1. Isaias will produce heavy rains and potentially life-threatening flash flooding and mudslides across the Dominican Republic, northern Haiti, Turks and Caicos, and the Bahamas. Heavy rains associated with Isaias may begin to affect south and east-central Florida late Friday night, and the eastern Carolinas by early next week, potentially resulting in isolated flash and urban flooding, especially in low-lying and poorly drained areas. Isolated minor river flooding is possible in the Carolinas early next week.

2. Hurricane conditions and dangerous storm surge are expected in portions of the Bahamas today and Saturday, and Hurricane Warnings are in effect. Preparations to protect life and property should be rushed to completion.

3. Tropical storm conditions are expected with hurricane conditions possible along portions of the Florida east coast beginning Saturday, and a Tropical Storm Warning and Hurricane Watch are in effect. Storm surge watches or warnings could be needed for part of this area this afternoon.

4. There is a risk of impacts from winds, heavy rainfall, and storm surge beginning late this weekend along the northeastern Florida coast and spreading northward along the remainder of the U.S. east coast through early next week. Interests along the entire U.S. east coast should monitor the progress of Isaias and updates to the forecast.

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 VolusiaBrevard 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 VolusiaBrevard 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 tropicalstormforce 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.

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 lifethreatening 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 eastCentral 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 lowlying 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 lowlying 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.

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 northnorthwest. 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.

Hurricaneforce winds extend outward up to 35 miles (55 km) from the center and tropicalstormforce 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).

After a brief convective hiatus earlier this morning, a small burst of deep convection with cloud tops as cold as -80C to -85C have developed over the previously exposed low-level center. Dry downslope air coming off of Hispaniola wrapped into the center, eroding the inner-core convection somewhat. However, a surge of moist southwesterly inflow moving through the Windward Passage now appears to be fueling the recent increase in convection. The upper-level outflow has improved somewhat in the western semicircle but still remains restricted due to some modest southwesterly vertical wind shear. The initial intensity has been lowered to 65 kt based on 700-mb flight-level winds of near 70 kt and an increase in the central pressure of 992 mb, which is based on a dropsonde report of 995 mb with 26-kt surface winds.

Isaias is continuing on a steady northwestward motion of 305/14 kt. This motion is expected to continue for the next 36 hours or so as the hurricane rounds the southwestern periphery of the Bermuda-Azores High. A gradual turn to the north-northwest and north is expected by 48-60 hours due to a break in the ridge developing in response to a central U.S. shortwave trough digging into the southeastern United States. The timing and strength of this trough will determine how far west Isaias moves before the hurricane turns northward. The 06Z UKMET and and GFS have shifted westward, closer to the Florida coast, which is similar to the westward shift seen in the 00Z ECMWF model fields. By 72 hours, the hurricane is forecast to begin accelerating northeastward, possibly passing over eastern North Carolina by day 4 and across eastern New England on day 5. As a result of the westward shift in the latest model guidance, the new NHC forecast track has also been shifted farther west closer to the southeastern U.S. coast, and lies a little to the west of the consensus models TVCA and NOAA-HCCA. The westward shift in the track forecast has required the issuance of a Hurricane Watch for portions of the Florida east coast.

Although some slight weakening has occurred, radar data from the aircraft and the Bahamas radar indicate about a 60-percent eyewall has formed in the northeastern semicircle, which is an indication that the cyclone is trying to reorganize. As a result, strengthening is still expected during the next day or so, especially tonight and Saturday morning during the convective maximum period when the hurricane will be moving over the Gulf Stream where SSTs are 30C or warmer and while the vertical remains reasonably low. Increasing southwesterly shear could cause a gradual decrease in intensity over the weekend. The new official intensity forecast is similar to the previous advisory, and is a little above the available model guidance out of respect for continuity.