Isaac Gaining Strength – Significant Storm Surge Threat Expected for Northern Gulf Coast, Aug. 27, 2012

Tropical Storm Isaac Surface Wind Field – Aug. 27, 2012 – 4 PM CDT

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Miami, Florida—(ENEWSPF)—August 27, 2012 – UPDATE 4 pm CDT (2100 UTC). The National Hurricane Center reports that a Reconnaissance Aircraft indicates Isaac is getting stronger. Significant storm surge threat is expected for the northern gulf coast. Isaac is now located 26.4 north, 86.2 west, about 320 miles (515 km) south-southeast of Mobile, Alabama, about 255 miles (415 km) southeast of the mouth of the Mississippi River. Maximum sustained winds are 70 mph (110 km/h). Present movement is northwest or 305 degrees at 12 mph (19 km/h).

Changes in Watches and Warnings with this Advisory

The Hurricane Warning from the Florida-Alabama border to Destin has been changed to a Tropical Storm Warning.

Summary of Watches and Warnings in Effect

A hurricane warning is in effect for:

East of Morgan City Louisiana to the Alabama-Florida border, including metropolitan New Orleans, Lake Pontchartrain, and Lake Maurepas.

A hurricane watch is in effect for:

Intracoastal City to Morgan City, Louisiana.

A tropical storm warning is in effect for:

From the Alabama-Florida border to the Aucilla River,
Intracoastal City to Morgan City, Louisiana.

A tropical storm watch is in effect for:

East of Sabine pass to west of Intracoastal City, Louisiana.

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

A Tropical Storm Watch means that Tropical Storm conditions are possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor products issued by your local National Weather Service Forecast Office.

Discussion and 48-hour Outlook

At 400 pm CDT (2100 UTC), the center of Tropical Storm Isaac was located by an Air Force Reserve Reconnaissance Aircraft near latitude 26.4 north, longitude 86.2 west. Isaac is moving toward the northwest near 12 mph (19 km/h) and this general motion is expected to continue today with a gradual decrease in forward speed. On the forecast track, the center of Isaac will move over the eastern Gulf of Mexico tonight and be near the northern gulf coast in the hurricane warning area by late Tuesday.

Maximum sustained winds have increased and are now near 70 mph (110 km/h) with higher gusts. Additional strengthening is forecast, and Isaac is expected to become a hurricane later tonight or early Tuesday, and continue to strengthen until landfall occurs along the northern gulf coast.

Tropical-storm-force winds extend outward up to 205 miles (335 km) from the center.

The estimated minimum central pressure based on reports from the aircraft and nearby NOAA Buoys is 981 mb (28.97 inches).

Hazards Affecting Land

Storm Surge. The combination of a storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters. The water could reach the following depths above ground if the peak surge occurs at the time of high tide:

Southeast Louisiana and Mississippi…6 to 12 ft.,
Alabama…6 to 9 ft.,
South-central Louisiana…3 to 6 ft.,
Florida Panhandle…3 to 6 ft., and
Florida west coast including Apalachee Bay…1 to 3 ft.

The deepest water will occur along the immediate coast in areas of onshore flow. Surge-related flooding depends on the relative timing of the surge and the tidal cycle, and can vary greatly over short distances. For information specific to your area, please see products issued by your local Weather Service Office. Near the coast, the surge will be accompanied by large and dangerous waves.

Wind. Tropical Storm conditions are expected to spread northward into the Florida Big Bend area and the Florida Panhandle in the Tropical Storm warning area tonight and Tuesday.

Tropical Storm conditions are expected to reach the northern gulf coast in the hurricane warning area tonight, with hurricane conditions expected on Tuesday.

Rainfall. Isaac is expected to produce additional rain accumulations of 1 to 3 inches over the eastern Florida peninsula, with isolated storm maximum totals of 15 to 20 inches possible. Total rainfall amounts of 6 to 12 inches, with maximum amounts of 18 inches. Are possible in southeastern Louisiana, southern Mississippi, southern Alabama and the extreme western Florida Panhandle.

Tornadoes. Isolated tornadoes are possible across west-central and northwestern Florida through tonight…and along the northern gulf coast late tonight and Tuesday.

Surf…dangerous surf and rip current conditions will continue to affect the Florida coastline and the Florida Keys during the next day or so, and begin to affect portions of the northern gulf coast tonight.

Source: nhc.noaa.gov