Hay growers may need to learn a whole new weather language in months ahead. Many meteorologists are turning to the Atlantic and the North Atlantic Oscillation (NAO) to forecast what’s likely to happen during the 2012 growing season.
“In terms of forecasting, you can’t look out months ahead (with NAO) like you can with a La Niña or an El Niño. You can only look out a couple of weeks. So it gives you a highly uncertain forecast. But with La Niña now appearing to be fading away, it’s all we have to go on,” says USDA staff meteorologist Brad Rippey.
There is some evidence that, once an NAO phase develops, it can lock into place for months at a time. It has been in what meteorologists refer to as a “positive phase” since last fall. If that continues through March, April and May, Rippey says, the south-central U.S., including Texas and Oklahoma, could see some relief from the drought that dominated the region in 2011. On the other hand, areas likely to have “some concern for dryness” this year would include portions of the southeastern U.S. and the western Corn Belt, particularly northwestern Iowa and South Dakota.
If the NAO positive conditions hold, it’s unlikely that there will be a repeat of extreme wet conditions that characterized spring planting in many areas of the northern U.S. last year, says Rippey. “We have seen some pockets of significant moisture in the eastern Corn Belt, but the warm weather of the last couple of weeks should help dry things out there. We could see some areas of lingering wetness, but it will be a far cry from last year’s situation.”
For the immediate future, there’s a strong likelihood of a significant, slow-moving storm bringing “tremendous rainfall amounts” to the Southeastern Plains and lower half of the Mississippi River Valley this week, Rippey says. “Some areas could see 5-10” of rainfall. And there could be some additional flooding in areas that are already wet.”
The NAO positive phase explains the relatively open winter and mild spring in many regions of the U.S., he adds.
“What you get in this case is the jet stream moving farther north and blocking cold air far to the north in Canada. The jet stream acts like a freight train and moves the cold out before it reaches the U.S.”