Monthly Archives: August 2018

Typhoon Jebi Strengthens to Equivalent of Cat. 5 Hurricane

Powerful Typhoon Jebi strengthened into the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale on Friday.  At 11:00 a.m. EDT on Friday the center of Typhoon Jebi was located at latitude 18.8°N and longitude 141.0°E which put it about 400 miles (645 km) south of Iwo To.  Jebi was moving toward the west-northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 175 m.p.h. (280 km/h) and there were wind gusts to 210 m.p.h. (335 km/h).  The minimum surface pressure was 907 mb.

The circulation of Typhoon Jebi was very well organized and symmetrical.  There was a circular eye at the center of circulation.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Numerous bands of showers and thunderstorms were revolving around the core of the circulation.  Storms near the core were generating strong upper level divergence which was pumping mass away from the typhoon in all directions.

Jebi is a large and powerful typhoon.  Winds to typhoon force extended out about 65 miles (105 km) from the center of circulation.  Winds to tropical storm force extended out about 195 miles (315 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Jebi was 40.4.  The Hurricane Size Index (HSI) was 21.6 and the Hurricane Wind intensity Size Index (HWISI) was 62.0.

Typhoon Jebi may have reached its maximum intensity.  Microwave satellite imagery suggested that an inner rainband may have wrapped around the existing eye and eyewall.  If that has occurred, then an eyewall replacement cycle may have begun.  An eyewall replacement cycle will cause a typhoon to weaken when the inner eyewall, where the strongest wind are, dissipates.

Typhoon Jebi will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  Jebi will gradually turn toward the north as it moves around the end of the ridge.  On its anticipated track Typhoon Jebi should pass west of Iwo To.  Jebi could be approaching Japan in three days or so.

Hurricane Norman Rapidly Intensifies to Cat. 4

Hurricane Norman rapidly intensified to Category 4 on the Saffir-Simpson Scale on Thursday.  At 5:00 p.m. EDT on Thursday the center of Hurricane Norman was located at latitude 17.5°N and longitude 118.8°W which put it about 685 miles (1105 km) west-southwest of the southern tip of Baja California.  Norman was moving toward the west at 8 m.p.h. (13 km/h).  The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 175 m.p.h. (285 km/h).  The minimum surface pressure was 937 mb.

The circulation Hurricane Norman is very symmetrical.  There is a small eye at the center of circulation and the eye is surrounded by a ring of strong thunderstorms.  The strongest winds are occurring in that ring of storms.  Several bands of showers and thunderstorms were revolving around the core of Hurricane Storm.  Storms near the core were generating strong upper level divergence which was pumping mass away from the hurricane in all directions.

Hurricane Norman has a small circulation.  Winds to hurricane force extend out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force only extend out about 80 miles (130 km) from the center.  The Hurricane Intensity Index (HII) for Norman is 31.6.  The Hurricane Size Index (HSI) is 8.6 and the Hurricane Wind Intensity Size Index (HWISI) is 40.2.  Hurricane Norman is a small, but powerful hurricane.

Hurricane Norman will remain in a very favorable environment for another day or so.  Norman will move over water where the Sea Surface Temperature is 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 Norman could strengthen a little more during the next 24 hours unless an eyewall replacement cycle begins.  Norman is likely to move over slightly cooler water during the weekend and there may not be enough energy to maintain such a powerful hurricane.

Hurricane Norman will move south of a subtropical ridge over the Eastern North Pacific Ocean.  The ridge will steer Norman a little to the south of a due westerly course.  On its anticipated track Hurricane Norman will move toward the Central Pacific.

Elsewhere over the Central Pacific Ocean, Hurricane Miriam turned toward the north-northwest.  At 5:00 p.m. EDT on Thursday the center of Hurricane Miriam was located at latitude 15.7°N and longitude 141.6°W which put it about 930 miles (1495 km) east-southeast of Hilo, Hawaii.  Miriam was moving toward the north-northwest at 8 m.p.h. (13 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 982 mb.

