Monthly Archives: September 2021

Tropical Cyclone Gulab Redevelops over the Arabian Sea

Tropical Cyclone Gulab redeveloped over the Arabian Sea on Thursday. At 5:00 p.m. EDT on Thursday the center of Tropical Cyclone Gulab was located at latitude 22.8°N and longitude 65.1°E which put it about 175 miles (280 km) south-southwest of Karachi, Pakistan. Gulab was moving toward the west 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 994 mb.

Tropical Cyclone Gulab redeveloped over the Arabian Sea south of Pakistan on Thursday. Gulab originally formed over the northern Bay of Bengal a few days ago. Gulab made landfall on the coast of India near Tekkali and then it moved westward across India. Even though Tropical Cyclone Gulab weakened after it made landfall, the circulation remained relatively intact because of a favorable upper level environment. There was not a lot of vertical wind shear. In fact, upper level divergence continued to pump away mass and allow the surface low pressure system to persist. The circulation began to intensify as Gulab approached the Arabian Sea and it strengthened once the low level center was back over water.

The circulation around Tropical Cyclone Gulab exhibited more organization on Thursday. More thunderstorms developed in bands revolving around the center of Gulab. The strongest thunderstorms were occurring in bands in the southern half of Tropical Cyclone Gulab. Bands in the northern half of the circulation consisted primarily of showers and lower clouds. The northern half of Gulab appeared to be pulling drier air from Asia into its circulation. Winds to tropical storm force extended out 140 miles (220 km) on the northern side of Tropical Cyclone Gulab. Winds to tropical storm force extended out 60 miles (95 km) on the southern side of the circulation.

Tropical Cyclone Gulab will move through an environment favorable for intensification during the next 36 hours. Gulab will move over water where the Sea Surface Temperatures are near 29˚C. It will move under the middle of an upper level ridge over Southwest Asia and the northern Arabian Sea. The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear. Dry air from Asia could continue to limit the development of thunderstorms in the northern half of Gulab. Tropical Cyclone Gulab will intensify during the next 36 hours and it could strengthen to the equivalent of a hurricane/typhoon.

Tropical Cyclone Gulab will move around the southern side of a high pressure system over Southwest Asia. The high will steer Gulab toward the west during the next 36 hours. On its anticipated track Tropical Cyclone Gulab could approach the coast of Oman near Muscat in 60 hours.

Typhoon Mindulle Passes South of Tokyo

Typhoon Mindulle passed south of Tokyo on Thursday. At 5:00 p.m. EDT on Thursday the center of Typhoon Mindulle was located at latitude 31.1°N and longitude 140.0°E which put it about 340 miles (545 km) south of Tokyo, Japan. Mindulle was moving toward the northeast at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 90 m.p.h. (145 km/h) and there were wind gusts to 105 m.p.h. (165 km/h). The minimum surface pressure was 969 mb.

The core of Typhoon Mindulle passed well to the south of Tokyo on Thursday. However, the circulation around Typhoon Mindulle was so large, that bands of showers and thunderstorms on the northern periphery of Mindulle were bringing gusty winds and rain to parts of Honshu. Winds to typhoon force extended out 130 miles (210 km) on the eastern side of Typhoon Mindulle. Winds to typhoon force extended out 75 miles in the western half of Mindulle. Winds to tropical storm force extended out 310 miles (500 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 13.9. The Hurricane Size Index (HSI) was 37.6 and the Hurricane Wind intensity Size Index (HWISI) was 51.5.

Typhoon Mindulle weakened as it moved over cooler water and into a region where westerly winds in the upper levels caused more vertical wind shear. A larger eye was present at the center of Mindulle, but breaks were developing in the ring of thunderstorms around the eye. The upper level westerly winds in the middle latitudes were beginning to affect the structure of Typhoon Mindulle. Those winds were blowing toward the top of Mindulle’s circulation and they were causing increasing vertical wind shear. The strongest thunderstorms were occurring in bands north and east of the center of the typhoon. Bands south and west of the center consisted primarily of showers and lower clouds. The combination of cooler water and more wind shear was causing Typhoon Mindulle to start a transition to an extratropical cyclone.

The westerly winds in the upper levels will steer Typhoon Mindulle quickly toward the northeast during the next 48 hours. On its anticipated track the core of Mindulle will pass well to the east of Honshu and Hokkaido. Bands on the northern side of Typhoon Mindulle could bring gusty winds and heavy rain to coastal parts of northern Honshu and eastern Hokkaido. Big waves will affect shipping southeast of Japan. Mindulle will weaken gradually during the next 48 hours while it makes a transition to an extratropical cyclone.

