Monthly Archives: September 2018

Florence Strengthens Into a Major Hurricane

Hurricane Florence strengthened rapidly into a major hurricane on Wednesday morning.  At 11:00 a.m. EDT on Wednesday the center of Hurricane Florence was located at latitude 22.0°N and longitude 45.7°W which put it about 1370 miles (2205 km) east-southeast of Bermuda.  Florence was moving toward the northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 125 m.p.h. (205 km/h) and there were wind gusts to 145 m.p.h. (235 km/h).  The minimum surface pressure was 957 mb.

Hurricane Florence strengthened rapidly on Wednesday morning.  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 showers and thunderstorms were revolving around the core of Hurricane Florence.  Storms near the core were generating upper level divergence which was pumping mass away from the hurricane.

The circulation of Hurricane Florence is small.  Winds to hurricane force extend out about 20 miles (30 km) from the center of circulation.  Winds to tropical storm force extend out about 95 miles (155 km) from the center.  The Hurricane Intensity Index (HII) for Hurricane Florence is 23.6.  The Hurricane Size Index (HSI) is 7.0 and the Hurricane Wind Intensity Size Index (HWISI) is 30.6.

Hurricane Florence will move through an environment capable of supporting a strong hurricane.  Florence is currently over water where the Sea Surface Temperature is near 27°C and it will move over warmer water during the next several days.  An upper level trough north of Florence is producing westerly winds which are blowing toward the top of the hurricane.  However, those winds do not seem to be creating significant vertical wind shear.  Hurricane Florence could maintain its intensity and there is a chance it could get stronger when it moves over warmer water.  Because of the small circulation, if there are changes in the environment around Hurricane Florence, then the intensity could change quickly.  Also, any eyewall replacement cycles could cause the intensity to fluctuate.

Hurricane Florence will move south of a subtropical high pressure system over the Atlantic Ocean.  The high will steer Florence in a general northwesterly direction during the next few days.  On its anticipated track Hurricane Norman could be southeast of Bermuda by early next week.  The guidance from the numerical models has been variable and there is still much uncertainty about the track Hurricane Florence will take later next week.

Elsewhere, Tropical Depression Gordon was dropping rain on Alabama and Mississippi.  At 11:00 a.m. EDT on Wednesday the center of Tropical Depression Gordon was located at latitude 32.3°N and longitude 90.2°W which put it about 5 miles (10 km) west of Jackson, Mississippi.  Gordon was moving toward the northwest at 14 m.p.h. (22 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 1008 mb.

Tropical Storm Gordon Makes Landfall on the Gulf Coast.

Tropical Storm Gordon made landfall on the Gulf Coast near Pascagoula, Mississippi on Tuesday night.  At 11:30 p.m. EDT on Tuesday the center of Tropical Storm Gordon was located at latitude 30.4°N and longitude 88.4°W which put it about 30 miles (50 km) east of Biloxi, Mississippi.  Gordon was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 70 m.p.h. (110 km/h) and there were wind gusts to 85 m.p.h. (135 km/h).  The minimum surface pressure was 997 mb.

A Hurricane Warning was in effect for the portion of the coast from the Mouth of the Pearl River to the Alabama-Florida border.  A Tropical Storm Warning was in effect for the portion of the coast from the Okaloosa-Walton County line to the Alabama-Florida border.

The circulation of Tropical Storm Gordon was asymmetrical.  The strongest bands of showers and thunderstorms were north and east of the center of circulation.  The strongest winds were occurring in those bands.  A C-MAN station on Dauphin Island, Alabama reported a sustained wind speed of 62 m.p.h. (100 km/h) and a wind gust of 72 m.p.h. (117 km/h).  The winds were much weaker south and west of the center of Tropical Storm Gordon and there was little rain in those parts of the tropical storm.

Tropical Storm Gordon will start to weaken as the center moves inland.  Gordon will continue to move around the western end of a high pressure system over the western Atlantic Ocean.  The high will steer Tropical Storm Gordon toward the northwest during the next day or two.  On its anticipated track Tropical Storm Gordon will move across southern Mississippi on Wednesday and over Arkansas on Thursday.  The wind will be strong enough to cause minor damage and it will cause some power outages.  Locally heavy rain and the potential for flash floods are the greater risks.  Flash Flood Warnings were in effect for parts of West Florida and Southwest Alabama.  Flash Flood Watches were in effect for Mississippi and Southeastern Arkansas.