Potential Tropical Cyclone Six Causes Warning for Cabo Verde Islands

The potential strengthening of Potential Tropical Cyclone Six caused the government of the Cabo Verde Islands to issue Tropical Storm Warnings for some of the southern islands on Thursday.  Tropical Storm Warnings were issued to Santiago, Fogo and Brava.  At 5:00 p.m. EDT on Thursday the center of Potential Tropical Cyclone Six was located at latitude 12.9°N and longitude 19.4°W which put it about 360 miles (580 km) east-southeast of the Cabo Verde Islands.  It was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h).  The minimum surface pressure was 1007 mb.

The circulation of of Potential Tropical Cyclone Six was still organizing.  There was a broad area of low pressure, but there was not a well defined center of circulation.  Numerous bands of showers and thunderstorms were revolving around the circulation of the broad low.  Many of the stronger thunderstorms were in the outer part of the circulation.  Since there were few thunderstorm in the inner portion of the circulation, it had not started to generate upper level divergence.

Potential Tropical Cyclone Six will be moving through an area favorable for intensification.  It will move over water where the Sea Surface Temperature is near 28°C.  It will move through a region where there will be little vertical wind shear.  Potential Tropical Cyclone Six is forecast to become a tropical depression during the next 12 hours.  It could strengthen into a tropical storm on Friday and it could intensify into a hurricane during the weekend.

Potential Tropical Cyclone Six will move south of a subtropical ridge over the eastern Atlantic Ocean during the next few days.  The ridge will steer the system toward the west-northwest.  On its anticipated track Potential Tropical Cyclone Six will pass near the southern Cabo Verde Islands on Friday, which is why the Tropical Storm Warning was issued.

Typhoon Jebi Hits Northern Marianas

Typhoon Jebi hit the Northern Mariana Islands on Thursday.  At 11:00 a.m. EDT on Thursday the center of Typhoon Jebi was located at latitude 17.8°N and longitude 146.2°E which put it about 35 miles (55 km) east-southeast of Pagan.  Jebi was moving toward the west at 14 m.p.h. (22 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. (230 km/h).  The minimum surface pressure was 940 mb.  A Typhoon Warning was in effect for Agrihan, Pagan and Alamagan.

Typhoon Jebi was very well organized.  There was a small eye at the center of circulation.  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 Jebi.  Storms near the core were generating strong upper level divergence which was pumping mass away from the typhoon.

Winds to typhoon force extended out about 50 miles (80 km) from the center of circulation.  Winds to tropical storm force extended out about 185 miles (295 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Jebi was 23.6.  The Hurricane Size Index (HSI) was 19.4 and the Hurricane Wind Intensity Size Index (HWISI) was 43.0.  Those indices indicate that Typhoon Jebi was capable of causing major damage.

Typhoon Jebi will be moving through an environment favorable for intensification during the next day or so.  Jebi will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there is little vertical wind shear.  Typhoon Jebi is forecast to intensify during the next 24 hours.  If an outer rainband wraps around the existing eye and eyewall, then an eyewall replacement cycle could cause the typhoon to weaken at least temporarily.

Typhoon Jebi will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  Jebi will make a gradual turn toward the north during the next few days while it moves around the end of the ridge.  On its anticipated track Typhoon Jebi will move slowly away from the Northern Marianas.  Weather conditions should slowly improve when Jebi moves away.  The center of Jebi is forecast to pass south of Iwo To.  Typhoon Jebi could approach Honshu in four or five days.

Typhoon Jebi Intensifies Rapidly East of Northern Marianas

Typhoon Jebi intensified rapidly east of the Northern Marianas on Wednesday.  At 5:00 p.m. EDT on Wednesday the center of Typhoon Jebi was located at latitude 17.5°N and longitude 149.8°E which put it about 270 miles (435 km) east of Pagan.  Jebi was moving toward the west at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 105 m.p.h. (170 km/h) and there were wind gusts to 125 m.p.h. (205 km/h).  The minimum surface pressure was 959 mb.  A Typhoon Warning was in effect for Agrihan, Pagan and Alamagan in the Northern Marianas.

The circulation of Typhoon Jebi was very well organized and it was symmetrical.  A small circular eye formed at the center of circulation.  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 Jebi.  Storms around the core were generating strong upper level divergence which was pumping large quantities of mass away from the typhoon.  Winds to typhoon force extended out about 25 miles (40 km) from the center of circulation.  Winds to tropical storm force extended out about 100 miles (160 km) from the center.

