Monday, May 25, 2009
Weather columnist Kevin Myatt: La Nina never quite matured
Kevin Myatt is The Roanoke Times' weather columnist.
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La Nina is no more, or didn't quite make it, depending on how you look at it.
La Nina conditions existed for several months, as sea surface temperatures in the equatorial Pacific averaged more than half a degree Celsius below normal since late fall.
But to officially qualify as a La Nina event, it must average half a degree below normal for five consecutive three-month periods. It made it to four, but with sea surface temperatures now near normal to even slightly above normal, the March-May period will almost certainly fall a little below that threshold.
La Nina has a loose correlation with mild to warm, dry weather across much of the southern half of the United States. Severe drought conditions developed in much of the Southeast, southern Appalachians and mid-Atlantic during the past two years, when La Nina conditions were common, but have recently been relieved in most areas by spring rains.
The equatorial Pacific is now considered to be "neutral," meaning there is neither a La Nina nor an El Nino. Forecasts suggest neutral conditions will continue through the summer, but after that, it is possible the Pacific will move toward a warm El Nino cycle. El Nino loosely correlates with fewer Atlantic hurricanes in the fall, and a wet winter in much of the U.S.
I say "loosely correlates" because, when it comes to weather, there is never only one factor at work. Always be skeptical when anyone blames any kind of weather on a lone factor.
