Monthly Archives: October 2023

Norma Prompts Hurricane Warning for Baja California

The potential risk posed by Hurricane Norma prompted the issuance of a Hurricane Warning for the southern part of Baja California. At 11:00 p.m. EDT on Thursday the center of Hurricane Norma was located at latitude 18.2°N and longitude 108.1°W which put it about 345 miles (555 km) south-southeast of Cabo San Lucas, Mexico. Norma 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 140 m.p.h. (220 km/h). The minimum surface pressure was 948 mb.

A Hurricane Warning was in effect for the portion of the coast from Todos Santos to Los Barriles, Mexico. The Hurricane Warning included Cabo San Lucas. A Tropical Storm Watch was in effect for Los Islas Marias. Tropical Storm Watches were also in effect for the portions of the coast from Todos Santos to Santa Fe, Mexico and from Los Barriles to La Paz, Mexico.

Hurricane Norma weakened slowly on Thursday evening. An upper level trough west of Baja California was producing southwesterly winds that were blowing toward the top of Norma’s circulation. Those winds were causing the vertical wind shear to increase. The eye at the center of Hurricane Norma was less distinct on satellite images. Bands of showers and thunderstorms were revolving around the core of Norma’s circulation. Storms near the core generated upper level divergence that pumped mass away from the hurricane.

Winds to hurricane force extended out 35 miles (55 km) from the center of Hurricane Norma. Winds to tropical storm force extended out 150 miles (240 km) from the center of Norma’s circulation. The Hurricane Intensity Index (HII) for Hurricane Norma was 22.1. The Hurricane Size Index (HSI) was 12.5 and the Hurricane Wind Intensity Size Index (HWISI) was 34.6. Hurricane Norma was similar in size and intensity to Hurricane Delta when Delta hit southwest Louisiana in 2020.

Hurricane Norma will move through an environment unfavorable for intensification during the next 24 hours. Norma will move over water where the Sea Surface Temperatures are near 29°C. However, the upper level trough west of Baja California will continue to produce southwesterly winds that will blow toward the top of Norma’s circulation. Those winds will cause moderate vertical wind shear. The wind shear will cause Hurricane Norma will to weaken during the next 24 hours.

Hurricane Norma will move around the western part of a high pressure system over Mexico. The high pressure system will steer Norma toward the north during the next 24 hours. On its anticipated track, Hurricane Norma could approach the southern end of Baja California on Friday night. Norma will bring strong winds and locally heavy rain to the southern end of Baja California. Heavy rain is likely to cause flash floods in some locations.

Tropical Storm Sanba Drops Heavy Rain on Southern China

Tropical Storm Sanba dropped heavy rain on parts of southern China on Thursday. At 5:00 p.m. EDT on Thursday the center of Tropical Storm Sanba was located at latitude 21.3°N and longitude 109.2°E which put it about 25 miles (40 km) southeast of Beihai China. Sanba was moving toward the north-northeast 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 1001 mb.

Tropical Storm Sanba dropped heavy rain on parts of Guangxi and Guangdong in southern China on Thursday. The center of Sanba’s circulation was still over the northeastern Gulf of Tonkin. Much of the northern half of Tropical Storm Sanba was over southern China. Part of the eastern side of Sanba’s circulation was over Hainan. Winds to tropical storm force extended out 60 miles (95 km) from the center of Tropical Storm Sanba.

An upper level trough over eastern Asia and an upper level ridge centered north of the Philippines were interacting to produce southwesterly winds that were blowing toward the top of Sanba’s circulation. Those winds were causing moderate vertical wind shear and they were also causing the distribution of thunderstorms to be asymmetrical. Thunderstorms were occurring in bands in the northern and eastern parts of Tropical Storm Sanba. Bands in the southern and western parts of Sanba’s circulation consisted primarily of showers and lower clouds.

Tropical Storm Sanba will be in an environment that is mostly unfavorable for intensification during the next 24 hours. Sanba will move over water where the Sea Surface Temperatures are near 28°C. The upper level trough over eastern Asia and the upper level ridge north of the Philippines will continue to cause moderate vertical wind shear. Almost half of Sanba’s circulation will be over land and increased friction will slow the wind in those areas. Tropical Storm Sanba is likely to weaken during the next 24 hours even if the center of circulation does not move over southern China.