Typhoon Jebi will be moving through an environment very favorable for further intensification.  Jebi will move over water where the Sea Surface Temperature is near 29°C.  It will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Jebi is likely to intensify into the equivalent of a major hurricane on Thursday.

Typhoon Jebi will move south of a subtropical ridge over the Western North Pacific for several more days.  The ridge will steer Jebi in a general westerly direction during that time.  Typhoon Jebi will reach the western end of the ridge in about 48 hours.  Jebi will make a gradual turn toward the north when it reaches the end of the ridge.  On its anticipated track Typhoon Jebi will reach the northernmost Mariana Islands within 24 hours.  Jebi will be capable of causing major damage when it arrives.  Jebi is forecast to pass south of Iwo To, but it will turn toward the major islands of Japan during the weekend.

Miriam and Norman Become Hurricanes

Both former Tropical Storm Miriam and Tropical Storm Norman strengthened into hurricanes over the Eastern North Pacific on Wednesday afternoon.  At 5:00 p.m. EDT on Wednesday the center of Hurricane Miriam was located at latitude 14.0°N and longitude 139.7°W which put it about 1090 miles east of Hilo, Hawaii.  Miriam was moving toward the west at 9 m.p.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 992 mb.

At 5:00 p.m. EDT on Wednesday the center of Hurricane Norman was located at latitude 17.6°N and longitude 116.9°W which put it about 545 miles (875 km) southwest of the southern tip of Baja California.  Norman was moving toward the west at 9 m.p.h. (15 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts t0 90 m.p.h. (145 km/h).  The minimum surface pressure was 987 mb.

An inner rainband wrapped much of the way around the center of circulation and an eye developed at the center  of Hurricane Miriam on Wednesday.  Storms near the core of Miriam generated strong upper level divergence which pumped mass away from the hurricane.  Several bands of showers and thunderstorms were revolving around the core of the circulation.  The strongest rainbands were south and east of the center of Hurricane Miriam.  Rainbands on the northwest side of the circulation contained more showers and low clouds.

An inner rainband also wrapped most of the way around the center of Hurricane Norman on Wednesday and an eye appeared to be forming at the center of circulation.  Several bands of showers and thunderstorms were revolving around the core of Norman.  The distribution of thunderstorms in Norman was more symmetrical.  Storms around the core of Hurricane Norman were generating well developed upper level divergence.

Both Hurricane Miriam and Hurricane Norman were moving south of a subtropical ridge over the Eastern North Pacific Ocean.  Miriam could reach the end of the ridge in the next day or two and turn toward the north.  The ridge is forecast to steer Hurricane Norman westward during the next two or three days.

Hurricane Miriam will approach an upper level trough east of Hawaii.  The trough will produce southwesterly winds which will increase vertical wind shear.  The shear is forecast to cause Miriam to weaken.  Hurricane Norman will move over water where the Sea Surface Temperature is near 28°C.  Norman will move through a region where the upper level winds are weak and there will be little vertical wind shear.  Norman is forecast to intensify into a major hurricane.

Tropical Storm Norman Forms Southwest of Baja California

Tropical Storm Norman formed southwest of Baja California on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Norman was located at latitude 17.5°N and longitude 113.9°W which put it about 455 miles (730 km) southwest of the southern tip of Baja California.  Norman was moving toward west-northwest at 10 m.p.h. (16 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.

The circulation of Tropical Storm Norman organized quickly on Wednesday.  A distinct low level center of circulation developed in an area of thunderstorms southwest of Baja California and the National Hurricane Center designated the system as Tropical Storm Norman.  A primary rainband wrapped part of the way around the center of circulation.  Several other bands of showers and thunderstorms formed and began to revolve around the core of Norman.  Storms near the core started to generate strong upper level divergence which was pumping mass away from the tropical storm in all directions.

Tropical Storm Norman will be moving through an environment favorable for intensification during the next several days.  Norman 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.  Tropical Storm Norman could intensify to a hurricane in the next 24 hours.  Once an eye forms and the inner core is full organized, Norman could intensify rapidly.  It could strengthen into a major hurricane later this week.

Tropical Storm Norman will move south of a subtropical ridge over the Eastern North Pacific during the next few days.  The ridge will steer Norman in a general westerly direction.  On its anticipated track Tropical Storm Norman will move toward the Central Pacific.

