NEW ORLEANS--A tropical system struggling to form in the Gulf of Mexico is likely to bring 10 inches of rain to the New Orleans area over the weekend, with some locations receiving as much as 15 inches. The National Hurricane Center said there's an 80 percent chance of the system becoming a tropical cyclone within the next 48 hours.
The National Weather Service has issued a flash flood watch for the south shore of Lake Pontchartrain, which is likely to be extended to St. Tammany Parish and west towards Baton Rouge by this afternoon, said meteorologist Phil Grigsby.
"We already have some stronger storm cells developing," he said this morning.
A special weather statement was issued at 1:22 p.m.. for one storm moving west affecting New Orleans, upper Jefferson and St Charles parishes that threatened to drop 1 to 2 inches on some areas in an hour and was accompanied by winds of 35 to 40 mph. The thunderstorms are associated with the tropical wave and some along the coast and the Lake Pontchartrain shoreline could produce water spouts as well, which will be a risk all the way through the weekend.
Rainfall and winds have already disrupted smoke from a marsh fire in eastern New Orleans enough by mid-day today that state Department of Environmental Quality officials cancelled an air quality alert for the area because the rain washed dangerous particles out of the air.
Meanwhile, local government officials began lowering canal levels and shutting levee gates throughout the area in anticipation of the storm's formation.
The complex conditions governing formation of the tropical system are making it difficult to determine how strong it will become or where and when it might make landfall, said Eric Blake, a hurricane specialist at the National Hurricane Center. "Right now, Louisiana is expected to be on the wet side of this system. You'll have locally heavy rainfall and areas of flooding."
The low pressure system forming along a tropical wave in the Gulf is "kind of caught between a ridge of high pressure over the Southwestern United States and a trough (of low pressure) over the East Coast, and is caught in an area of light steering, so it's not going anywhere quickly," he said.
Computer models used to forecast the emerging storm's path take it in a wide variety of directions and several show the system going ashore and then re-emerging over the Gulf over the next week.
"Regarding how strong it might get, that depends on how far and long it stays offshore," Blake said. "A few models bring it over the upper Texas coast or Louisiana fairly quickly, and that wouldn't allow it to get very strong. But others bring it back away from the coast and allow it to sit several days."
Conditions in the Gulf are ripe for storm development, however, with water temperatures off Louisiana averaging 88 degrees.
A NOAA Hurricane Hunter airplane will survey the surface circulation in the low pressure system this afternoon.
Grigsby said the system is reminiscent of Tropical Storm Allison, which went ashore near Houston in June 2001, dropping 38 inches of rain there and as much as 21 inches of rain in Louisiana. That storm dumped between 12 and 15 inches of rain on the New Orleans area.
Strong winds out of the east already are causing higher than normal tides along Louisiana's coast, where a coastal flood watch has been posted. Tides are 2 to 3 feet above normal in Grand Isle, Leeville and Chauvin, threatening roads used at evacuation routes. Seas offshore have reached 8 feet.
"Obviously, if it becomes a closed low or a depression or a storm forms, the amounts could go higher," Grigsby said. He said weather service officials have been briefing local emergency management officials on the potential effects of the storm.
New Orleans Mayor Mitch Landrieu will hold a 2:30 p.m. press briefing, available on the city's web site, to describe city preparations for the storm.
Sewerage & Water Board spokesman Robert Jackson said Thursday around 1 p.m., that the agency's 23 drainage pump stations, as well as support facilities including the in-house power plant along South Claiborne Avenue, are fully manned.
"Everything is working 100 percent," he said. "Everybody's manned, getting ready to find out what we're going to see."
No street flooding or mechanical problems have been reported in connection with strong thunderstorms that began to move through the area late Thursday morning, Jackson said.
In Jefferson Parish, officials are pumping down the canals and prepping Lafitte and Grand Isle for potential tidal issues.
Rain will be the primary problem for most of the parish and crews will be manning the pumps continuously until the end of the weather event, Parish President John Young said. The canals that run through the parish are being pumped down to their lowest levels in anticipation of significant rain, Young said.
However, officials still expect there will be street flooding over the weekend, he said.
Parish officials are in regular contact with the mayors of Lafitte and Grand Isle to ensure those communities are prepared for the storm. The parish has begun sandbagging in some low-lying areas of Lafitte and are activating pumps in the area that were purchased after Hurricane Ike, Young said.
The Southeast Louisiana Flood Protection Authority-East began monitoring closure efforts for the three levee districts it oversees.
Orleans Levee District officials expect to have to close low-sill floodgates along the Industrial Canal, a spokeswoman said. Officials there also will be checking to insure that a contractor is putting Hesco baskets in place in a floodwall opening on the west side of the canal at France Road.
High tides also have prompted the closing of the Bayou Bienvenue floodgate. It may be opened briefly at low tide, about 6 p.m., but then will be closed for the rest of the weekend. The Bayou Dupre floodgate has been closed because of construction work.
Plaquemines Parish President Billy Nungesser sent an email to residents this afternoon announcing the pumping down of drainage canals so they can retain as much water as possible. Nungesser asks residents to help remove any debris in drainage system, and to move garbage cans out of streets and driveways to more secure locations.
St. Charles Parish officials announced similar preparations.
Posted By: Siebra Muhammad
Saturday, September 3rd 2011 at 4:19PM
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