in bands revolving around the center of circulation. Storms near the center began to generate upper level divergence that pumped mass away from the depression.

Tropical Depression Twenty-W will move through an environment favorable for intensification during the next few days. The tropical depression will move over water where the Sea Surface Temperatures are near 30˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Depression Twenty-W could strengthen to a tropical storm during the next 12 hours. It could intensify more rapidly after an inner core becomes more well developed. It could intensify to a typhoon within 36 hours.

Tropical Depression Twenty-W will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next several days. The high will steer the tropical depression toward the northwest during the next 36 hours. On its anticipated track the tropical depression could reach the Marianas in less than 24 hours. Tropical Depression Twenty-W could intensify to a tropical storm before it reaches the Marianas. It will bring gusty winds and locally heavy rain to the Marianas including Guam.

Elsewhere over the Western North Pacific Ocean, Tropical Depression Twentyone-W formed over the South China Sea east of Vietnam. At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Twentyone-W was located at latitude 12.9°N and longitude 112.8°E which put it about 400 miles (605 km) east-southeast of Da Nang, Vietnam. The tropical depression moving toward the west-northwest 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). T he minimum surface pressure was 1005 mb. Tropical Depression Twentyone-W is forecast to move toward the west-northwest and to strengthen to a tropical storm. It could reach the coast of Vietnam south of Da Nang in about 24 hours.

Tropical Storm Peter Passes Northeast of Leeward Islands

Tropical Storm Peter passed northeast of the Leeward Islands on Monday. At 11:00 a.m. EDT on Monday the center of Tropical Storm Peter was located at latitude 19.5°N and longitude 60.9°W which put it about 170 miles (275 km) northeast of the Leeward Islands. Peter was moving toward the west-northwest at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 50 m.p.h. (75 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 1007 mb.

An upper level trough north of Puerto Rico and an upper level ridge east of the Leeward Islands were interacting to produce strong southwesterly winds that were blowing across the circulation around Tropical Storm Peter. Those winds were causing strong vertical wind shear. The low level center of circulation was clearly evident on visible satellite images and it was surrounded by showers and lower clouds. Thunderstorms were occurring in bands on the eastern and northern periphery of the circulation around Tropical Storm Peter. Bands in the western and southern parts of Peter consisted primarily of showers and lower clouds. Winds to tropical storm force extended out 125 miles (200 km) in the northeastern quadrant of Peter’s circulation. The winds in the other parts of the circulation were blowing at less than tropical storm force.

Tropical Storm Peter will move through an environment unfavorable for intensification during the next 36 hours. Peter will move over water where the Sea Surface Temperatures are near 29˚C. However, the upper level trough and the upper level ridge will continue to produce strong vertical wind shear. The strong wind shear will inhibit intensification. Tropical Storm Peter could weaken gradually during the next 36 hours.

Tropical Storm Peter will move around the southern side of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Peter toward the west-northwest during the next 36 hours. On its anticipated track Tropical Storm Peter will pass north of the Northern Leeward Islands, the Virgin Islands and Puerto Rico.

Elsewhere over the Atlantic Ocean, Tropical Storm Rose moved away from the Cabo Verde Islands. At 11:00 a.m. EDT on Monday the center of Tropical Storm Rose was located at latitude 17.3°N and longitude 33.4°W which put it about 620 miles (1000 km) west-northwest of the Cabo Verde Islands. Rose was moving toward the northwest at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1007 mb.

Tropical Depression 16 Strengthens to Tropical Storm Peter

Former Tropical Depression Sixteen strengthened to Tropical Storm Peter on Sunday morning. At 9:00 a.m. EDT on Sunday the center of Tropical Storm Peter was located at latitude 17.6°N and longitude 56.0°W which put it about 470 miles (755 km) east of the Northern Leeward Islands. Peter was moving toward the west-northwest at 15 m.p.h. (24 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 1008 mb.

Infrared satellite images and satellite derived scatterometer estimates of surface winds indicated that former Tropical Depression Sixteen had strengthened on Sunday morning and the National Hurricane Center designated the system as Tropical Storm Peter. Early morning visible satellite images revealed that strong vertical wind shear was affecting Tropical Storm Peter. An upper level trough north-northeast of Puerto Rico and an upper level ridge east of the Leeward Islands were interacting to produce strong southwesterly winds that were blowing across Peter’s circulation. The low level center of circulation was clearly visible on those images and it was surrounded by showers and lower clouds. Thunderstorms were occurring in bands on the eastern and northern periphery of the circulation around Tropical Storm Peter. Bands in the western and southern parts of Peter consisted primarily of showers and lower clouds.

Tropical Storm Peter will move through an environment marginally favorable for intensification during the next 24 hours. Peter will move over water where the Sea Surface Temperatures are near 29˚C. However, the upper level trough and the upper level ridge will continue to produce strong vertical wind shear. The strong wind shear will inhibit intensification. Tropical Storm Peter could strengthen a little during the next 24 hours. The upper level winds are forecast to get stronger on Monday. Increased vertical wind shear could cause Peter to weaken back to a tropical depression.

Tropical Storm Peter will move around the southern side of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer the depression toward the west-northwest during the next 48 hours. On its anticipated track Tropical Storm Peter could be northeast of the Northern Leeward Islands by Monday morning.

Elsewhere over the Atlantic Ocean, Tropical Depression Seventeen formed southwest of the Cabo Verde Islands. At 5:00 a.m. EDT on Sunday the center of Tropical Depression Seventeen was located at latitude 11.8°N and longitude 28.21°W which put it about 330 miles (530 km) southwest of the Cabo Verde Islands. The tropical depression was moving toward the north-northwest 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 1007 mb. The tropical depression is forecast to move away from the Cabo Verde Islands and to strengthen to a tropical storm.