Tag Archives: HWISI

Typhoon Bolaven Rapidly Intensifies to Equivalent of a Major Hurricane

Typhoon Bolaven rapidly intensified to the equivalent of a major hurricane over the Western North Pacific Ocean north of Guam on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Typhoon Bolaven was located at latitude 16.4°N and longitude 144.3°E which put it about 100 miles (160 km) northwest of Tinian. Bolaven was moving toward the north-northwest at 11 m.p.h. (17 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. (230 km/h). The minimum surface pressure was 959 mb.

A Typhoon Warning was in effect for Rota, Tinian and Saipan. A Typhoon Watch was in effect for Guam. A Tropical Storm Warning was in effect for Guam.

Typhoon Bolaven brought strong winds and heavy rain to Guam, Rota, Tinian and Saipan. The center of Bolaven passed between Rota and Tinian and the strongest winds likely occurred in those places. A weather station in Saipan reported a sustained wind speed of 49 m.p.h. (79 km/h) and a wind gust of 68 m.p.h. (110 km/h). A weather station at Guam International Airport reported a sustained wind speed of 32 m.p.h. (52 km/h) and a wind gust of 46 m.p.h. (74 km/h). That weather station also measured 4.54 inches (115.3 mm) of rain.

Typhoon Bolaven began to intensify rapidly as it moved west of the Marianas. A small circular eye with a diameter of 14 miles (22 km) developed at the center of Bolaven’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Bolaven. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

The size of the circulation around Typhoon Bolaven increased when it intensified on Tuesday. Winds to typhoon force extended out 25 miles (40 km) from the center of Bolaven’s circulation. Winds to tropical storm force extended out 185 miles (295 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Bolaven was 20.6. The Hurricane Size Index (HSI) was 11.5 and the Hurricane Wind Intensity Size Index (HWISI) was 32.1.

Typhoon Bolaven will move through an environment favorable for intensification during the next 24 hours. Bolaven will move over water where the Sea Surface Temperatures are near 30°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Bolaven will intensify during the next 24 hours. Bolaven could intensify rapidly at times. Typhoon Bolaven could strengthen to the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale.

Typhoon Bolaven will move around the western part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Bolaven toward the north-northwest during the next 24 hours. On its anticipated track, the Typhoon Bolaven will stay west of the Marianas during the next 24 hours.

Lidia Rapidly Intensifies to a Major Hurricane Southwest of Puerto Vallarta

Hurricane Lidia rapidly intensified to a major hurricane over the Eastern North Pacific Ocean southwest of Puerto Vallarta on Tuesday afternoon. At 2:00 p.m. EDT on Tuesday the center of Hurricane Lidia was located at latitude 19.2°N and longitude 107.2°W which put it about 155 miles (255 km) southwest of Puerto Vallarta, Mexico. Lidia was moving toward the east-northeast at 15 m.p.h. (24 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 135 m.p.h. (220 km/h). The minimum surface pressure was 959 mb.

A Hurricane Warning was in effect for the portion of the coast from Manzanillo to El Roblito, Mexico. A Hurricane Warning was in effect for Las Islas Marias. A Tropical Storm Warning was in effect for the portion of the coast from El Roblito to Mazatlan, Mexico. A Tropical Storm Warning was also in effect for the portion of the coast from Manzanillo to Punta San Telmo, Mexico.

Hurricane Lidia rapidly intensified to a major hurricane on Tuesday. A U.S. Air Force Reserve Hurricane Hunter plane reported a circular eye with a diameter of 17 miles (28 km) was present at the center of Lidia’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the center of Hurricane Lidia. Storms near the center generated upper level divergence that pumped mass away from the hurricane.

The size of the circulation around Hurricane Lidia increased on Tuesday. Winds to hurricane force extended out 30 miles (50 km) from the center of Lidia. Winds to tropical storm force extended out 125 miles (200 km) from the center of circulation. The Hurricane Intensity Index (HII) was 20.6. The Hurricane Size Index (HSI) was 8.5 and the Hurricane Wind Intensity Size Index (HWISI) was 29.1. Hurricane Lidia was similar in size and intensity to Hurricane Zeta when Zeta made landfall in Louisiana in 2020.

