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Posted at 12:08 PM ET, 08/28/2012

Isaac reaches hurricane strength, approaching landfall in SE Louisiana

5:45 p.m.: Link - new live blog for Hurricane Isaac, covering evening hours

4:50 p.m.: The 5 p.m. advisory from the National Hurricane Center indicates Isaac’s maximum sustained winds have increased to 80 mph. It is positioned 30 miles south-southwest of the mouth of the Mississippi and is headed northwest at 8 mph.

Due to the storm’s reduction in forward speed, landfall will be delayed into overnight - perhaps due south or just southwest of New Orleans in the Delta region. Maximum surge is forecast for the Mississippi and SE Louisiana coast - up to 6-12 feet above ground at high tide. [end of live blog]

4:40 p.m.: Dramatic movies of Isaac’s development in high resolution: Hurricane formation today | Tropical storm growth Friday through Monday

4:10 p.m.: Some wind gusts as of 4 p.m.: Apache Oil Platform (offshore) 93 mph (279 feet above water), Boothville 53 mph, New Orleans International Airport 36 mph.

4:00 p.m.: The storm surge continues to build along the northern Gulf Coast. At Shell Beach, Louisiana, the surge has reached 5.5 feet and in Pensacola it has reached 3 feet.

Hurricane Isaac at 2:45 p.m. EDT (NOAA)
3:40 p.m.: Just hours away from landfall, Isaac looks about as healthy as it has during its lifetime, going back about 7 days. It’s fairly symmetric, has well-established outflow and deep convection wrapping around the center. The eye isn’t clearly defined like an intense hurricane but it’s apparent. This is not great news for the northern Gulf Coast, but even as it gets its act together as it nears the shore, there is not much time left for significant intensification.

3:15 p.m.: Boothville, Louisiana, near mouth of Mississippi reports heavy rain and wind gusts to 66 mph at 3:00 p.m. At 2:50 p.m. the Louisiana Offshore Oil Port recorded a gust to 87 mph (at an elevation of 190 feet above sea level).

3:10 p.m.: Some storm surge flooding photos from Panama City, Florida: Photo 1, Photo 2, Photo 3

3:00 p.m.: Picture of flooding in Charleston, SC where flash flood warning has been extended until 5:30 p.m. Radar indicates 5-8” of rain has fallen there today as the circulation from Isaac has fed deep tropical moisture into that region. (See also 12:20 p.m. update below). Link: Raw video of Charleston flooding.

2:50 p.m.: No doubt Isaac will impact gas prices. The Bureau of Safety and Environmental Enforcement reports as of 11:30 a.m. CDT “personnel have been evacuated from a total of 503 production platforms, equivalent to 84.4 percent of the 596 manned platforms in the Gulf of Mexico.” BloombergTV tweeted: “#Isaac shuts 93% of oil output, 67% of natural gas output in the Gulf of Mexico.”

Overview: As our tropical weather expert Brian McNoldy stressed in his latest update, hurricane Isaac will produce a range of hazardous impacts in a wide swath along the northern Gulf Coast as it makes landfall this afternoon into this evening in southeast Louisiana. Destructive winds, flooding rain, a dangerous storm surge and tornadoes are possible in southeast Louisiana, Mississippi, Alabama and the western panhandle of Florida. This region includes New Orleans, Gulfport, Biloxi, Mobile and Pensacola.

Keep reading for earlier updates and useful links

2:35 p.m.: Wind gust to 81 mph just clocked at elevation of 80 feet near mouth of Mississippi in Southwest Pass, Louisiana at 2:06 p.m. (ET). Wind was sustained at 60 mph.

2:20 p.m.: Video of storm surge pushing Gulf of Mexico water over road along coast in Waveland, Mississipi.

Radar view of eye of Isaac at 2:00 p.m. EDT (Radarscope)
2:10 p.m.: Latest radar imagery shows Isaac’s northern eyewall getting very close to the mouth of the Mississippi River in southeast Louisiana. The storm center is officially 55 miles south southeast of that location. Winds are picking up around New Orleans. At 2 p.m. (1 p.m. CDT), sustained winds were 35 mph gusting to 48 mph at New Orleans Lakefront airport

1:45 p.m.: The National Hurricane Center reports an observing site at Southwest Pass, Louisiana recently measured sustained winds to 60 mph and a gust to 76 mph.