The movement of Tropical Storm Sanba during the next 24 hours will depend on how strong the vertical wind shear is. If the wind shear is moderate and the upper and lower parts of Sanba’s circulation remain connected, then southwesterly winds will steer Tropical Storm Sanba toward the north-northeast. If Sanba moves north-northeast it will move inland over southern China. If the vertical wind shear gets stronger, then the upper level winds will push the top part of Sanba’s circulation toward the north-northeast. If the wind shear rips the top off of Tropical Storm Sanba, then the lower part of the circulation could meander over the northeastern Gulf of Tonkin during the next 24 hours.

Tropical Storm Sanba will continue to drop heavy rain over southern China during the next 24 hours. Heavy rain will fall on parts of Guangxi and Guangdong. Prolonged heavy rain will cause floods in some locations.

Norma Rapidly Intensifies to a Major Hurricane

Hurricane Norma rapidly intensified to a major hurricane over the Eastern North Pacific Ocean on Thursday morning. At 8:00 a.m. EDT on Thursday the center of Hurricane Norma was located at latitude 17.0°N and longitude 107.5°W which put it about 430 miles (690 km) south-southeast of Cabo San Lucas, Mexico. Norma was moving toward the north at 6 m.p.h. (10 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 950 mb.

A Hurricane Watch was in effect for the portion of the coast from Todos Santos to Los Barriles, Mexico. The Hurricane Watch included Cabo San Lucas.

Hurricane Norma rapidly intensified to a major hurricane on Thursday morning. A circular eye with a diameter of 23 miles (37 km) was at the center of Norma’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 Hurricane Norma. Storms near the core generated strong upper level divergence that pumped mass away from the hurricane.

Winds to hurricane force extended out 25 miles (40 km) from the center of Hurricane Norma. Winds to tropical storm force extended out 150 miles (240 km) from the center of Norma’s circulation. The Hurricane Intensity Index (HII) for Hurricane Norma was 23.6. The Hurricane Size Index (HSI) was 10.6 and the Hurricane Wind Intensity Size Index (HWISI) was 34.2. Hurricane Norma was similar in size and intensity to Hurricane Dennis when Dennis hit Northwest Florida in 2005.

Hurricane Norma will move through an environment favorable for intensification during the next 12 hours. Norma 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. Hurricane Norma could continue to intensify during the next 12 hours. An upper level trough west of Baja California will approach Norma later on Thursday. The upper level trough will produce southwesterly winds that will blow toward the top of Norma’s circulation. Those winds will cause the vertical wind shear to increase. Hurricane Norma will start to weaken when the wind shear increases.

Hurricane Norma will move around the western part of a high pressure system over Mexico. The high pressure system will steer Norma toward the north during the next 24 hours. On its anticipated track, Hurricane Norma could approach the southern end of Baja California on Friday night. Norma will bring strong winds and locally heavy rain to the southern end of Baja California. Heavy rain is likely to cause flash floods in some locations.

Tropical Storm Tammy Strengthens East of the Lesser Antilles

Tropical Storm Tammy strengthened east of the Lesser Antilles on Thursday morning. At 8:00 a.m. EDT on Thursday the center of Tropical Storm Tammy was located at latitude 13.5°N and longitude 55.1°W which put it about 465 miles (745 km) east of Guadeloupe. Tammy was moving toward the west at 16 m.p.h. (26 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 1004 mb.

Tropical Storm Watches were in effect for Barbados, Dominica, Martinique, Guadeloupe, Antigua, Barbuda, Montserrat, St. Kitts, Nevis, Saba, St. Eustatius.

A NOAA research plane found that Tropical Storm Tammy had strengthened during Wednesday night. More thunderstorms developed near the center of Tammy’s circulation. However, the distribution of thunderstorms was still asymmetrical. Many of the thunderstorms were occurring in bands in the eastern side of Tropical Storm Tammy. Bands in the western side of Tammy’s circulation consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence that pumped mass away to the north and east of the tropical storm. Winds to tropical storm force extended out 140 miles (220 km) in the eastern side of Tropical Storm Tammy. Winds to tropical storm force extended out 70 miles (110 km) in the western side of Tammy.

