Hurricane Isaac Drenching Southeastern Louisiana; Dangerous Storm Surge and Flood Threat to Continue through Tonight, Aug. 29, 2012 – UPDATE 10 am CDT

Hurricane Isaac Surface Wind Field

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Miami, Florida—(ENEWSPF)—August 29, 2012 – UPDATE 10 am CDT (1500 UTC).  Hurricane Isaac is drenching southeastern Louisiana. Dangerous storm surge and flood threat from heavy rains is likely to continue through tonight. Hurricane Isaac is located 29.6n, 90.7w, about 45 miles (75 km) southwest of New Orleans, Louisiana.  Maximum sustained winds of 75 mph (120 km/h). Present movement is northwest or 310 degrees at 6 mph (28.70 inches).

Changes in Watches and Warnings with this Advisory

The Tropical Storm warning has been discontinued east of the Alabama-Florida border.

Summary of Watches and Warnings in Effect

A Hurricane Warning is in effect for:

  • East of Morgan City, Louisiana to the Mississippi-Alabama 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:

  • East of the Mississippi-Alabama border to the Alabama-Florida border, and  
  • Morgan City to Sabine Pass, Texas.

A Tropical Storm Watch is in effect for:

  • East of High Island, Texas to just west of Sabine Pass.

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 1000 am CDT (1500 UTC) the center of Hurricane Isaac was located by NOAA Doppler Weather Radar near latitude 29.6 north, longitude 90.7 west, or very near Houma, Louisiana. Isaac is moving toward the northwest near 6 mph (9 km/h). This general motion is expected to continue through tonight, followed by a turn toward the north-northwest by Thursday night or early Friday. On the forecast track, the center of Isaac will move farther inland over Louisiana today and tomorrow, and over southern Arkansas by early Friday.

Maximum sustained winds have decreased to near 75 mph (120 km/h) with higher gusts. Isaac is a Category One Hurricane on the Saffir-Simpson Hurricane Wind Scale. Gradual weakening is forecast during the next 48 hours as Isaac continues moving farther inland, and Isaac is expected to weaken to a Tropical Storm later today.

Hurricane-force winds extend outward up to 45 miles (75 km), from the center, and tropical-storm-force winds extend outward up to 175 miles (280 km). A gust to 74 mph was recently reported at the Mid Lake Station in Lake Pontchartrain, and a wind gust to 63 mph was reported at New Orleans International Airport.

The estimated minimum central pressure based on nearby surface observations is 972 mb (28.70 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:

  • Mississippi and southeastern Louisiana…6 to 12 ft.,  
  • Alabama…3 to 6 ft.,  
  • South-central Louisiana…3 to 6 ft., and
  • Florida Panhandle and Apalachee Bay…2 to 4 ft.

The deepest water will occur along the immediate coast in areas of onshore winds.  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.  Storm surge values of near 8 feet have recently been reported at Shell Beach, Louisiana and Waveland, Mississippi.

Wind. Tropical Storm conditions will continue across the warning area today, and Hurricane conditions will continue to affect portions of southeastern Louisiana and Mississippi in the hurricane warning area into this afternoon. Winds affecting the upper floors of high-rise buildings will be significantly stronger than those near ground level. At about the 30th story, winds would likely be one Saffir-Simpson category stronger than at the surface.

Rainfall. Isaac is expected to produce total rainfall amounts of 7 to 14 inches, with possible isolated maximum amounts of 20 inches, over much of Louisiana, southern Mississippi, and southwest Alabama through Friday morning. These rains could result in significant lowland flooding. Rains are expected to increase northward into Arkansas on Thursday, with amounts of 3 to 6 inches expected over southern Arkansas by Friday morning.

Tornadoes. Isolated tornadoes are possible along the central gulf coast region and parts of the lower Mississippi river valley through Thursday.

Surf. Dangerous surf and rip current conditions will continue to affect the west coast of Florida and the northern gulf coast for the next day or so.

Source: nhc.noaa.gov