Hurricane (Typhoon) — St. Tammany, Louisiana

2012-08-28 to 2012-08-30 · St. Tammany, Louisiana

Wider weather episode

Isaac entered the Gulf of Mexico as a tropical storm on August 26, moving northwest after crossing Haiti, Cuba and the Florida Straits. Isaac strengthened into a hurricane on the morning of the 28th when it was 75 miles south-southeast of the mouth of the Mississippi River. Isaac made landfall in Plaquemines Parish as a Category 1 Hurricane near Southwest Pass of the Mississippi River on the evening of the 28th. A second landfall occurred near Port Fourchon the following morning. The storm weakened to a tropical storm on the afternoon of the 29th about 50 miles west southwest of New Orleans, and weakened further to a tropical depression on the afternoon of the 30th near Monroe, Louisiana.

The highest wind gust recorded on land in Louisiana was 75 knots, or 86 mph, measured by a portable weather station (Texas Tech University) near Buras on the evening at August 28. The maximum sustained wind in Louisiana was 65 knots, or 75 mph, at the same portable weather station near Buras on the evening of August 28. There were several marine observations near the coast that had slightly higher wind readings, but their observation heights were generally 80 ft or higher.

Due to Isaac's very large size, and slow forward speed, tropical storm force winds lasted in excess of 48 hours in many areas of coastal southeast Louisiana. Occasional hurricane gusts of 70 to 85 mph were recorded across southeast Louisiana during the night of the Aug 28th and early on the 29th, especially south of Lake Pontchartrain. Interior areas of southeast Louisiana such as around Baton Rouge and northward experienced tropical storm force winds. Widespread power outages occurred across the area. Local utility companies reported over 700,000 customers were without power at the peak of the storm in southeast Louisiana. Generally, most of the wind damage was limited to downed trees and power lines, and roof damage caused by wind and falling trees and tree limbs.

The minimum sea level pressure measured from a land station was 965 mb on the morning of Aug 29 at a portable weather station ( Texas Tech Univ) located near Larose. A pressure of 974.3 mb was measured at a NOAA gage at Bayou Gauche on the morning of August 29th. Close to the landfall location, a reading 969.8 mb was measured at the NOAA NOS station at Pilots Station near Southwest Pass on the evening of the 29th shortly after the first landfall. The height of this measurement was 24 meter or 79 feet.

A storm tide of 8 to 13 feet occurred in eastern Plaquemines Parish and St. Bernard Parish. A representative maximum storm tide of 13.21 ft NAVD88 was measured at a USGS tide gage near Pointe a la Hache. A local levee was overtopped or breached in the Braithwaite area of Plaquemines Parish early on August 29. A number of people had to be rescued from the flooded area, but a 60 year old woman and 52 year old man drowned in the storm surge.

Significant impact also occurred around Lakes Pontchartrain and Maurepas with a storm tide of 5 to 9 feet. 5 to 10 thousand homes were flooded in low lying areas of that border these lakes of the following parishes: St. Tammany, Tangipahoa, Livingston, Ascension, St James and St John the Baptist. Laplace in St. John the Baptist was especially hard hit with over 5,000 homes flooded by storm surge. An additional storm surge fatality occurred in St. Tammany Parish on the morning of the 30th when a 75 year old man drove his car into a storm surge filled ditch.

Storm surge flooding also affected areas south and southwest of New Orleans with a storm tide of 4 to 7 feet. Roadways and low lying property were flooded. Local levees around Lafitte and Myrtle Grove were overtopped and/or breached resulting flooding of numerous houses and property in this area.

Many areas of southeast Louisiana received 8 to 12 inches of rain with a few locations having 15 inches of rain or more. Maximum storm total rainfall was 20.66 inches at the New Orleans Carrollton gauge on the Mississippi River. Rainfall run-off produced moderate to major flooding on the Tangipahoa, Tchefuncte, Tickfaw, Amite, Pearl, Bogue Chitto and Bogue Falaya Rivers. Storm surge and high tides restricted outflow of the rivers near the coast and lakes exacerbating flooding in those areas.

Overall impacts of Isaac resulted in at least $600 million in damages in southeast Louisiana, 3 direct fatalities, and 2 indirect fatalities. Storm surge flooding accounted for the bulk of damage, estimated around $500 million and the three direct storm surge fatalities in Louisiana. Winds accounted for a much lesser amount of slightly more than a $100 million. As stated earlier, these are early damage estimates and will likely be adjusted upward due to later damage assessments.

During the recovery process there were two indirect fatalities. On Sept 1, A 67 year man was electrocuted when attempting to restore power to his house in Abita Springs, St Tammany Parish. On Sept 3, a 90 year old man died of heat related impacts in his house in Marrero, Jefferson Parish, where power had not been restored.

Source: NOAA Storm Events Database, event_id 409749. Narrative written by the NWS forecast office that issued the report.