Tag Archives: Hurricane Isaac

Hurricane Isaac Strengthens to Cat. 2 West of the Azores

Hurricane Isaac strengthened to Category 2 on the Saffir-Simpson Scale over the North Atlantic Ocean west of the Azores on Saturday.  At 11:00 a.m. EDT on Saturday the center of Hurricane Isaac was located at latitude 40.2°N and longitude 39.7°W which put the center about 695 miles (1120 km) west-northwest of the Azores.  Isaac was moving toward the east-northeast at 20 m.p.h. (32 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 968 mb.

Even though Hurricane Isaac was at latitude 40°N, it intensified to a Category 2 hurricane on the Saffir-Simpson Scale on Saturday morning.  A circular eye was present at the center of Isaac’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 Isaac.  Storms near the core of Isaac generated upper level divergence that pumped mass away from the hurricane.

The circulation around Hurricane Isaac was reasonably symmetrical given it high latitude.  Winds to hurricane force extended out 45 miles (75 km) from the center of Isaac’s circulation.  Winds to tropical storm force extended out 200 miles (320 km) from the center of Hurricane Isaac.

Hurricane Isaac will move through an environment unfavorable for intensification during the next 24 hours.  Isaac will move over water where the Sea Surface Temperatures are near 24°C.  It will move under the eastern side of an upper level trough that is southeast of Greenland.  The upper level trough will produce strong southwesterly winds that will blow toward the top of Isaac’s circulation.  Those winds will cause the vertical wind shear to increase.  The combination of cooler water and stronger vertical wind shear will cause Hurricane Isaac to weaken during the next 24 hours.

The upper level trough southeast of Greenland will steer Hurricane Isaac toward the east-northeast during the next 24 hours.  On its anticipated track, Hurricane Isaac will pass northwest of the Azores on Sunday.

Elsewhere, the circulation of former Hurricane Helene was spinning down south of the Ohio River and Tropical Storm Joyce was churning east of the Northern Leeward Islands.

At 11:00 a.m. EDT on Saturday the center of Tropical Depression Helene was located at latitude 36.6°N and longitude 86.4°W which put the center about 50 miles (80 km) northwest of Nashville, Tennessee.  Helene was moving toward the east at 3 m.p.h. (5 km/h).  The maximum sustained wind speed was 15 m.p.h. (25 km/h) and there were wind gusts to 25 m.p.h. (40 km/h).  The minimum surface pressure was 968 mb.

At 11:00 a.m. EDT on Saturday the center of Tropical Storm Joyce was located at latitude 20.0°N and longitude 46.0°W which put the center about 1120 miles (1805 km) east of the Northern Leeward Islands.  Joyce was moving toward the northwest at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 1004 mb.

Tropical Storm Helene Brings Heavy Rain and Floods to Southeast U.S.

Tropical Storm Helene brought heavy rain and floods to parts of the southeast U.S. on Friday.  At 11:00 a.m. EDT on Friday the center of Tropical Storm Helene was located at latitude 35.1°N and longitude 83.8°W which put the center about 30 miles (50 km) southwest of Bryson City, North Carolina.  Helene was moving toward the north at 32 m.p.h. (52 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 975 mb.

A Tropical Storm Warning is in effect for the portion of the coast from Savannah River, Georgia to Little River Inlet, South Carolina.

Tropical Storm Warnings were also in effect for inland locations in South Carolina, eastern Georgia, western North Carolina and eastern Tennessee. 

Even though former Hurricane Helene weakened to a tropical storm as it moved over the southeastern U.S. on Friday, Helene still was dropping very heavy rain.  Heavy rain fell over parts of Georgia, South Carolina, western North Carolina, eastern Tennessee, and western Virginia.  The heavy rain caused rivers and streams to rise quickly in those areas and numerous flash flood and flood warnings were issued.

The Catawba River at Pleasant Gardens, North Carolina was at Record Flood level.  The Saluda River at Greenville, South Carolina was at Major Flood level.  The French Broad River at Blantyre, North Carolina was at Record Flood level.  The Pigeon River at Canton, North Carolina was at Record Flood level.  The Pigeon River at Newport, Tennessee was at Major Flood level.  The Swannanoa River at Biltmore, North Carolina was at Record Flood level.  Numerous other rivers and streams in the region were also flooding.  Many roads were impassible.

Over four million customers in Florida, Georgia, South Carolina and North Carolina were experiencing electricity outages.

Tropical Storm Helene will move around the eastern side of an upper level low over the middle Mississippi River Valley.  The upper level low will steer Helene toward the north during the next 24 hours.  The circulation around Tropical Storm Helene will gradually merge with the circulation around the upper level low.

Tropical Storm Helene will continue to drop heavy rain on the southern Appalachians.  the heavy rain is likely to cause additional flash floods.  Helene will also bring gusty winds as far north as southern and central Ohio on Friday afternoon and evening.

Elsewhere over the Atlantic Ocean, former Tropical Storm Isaac intensified to a hurricane west of the Azores and Tropical Storm Joyce formed east of the Northern Leeward Islands.

At 11:00 a.m. EDT on Friday the center of Hurricane Isaac was located at latitude 37.4°N and longitude 46.8°W which put the center about 1080 miles (1740 km) west of the Azores.  Isaac was moving toward the east-northeast at 18 m.p.h. (30 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 981 mb.

At 11:00 a.m. EDT on Friday the center of Tropical Storm Joyce was located at latitude 18.1°N and longitude 42.9°W which put the center about 1325 miles (2130 km) east of the Northern Leeward Islands.  Joyce was moving toward the northwest at 13 m.p.h. (20 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 1006 mb.