Torrential rains inundate parts of south Louisiana

Published 7:00 am Tuesday, August 16, 2016

The weekend’s devastating floods along rivers and streams in east-central Louisiana were the result of mind-boggling rainfall totals in those regions Thursday night through Saturday.

About 15 miles northeast of Baton Rouge on the northern edge of Denham Springs, an observer’s rain gauge in the community of Watson recorded a little over 26 inches of rain Thursday, Thursday night, and Friday morning. The remainder of Friday, Friday night, and Saturday morning almost five more inches fell bringing the total rainfall in Watson to 31.39 inches in about 48 hours.

Numerous weather observers from Hammond, Louisiana, westward through Baton Rouge to Lafayette measured over 20 inches of rain during the deluge that began Thursday and continued through several waves into Saturday. The swath of extremely heavy rain extended northward just across the Mississippi line southwest of McComb, Mississippi.

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There is no way that the ground can absorb that much water, so the vast majority of the rain ran off into creeks and rivers producing record-breaking flooding on Louisiana rivers such as the Tchefuncte, Amite, and Comite.

In last week’s column I described the low pressure system and extremely humid atmospheric moisture levels that were forecast to slide westward along the Gulf Coast from Florida, and which ultimately produced the record rains and massive flooding. 

Early last week when I wrote that column, computer weather models were predicting that extreme rains were most likely to fall to our east and our south. I mentioned that a shift of 100 miles in those predictions could make the difference between us getting a couple of inches of rain and ten inches.

As the week wore on, forecasters continued to shift the predicted bullseye for heavy rain to the west, eventually posting flash flood watches for the affected areas.

As it turned out, rain totals in and around Picayune and Carriere were generally from just under two inches up to almost four inches for Thursday through Friday. The heaviest rain bands came as close as Franklinton, Louisiana, a mere 40 miles as the crow flies from us, where ten inches of rain fell.

By Sunday the low-pressure system that brought all of this rain and misery to Louisiana had drifted west into Texas and become part of a stationary front that stretched from that state north into the Great Lakes region. Meanwhile, the semitropical Bermuda High Pressure Ridge began nosing westward from the Atlantic into the Gulf of Mexico and the Gulf states.

The Bermuda High will be the dominant weather system affecting our weather this week. That means warm and humid with weak southerly breezes coming off the Gulf. Along with this pattern will come widely scattered to scattered afternoon and evening showers and thunderstorms. It’s impossible to know exactly where those showers will occur. The chances that it will rain where you are on any particular afternoon this week are about the same as, or just a little less than, your chances of getting tails when flipping a coin. 

In other words, after last week’s unusual weather, summer monotony returns for this week.

By Skip Rigney