Hurricane Lidia will move through an environment favorable for intensification during the next few hours. Lidia will move over water where the Sea Surface Temperatures are near 30°C. It will move under the eastern side of an upper level trough that is west of Baja California. The upper level trough will produce southwesterly winds that will blow toward the top of Lidia’s circulation. Those winds will cause some vertical wind shear, but the wind shear will not be strong enough to prevent intensification. Hurricane Lidia will intensity during the next few hours. Lidia could continue to intensify rapidly.

The upper level trough west of Baja California will steer Hurricane Lidia toward the northeast during the next 24 hours. On its anticipated track, the center of Hurricane Lidia will make landfall near Puerto Vallarta on Tuesday evening. Lidia will be a major hurricane when it makes landfall. Hurricane Lidia will bring strong, gusty winds and locally heavy rain. The strong winds will be capable of causing major damage. Regional outages of electricity are likely. Heavy rain will fall in Jalisco and Nayarit. The heavy rain is likely to cause flash floods in some locations. Hurricane Lidia could cause a storm surge of up to 13 feet (4 meters) along the coast of Jalisco.

Typhoon Koinu Lingers Near Hong Kong

Typhoon Koinu lingered over the Western North Pacific Ocean near Hong Kong on Saturday. At 11:00 p.m. EDT on Saturday the center of Typhoon Koinu was located at latitude 21.4°N and longitude 114.4°E which put it about 65 miles (105 km) south-southeast of Hong Kong. Koinu was moving toward the west-northwest at 4 m.p.h. (6 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 968 mb.

Typhoon Koinu weakened gradually on Saturday as it lingered near Hong Kong. Since Koinu moved very slowly, the strong winds in the lower atmosphere mixed cooler water to the surface of the ocean. Koinu was unable to extract as much energy from the cooler water and the typhoon weakened. Thunderstorms in Typhoon Koinu did not rise quite as high into the atmosphere.

Even though Typhoon Koinu weakened on Saturday, it still exhibited a well organized circulation. A very small eye was present at the center of Koinu’s circulation. The inner end of a rainband wrapped around the existing eye and eyewall, and concentric eyewalls could be developing. Bands of showers and thunderstorms revolved around the small core of Typhoon Koinu. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

The size of the circulation around Typhoon Koinu decreased as Koinu gradually weakened. Winds to typhoon force extended out 25 miles (40 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 90 miles (145 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 16.5. The Hurricane Size Index (HSI) was 8.6. and the Hurricane Wind Intensity Size Index (HWISI) was 25.1.

Typhoon Koinu will move through an environment somewhat unfavorable for intensification during the next 24 hours. Koinu will move over water where the Sea Surface Temperatures are near 27°C. It will move under axis of an upper level ridge over China. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. However, strong winds in the lower atmosphere will continue to mix cooler water to the surface of the ocean. In addition, the circulation around the northern side of Typhoon Koinu could draw in some drier air from China. Typhoon Koinu is likely to continue to weaken gradually during the next 24 hours due to the mix of cooler water to the surface of the ocean.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia. The high pressure system will steer Koinu slowly toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will move south of Hong Kong on Sunday.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 15W strengthened to Tropical Storm Bolaven east-southeast of Guam. At 11:00 p.m. EDT on Saturday the center of Tropical Storm Bolaven was located at latitude 9.6°N and longitude 152.9°E which put it about 630 miles (1020 km) east-southeast of Guam. Bolaven was moving toward the west-northwest at 5 m.p.h. (8 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. Typhoon Watches were in effect for Guam, Rota, Tinian and Saipan.

Typhoon Koinu Moves Southeast of Hong Kong

Typhoon Koinu moved southeast of Hong Kong on Friday night. At 11:00 p.m. EDT on Friday the center of Typhoon Koinu was located at latitude 21.1°N and longitude 115.3°E which put it about 115 miles (185 km) southeast of Hong Kong. Koinu was moving toward the west-southwest at 4 m.p.h. (6 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 952 mb.