Tropical Storm Victor Forms South of Cabo Verde Islands

Tropical Storm Victor formed south of the Cabo Verde Islands on Wednesday afternoon. At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Victor was located at latitude 8.3°N and longitude 25.5°W which put it about 540 miles (870 km) south of the Cabo Verde Islands. Victor was moving toward the west-northwest at 13 m.p.h. (20 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 a low pressure system west of Africa strengthened on Wednesday afternoon and the National Hurricane Center designated the system as Tropical Storm Victor. There was a large circulation around Tropical Storm Victor and the circulation was still in the early stages of organization. Bands of showers and thunderstorms were revolving around the center of Victor. More thunderstorms were starting to develop near the center of circulation. The strongest thunderstorms were occurring west of the center. Storms near the center started to generate upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 60 miles in the northern half of Victor’s circulation. The winds in the southern half of the circulation were blowing at less than tropical storm force.

Tropical Storm Victor will move through an environment favorable for intensification during the next 36 hours. Victor will move over water where the Sea Surface Temperatures are 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 Victor will strengthen gradually. Victor will intensify to a hurricane by Friday.

Tropical Storm Victor will move south of a high pressure system over the eastern Atlantic Ocean. The high will steer Victor toward the west-northwest during the next 36 hours. On its anticipated track Tropical Storm Victor will pass well to the southwest of the Cabo Verde Islands.

Elsewhere over the Atlantic Ocean, major Hurricane Sam was passing northeast of the Leeward Islands. At 5:00 p.m. EDT on Wednesday the center of Hurricane Sam was located at latitude 20.2°N and longitude 57.6°W which put it about 385 miles (620 km) east-northeast of the Northern Leeward Islands. Sam moving toward the northwest at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 945 mb.

Typhoon Mindulle Strengthens Back to Equivalent of a Major Hurricane

Typhoon Mindulle strengthened back to the equivalent of a major hurricane west-southwest of Iwo To on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Typhoon Mindulle was located at latitude 23.0°N and longitude 135.6°E which put it about 390 miles (630 km) west-southwest of Iwo To. Mindulle was moving toward the north at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 950 mb.

Typhoon Mindulle strengthened back to the equivalent of a major hurricane after it completed several Eyewall Replacement Cycles. A large circular eye with a diameter of 45 miles (75 km) was present at the center of Typhoon 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 Mindulle. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

The circulation around Typhoon Mindulle grew even larger after it completed the Eyewall Replacement Cycles. Winds to typhoon force extended out 70 miles (110 km) from the center of Mindulle. Winds to tropical storm force extended out 235 miles (380 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 22.1. The Hurricane size Index (HSI) was 27.4 and the Hurricane Wind Intensity Size Index (HWISI) was 49.5.

Typhoon Mindulle will move through an environment capable of sustaining a powerful typhoon during the next 36 hours. Mindulle will move over water where the Sea Surface Temperatures are near 29˚C. It will move into a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Mindulle could strengthen gradually during the next 36 hours.

Typhoon Mindulle will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next 48 hours. The high pressure system will steer Mindulle toward the north during the next 24 hours. Typhoon Mindulle will start to move toward the northeast after it moves around the western end of the high. On its anticipated track Typhoon Mindulle will pass west of Iwo To during the next 24 hours. Mindulle cold be south of Tokyo in 48 hours.

Hurricane Sam Strengthens Back to Cat. 4

Hurricane Sam strengthened back to Category 4 on the Saffir-Simpson Scale on Tuesday morning. At 11:00 a.m. EDT on Tuesday the center of Hurricane Sam was located at latitude 17.5°N and longitude 54.3°W which put it about 580 miles (935 km) east of the Northern Leeward Islands. Sam moving toward the northwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 954 mb.

Hurricane Sam strengthened back to Category 4 after completing several Eyewall Replacement Cycles. The Eyewall Replacement Cycles also resulted in an increase in the size of Hurricane Sam. A larger circular eye with a diameter of 40 miles (65 km) was present at the center of 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 upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Sam was larger after the completion of the Eyewall Replacement Cycles. Winds to hurricane force extended out 40 miles (65 km) from the center of Sam. Winds to tropical storm force extended out 140 miles (225 km) from the center of circulation. The Hurricane Intensity Index (HII) for Hurricane Sam was 25.1. The Hurricane Size Index (HSI) was 14.2 and the Hurricane Wind Intensity Size Index (HWISI) was 39.3.

Hurricane Sam will move through an environment capable of sustaining a major hurricane 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 could strengthen in the favorable environment.

