Meteorological Synopsis
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. The mid-level short wave which accompanied the cold front quickly exited to the northeast, causing the front to weaken and slow. By the evening of May 9, the cold front dissipated in the vicinity of Baton Rouge. The remnant frontal trough served as a focusing axis for heavy precipitation that continued into the late morning hours of May 10. An upper-level trough became negatively tilted to the west of the area, providing ample upper-level divergence as well as mid-level and upper-level cold and dry air advection. 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.
The massive rainfall totals were generally caused by the stalled out frontal system. Heavy, "training" thunderstorms continued to form over the same areas for several hours. Pumping stations were overwhelmed and could not pump out the water into Lake Pontchartrain. At the time, pumping stations were only rated to pump 1 inch (2.5 cm) per hour maximum.
Read more about this topic: May 8th 1995 Louisiana Flood