Tuesday, August 11, 2020

National Hurricane Center advisory on Hurricane Isaias

By on July 31, 2020

SAN JUAN — The National Hurricane Center issued the following public advisory on Friday:

Hurricane Isaias Advisory Number 14
NWS National Hurricane Center Miami FL AL092020
1100 AM EDT Fri Jul 31 2020

…HURRICANE WATCH ISSUED FOR PORTIONS OF THE FLORIDA EAST COAST…
…SQUALLY WEATHER OVER THE SOUTHEASTERN BAHAMAS AND THE TURKS AND CAICOS ISLANDS SPREADING INTO THE CENTRAL BAHAMAS…

SUMMARY OF 1100 AM EDT…1500 UTC…INFORMATION
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LOCATION…21.7N 74.5W ABOUT 365 MI…585 KM SSE OF GREAT ABACO ISLAND ABOUT 295 MI…470 KM SE OF NASSAU MAXIMUM SUSTAINED WINDS…75 MPH…120 KM/H PRESENT MOVEMENT…NW OR 305 DEGREES AT 16 MPH…26 KM/H MINIMUM CENTRAL PRESSURE…992 MB…29.30 INCHES

WATCHES AND WARNINGS
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CHANGES WITH THIS ADVISORY:

A Hurricane Watch has been issued for portions of the Florida east coast from north of Deerfield Beach northward to the Volusia-Brevard County Line.

A Tropical Storm Warning has been issued for portions of the Florida east coast from north of Ocean Reef northward to Sebastian Inlet and for Lake Okeechobee.

The government of the Dominican Republic has discontinued the Tropical Storm Warning for the Dominican Republic.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Hurricane Warning is in effect for… * Northwestern Bahamas including Andros Island, New Providence, Eleuthera, Abacos Islands, Berry Islands, Grand Bahamas Island, and Bimini * Southeastern Bahamas including the Acklins, Crooked Island, Long Cay, the Inaguas, Mayaguana, and the Ragged Islands * Central Bahamas, including Cat Island, the Exumas, Long Island, Rum Cay, and San Salvador

A Hurricane Watch is in effect for… * North of Deerfield Beach to the Volusia-Brevard County Line

A Tropical Storm Warning is in effect for… * Turks and Caicos Islands * North of Ocean Reef northward to Sebastian Inlet * Lake Okeechobee

Interests elsewhere along the southeast coast of the United States should monitor the progress of Isaias. Additional watches or warnings may be required later today.

A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area. Preparations to protect life and property should be rushed to completion.

A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous.

A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours.

For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service.

DISCUSSION AND OUTLOOK
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At 1100 AM EDT (1500 UTC), the center of Hurricane Isaias was located by an Air Force Reserve Hurricane Hunter aircraft and Bahamas radar near latitude 21.7 North, longitude 74.5 West. Isaias is moving toward the northwest near 16 mph (26 km/h), and a general northwestward motion with some decrease in forward speed is expected for the day or so followed by a turn toward the north-northwest. On the forecast track, the center of Isaias will continue to move near or over the Southeastern Bahamas today. Isaias is forecast to be near the Central Bahamas tonight, and move near or over the Northwestern Bahamas Saturday and near the east coast of the Florida peninsula Saturday afternoon through Sunday.

Data from the reconnaissance aircraft indicate that maximum sustained winds are near 75 mph (120 km/h) with higher gusts. Some strengthening is possible today and tonight, and Isaias is expected to remain a hurricane for the next few days.

Hurricane-force winds extend outward up to 35 miles (55 km) from the center and tropical-storm-force winds extend outward up to 205 miles (335 km).

Reports from the reconnaissance aircraft indicate that the minimum central pressure is 992 mb (29.30 inches).

HAZARDS AFFECTING LAND
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Key messages for Isaias can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC, and on the web at www.hurricanes.gov/text/MIATCDAT4.shtml.

STORM SURGE: A dangerous storm surge will raise water levels by as much as 3 to 5 feet above normal tide levels in areas of onshore winds in the Bahamas.

WIND: Tropical storm conditions will continue across portions of the Turks and Caicos this morning. Hurricane conditions in the southeastern Bahamas will spread northwestward into the central and northwestern Bahamas tonight and into Saturday.

Tropical storm conditions are expected in the warning area in Florida beginning Saturday. Hurricane conditions are possible in the Hurricane Watch area beginning Saturday night and continuing into Sunday.

RAINFALL: Isaias is expected to produce the following rain accumulations:

Dominican Republic and northern Haiti: 4 to 8 inches, with isolated maximum totals of 12 inches.

Bahamas, Turks and Caicos: 4 to 8 inches.

Cuba: 1 to 2 inches, with isolated maximum totals of 4 inches.

These rainfall amounts will lead to life-threatening flash flooding and mudslides, as well as river flooding. Urban and small stream flooding is expected for the U.S. Virgin Islands and Hispaniola.

From Friday night through Monday:

South Florida into east-Central Florida: 2 to 4 inches, with isolated maximum totals of 6 inches.

These rainfall amounts could result in isolated flash and urban flooding, especially in low-lying and poorly drained areas.

Heavy rains associated with Isaias may begin to affect the eastern Carolinas by early next week. This rain could result in isolated flash and urban flooding, especially in low-lying and poorly drained areas, as well as isolated minor river flooding.

SURF: Swells generated by Isaias are affecting portions of Hispaniola, eastern Cuba, the Turks and Caicos, and the southeastern and central Bahamas. These swells will spread into the central northwestern Bahamas later today and along the east coast of Florida on Saturday. These swells are likely to cause life- threatening surf and rip current conditions. Please consult products from your local weather office.