1:40 p.m..: At 1:15 p.m. EDT, a 90 mph wind gusts was measured atop an Apache Corp oil platform about 300 feet above sea level, 80 miles southeast of New Orleans. (h/t @WSJweather)

1:30 p.m.: Until track forecasts for Isaac converged on southeast Louisiana yesterday, there were lots of twists and turns. Originally, the Florida peninsula and the Florida panhandle were targeted. Watch this animation of the track forecast evolution.

1:20 p.m.: Tweet from CNN weather: “New Orleans Mayor says the 26 ft gates have been SHUT to protect the city from incoming storm surge from Isaac.”

1:15 p.m.: Strong language from the National Weather Service regarding the storm surge threat in southeast Louisiana: “Life threatening flooding possible in areas outside hurricane protection levees and in areas around Lakes Pontchartrain and Maurepas. Sections of west Jefferson, east St Charles and lower Lafourche hurricane protection levees could be over topped. Areas outside of hurricane protection levees will be severely inundated. People not heeding evacuation orders in single family, one or two story homes could face certain death.” It uses similar terms to describe the threat in Mississippi.

1:05 p.m.: Landfalling hurricanes frequently produce tornadoes. They are usually small spin-ups but can occasionally grow larger and become destructive. A tornado warning was issued for the area around Slidell, Louisiana at 12:50 EDT and continues through 1:15 p.m. The potential for tornadoes continues through 7 p.m. at least during which a tornado watch is in effect from southeast Louisiana to the western Florida panhandle.

12:55 p.m.: Great Wall Street Journal interactive display showing difference between Katrina and Isaac satellite appearance. There’s no comparison.

12:50 p.m.: Storm surge rushing ashore in Waveland, Mississippi, “covering entire road” Tweets storm chaser @reedtimmerTVN: Photo. Water also rising in Biloxi: Photo.

12:40 p.m.: Louisiana Governor Bobby Jindal is giving a live press conference on Hurricane Isaac. Watch here.

12:35 p.m.: Isaac is the 2012 Atlantic hurricane season’s 4th hurricane, on the heels of Chris, Ernesto, and Gordon.

12:30 p.m.: Isaac is now officially a hurricane according to the National Hurricane Center with maximum sustained winds to 75 mph.

Satellite image of Isaac and sprawling outer rain band (NOAA)
12:20 p.m.: The extent of Isaac’s circulation and moisture field is vast. So vast flooding is occurring in Charleston, South Carolina (photo). The National Weather Service reports 3 inches has fallen and another 2 to 4 inches are possible. A flash flood warning remains in effect through 2:30 p.m. EDT.

12:15 p.m.: USA Today weather (on Twitter) reminds us: “More than 60 percent of hurricane-related deaths occur far from the coast because of flooding, mudslides and tornadoes”

12:10 p.m.: Latest flight recon data indicate pressure down to 975 mb and peak surface winds to 76 mph, indicating Isaac has reached hurricane intensity. Isaac has not officially been named a hurricane by the National Hurricane Center, but this is probably forthcoming.

Noon: Through 11 a.m., some impressive wind gusts have already begun battering the Gulf coast. Grandle Isle recorded a 64 mph gust at 9:35 a.m. EDT. A buoy offshore measured a gust to 82.6 mph. New Orleans Lakefront airport has gusted to 43 mph.

Wind gusts as of 11 a.m. (Earth Networks StreamerRT)
11:45 a.m.: Weather Underground says the center of Isaac is just 50 miles from the Mississippi River Delta. Given its (relatively slow) forward speed of 10 mph, a good approximation for landfall is around 4 p.m. CDT.

Useful Links:

Washington Post Interactive tracking map

Interactive map for tracking tides/storm surges

Webcams along northern Gulf Coast

Isaac radar loops

By  |  12:08 PM ET, 08/28/2012

Categories:  Latest, Tropical Weather

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