Typhoon Koinu intensified back to the equivalent of a major hurricane over the South China Sea southeast of Hong Kong on Friday. A circular eye with a diameter of 12 miles (19 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms revolved around the core of Typhoon Koinu. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

Wins to typhoon force extended out 40 miles (65 km) from the center of Typhoon Koinu. Winds to tropical storm force extended out 285 miles (460 km) in the northeast quadrant of Koinu’s circulation. Winds to tropical storm force extended out 130 miles (210 km) in the other parts of Typhoon Koinu. The Hurricane Intensity Index (HII) for Typhoon Koinu was 22.1. The Hurricane Size Index (HSI) was 14.9 and the Hurricane Wind Intensity Size Index (HWISI) was 37.0. Typhoon Koinu was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Koinu will move through an environment somewhat favorable for a strong typhoon during the next 24 hours. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level ridge over China. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some vertical wind shear. The wind shear will inhibit intensification. The circulation around the northern side of Typhoon Koinu could draw in some drier air from China. Typhoon Koinu could maintain its intensity during the next 24 hours if the drier air does not reach the inner core of the circulation. Koinu is likely to weaken if the drier penetrates to the core of the circulation.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia. The high pressure system will steer Koinu slowly toward the west-southwest during the next 24 hours. On its anticipated track the center Typhoon Koinu will move south of Hong Kong on Saturday.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 15W formed east-southeast of Guam. At 11:00 p.m. EDT on Friday the center of Tropical Depression 15W was located at latitude 9.9°N and longitude 154.2°E which put it about 700 miles (1130 km) east-southeast of Guam. The tropical depression was moving toward the west-northwest at 13 m.p.h. (21 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 1003 mb.

Typhoon Koinu Brings Wind and Rain to Taiwan

Typhoon Koinu brought wind and rain to Taiwan on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Typhoon Koinu was located at latitude 22.1°N and longitude 120.6°E which put it about 10 miles (15 km) west of Hengchun, Taiwan. Koinu was moving toward the west-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 125 m.p.h. (200 km/h) and there were wind gusts to 155 m.p.h. (250 km/h). The minimum surface pressure was 945 mb.

Typhoon Koinu brought strong winds and heavy rain to southern Taiwan on Wednesday night. The eye of Koinu passed over the southern tip of Taiwan. The northern half of the eyewall moved across southern Taiwan. Typhoon Koinu was the equivalent of a major hurricane when it moved across Taiwan. Winds to typhoon force extended out 70 miles (110 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 230 miles (370 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 23.6. The Hurricane Size Index (HSI) was 21.6 and the Hurricane Wind Intensity Size Index (HWISI) was 45.2. Typhoon Koinu was stronger than Hurricane Rita was when Rita hit southwest Louisiana in 2005. Koinu was a little smaller than Rita was.

Easterly winds blowing around the northern side of Typhoon Koinu will rise up the eastern slopes of mountains in Taiwan. The enhanced rising motion will produce very heavy rainfall on those eastern slopes. The heavy rain is likely to cause flash floods in some locations.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will move over the South China Sea on Thursday.

The core of Typhoon Koinu was partially disrupted when the eye and northern part of the eyewall moved across southern Taiwan. The disruption of the inner core of Koinu’s circulation is likely to cause Typhoon Koinu to weaken during the next 24 hours even though Koinu will move through an environment favorable for intensification. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level ridge over China. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some little vertical wind shear, but the wind shear will not be too strong. Typhoon Koinu is likely to weaken gradually during the next 24 hours because of the disruption of its inner core.

Typhoon Koinu Approaches Taiwan

Typhoon Koinu approached Taiwan from east on Tuesday night. At 11:00 p.m. EDT on Tuesday the center of Typhoon Koinu was located at latitude 22.1°N and longitude 123.3°E which put it about 175 miles (280 km) east of Hengchun, Taiwan. Koinu was moving toward the west-northwest at 7 m.p.h. (11 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. (230 km/h). The minimum surface pressure was 953 mb.

Typhoon Koinu was the equivalent of a major hurricane as it approached Taiwan on Tuesday night. A circular eye with a diameter of 30 miles (50 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the core of Typhoon Koinu. Storms near the core generated strong upper level divergence that pumped large quantities of mass away from the typhoon.