Elsewhere over the tropical Atlantic Ocean, Hurricane Florence was continuing to intensify east of the northern Leeward Islands.  At 11:00 p.m. EDT on Tuesday the center of Hurricane Florence was located at latitude 20.7°N and longitude 43.9°W which put it about 1515 miles (2440 km) east-southeast of Bermuda.  Florence was moving toward the west-northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 100 m.p.h (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h).  The minimum surface pressure was 976 mb.

Tropical Storm Gordon Nears Gulf Coast

Tropical Storm Gordon moved closer to the Gulf Coast of the U.S. on Tuesday morning.  At 11:00 a.m. EDT on Tuesday the center of Tropical Storm Gordon was located at latitude 28.5°N and longitude 86.8°W which put it about 145 miles (235 km) east-southeast of the mouth of the Mississippi River.  Gordon was moving toward the northwest at 15 m.p.h. (24 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were wind gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 1001 mb.

A Hurricane Warning was in effect for the portion of the coast from the mouth of the Pearl River to the Alabama-Florida border.  Tropical Storm Warnings were in effect for the portions of the coast from Grand Isle, Louisiana to the mouth of the Pearl River including Lake Pontchartrain and from the Alabama-Florida border to the Okaloosa-Walton County line in Florida.

The circulation of Tropical Storm Gordon appeared to be getting more organized on Tuesday morning.  More thunderstorms developed near the center of circulation.  Storms near the center were generating upper level divergence which was pumping mass away to the east of the tropical storm.  Several bands of showers and thunderstorms north and east of the center were moving toward the Gulf Coast.  The bands southwest of the center consisted primarily of showers and lower clouds.  Winds to tropical storm force extended out about 80 miles (130 km) from the center of circulation, but the winds were weaker in the southwestern quadrant of Tropical Storm Gordon.

Tropical Storm Gordon could strengthen into a hurricane before it makes landfall.  Gordon will move over water where the Sea Surface Temperature is near 30°C.  An upper level trough over the southeastern U.S. was producing southwesterly winds which were blowing toward the top of the circulation.  Those winds were causing some vertical shear, but they will not be strong enough to prevent intensification.  The surface pressure decreased slightly on Tuesday morning.  Increased friction near the coast could cause the circulation to tighten around the center, when Tropical Storm Gordon gets closer to the Gulf Coast.

Tropical Storm Gordon will move around the southwestern end of a subtropical high pressure system over the western Atlantic Ocean.  The high will steer Gordon in a general northwesterly direction during the next several days.  On its anticipated track the center of Hurricane Gordon is likely to make landfall on the northern Gulf Coast on Tuesday night.  Gordon will produce winds to near hurricane force at the coast.  It could cause a storm surge of 5 to 8 feet (1.5 to 2.5 meters) east of the center where the wind blows water toward the coast.  The highest storm surge will occur in bays and the mouths of streams and rivers where the shape of the coast funnels water into those areas.  Tropical Storm Gordon will also drop heavy rain over portions of northwest Florida, southwest Alabama, Mississippi and eastern Louisiana.  Locally heavy rain could create the potential for flash floods.

Elsewhere over the Atlantic Ocean, former Tropical Storm Florence strengthened into the third Atlantic hurricane of 2018.  At 11:00 a.m. EDT on Tuesday the center of Hurricane Florence was located at latitude 19.7°N and longitude 42.5°W which put it about 1270 miles (2045 km) east-northeast of the Lesser Antilles.  Florence was moving toward the west-northwest at 12 m.p.h. (19 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 990 mb.

Typhoon Jebi Brings Wind and Rain to Japan

Typhoon Jebi brought wind and rain to Japan on Monday night.  At 11:00 p.m. EDT on Monday the center of Typhoon Jebi was located at latitude 33.9°N and longitude 134.4°E which put it about 15 miles (25 km) southwest of Tokushima.  Jebi was moving toward the north-northeast at 25 m.p.h. (40 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. (170 km/h).  The minimum surface pressure was 945 mb.

Typhoon Jebi made landfall over eastern Shikoku on Monday night.  Jebi brought strong winds and dropped heavy rain over Shikoku and Honshu.  It retained about two thirds of an eyewall and the strongest winds were occurring in that partial eyewall.  There was a gap in the eyewall west of the center of circulation.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Jebi.  Winds to typhoon force extended out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extended out about 200 miles from the center.

