May 8th 1995 Louisiana Flood

The May 1995 Louisiana flood, also known as the May 1995 Southeast Louisiana and Southern Mississippi Flood, was a heavy rainfall event which occurred across an area stretching from the New Orleans metropolitan area into southern Mississippi. A storm total rainfall maximum of 27.5 inches (70 cm) was recorded near Necaise, Mississippi. Considerable flooding was caused by the rainfall including several record flood crests along impacted river systems.

The flooding caused six fatalities and more than $3.1 billion in damage.

The entire 40-hour event from the evening of Monday, May 8, through the morning of Wednesday, May 10, consisted of two distinct heavy rainfalls. By Wednesday morning, storm total rainfall amounts of 10 to 20 inches (25 to 51 cm) were common across portions of southeast Louisiana and south Mississippi.

A cold front approached the region from the west, preceded by a squall line. The airmass that entered western Louisiana on May 8 exhibited considerably lower dewpoints than the tropical airmass across east Louisiana and southeast Mississippi. By the evening of May 9, the cold front dissipated in the vicinity of Baton Rouge. The remains of the front served as a focusing axis for heavy precipitation that continued into the late morning hours of May 10. An upper-level trough helped to provide upper-level support to the system. At the surface, warm and moist air moved in from the Gulf of Mexico continually during the event. The swath of highest rainfall totals was closely tied to a theta-e ridge at the 850mb pressure surface, which stretched from the central Gulf of Mexico into the Mississippi River Delta area.

During each wave of rainfall, heavy, "training" thunderstorms continued to form over the same areas for multiple hours. In the New Orleans area, pumping stations were overwhelmed and could not pump rainfall into Lake Pontchartrain as quickly as it was falling. At the time, pumping stations were only rated to pump 1 inch (2.5 cm) per hour maximum.

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