Tropical Storm Tammy will move through an environment somewhat favorable for intensification during the next 24 hours. Tammy will move over water where the Sea Surface Temperatures are near 30°C. It will move under the far eastern part of an upper level low over the Eastern Caribbean Sea. The upper level low will produce southwesterly winds that will blow toward the top of Tammy’s circulation. The winds in the lower levels of the atmosphere are blowing from the east. The difference in wind direction between the upper and lower levels of the atmosphere will cause moderate vertical wind shear. The wind shear will inhibit intensification. Tropical Storm Tammy could intensify gradually during the next 24 hours.

Tropical Storm Tammy will move south of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Tammy toward the west-northwest during the next 24 hours. On its anticipated track, Tropical Storm Tammy could approach the central and northern Leeward Islands on Friday.

Tropical Storm Tammy is likely to bring gusty winds and locally heavy rain to the central and northern Leeward Islands. Heavy rain is likely to cause flash in some locations. Tropical Storm Tammy could cause a storm surge of up to seven feet (two meters) along the coasts of some of the islands.

Norma Rapidly Intensifies to a Hurricane

Former Tropical Storm Norma rapidly intensified to a hurricane over the Eastern North Pacific Ocean south of Baja California on Wednesday. At 5:00 p.m. EDT on Wednesday the center of Hurricane Norma was located at latitude 15.6°N and longitude 108.0°W which put it about 520 miles (835 km) south-southeast of Cabo San Lucas, Mexico. Norma was moving toward the north at 8 m.p.h. (13 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 984 mb.

Former Tropical Storm Norma rapidly intensified to a hurricane on Wednesday. The inner end of a rainband wrapped around the center of Norma’s circulation and an eye was forming at the center. Bands of showers and thunderstorms were revolving around the core of Hurricane Norma. Storms near the core generated upper level divergence that pumped mass away from the hurricane. Winds to hurricane force extended out 25 miles (40 km) in the eastern side of Norma’s circulation. Winds to tropical storm force extended out 140 miles (220 km) from the center of Hurricane Norma.

Hurricane Norma will move through an environment very favorable for intensification during the next 24 hours. Norma 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. Hurricane Norma will intensify during the next 24 hours. Norma could intensify rapidly to a major hurricane on Thursday.

Hurricane Norma will move around the western part of a high pressure system over Mexico. The high pressure system will steer Norma toward the north during the next 24 hours. On its anticipated track, Hurricane Norma could approach the southern end of Baja California on Saturday. Norma is likely to be a hurricane when it approaches Baja California.

Tropical Storm Tammy Forms East of the Lesser Antilles

Tropical Storm Tammy formed over the Atlantic Ocean east of the Lesser Antilles on Wednesday afternoon. At 5:00 p.m. EDT on Wednesday the center of Tropical Storm Tammy was located at latitude 13.0°N and longitude 51.7°W which put it about 625 miles (1005 km) east of the Lesser Antilles. Tammy was moving toward the west at 23 m.p.h. (37 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1007 mb.

Tropical Storm Watches were issued for Barbados, Dominica, Martinique and Guadeloupe.

A low pressure system over the Atlantic Ocean east of the Lesser Antilles strengthened on Wednesday afternoon and the U.S. National Hurricane Center designated the system as Tropical Storm Tammy. The circulation around Tropical Storm Tammy was not well organized. Many of the thunderstorms were occurring in bands in the eastern part of Tammy’s circulation. Bands in the western part of Tropical Storm Tammy consisted primarily of showers and lower clouds. Storms near the center of Tammy’s circulation were beginning to generate upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 140 miles (220 km) in the northeastern quadrant of Tropical Storm Tammy. The winds in the other parts of Tammy were blowing at less than tropical storm force.

Tropical Storm Tammy will move through an environment somewhat favorable for intensification during the next 24 hours. Tammy will move over water where the Sea Surface Temperatures are near 30°C. It will move under the far eastern part of an upper level low over the Eastern Caribbean Sea. The upper level low will produce southwesterly winds that will blow toward the top of Tammy’s circulation. The winds in the lower levels of the atmosphere are blowing from the east. The difference in wind direction between the upper and lower levels of the atmosphere will cause moderate vertical wind shear. The wind shear will inhibit intensification. Tropical Storm Tammy could intensify a little during the next 24 hours, if the winds in the lower levels weaken. However, if the winds in the lower levels get stronger, then Tammy could weaken to a tropical depression.