The size of the circulation around Typhoon Koinu increased on Tuesday. Winds to typhoon force extended out 90 miles (145 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 20.6. The Hurricane Size Index (HSI) was 29.2 and the Hurricane Wind Intensity Size Index (HWISI) was 49.8. Typhoon Koinu was similar in size and intensity to Hurricane Frances when Frances hit southeast Florida in 2004.

Typhoon Koinu will move through an environment favorable for intensification during the next 12 hours. Koinu 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. Typhoon Koinu is likely to intensify during the next 12 hours.

Typhoon Koinu will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will reach the coast of southeast Taiwan in less than 24 hours. Typhoon Koinu is likely to be the equivalent of a major hurricane when it approaches Taiwan. Koinu will bring strong, gusty winds and locally heavy rain to Taiwan. Heavy rain will cause flash floods in some locations. Typhoon Koinu could also cause widespread outages of electricity.

Hurricane Lee Moves Toward Nova Scotia

Hurricane Lee moved toward Nova Scotia on Friday. At 5:00 p.m. EDT on Friday the center of Hurricane Lee was located at latitude 37.9°N and longitude 66.7°W which put it about 490 miles (790 km) south-southwest of Halifax, Nova Scotia. Lee was moving toward the north at 20 m.p.h. (32 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 965 mb.

A Hurricane Watch was also in effect for the portion of the coast from the U.S./Canada border to Point Lepreau, New Brunswick. That Hurricane Watch included Grand Manan Island. A Hurricane Watch was in effect for the portion of the coast from Digby to Ecum Secum, Nova Scotia.

Tropical Storm Warning was in effect for the portion of the coast from Westport, Massachusetts to the U.S. Canada border. That Tropical Storm Warning included Martha’s Vineyard and Nantucket. A Tropical Storm Warning was in effect for the portion of the coast from the U.S./Canada border to Fort Lawrence, New Brunswick. That Tropical Storm Warning included Grand Manan Island. A Tropical Storm Warning was also in effect for the portion of the coast from Shediac to Tidnish, New Brunswick. A Tropical Storm Warning was in effect for the portion of the coast from Fort Lawrence, New Brunswick to Point Tupper, Nova Scotia.

A Tropical Storm Watch was in effect for Prince Edward Island and the Magdalen Islands. A Tropical Storm Watch was in effect for the portion of the coast from Belledune to Shediac, New Brunswick. A Tropical Storm Watch was in effect for the portion of the coast from Tidnish, New Brunswick to Aulds Cove, Nova Scotia. A Tropical Storm Watch was also in effect for the portion of the coast from Aulds Cove to Meat Cove to Point Tupper, Nova Scotia.

Hurricane Lee was in the middle of a transition to an extratropical cyclone on Friday afternoon. There was no longer a well formed eye at the center of Lee’s circulation. Drier air was being pulled around the southern side of Hurricane Lee. An upper level trough over the eastern U.S. was producing southerly winds that were blowing toward the top of Lee’s circulation. Those winds were causing moderate vertical wind shear. The effects of the drier air and the vertical wind shear were causing an asymmetrical distribution of thunderstorms in Hurricane Lee. Most of the thunderstorms were occurring in bands in the northern half of Lee’s circulation, Bands in the southern half of Hurricane Lee consisted primarily of showers and lower clouds.

The changes to the structure of Hurricane Lee produced a large area of tropical storm force winds. Winds to hurricane force extended out 115 miles (185 km) from the center of Lee’s circulation. Winds to tropical storm force extended out 345 miles (555 km) from the center of circulation. The Hurricane Intensity Index (HII) was 11.5. The Hurricane Size Index (HSI) was 39.8 and the Hurricane Wind Intensity Size Index (HWISI) was 51.3. Hurricane Lee was about three-fourths as large as Hurricane Sandy was in 2012.