An upper level trough northwest of Japan will steer Typhoon Jebi quickly toward the north-northeast.  On its anticipated track Typhoon Jebi will move quickly across eastern Shikoku.  The center of  Jebi will make landfall on Honshu near Kobe and it will move quickly toward the Sea of Japan.  Typhoon Jebi will drop heavy rain over Kobe, Osaka and Kyoto.  Heavy rain could cause flash floods in some parts of Shikoku and Honshu.  Jebi will weaken when it moves over the cooler water in the Sea of Japan.

Tropical Storm Gordon Forms, Causes Warnings for South Florida

Former Potential Tropical Cyclone Seven developed a distinct center of circulation on Sunday morning and the National Hurricane Center upgraded the system to Tropical Storm Gordon.  At 8:30 a.m. EDT on Sunday the center of Tropical Storm Gordon was located at latitude 25.1°N and longitude 80.6°W which put it about 10 miles (15 km) west of Key Largo, Florida.  Gordon was moving toward the west-northwest at 16 m.p.h. (26 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 1009 mb.

A Tropical Storm Warning was in effect for the portion of the coast from Golden Beach to Bonita Beach, Florida.  A Tropical Storm Warning was in effect for the Florida Keys from Craig Key to Ocean Reef including Florida bay.  A Tropical Storm Warning was in effect for the portion of the coast from the Alabama-Florida border to Morgan City, Louisiana including Lake Pontchartrain.

The circulation of Tropical Storm Gordon became much better organized during the past 12 hours.  A distinct low level center of circulation formed and many more thunderstorms developed.  A C-MAN station on Fowey Rock, Florida reported sustained winds of 49 m.p.h. (80 km/h) supporting the designation as a tropical storm.  The circulation of Tropical Storm Gordon was still organizing.  More thunderstorms were developing in bands northeast of the center of circulation than in other parts of the tropical storm.  Those storms were beginning to generate upper level divergence which was pumping mass away from the core of Gordon.

Tropical Storm Gordon will be moving through an environment favorable for intensification during the next 36 hours.  Gordon will be moving over water where the Sea Surface Temperature is near 30°C.  It will be moving through a region where the upper level winds will be weak and there will be little vertical wind shear.  Tropical Storm Gordon will continue to intensify and it could intensify more rapidly once the inner core becomes better organized.  There is a chance that Gordon could strengthen into a hurricane before it reaches the north coast of the Gulf of Mexico.

Tropical Storm Gordon will move around the west end of a subtropical high pressure system over the western Atlantic Ocean.  The ridge will steer Gordon in  a general west-northwesterly direction.  On its anticipated track Tropical Storm Gordon will move away from South Florida later today.  Gordon could approach the north coast of the Gulf of Mexico late on Tuesday.  Locally heavy rain could cause floods in South Florida.  Tropical Storm Gordon could produce a storm surge of 6 to 9 feet (2 to 3 meters) along parts of the northern Gulf Coast.

Typhoon Jebi Moves Closer to Japan

Typhoon Jebi moved closer to Japan on Sunday.  At 11:00 p.m. EDT on Sunday the center of Typhoon Jebi was located at latitude 26.7°N and longitude 133.0°E which put it about 620 miles (1000 km) south of Kyoto, Japan.  Jebi was moving toward the northwest at 13 m.p.h. (20 km/h).  The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (235 km/h).  The minimum surface pressure was 940 mb.

The circulation of Typhoon Jebi remained very well organized.  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.  Several bands of showers and thunderstorms were revolving around the core of Typhoon Jebi.  Storms around the core were generating upper level divergence which was pumping mass away toward the northeast of the typhoon.

Winds to typhoon force extended out about 70 miles (110 km) from the center of circulation.  Winds to tropical storm force extended out about 230 miles (370 km) from the center.  The Hurricane Intensity Index (HII) for Typhoon Jebi was 20.6.  The Hurricane Size Index (HSI) was 24.4 and the Hurricane Wind Intensity Size Index (HWISI) was 45.0.