Hurricane Sam will move around the southwestern part of a subtropical high pressure system over the Atlantic Ocean. The high will steer Sam toward the northwest during the next 48 hours. On its anticipated track Hurricane Sam could pass northeast of the Northern Leeward Islands on Thursday. Sam could be southeast of Bermuda by Friday.

Hurricane Sam Peaks Just Shy of Cat. 5

Hurricane Sam peaked just shy of Category 5 on the Saffir-Simpson Scale on Sunday. At 11:00 p.m. EDT on Sunday the center of Hurricane Sam was located at latitude 14.7°N and longitude 50.8°W which put it about 850 miles (1365 km) east-southeast of the Northern Leeward Islands. Sam moving toward the northwest at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 170 m.p.h. (280 km/h). The minimum surface pressure was 943 mb.

The National Hurricane Center indicated that the maximum sustained wind speed in Hurricane Sam may have peaked at 155 m.p.h. (250 km/h) on Sunday afternoon before an Eyewall Replacement Cycle halted intensification. The inner end of a rainband wrapped around the existing small eye and eyewall at the center of Hurricane Sam. There were two concentric eyewalls for a period of time and then the inner eyewall began to dissipate. Low level convergence became primarily concentrated on the outer eyewall. The outer eyewall had a diameter of 16 miles (26 km). The western side of the outer eyewall was weaker and the rainbands on the western side of Hurricane Sam were also weaker.

The size of the circulation around Hurricane Sam only increased slightly as a result of the Eyewall Replaement Cycle. Winds to hurricane force extended out 30 miles (50 km) from the center of Sam. Winds to tropical storm force extended out 90 miles (145 km) from the center of circulation. The Hurricane Intensity Index (HII) was 29.9. The Hurricane Size Index (HSI) was 9.8 and the Hurricane Wind Intensity Size Index (HWISI) was 39.7.

Hurricane Sam will move through an environment capable of sustaining a major hurricane 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. The current Eyewall Replacement Cycle will cause Hurricane Sam to weaken until the outer eyewall becomes full developed. Additional Eyewall Replacement Cycles could occur which would cause fluctuations in the intensity of Hurricane Sam.

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 northwest during the next 48 hours. On its anticipated track Hurricane Sam could be east of the Northern Leeward Islands by Wednesday.

Typhoon Mindulle Develops Concentric Eyewalls

Large Typhoon Mindulle developed concentric eyewalls southwest of Iwo To on Sunday. At 11:00 p.m. EDT on Sunday the center of Typhoon Mindulle was located at latitude 19.9°N and longitude 136.4°E which put it about 445 miles (720 km) southwest of Iwo To. Mindulle moving toward the north at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 947 mb.

Typhoon Mindulle developed concentric eyewalls on Sunday when the inner end of a rainband wrapped around an existing eye and eyewall. When the larger outer eyewall formed, much of the low level convergence of air shifted to the outer eyewall. The inner eyewall began to weaken because there was less low level convergence into it. Since the strongest winds were occurring in the existing inner eyewall, the maximum wind speed decreased when it weakened. The inner eyewall was still present, although it was much weaker. There was a break in the northwestern part of the outer eyewall. The existence of the two eyewalls was disrupting the inner core of Typhoon Mindulle.

The ongoing Eyewall Replacement Cycle was causing the circulation around Typhoon Mindulle to get larger. Winds to typhoon force extended out 65 miles (105 km) from the center of Mindulle. Winds to tropical storm force extended out 205 miles (330 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 23.6. The Hurricane size Index (HSI) was 23.2 and the Hurricane Wind Intensity Size Index (HWISI) was 46.8.

Typhoon Mindulle will move through an environment capable of sustaining a powerful typhoon during the next 36 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. The ongoing Eyewall Replacement Cycle will likely cause Typhoon Mindulle to weaken during the next 12 hours. If the inner eyewall dissipates and the outer eyewall becomes more well developed, then Mindulle could strengthen again. Typhoon Mindulle will move slowly. The strong winds in Mindulle could mix cooler water to the surface. Cooler water and an Eyewall Replacement Cycle could limit the potential for Typhoon Mindulle to intensify.

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 north-northwest during the next 36 hours. On its anticipated track Typhoon Mindulle could be west of Iwo To in 48 hours. Mindulle could be south of Tokyo in four days.