Hurricane Lee will move through an environment that will be unfavorable for intensification of a hurricane during the next 24 hours. Lee will move over water where the Sea Surface Temperatures are colder than 26°C. The upper level trough over the eastern U.S. will continue to will cause moderate vertical wind shear. The circulation around Lee will also pull in more drier air. The combination of colder water, moderate vertical wind shear and the drier air will cause Hurricane Lee to weaken gradually during the next 24 hours. That same combination of environmental factors will also cause Hurricane Lee to complete a transition to an extratropical cyclone on Saturday.

Hurricane Lee will move around the western part of a subtropical high pressure system over the Atlantic Ocean. The high pressure system and the upper level trough over the eastern U.S. will steer Lee toward the north during the next 24 hours. On its anticipated track, Hurricane Lee reach Nova Scotia on Saturday. Even though Hurricane Lee will be making a transition to an extratropical cyclone on Saturday, Lee will bring strong, gusty winds and locally heavy rain to the coast of the Northeast U.S. and to Nova Scotia, New Brunswick, and Prince Edward Island. Widespread outages of electricity are possible. Heavy rain could cause flash floods in come locations. The winds blowing around the northern side of Hurricane Lee will push water toward the coast. The water level could rise as much as four feet (one meter) along parts of the coast.

Elsewhere over the Atlantic Ocean, former Hurricane Margot weakened to a tropical storm west of the Azores and Tropical Depression Fifteen formed east of the Lesser Antilles. At 5:00 p.m. EDT on Friday the center of Tropical Storm Margot was located at latitude 36.0°N and longitude 37.9°W which put it about 615 miles (990 km) west of the Azores. Margot was moving toward the southeast at 3 m.p.h. (5 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 990 mb.

At 5:00 p.m. EDT on Friday the center of Tropical Depression Fifteen was located at latitude 15.4°N and longitude 44.0°W which put it about 1150 miles (1885 km) west of the Azores. The tropical depression was moving toward the northwest at 13 m.p.h. (21 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.

Hurricane Lee Causes Gusty Winds in Bermuda

Hurricane Lee caused gusty winds in Bermuda on Thursday. At 11:00 p.m. EDT on Thursday the center of Hurricane Lee was located at latitude 32.9°N and longitude 67.6°W which put it about 170 miles (275 km) west-northwest of Bermuda. Lee was moving toward the north at 14 m.p.h. (22 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 957 mb.

A Hurricane Watch was in effect for the portion of the coast from Stonington, Maine to the U.S./Canada border. A Hurricane Watch was also in effect for the portion of the coast from the U.S./Canada border to Point Lepreau, New Brunswick. That Hurricane Watch included Grand Manan Island. A Hurricane Watch was in effect for the portion of the coast from Digby to Medway Harbour, Nova Scotia.

A Tropical Storm Warning was in effect for Bermuda. A Tropical Storm Warning was in effect for the portion of the coast from Westport, Massachusetts to the U.S. Canada border. That Tropical Storm Warning included Martha’s Vineyard and Nantucket. A Tropical Storm Warning was in effect for the portion of the coast from the U.S./Canada border to Fort Lawrence, New Brunswick. That Tropical Storm Warning included Grand Manan Island. A Tropical Storm Warning was in effect for the portion of the coast from Fort Lawrence, New Brunswick to Point Tupper, Nova Scotia.

The circulation around the eastern side of Hurricane Lee was producing gusty winds in Bermuda on Thursday night. A weather station at the L.F. Wade International Airport (TXKF) reported a sustained wind speed of 43 m.p.h. (69 km/h) and a wind gust of 62 m.p.h. (100 km/h). The center of Hurricane Lee passed about 75 miles (120 km) east of NOAA buoy 41048 earlier in Thursday. The buoy reported a sustained wind speed of 65 m.p.h. (105 km/h) and a wind gust of 92 m.p.h. (148 km/h).

Hurricane Lee was beginning to exhibit the typical structure of a hurricane moving northward off the east coast of the U.S. There was no longer a well formed eye at the center of Lee’s circulation. Drier air was being pulled around the southern side of Hurricane Lee. An upper level trough over the eastern U.S. was producing southwesterly winds that were blowing toward the top of Lee’s circulation. Those winds were causing moderate vertical wind shear. The effects of the drier air and the vertical wind shear were causing an asymmetrical distribution of thunderstorms in Hurricane Lee. Most of the thunderstorms were occurring in bands in the northern and western sides of Lee’s circulation, Bands in the eastern and southern sides of the circulation consisted primarily of showers and lower clouds.