Tropical Storm Tammy will move south of a subtropical high pressure system over the Atlantic Ocean. The high pressure system will steer Tammy toward the west-northwest during the next 24 hours. On its anticipated track, Tropical Storm Tammy could be near Barbados in 36 hours.

Tropical Storm Tammy is likely to bring gusty winds and locally heavy rain to Barbados, Dominica, Martinique and Guadeloupe. Heavy rain is likely to cause flash in some locations.

Tropical Storm Sanba Forms East of Vietnam

Tropical Storm Sanba formed over the Gulf of Tonkin east of Vietnam on Wednesday. At 11:00 a.m. EDT on Wednesday the center of Tropical Storm Sanba was located at latitude 18.9°N and longitude 108.2°E which put it about 180 miles (280 km) southeast of Haiphong, Vietnam. Sanba was moving toward the northwest at 9 m.p.h. (15 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 1003 mb.

A low pressure system over the Gulf of Tonkin east of Vietnam strengthened on Wednesday and the Japan Meteorological Agency designated the system as Tropical Storm Sanba. The distribution of thunderstorms in Tropical Storm Sanba was asymmetrical. Many of the thunderstorms were occurring in bands in the eastern side of Sanba’s circulation. Bands in the western part of Tropical Storm Sanba consisted primarily of showers and lower clouds. Storms near the center of Sanba’s circulation generated upper level divergence that pumped mass away to the west and north of the tropical storm. Winds to tropical storm force extended out 50 miles (80 km) in the eastern side of Tropical Storm Sanba. The winds in the western part of Sanba’s circulation were blowing at less than tropical storm force.

Tropical Storm Sanba will move through an environment somewhat favorable for intensification during the next 24 hours. Sanba will move over water where the Sea Surface Temperatures are near 28°C. It will move under the western part of an upper level ridge centered northwest of the Philippines. The upper level ridge will produce southeasterly winds that will blow toward the top of Sanba’s circulation. Those winds will cause some vertical wind shear but the wind shear will not be strong enough to prevent intensification. Some of the air circulating around the eastern side of Tropical Storm Sanba will flow over Hainan. The additional friction caused by the land will cause the air in that part of Sanba’s circulation to slow down. Tropical Storm Sanba could intensify gradually during the next 24 hours.

Tropical Storm Sanba will move around the western part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Sanba toward the north-northwest during the next 24 hours. On its anticipated track the center of Tropical Cyclone Sanba will pass west of Hainan. Sanba will move toward northeastern Vietnam.

Bands in the eastern side of Tropical Storm Sanba are already producing gusty winds and locally heavy rain in parts of Hainan. Bands in the western side of Sanba’s circulation are bringing rain showers to parts of northern Vietnam. Tropical Storm Sanba will continue to produce gusty winds and locally heavy rain in parts of Hainan and northern Vietnam. Heavy rain could cause flash floods in some locations.

Tropical Storm Norma Forms South of Baja California

Tropical Storm Norma formed over the Eastern North Pacific Ocean south of Baja California on Tuesday afternoon. At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Norma was located at latitude 13.2°N and longitude 107.3°W which put it about 690 miles (1110 km) south-southeast of Cabo San Lucas, Mexico. Norma was moving toward the west-northwest at 10 m.p.h. (16 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 low pressure system over the Eastern North Pacific Ocean south of Baja California strengthened on Tuesday and the U.S. National Hurricane Center designated the system as Tropical Storm Norma. The circulation around Tropical Storm Norma exhibited more organization on Tuesday afternoon. Bands of showers and thunderstorms were revolving around the center of Norma’s circulation. Storms near the center of circulation generated upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 140 miles (220 km) in the northern side of Tropical Storm Norma. Winds in the southern side of Norma’s circulation were blowing at less than tropical storm force.

