Posted: Sep 20, 2013 8:33 AM by Dave Baker
The combination of Gulf and Pacific moisture converging over Louisiana could mean for some hefty rainfall totals over the weekend. Most areas of Acadiana need the rain as it has been very dry with little or no rain over the past few weeks. This is most noticeable over the central and northern parts of Acadiana where less than one inch of rain has fallen in the past 30 days. Normally Acadiana sees about four inches of rain over a 30 day period during the August/September time frame.
Coastal sections, especially lower St. Martin and St. Mary parishes have been catching scattered rain and storms over the past few weeks. From Franklin to Stephensville down to Morgan City rainfall totals over the past month have been above normal.
Computer models are showing all of Acadiana should grab between two and four inches of rain over the three day period Friday through Sunday. But some of the storms will develop and run across the same areas over and over. This is called "training" because it looks like the storms are on train tracks and storm after storm rolls over the same geographic area. When this occurs, isolated areas can pick up much more rain than the average totals elsewhere.
There are indications that as the front moves in from the northwest, the Pacific moisture from the remnants of Hurricane Manuel will precede the front. Gulf moisture will drift in from the southeast at the same time. This sets the stage for the heavy rain event. Some areas of Acadiana can potentially see up to eight inches of rain before the end of the day Sunday. Flash flood guidance shows most areas can handle 3-4 inches of rain in a six hour period. Problems could occur if we exceed five inches.
A tight pressure gradient and the recent full moon will have tides running one to one and a half feet above normal so a Coastal Flood Advisory is in effect for the Louisiana coastal parishes.