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Hurricane Erin Passes South of Cape Cod

Hurricane Erin passed south of Cape Cod on Thursday afternoon.  At 5:00 p.m. EDT on Thursday the center of Hurricane Erin was located at latitude 36.4°N and longitude 69.1°W which put the center about 320 miles (520 km) south of Nantucket Island.   Erin was moving toward the northeast at 20 m.p.h. (32 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 952 mb.

A Tropical Storm Warning is in effect for the portion of the coast from Duck, North Carolina to Chincoteague, Virginia.

A Storm Surge Warning is in effect for the portion of the coast from Cape Lookout to Duck, North Carolina.

A Tropical Storm Warning is in effect for Bermuda.

Hurricane Erin started to weaken slowly as it moved over the Atlantic Ocean between Cape Cod and Bermuda on Thursday.  No eye was visible at the center of Erin’s circulation on satellite images.  Bands of showers and thunderstorms were revolving around the center of Hurricane Erin.  Storms near the center of Erin were still generating upper level divergence that pumped mass away from the hurricane.  The removal of mass in the upper levels of the atmosphere almost matched the inflow of mass in the lower levels.  There was slightly more mass flowing into the center of Erin’s circulation.  So, the surface pressure was slowly increasing.

The circulation around Hurricane Erin was very large.  Winds to hurricane force extend out 100 miles (160 km) from the center of Erin’s circulation.  Winds to tropical storm force extend out 320 miles (520 km) from the center of Hurricane Erin.

The Hurricane Intensity Index (HII) for Hurricane Erin is 16.5.  The Hurricane Size Index (HSI) is 36.9 and the Hurricane Wind Intensity Size Index (HWISI) is 53.4.  Hurricane Erin is similar in size and intensity to Hurricane Ike when Ike hit Texas in 2008.  Erin is not quite as strong as Ike was, but Hurricane Erin is bigger than Hurricane Ike was.

Hurricane Erin will move through an environment that will be unfavorable for intensification of a hurricane during the next 24 hours.  Erin will move over water where the Sea Surface Temperatures are near 26°C.  It will move under the eastern side of an upper level trough over the Northeast U.S. and the Great Lakes.  The upper level trough will produce southwesterly winds that will blow toward the top of Erin’s circulation.  Those winds will cause moderate vertical wind shear.  Hurricane Erin will weaken slowly during the next 24 hours.  Erin is likely to make a transition to a strong extratropical cyclone during the weekend.

The upper level trough over the Northeast U.S. and the Great Lakes will steer Hurricane Erin toward the east-northeast during the next 24 hours.  On its anticipated track, the center of Hurricane Erin will pass south of Nova Scotia on Friday.

The large circulation around Hurricane Erin will continue to produce large waves that will move toward the east coast of the U.S.  Erin could continue to cause a storm surge of up to four feet (one meter) along the Outer Banks of North Carolina on Thursday night.  Mandatory evacuations are in effect for Hatteras Island and Ocracoke Island.  Water has already washed over parts of Hatteras Island.  The large waves are likely to cause significant beach erosion.  Conditions along the Outer Banks should start to improve on Friday when Hurricane Erin moves farther away.

The large circulation around Hurricane Erin could also produce tropical storm force winds in Bermuda.

Hurricane Erin Moves Southeast of Cape Hatteras

Hurricane Erin moved southeast of Cape Hatteras on Wednesday night.  At 11:00 p.m. EDT on Wednesday the center of Hurricane Erin was located at latitude 32.8°N and longitude 73.1°W which put the center about 215 miles (345 km) southeast of Cape Hatteras, North Carolina.  Erin was moving toward the north-northeast at 16 m.p.h. (26 km/h).  The maximum sustained wind speed was 110 m.p.h. (175 km/h) and there were wind gusts to 130 m.p.h. (210 km/h).  The minimum surface pressure was 942 mb.

A Tropical Storm Warning is in effect for the portion of the coast from Beaufort Inlet, North Carolina to Chincoteague, Virginia.

A Storm Surge Warning is in effect for the portion of the coast from Cape Lookout to Duck, North Carolina.

A Tropical Storm Watch is in effect for Bermuda.

Concentric eyewalls formed again in Hurricane Erin on Wednesday.  The inner eyewall had a radius of 17 miles (28 km).  The outer eyewall had a radius of 75 miles (120 km).  The strongest winds were occurring in the outer eyewall.  Bands of showers and thunderstorms were revolving around the concentric eyewalls.  Storms near the center of Erin generated strong upper level divergence that pumped mass away from the hurricane.  The removal of large quantities of mass caused the surface pressure to decrease on Wednesday.

The circulation around Hurricane Erin was very large.  Winds to hurricane force extend out 90 miles (145 km) from the center of Erin’s circulation.  Winds to tropical storm force extend out 265 miles (425 km) from the center of Hurricane Erin.