Typhoon Jebi will move into an environment that will become less favorable for strong typhoons.  Jebi will move over water where the Sea Surface Temperature is near 28°C.  So, there will be enough energy in the upper ocean to maintain the circulation.  However, an upper level trough northwest of Japan will produce southwesterly winds which will blow toward the top of the circulation.  Those winds will produce increasing vertical wind shear.  They will also inhibit the upper level divergence to the south of the typhoon.  Jebi will likely continue to weaken slowly on Monday.

Typhoon Jebi will move around the western end of a ridge over the Western North Pacific Ocean.  Jebi will move toward the north when it rounds the end of the ridge.  The upper level trough northwest of Japan will steer Typhoon Jebi toward the northeast when it nears Japan.  On its anticipated track Typhoon Jebi could approach Shikoku and Honshu in a little over 24 hours.  Jebi is forecast to be a typhoon when it reaches Japan.  It will bring gusty winds and drop locally heavy rain.  The rain will create the potential for flash floods.

Potential Tropical Cyclone Seven Causes Tropical Storm Watch for U.S. Gulf Coast

Potential Tropical Cyclone Seven caused the National Hurricane Center to issue a Tropical Storm Watch for a portion of the U.S. Gulf Coast on Sunday afternoon.  A Tropical Storm Watch was in effect for the portion of the coast from the Alabama-Florida border to Morgan City, Louisiana including Lake Pontchartrain.  At 5:00 p.m. EDT on Sunday the center of Potential Tropical Cyclone Seven was located at latitude 22.7°N and longitude 77.3°W which put it about 275 miles (445 km) east-southeast of Marathon, Florida.  It was moving toward the west-northwest at 15 m.p.h (24 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 1012 mb.

Bands of showers and thunderstorms began to form in a tropical wave over the Bahamas and the National Hurricane Center designated the system as Potential Tropical Cyclone Seven in order to be able to issue the Tropical Storm Watch for the north coast of the Gulf of Mexico.  The circulation of Potential Tropical Cyclone Seven was still organizing.  A distinct low level center of circulation had not formed.  Bands of showers and thunderstorms were developing and the bands were starting to revolve around the inner part of the weather system.  Thunderstorms were beginning to generate some upper level divergence.

Potential Tropical Cyclone Seven will be moving into an environment favorable for intensification.  It will move over water where the Sea Surface Temperature is near 30°C.  An upper level ridge is forecast to develop over Potential Tropical Cyclone Seven.  If that occurs, then the upper level winds would be weak and there would be little vertical wind shear.  Potential Tropical Cyclone Seven is forecast to intensify into Tropical Storm Gordon.  If the system moves slowly enough, there is a chance it could strengthen into a hurricane before it reaches the Gulf Coast.

Potential Tropical Cyclone Seven will move around the western end of a subtropical high pressure system over the western Atlantic Ocean.  The high will steer Potential Tropical Cyclone Seven in a general west-northwesterly direction.  On its anticipated track the system will move over the Florida Keys on Monday.  It will be over the eastern Gulf of Mexico on Tuesday and the system could reach the northern Gulf Coast late on Tuesday or early on Wednesday.

Elsewhere over the tropical Atlantic, Tropical Storm Florence was moving quickly away from the Cabo Verde Islands.  At 5:00 p.m. EDT on Sunday the center of Tropical Storm Florence was located at latitude 17.4°N and longitude 34.6°W which put it about 700 miles (1125 km) west of the Cabo Verde Islands.  Florence was moving toward the west-northwest at 15 m.p.h. (24 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 Olivia Forms South of Baja California

Tropical Storm Olivia formed south of Baja California on Sunday morning.  At 11:00 a.m. EDT on Sunday the center of Tropical Storm Olivia was located at latitude 17.0°N and longitude 112.4°W which put it about 440 miles (705 km) south-southwest of the southern tip of Baja California.  Olivia was moving toward the northwest at 7 m.p.h. (11 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 1002 mb.

The circulation of Tropical Storm Olivia was not well organized.  Most of the stronger thunderstorms were occurring in bands southwest of the center of circulation.  The bands in the other parts of the tropical storm consisted primarily of showers and lower clouds.  Olivia was located southeast of an upper level ridge.  The ridge was producing northeasterly winds which were blowing across the top of the circulation.  Those winds were causing vertical wind shear and they were probably the reason why the stronger thunderstorms were confined to the southwestern part of Tropical Storm Olivia.