Tropical Storm Norma will move through an environment favorable for intensification during the next 36 hours. Norma will move over water where the Sea Surface Temperatures are near 27°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Tropical Storm Norma will intensify during the next 36 hours. Norma could strengthen to a hurricane within 36 hours. Tropical Storm Norma could start to intensify rapidly after an inner core with an eye and eyewall develop.

Tropical Storm Norma will move around the southwestern part of a high pressure system over Mexico. The high pressure system will steer Norma toward the northwest during the next 24 hours. Tropical Storm Norma will move more toward the north later this week when it moves around the western end of the high pressure system. On its anticipated track Norma could approach the southern end of Baja California during the weekend. Norma is likely to be a hurricane when it approaches Baja California.

Sean Weakens to a Tropical Depression

Former Tropical Storm weakened to a tropical depression east of the Leeward Islands on Saturday. At 11:00 a.m. EDT on Saturday the center of Tropical Depression Sean was located at latitude 16.0°N and longitude 44.2°W which put it about 1255 miles (2020 km) east of the Northern Leeward Islands. Sean was moving toward the northwest at 8 m.p.h. (13 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.

Former Tropical Storm Sean weakened slowly during the past 36 hours and the U.S. National Hurricane Center downgraded Sean to a tropical depression on Saturday morning. A few more thunderstorms developed near the center of Sean’s circulation after it was downgraded to a tropical depression. There were also a few more thunderstorms in bands revolving around the center of Tropical Depression Sea. However, some bands still consisted primarily of showers and lower clouds.

Tropical Depression Sean will move through an environment mostly unfavorable for intensification during the next 24 hours. Sean will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern side of an upper level ridge over the eastern Atlantic Ocean. The upper level ridge will produce northeasterly winds that will blow toward the top of Sean’s circulation. Those winds will cause moderate vertical wind shear. Tropical Depression Sean will move into an area where there is drier air. The vertical wind shear and the drier air are likely to cause Tropical Depression Sean to weaken during the next 24 hours.

Tropical Depression Sean will move around the southwestern part of a high pressure system that extends from West Africa to the central Atlantic Ocean. The high pressure system will steer Sean toward the west-northwest during the next 24 hours. On its anticipated track, Tropical Depression Sean will remain far east of the Northern Leeward Islands.

Typhoon Bolaven Passes East of Iwo To

Typhoon Bolaven passed east of Iwo To on Thursday evening. At 11:00 p.m. EDT on Thursday the center of Typhoon Bolaven was located at latitude 26.2°N and longitude 147.8°E which put it about 350 miles (570 km) east of Iwo To. Bolaven was moving toward the northeast at 23 m.p.h. (37 km/h). The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 175 m.p.h. (285 km/h). The minimum surface pressure was 928 mb.

Concentric eyewalls developed at the center of Typhoon Bolaven on Thursday. The inner end of a rainband wrapped around the existing small eye and eyewall. The larger outer eyewall surrounded the inner eye and eyewall. Bands of showers and thunderstorms revolved around the concentric eyewalls. Storms near the eyewalls generated upper level divergence that pumped mass away to the northeast of the typhoon.

The size of Typhoon Bolaven increased when the concentric eyewalls developed. Winds to typhoon force extended out 60 miles (95 km) from the center of Bolaven’s circulation. Winds to tropical storm force extended out 265 miles (425 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Bolaven was 29.9. The Hurricane Size Index (HSI) was 21.3 and the Hurricane Wind Intensity Size Index (HWISI) was 51.2.

Typhoon Bolaven will move through an environment that will become more unfavorable for a powerful typhoon during the next 24 hours. Bolaven will move over water where the Sea Surface Temperatures are near 27°C. It will move under the eastern side of an upper level trough near Japan. The upper level trough will produce southwesterly winds that will blow toward the top of Bolaven’s circulation. Those winds will cause the vertical wind shear to increase. Typhoon Bolaven is likely to weaken during the next 24 hours as it goes through an eyewall replacement cycle and the vertical wind shear increases. Bolaven could make a transition to a strong extratropical cyclone when it moves over cooler water south of Alaska.

The upper level trough near Japan will steer Typhoon Bolaven quickly toward the northeast during the next 24 hours. On its anticipated track, Typhoon Bolaven will pass far to the east of Japan on Friday. Bolaven could move south of the Aleutian Islands during the weekend.