Elsewhere over the Eastern North Pacific Ocean, Tropical Storm Miriam continued to move westward.  At 11:00 p.m. EDT on Wednesday the center of Tropical Storm Miriam was located at latitude 14.1°N and longitude 137.4°W which put it about 1230 miles (1980 km) east of HIlo, Hawaii.  Miriam was moving toward the west at 13 m.p.h. (20 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 1000 mb.

Tropical Storm Jebi Forms East of the Marianas

Tropical Storm Jebi formed east of the Marianas on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Storm Jebi was located at latitude 15.8°N and longitude 156.6°E which put it about 745 miles (1200 km) east of Saipan.  Jebi 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 1004 mb.

A distinct low level center of circulation developed in a cluster of showers and thunderstorms east of the Northern Marianas and the Japan Meteorological Agency designated the system as Tropical Storm Jebi.  The circulation of Jebi was still organizing.  A primary rainband wrapped around the eastern and northern sides of the center of circulation.  Other bands of showers and thunderstorms were developing in the eastern half of the circulation.  Storms near the center started to generate upper level divergence.

Tropical Storm Jebi will move through an environment favorable for intensification during the next several days.  Jebi will move over water where the Sea Surface Temperature is near 29°C.  It will move under the western end of an upper level ridge.  The ridge will produce southerly winds which will cause some vertical wind shear.  Two upper level lows northwest and northeast of Jebi will enhance upper level divergence to the north of the tropical storm.  Tropical Storm Jebi will strengthen and it could become a typhoon later this week.

Tropical Storm Jebi will move southwest of a ridge over the Western North Pacific Ocean.  The ridge is forecast to strengthen and it will steer Jebi in a general west-northwesterly direction during the next several days.  On its anticipated track Tropical Storm Jebi could be near the northernmost Mariana Islands in about three days.  Jebi could be a typhoon by that time.  Jebi could be south of Iwo To by the end of the week.

Tropical Storm Miriam Forms Southwest of Baja California

Tropical Storm Miriam formed southwest of Baja California on Sunday morning.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Miriam was located at latitude 13.2°N and longitude 125.3°W which put it about 1210 miles (1950 km) west-southwest of the southern tip of Baja California.  Miriam was moving toward the west at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 1004 mb.

The circulation of Tropical Storm Miriam organized quickly on Sunday morning.  Several bands of showers and thunderstorms developed and the bands began to revolve around the center of circulation.  Storms near the core of Miriam started to generate upper level divergence which was pumping mass away in all directions.

Tropical Storm Miriam will move through an environment favorable for intensification during the next several days.  Miriam will move over water where the Sea Surface Temperature is near 28°C.  It will move through an area where the upper level winds are weak and there will be little vertical wind shear.  Tropical Storm Miriam could intensify into a hurricane on Monday.  Miriam could intensify rapidly once the inner core becomes fully organized and an eye develops at the center of circulation.

Tropical Storm Miriam will move south of the subtropical ridge over the Eastern North Pacific Ocean.  The ridge will steer Miriam in a general westerly direction during the next two or three days.  On its anticipated track Tropical Storm Miriam will move farther away from Baja California.

Weakening Tropical Storm Lane Moves Away from Hawaii

A weakening Tropical Storm Lane moved away from Hawaii on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Lane was located at latitude 19.5°N and longitude 160.2°W which put it about 195 miles (310 km) southwest of Honolulu, Hawaii.  Lane was moving toward the west at 9 m.p.h. (15 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 998 mb.  All Tropical Storm Warnings and Watches for the Hawaiian Islands have been discontinued.

An upper level trough west of the Hawaiian Islands produced strong southwesterly winds which blew the upper portion of the circulation of former Hurricane Lane off the lower part of the circulation.  Tropical Storm Lane consisted primarily of a well develop low level circulation of bands of showers and lower clouds.  A few thunderstorms continued to develop in outer bands on the eastern side of the circulation.

Since Tropical Storm Lane exists primarily in the lower levels of the atmosphere, it is being steered westward by a subtropical ridge over the Central Pacific Ocean.  A general westerly motion is forecast during the next several days.  The upper level trough will continue to cause strong vertical wind shear and Tropical Storm Lane will continue to weaken.