I recently completed a look back at the 2011-12 winter, and there are several stories to tell.
As many recall, much of the state was still in the throes of a two-year drought as we entered the winter season. "Severe to extreme" drought plagued much of western Louisiana right through January. Thankfully, relief in the form of much-needed rains arrived in February for just about the entire state. As of early March, soils were still a bit drier-than-normal for southern and northwestern sections of the state, but all-in-all, spring 2012 soil-moisture (especially the deeper soil water) was in far better shape than what we saw at the start of the 2011 spring.
But the other story for the past winter is the unusual warmth -- not record warm for the state as a whole, but one of the five warmest winters in the last 30+ years or so. A look at sites across the state shows that many locations saw only about half the usual numbers of "freeze days" between October and April, and temperatures for the "winter" months (Dec, Jan & Feb) were typically about 4° to 5°F above the norm.
While 4° to 5° above-average for the winter may not sound like a lot, that kind of persistent departure through the "cold" month can translate into some substantial reductions in heating demand. Residents across the state were likely pleased by the energy savings. On the other hand, I know at least one disgruntled peach grower in the northern half of the state because his trees didn't get close to the number of chill-hours required for a productive crop.
And the warmth just kept coming.
For the vast majority of sites across Louisiana, the first four months of 2012 rank as the "warmest" January-thru-April on record: temperatures through the first four months of the year generally averaged about 5° to 6° above-normal statewide. Warmer-than-normal weather often reflects a run of drier-than-normal weather, but thanks to February and March rains, that has not been the case this year. In fact, we've seen some significant flooding over the past few months.
Winter and spring flooding is not anything new to the Bayou State, but the severity of some of the flooding has come as a bit of a surprise, since the winter and early spring have coincided with a La Niña event. Remember that La Niñas are usually associated with drier-than-normal winters and springs -- in fact, about 3-in-4 La Niñas result in drier-than-normal winters and springs for the southern half of the state.
This spring has turned out to be one of those "other" 1-in-4s, with somewhat unexpected rains helping to end the two-year drought! And as of early May, the experts have declared the recent La Niña as "deceased."
Now many are asking: does a warm winter mean a hot summer?
The short answer is no: there is no direct correlation between mild-to-warm winters and warmer-than-normal summers. But warm and dry springs can take us into a hotter-than-average summer. And yes, we have clearly been "warm" so far this year, but most parishes are not unusually dry.
All that said, the long-range climate experts are leaning towards a "forecast" that calls for roughly a 70% to 75% chance that temperatures will average between "near normal" and "above-normal" statewide through the remainder of the spring and right through the heart of summer. Looks like the A/Cs will be doing a little overtime in the coming months!
Unfortunately, those same long-range forecasters offer no insight as to what we can expect for late spring and summer rainfall. Frankly, the science is just not there yet: long-range forecasting of rains during the warm months is far too difficult and is further complicated by the effects of tropical systems. By tropical systems, we're not just talking tropical storms and hurricanes: even a "healthy" tropical wave (a precursor for tropical depressions and tropical storms) can dump a month's worth of rain in a couple of days!
Oh, wait … that's right! Hurricane Season is just around the corner!