Marine Hurricane/Typhoon · Gulf of Mexico

The Lake Pontchartrain Causeway Commission reported about $3 million worth of damage to the bridge across Lake Pontchartrain and supporting infrastructure. Tropical storm force winds were reported for approximately 36 hours over the lake.

Hurricane 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 NOAA-NOS observation site at Pilot Station at the Southwest Pass of the Mississippi River recorded a sustained wind of 65 knots with gust to 82 knots shortly after midnight, early on August 29th. Observation height of this instruments is 24 meter above sea surface. Wind gusts of 85 and 92 knots were recorded on elevated oil production platforms in coastal waters. The NOAA-NOS station at Pilots Station near Southwest Pass recorded a minimum pressure of 969.8 millibars on the evening of the 28th shortly after the first landfall.

A storm surge of 5 to 9 feet above normal was observed around Lakes Pontchartrain and Maurepas. The highest storm surge, 9 to 12 feet, occurred in eastern Plaquemines Parish and St. Bernard Parish.