2011 was a very busy, deadly and costly year from a weather perspective. The feds report that there were at least a dozen U.S. weather/climate events (including the Southern Drought) that generated losses of $1 billion dollars or more -- each! Preliminary estimates from just twelve U.S. weather disasters total more than $50 billion, and by the time all is said and done, nationwide weather-related losses likely will far exceed $60 billion for the year.
And Louisiana was not spared.
Any review of 2011's weather for the Bayou State would be dominated by the "D" word -- drought. The current Southern Drought that has gained so much national attention -- mainly due to impacts across the Southern Plains -- can be traced to its beginnings over northern Louisiana back in 2010, then expanded westward from there and still persists today. Some portion of northern Louisiana has been "in drought" since April 2010 according to the weekly U.S. Drought Monitor (USDM), a run of 20 months! During this past summer's peak for the drought across Louisiana, roughly two-thirds of the state was rated as suffering "Exceptional Drought" (the most critical level) by the USDM.
Other Louisiana weather stories for 2011 include a monster year for tornadoes in the Bayou State. The NWS preliminary count for the Pelican State approaches 90 twisters for the year, more than double the average. Interestingly, roughly one-fifth of those struck between April 25-26, just 1-2 days before the deadly super outbreak across central and northern Alabama, and all generated by the same weather set-up.
Ol' Man River reminded us that upstream downpours can become a downstream disaster, even when we are the ones praying for rain! The Mississippi River approached record flows during the spring, producing widespread flooding for those along the river in northeast Louisiana and prompting only the second opening of the Morganza Spillway since its construction. Let's not forget the irony -- floodwaters from the Ohio, Upper Mississippi and Missouri rivers threatened Louisiana while 'she' was deep in drought, a reminder that the Mississippi's flow is all but unaffected by our local weather and climate trends.
When it turns dry, it tends to get warmer than normal. Dry soils usually mean higher temperatures, and the numbers confirm that the 2011 summer was the "hottest on record" across Louisiana. Shreveport reached or exceeded 100ºF on 62 days, smashing that city's previous record. The record heat stressed livestock, shriveled crops and natural vegetation, and drove cooling costs through the roof statewide.
Then came September's Lee, Louisiana's first tropical visitor since 2008's Gustav and Ike. Fortunately, Lee was a modest tropical storm and wind damage was relatively minor. Rain, on the other hand, was a different story, with sections of southeast Louisiana receiving from 10" to 15" over a 5-day period. Normally such heavy rains would produce considerable flooding and certainly there was notable property damage. But drought conditions at the time of Lee's arrival helped reduce the storm's impact, and for many, Lee was more blessing as a temporary "drought buster" than a curse.
In the end, however, it was the lack of rain for most that topped 2011's weather news for Louisiana. Preliminary statewide rainfall for 2011 averaged just 42.9", roughly 14" below the 100-year average, making 2011 one of the ten "driest" years on record for the state.
Yes, that's very dry, but not as dry as it was during 2010!
And here is what may be the #1 developing climate story for Louisiana: 2010 and 2011 are the "driest" back-to-back years on record, and a look at the 100+ year record of annual rainfall (see rainfall timeline below) suggests that we may be in a period of moderately reduced rainfall, especially when compared to the "wet run" of the 1980s and most of the 1990s. Statewide annual rainfall since 1999 has averaged about 55", 10% less than the statewide average during the previous 20 years.
Now don't panic, at least not yet! We aren't anticipating year-after-year repeats of the past two, with annual totals under 45" becoming the rule. But there is some evidence suggesting that not only is Louisiana's "wet run" long over, but that the more recent trend towards a somewhat "drier" climate may be more rule-than-exception, at least for the next several years.
In addition -- and possibly more importantly -- the last two years have reminded us that even for the "wettest state in the Lower 48," rain and surface water are precious resources and must be managed efficiently to meet the state's current and future environmental, agricultural, human and business needs.
