On the heels of last year's El Niño-driven weather, the Delta should experience more normal weather patterns this spring.
“Right now, using data from mid-February, the forecast for the northern Louisiana border south calls for below normal temperatures and normal rainfall through March,” said Barry Keim, Louisiana state climatologist. “Rain is expected to pick up, though, because through May the entire Delta area and Southeast should see above normal precipitation with below normal temperatures.”
A weakening El Niño is at least partly responsible for the prediction. Over the next three months, it's expected that the El Niño will fade to neutral conditions. There's no indication it will morph into a La Niña.
“Anything is possible, of course, but there's no indication that switch will happen,” said Keim. “While there are different thresholds, typically we say El Niños tend to come around every three to seven years, although over the last several decades, they've come more frequently. La Niñas are less frequent.” For the summer, Keim is expecting another slight shift. The forecast for June through August for the entire Delta region is for above normal temperatures and normal precipitation.
El Niños and La Niñas originate in the tropical Pacific Ocean. El Niños — warm phases — occur when a large pool of warm water “piles up” in the eastern tropical Pacific Ocean off the South American coast. The warm water is deep and stores tremendous energy. That energy tends to disrupt the general circulation of the atmosphere, resulting in weather anomalies that pop up around the globe.
During La Niña, water off the South American coast becomes colder than normal, causing weather anomalies as well.
It doesn't necessarily follow that an El Niño will cycle into a neutral phase and then to a La Niña. An El Niño can move into a neutral phase and then back to an El Niño.
“A lot of times when there's a very strong El Niño, the pendulum will swing drastically in the opposite direction. It's very common to have a strong El Niño followed by a strong La Niña.”
How do the two affect hurricane season? “During El Niños, believe it or not, hurricanes are usually reduced — about half normal. During a La Niña, it's the exact opposite and hurricane possibilities are enhanced.
“We weren't in an El Niño during the last hurricane season.”
Something that could “throw a monkey wrench” into Keim's prediction is the tropical season. Currently, a “slightly above average” hurricane season is forecast for the Atlantic in 2005.
“Last year, they had an above normal forecast — which was a good one.”
Keim has been getting a few calls from producers about late freezes.
“In south Louisiana, we haven't had a significant freeze (since early February), at least. The chances of getting one around Baton Rouge now are slim — maybe less than 10 percent.”
So far, the Midwest March has been a bit cooler than normal.
“As we move into summer, the El Niño we're in the midst of should begin to fade away,” said Tony Lupo, associate professor of atmospheric sciences at the University of Missouri at Columbia. “In fact, over the last month, we've seen the El Niño already beginning to weaken.
“Generally, when an El Niño weakens in the spring and summer, they go into a neutral phase or they become a La Niña. Right now, the best guess is this one will end up in the neutral phase, somewhere between an El Niño and a La Niña.”
Past statistics show that 75 percent of the times this occurs, the Missouri area — “especially from Kansas over to central Missouri, although it applies to the Bootheel as well” — tends to be drier and warmer than normal.
“Last year, we certainly had a wetter, more ideal summer. In terms of how cool it was, last year was a top five for Missouri. That helped us to record harvests — especially for the Midwest area. This year, we probably won't see the same. It's rare when we see such conditions two years in a row.”
Lupo said that his drier, warmer prediction doesn't mean “we'll see disastrous conditions. This has to do with statistical forecasting — there's no reason for panic.”
Lupo said he enjoys speaking to audiences of farmers. “They're the best. They really listen and ask great questions. More than others, they know to take long-range forecasts for what they are: a best estimate.”
Generally, the Bootheel is on the cusp of Lupo's prediction area.
“Many times, when summers are dry from central Missouri west, fronts will pick up moisture from the Gulf of Mexico just a bit further east. That allows the Bootheel to get moisture that the rest of Missouri doesn't. The Bootheel is fortunate to be situated where it is so that Gulf-generated moisture impacts them more often.”
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