The Hurricane Intensity Index (HII) for Hurricane Erin is 19.2.  The Hurricane Size Index (HSI) is 33.0 and the Hurricane Wind Intensity Size Index (HWISI) is 52.2.  Hurricane Erin is similar in size and intensity to Hurricane Ike when Ike hit Texas in 2008.

Hurricane Erin will move through an environment that will become unfavorable for intensification during the next 24 hours.  Erin will move over water where the Sea Surface Temperatures are near 28°C.  It will move under the eastern side of an upper level trough over the Northeast U.S. and the Great Lakes.  The upper level trough will produce southeasterly winds that will blow toward the top of Erin’s circulation.  Those winds will cause the vertical wind shear to increase on Thursday.  Hurricane Erin will start to weaken when the vertical wind shear increases.

The upper level trough over the Northeast U.S. and the Great Lakes will steer Hurricane Erin toward the northeast during the next 24 hours.  On its anticipated track, the center of Hurricane Erin will be move away from Cape Hatteras on Thursday.  Erin will pass far to the south of Long Island on Thursday.

The large circulation around Hurricane Erin will produce large waves that will move toward the east coast of the U.S.  Erin could cause a storm surge of up to four feet (one meter) along the Outer Banks of North Carolina.  Mandatory evacuations have been ordered for Hatteras Island and Ocracoke Island.  Water is already washing over parts of Hatteras Island.  The large waves are likely to cause significant beach erosion.  The large circulation around Hurricane Erin could also bring tropical storm force winds to the Outer Banks.  Conditions along the Outer Banks should start to improve on Friday when Hurricane Erin moves farther away.

Hurricane Erin Prompts Watches for Outer Banks

The potential risks posed by Hurricane Erin prompted the issuance of a Tropical Storm Watch and a Storm Surge Watch for the North Carolina Outer Banks on Monday afternoon.  At 5:00 p.m. EDT on Monday the center of Hurricane Erin was located at latitude 24.0°N and longitude 71.3°W which put the center about 815 miles (1310 km) south-southeast of Cape Hatteras, North Carolina.  Erin was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 140 m.p.h. (225 km/h) and there were wind gusts to 165 m.p.h. (265 km/h).  The minimum surface pressure was 937 mb.

A Tropical Storm Watch is in effect for the portion of the coast from Beaufort Inlet to Duck, North Carolina.  The Tropical Storm Watch includes Pamlico Sound.

A Storm Surge Watch is in effect for the portion of the coast from Cape Lookout to Duck, North Carolina.

A Tropical Storm Warning is in effect for the Turks and Caicos.  A Tropical Storm Warning is in effect for the Southeast Bahamas.

A Tropical Storm Watch is in effect for the Central Bahamas.

Hurricane Erin was maintaining its intensity on Monday afternoon.  A circular eye with a diameter of 45 miles (75 km) was at the center of Erin’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 Erin’s circulation.  Storms near the core of Erin were generating strong upper level divergence that was pumping mass away from the hurricane.  The removal of mass in the upper levels was approximately equal to the inflow of mass in the lower levels of the atmosphere/  The balance of outflow and inflow of mass caused the surface pressure to remain nearly constant.

An earlier eyewall replacement cycle increased the size of the circulation around Hurricane Erin.  Winds to hurricane force extended out 80 miles (130 km) from the center of Erin’s circulation.  Winds to tropical storm force extended out 230 miles (370 km) from the center of Hurricane Erin.

The Hurricane Intensity Index (HII) for Hurricane Erin is 28.3.  The Hurricane Size Index (HSI) is 24.4 and the Hurricane Wind Intensity Size Index (HWISI) is 52.7.  Hurricane Erin is similar in size and intensity to Hurricane Helene in 2024.

Hurricane Erin will move through an environment that will become less favorable for intensification during the next 24 hours.  Erin 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.  However, Erin will move into a region of drier air on Tuesday.  The drier air is likely to cause Hurricane Erin to start to weaken slowly.

Hurricane Erin will move around the southwestern side of a high pressure system over the Atlantic Ocean.  The high pressure system will steer Erin toward the northwest during the next 24 hours.  On its anticipated track, the center of Hurricane Storm Erin will pass of the Bahamas on Tuesday.

The large circulation around Hurricane Erin will produce large waves that will move toward the east coast of the U.S.  Erin could cause a storm surge of up to four feet (one meter)  along the Outer Banks of North Carolina.  Mandatory evacuations have been ordered for Hatteras Island and Ocracoke Island.  The large waves could also cause significant beach erosion.  The large circulation around Hurricane Erin could also bring tropical storm force winds to the Outer Banks.

Bands in the western side of Hurricane Erin will continue to bring gusty winds and heavy rain to the Turks and Caicos and to the Southeast Bahamas until Erin moves farther away. The gusty winds and heavy rain could spread over the Central Bahamas on Tuesday.  Heavy rain could cause floods in some locations.