Another Excessive Rainfall/Flash Flooding Episode for Louisiana

Tropical Storm Likely Southwest Gulf of Mexico later Weekend/Early Next Week
09/10/2021, 8:18 am EDT
Winter 2021-22 HDD Forecasts Trending Colder for U.S.
09/16/2021, 6:32 am EDT
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The arc of heavy to excessive rainfall associated with Nicholas shifts into Louisiana the next 2-3 days as the storm weakens to a depression and eventually dissipates in Louisiana. Life threatening flash flooding persists despite the storms inland location.

Highlight: Nicholas is inland but excessive rain/life-threatening flash flooding continues.

Discussion: “Life threatening” flash flooding is ongoing in the upper Texas/southwest Louisiana region and will continue into Thursday despite Nicholas moving inland and now weakening. The NOAA/NHC rainfall forecast indicates an additional 6-10 in. of rain across much of Louisiana with near 15 in. high spots (Fig. 1). A persistent tornado risk is also likely in the heavy rain zone. Flash flooding is at greatest risk in the Port Arthur area today and across all of southern Louisiana throughout today and tomorrow likely lingering into Thursday (Fig. 2).

At 8AM EDT, Tropical Storm Nicholas was located at 29.5N/95.5W or about 15 miles south-southwest of Houston, TX. Nicholas is moving north-northeast at 8 mph with top wind 60 mph and lowest pressure 999 MB. Nicholas will continue to weaken and slowly turn northeast and east-northeast settling in Louisiana before dissipating later this week.

Fig. 1: NOAA/NHC rainfall outlook associated with T.S. Nicholas.

Fig. 2: NOAA/NHC flash flood risk areas associated with T.S. Nicholas.