Tropical Storm Olivia will move into an environment that is more favorable for intensification.  Olivia will move over water where the Sea Surface Temperature is near 29°C.  It will move away from the northeasterly winds in the upper levels and the vertical wind shear is likely to decrease.  Intensification will occur slowly until the circulation becomes more well organized.  Once more thunderstorms form in other parts of the circulation, Tropical Storm Olivia could strengthen more quickly.

Tropical Storm Olivia will move south of a ridge of high pressure over the Eastern North Pacific Ocean.  The ridge will steer Olivia in a westerly direction during the next several days.  On its anticipated track Tropical Storm Olivia will move away from Baja California.

Elsewhere over the Eastern North Pacific Ocean, Hurricane Norman strengthened back to Category 4 on the Saffir-Simpson Scale.  At 11:00 a.m. EDT on Sunday the center of Hurricane Norman was located at latitude 17.6°N and longitude 129.1°W which put it about 1295 miles (2085 km) west-southwest of the southern tip of Baja California.  Norman was moving toward the west-northwest at 18 m.p.h. (30 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 949 mb.  Norman could be northeast of Hawaii in four or five days.

Typhoon Jebi Turns Toward Japan

Typhoon Jebi turned toward Japan on Saturday.  At 11:00 p.m. EDT on Saturday the center of Typhoon Jebi was located at latitude 23.1°N and longitude 135.4°E which put it about 410 miles (665 km) west-southwest of Iwo To.  Jebi was moving toward the northwest at 14 m.p.h. (22 km/h).  The maximum sustained wind speed was 130 m.p.h. (215 km/h) and there wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 939 mb.

Typhoon Jebi was nearing the completion of an eyewall replacement cycle on Saturday night.  The original inner eyewall had mostly dissipated, although a portion of the lower part of that eyewall was evident on satellite images.  A large circular eye was present at the center of Typhoon Jebi.  The eye was surrounded by a ring of strong thunderstorms and the strongest winds were occurring in that ring of storms.  Multiple bands of showers and thunderstorms were revolving around the core of Typhoon Jebi.  Storms around the core were generating strong upper level divergence.  Winds to typhoon force extended out about 45 miles (75 km) from the center of circulation.  Winds to tropical storm force extended out about 175 miles (280 km) from the center.

Typhoon Jebi will move through an environment capable of supporting a typhoon during the next 48 hours.  Jebi will move over water where the Sea Surface Temperature is near 28°C.  Typhoon Jebi will move through an area where the upper level winds are relatively weak on Sunday. Jebi will move closer to an upper level trough northwest of Japan on Monday.  Stronger southwesterly winds will cause more vertical wind shear and Typhoon Jebi will start to weaken at that time.

Typhoon Jebi will move around the western end of a subtropical ridge over the Western North Pacific Ocean.  Jebi will turn more toward the north on Sunday.  The upper level trough northwest of Japan will steer Typhoon Jebi more toward the northeast on Monday.  On its anticipated track Typhoon Jebi could approach Shikoku and Honshu in about two days.  Jebi is forecast to be a typhoon when it approaches Japan.

Tropical Storm Florence Develops West of Cabo Verde Islands

Tropical Storm Florence developed west of the Cabo Verde Islands on Saturday.  At 5:00 p.m. EDT on Saturday the center of Tropical Storm Florence was located at latitude 15.6°N and longitude 29.0°W which put it about 310 miles (500 km) west of the Cabo Verde Islands.  Florence was moving toward the west-northwest at 16 m.p.h. (26 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 1002 mb.

The circulation of former Tropical Depression Six became better organized on Saturday and the National Hurricane Center designated the system as Tropical Storm Florence.  The center of circulation became more well defined and more thunderstorms developed closer to the center.  Numerous bands of showers and thunderstorms began to form.  The forming rainbands were revolving around the center of circulation.  Storms near the center started to generate upper level divergence.

Tropical Storm Florence will be moving through an environment somewhat favorable for intensification during the next day or two.  Florence will move over water where the Sea Surface Temperature is near 26°C.  It will move through a region where the upper level winds will be weak and there will be little vertical wind shear.  Tropical Storm Florence is likely to intensify during the next 24 to 48 hours.

Tropical Storm Florence will be moving south of a subtropical ridge over the eastern Atlantic Ocean.  The ridge will steer Florence in a general west-northwesterly motion during the next two or three days.  On its anticipated track the center of Tropical Storm Florence will move farther away from the Cabo Verde Islands.