The changes to the structure of Hurricane Lee produced a large area of tropical storm force winds. Winds to hurricane force extended out 105 miles (165 km) from the center of Lee’s circulation. Winds to tropical storm force extended out 345 miles (555 km) from the center of circulation. The Hurricane Intensity Index (HII) was 12.7. The Hurricane Size Index (HSI) was 37.6 and the Hurricane Wind Intensity Size Index (HWISI) was 50.3. Hurricane Lee was about three-fourths as large as Hurricane Sandy was in 2012.

Hurricane Lee will move through an environment that will be unfavorable for intensification of a hurricane during the next 24 hours. Lee will move over water where the Sea Surface Temperatures are near 27°C. The upper level trough over the eastern U.S. will continue to will cause moderate vertical wind shear. The circulation around Lee will also pull in more drier air. The combination of moderate vertical wind shear and the drier air will cause Hurricane Lee to weaken gradually during the next 24 hours. The combination of vertical wind shear and drier air will also cause Hurricane Lee to make a gradual transition to an extratropical cyclone during the next 48 hours.

Hurricane Lee will move around the western part of a subtropical high pressure system over the Atlantic Ocean. The high pressure system and the upper level trough over the eastern U.S. will steer Lee toward the north during the next 24 hours. On its anticipated track, the center of Hurricane Lee will be southeast of Cape Cod by Friday night. Lee will affect Maine, New Brunswick and Nova Scotia later on Saturday. Hurricane Lee could be in the middle of a transition to an extratropical cyclone on Saturday. Lee will bring strong, gusty winds and locally heavy rain to the coast of the Northeast U.S. and Nova Scotia. Heavy rain could cause flash floods in come locations. The winds blowing around the northern side of Hurricane Lee will push water toward the coast. The water level could rise as much as four feet (one meter) along parts of the coast.

Elsewhere over the Atlantic Ocean, Hurricane Margot was churning west of the Azores. At 11:00 p.m. EDT on Thursday the center of Hurricane Margot was located at latitude 36.9°N and longitude 38.9°W which put it about 655 miles (1055 km) west of the Azores. Margot was moving toward the east-northeast at 3 m.p.h. (5 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 982 mb.

Hurricane Lee Prompts Watches for Northeast U.S.

The risk posed by Hurricane Lee prompted the issuance of a Hurricane Watch and a Tropical Storm Watch for a portion of the Northeast U.S. on Wednesday afternoon. At 5:00 p.m. EDT on Wednesday the center of Hurricane Lee was located at latitude 27.4°N and longitude 67.6°W which put it about 380 miles (610 km) south-southwest of Bermuda. Lee was moving toward the north-northwest at 9 m.p.h. (15 km/h). The maximum sustained wind speed was 105 m.p.h. (165 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 952 mb.

A Hurricane Watch was in effect for the portion of the coast from Stonington, Maine to the U.S./Canada border. A Tropical Storm Warning was in effect for Bermuda. A Tropical Storm Watch was in effect for the portion of the coast from Watch Hill, Rhode Island to Stonington, Maine. The Tropical Storm Watch included Block Island, Martha’s Vineyard and Nantucket.

Hurricane Lee weakened a little on Wednesday, but Lee remained a large and powerful hurricane. A circular eye with a diameter of 36 miles (50 km) was at the center of Lee’s circulation. The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms were revolving around the center of Hurricane Lee. Storms near the center of Lee’s circulation generated upper level divergence that pumped mass away from the hurricane.

Hurricane Lee was still a very large hurricane. Winds to hurricane force extended out 115 miles (185 km) from the center of Lee’s circulation. Winds to tropical storm force extended out 265 miles (425 km) from the center of circulation. The Hurricane Intensity Index (HII) was 17.8. The Hurricane Size Index (HSI) was 28.2 and the Hurricane Wind Intensity Size Index (HWISI) was 46.0. Hurricane Lee was similar in size and intensity to Hurricane Frances when Frances hit Southeast Florida in 2004.