Hurricane Sam Rapidly Intensifies to Cat. 4

Hurricane Sam rapidly intensified to Category 4 on the Saffir-Simpson Scale on Saturday night. At 11:00 p.m. EDT on Saturday the center of Hurricane Sam was located at latitude 13.5°N and longitude 49.0°W which put it about 990 miles (1595 km) east-southeast of the Northern Leeward Islands. Sam moving toward the west-northwest at 8 m.p.h. (13 km/h). The maximum sustained wind speed was 145 m.p.h. (230 km/h) and there were wind gusts to 170 m.p.h. (280 km/h). The minimum surface pressure was 943 mb.

A NOAA plane conducting a research mission in Hurricane Sam fund that Sam had rapidly intensified to Category 4 on the Saffir-Simpson Scale. A circular eye with a diameter of 12 miles (19 km) 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 30 miles (50 km) from the center of Sam. Winds to tropical storm force extended out 100 miles (160 km) from the center of circulation. The Hurricane Intensity Index (HII) for Hurricane Sam was 30.0. The Hurricane Size Index (HSI) was 9.2 and the Hurricane Wind Intensity Size Index (HWISI) was 39.2.

Hurricane Sam will move through an environment capable of sustaining a major hurricane 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. The NOAA aircraft did report that there was some drier air in the middle troposphere in the environment around Hurricane Sam. The drier air could weaken Sam if it gets pulled into the core of the circulation. In addition, if the inner end of a rainband wraps around the existing eye and eyewall, then concentric eyewalls could form. An eyewall replacement cycle would cause Hurricane Sam to weaken.

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.

Typhoon Mindulle Rapidly Intensifies to Equivalent of Cat. 5 Hurricane

Typhoon Mindulle rapidly intensified to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Saturday night. At 11:00 p.m. EDT on Saturday the center of Typhoon Mindulle was located at latitude 18.7°N and longitude 136.8°E which put it about 510 miles (825 km) southwest of Iwo To. Mindulle moving toward the northwest at 4 m.p.h. (6 km/h). The maximum sustained wind speed 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 915 mb.

Typhoon Mindulle continued to intensify rapidly over the Western North Pacific Ocean on Saturday night. A circular eye with a diameter of 18 miles (29 km) 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 strong 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 more than twice as large as the circulation of Hurricane Sam which was over the Atlantic Ocean. Winds to typhoon force extended out 50 miles (80 km) from the center of Mindulle. Winds to tropical storm force extended out 210 miles (340 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Mindulle was 35.0. The Hurricane Size Index (HSI) was 19.4 and the Hurricane Wind Intensity Size Index (HWISI) was 54.4.

Typhoon Mindulle will move through an environment capable of sustaining a powerful typhoon during the next 36 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 may be near its peak intensity. 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 slowly. The strong winds in Mindulle could mix cooler water to the surface. That would also cause 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 days.

Tropical Cyclone Gulab forms over Northern Bay of Bengal

Tropical Cyclone Gulab formed over the northern Bay of Bengal on Saturday. At 11:00 a.m. EDT on Saturday the center of Tropical Cyclone Gulab was located at latitude 18.3°N and longitude 88.0°W which put it about 245 miles (395 km) east of Tekkali, India. Gulab was moving toward the west at 8 m.p.h. (13 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.

The circulation around a low pressure system over the northern Bay of Bengal strengthened on Saturday and the India Meteorological Department designated the system as Tropical Cyclone Gulab. The distribution of thunderstorms around Tropical Cyclone Gulab was asymmetrical. The strongest thunderstorms were occurring in bands in the western half of Gulab’s circulation. Bands in the eastern half of the tropical cyclone consisted primarily of showers and lower clouds. An upper level ridge over southern Asia was producing northeasterly winds that were blowing toward the top of Tropical Cyclone Gulab. Those winds were causing moderate vertical wind shear and they were contributing to the asymmetrical distribution of thunderstorms. Winds to tropical storm force extended out 60 miles (96 km) from the center of Gulab.

Tropical Cyclone Gulab will move through an environment that is marginally favorable for intensification during the next 24 hours. Gulab will move over water where the Sea Surface Temperatures are near 29˚C. However, the upper level ridge over southern Asia will continue to cause moderate vertical wind shear. The wind shear will inhibit intensification. Tropical Cyclone Gulab could strengthen a little during the next 24 hours if the wind shear does not increase. If the upper level winds get stronger, then the wind shear will cause Gulab to weaken.

Tropical Cyclone Gulab will move south of a high pressure system over southern Asia. The high will steer Gulab toward the west during the next 24 hours. On its anticipated track Tropical Cyclone Gulab could approach the coast of Andhra Pradesh near Tekkali in 24 hours. Gulab will bring gusty winds and locally heavy rain to northeastern Andhra Pradesh and southern Odisha. Heavy rain could cause flash floods in some locations.