“Historically, there is a tendency for strong La Niña events to last for two or more years. More recently, ocean temperatures along with wind and cloudiness patterns over the Pacific are indicating that the redevelopment of the cold water is likely after a summer of neutral conditions,” he says.

The expected dry pattern could prolong or even worsen the widespread drought affecting the region, adds Zierden. Potential deficits in rainfall during the winter in these areas can be critical, as winter is the primary recharge season for surface and groundwater.

“Warmer temperatures may slow the necessary chill accumulation in flowering fruits such as blueberries, peaches and strawberries but may enhance development of other crops,” he says.

“The forecasted warm and dry conditions are unfavorable for the production of winter forage for cattle when irrigation is not available.

While mild freezes can be expected every year in north and central Florida, La Niña reduces the risk of severe freezes in the citrus and vegetable belts.”

The warmer temperatures, says Zierden, will result in less chill accumulation over the course of the winter season.

“Warmer temperatures will also mean greater evaporation rates. Due to the jet stream configuration, severe or damaging freezes are less likely during La Niña than in neutral years. We understand that many crops are at risk from an early season freeze due to delayed planting from the drought.

“However, the risk of early or late season freezes does not seem to be affected by the Pacific Ocean.”

The shift towards drier than normal conditions becomes much more pronounced in Florida and coastal Georgia, Alabama, and the Carolinas as fall progresses into winter, resulting in much higher confidence in a forecast of dry conditions in these areas, he says.

“Keep in mind that winter rainfall is vital to the recharge of surface and groundwater in Georgia, Alabama and the Carolinas.

While the worsening of drought may slow during the winter months when water demand is much lower, it may intensify quickly come spring.

Summer evapotranspiration rates are greater even with normal rainfall, so heading into the spring with deficits already accumulating from winter is a sure recipe for rapid drought intensification.

“In Florida, where drought concerns are lower right now with recent rainfall, there is a strong possibility for drought to re-intensify this winter and spring. Wildfires will also be a concern, where studies show that La Niña normally leads to an active wildfire season in Florida and south Georgia.”

Beginning in November, says Zierden, the Southeast can expect rainfall patterns of from 10 to 30 percent less than normal. “We’ll see similar rainfall patterns through the winter that we saw last year.”

phollis@farmpress.com