Hurricane Lee will move through an environment that will become more unfavorable for a major hurricane during the next 24 hours. Lee will move over water where the Sea Surface Temperatures are near 28°C. An upper level trough over the eastern U.S. will produce southwesterly winds that will blow toward the top of Lee’s circulation. Those winds will cause the vertical wind shear to increase on Thursday. Hurricane Lee will move over cooler water later on Thursday. The combination of more vertical wind shear and cooler water will cause Hurricane Lee to weaken gradually during the next 24 hours.

Hurricane Lee will move around the western part of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Lee toward the north during the next 24 hours. On its anticipated track, the center of Hurricane Lee will pass west of Bermuda on Thursday evening. Bands in the eastern side of Lee’s circulation will bring gusty winds and locally heavy rain to Bermuda on Thursday.

Hurricane Lee could be east of Cape Cod by Saturday morning. Lee will affect Maine and Nova Scotia later on Saturday. Hurricane Lee could be in the middle of a transition to an extratropical cyclone on Saturday. Lee will bring strong, gusty winds and locally heavy rain to the coast of the Northeast U.S. and Nova Scotia. Heavy rain could cause flash floods in come locations. The winds blowing around the northern side of Hurricane Lee will push water toward the coast. A Storm Surge Watch has been issued for Cape Cod Bay and Nantucket, Massachusetts.

Elsewhere over the Atlantic Ocean, Hurricane Margot was spinning over the Central Atlantic. At 5:00 p.m. EDT on Wednesday the center of Hurricane Margot was located at latitude 34.7°N and longitude 40.6°W which put it about 790 miles (1270 km) west-southwest of the Azores. Margot was moving toward the north at 7 m.p.h. (11 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 971 mb.

Hurricane Lee Prompts Tropical Storm Watch for Bermuda

The potential effects of Hurricane Lee prompted the issuance of a Tropical Storm Watch for Bermuda on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Hurricane Lee was located at latitude 24.7°N and longitude 66.4°W which put it about 530 miles (860 km) south of Bermuda. Lee was moving toward the northwest at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 135 m.p.h. (215 km/h). The minimum surface pressure was 946 mb.

A Tropical Storm Watch was in effect for Bermuda.

Hurricane Lee completed an eyewall replacement cycle on Tuesday. A large eye with a diameter of 45 miles (75 km) was at the center of Lee’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms revolved around the center of Hurricane Lee. Storms near the center of Lee’s circulation generated upper level divergence that pumped mass away from the hurricane.

The size of the circulation around Hurricane Lee increased on Tuesday after the eyewall replacement cycle. Winds to hurricane force extended out 125 miles (200 km) from the center of Lee’s circulation. Winds to tropical storm force extended out 240 miles (390 km) from the center of circulation. The Hurricane Intensity Index (HII) was 20.6. The Hurricane Size Index (HSI) was 36.2 and the Hurricane Wind Intensity Size Index (HWISI) was 56.8. Hurricane Lee was similar in size and intensity to Hurricane Ivan when Ivan hit the Gulf Coast in 2004.

Hurricane Lee will move through an environment that will be favorable for intensification during the next 24 hours. Lee 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. The large size of the circulation around Hurricane Lee could limit changes of intensity during the next 24 hours. Lee could intensify a little on Wednesday. An upper level trough over the Great Lakes will cause the vertical wind shear to increase later this week.

Hurricane Lee will move around the western part of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Lee toward the north-northwest during the next 24 hours. On its anticipated track, Hurricane Lee will move south-southwest of Bermuda on Wednesday.

Elsewhere over the Atlantic Ocean, Hurricane Margot moved north over the Central Atlantic. At 5:00 p.m. EDT on Tuesday the center of Hurricane Margot was located at latitude 31.7°N and longitude 39.6°W which put it about 835 miles (1345 km) west-southwest of the Azores. Margot was moving toward the north at 14 m.p.h. (22 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 977 mb.