Here comes our long hot summer. Us folks in the Southeast had better prepare for further drought. In other words, same old, same old.
.....Alan.
http://agroclimate.org/forecasts/cur...te_outlook.php
SECC Winter Climate Outlook
Current Conditions
La Niña returns suddenly to the Pacific Ocean, winter forecast is now for warm and dry conditions. Last month, the Pacific Ocean was still in the neutral phase and the Southeast Climate Consortium predicted rainfall and temperature patterns that are close to normal, but with greater variability within the season. Now, the Pacific Ocean has switched rather abruptly to La Niña (colder than normal ocean temperatures along the equator in the eastern and central Pacific) and that forecast has been amended to warm and dry for the remainder of the winter and early spring. With much colder than normal ocean waters now in place in the tropical Pacific Ocean, it is nearly certain that La Niña will persist and possibly strengthen during the remainder of the winter and well into the spring season. La Niña conditions usually bring warmer weather to the entire region, with temperatures generally averaging 2 to 4 degrees F higher than normal from November through March.
La Niña also brings drier weather to much of the three states. During the winter season, the dry pattern actually pushes southward and intensifies over the peninsula of Florida and the immediate coasts of Alabama, Georgia, and the Carolinas where average La Niña rainfall is 30% to 60% less than normal. Inland North Carolina, Central Alabama, central Georgia, and northern Georgia usually see near normal rainfall during this time, while northwest Alabama actually tends to be wetter than normal.
The reason for the rainfall patterns seen in January can be attributed to the predominant jet stream configuration that sets up during a La Niña winter. While the position of the jet stream will fluctuate with the passing of individual low pressure systems, fronts, and air masses, the preferred or average setup of the jet steam is that of high pressure or "ridging" over the Pacific near the U.S. west coast and low pressure or "troughing" over the mid-section of the country. This configuration tends to steer winter storms up the Mississippi Valley and Midwest. Unfortunately, this storm track often leaves the Southeast dry and the cold fronts with a little less punch.
How certain is the forecast? Thus far, the maps above and the discussion have centered around "average" shifts in temperature and precipitation due to La Niña. However, no two La Niña episodes are alike, nor are the climate impacts seen from these events. It is important to consider the range of possibilities that accompanies La Niña episodes rather than counting on climate patterns close to the "average" for La Niña. The figures below represent the range of possible precipitation amounts in January for four selected counties in the region plotted as exceedance curves. Simply put, each bar in the graphs gives the probability of rainfall equaling or exceeding the given amount for both La Niña and Neutral (ocean temperature close to normal) climate phases. The graphs demonstrate how the range of possibilities are nearly the same for the two climate phases in central Alabama and Georgia, but shift dramatically towards drier in south Georgia and Florida.
Will a strong La Niña make a difference in the forecast? With this La Niña beginning so late in the winter, we are unsure if it will grow to be a moderate to strong event. Analyses have shown that strong La Niña's tend to bring even more intense dryness to the affected areas, and that the dry conditions actually extend farther north into central and northern Georgia and Alabama during the winter. The transition zone between dry and wet moves from central Georgia and Alabama into the mountainous regions. With this in mind, drier than normal winter conditions are more likely in the drought-plagued areas of north Georgia and the Carolinas if the Pacific Ocean continues cooling.
So what are the implications for the Southeast? The warmer temperatures will impact winter crops and fruit production, resulting 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 described above, severe or damaging freezes are less likely during La Niña than in neutral years. However, the risk of early or late season freezes (like in April of 2007) 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. La Niña does not impact central and northern Georgia and Alabama nearly as much, nor inland North Carolina, so there is much more uncertainty in the precipitation forecast for these areas and near normal is more likely. Even with near normal rainfall, drought conditions are likely to persist in the mountainous regions of Georgia and North Carolina, but some lessening of the severity is possible with the winter rainfall. Keep in mind that winter rainfall is vital to the recharge of surface and groundwater in Georgia, Alabama, and the Carolinas where summer evapotranspiration rates are greater than normal rainfall, usually resulting in falling water levels. In Florida and southeast Georgia where drought concerns were eased with recent rainfall, there is a strong possibility for drought to reintensify 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.
For more detailed information on El Niño climate shifts in your particular county, please refer to the Climate Risk Tool at AgroClimate:
Might be a tad difficult when I get to the mountains, but we'll give it a try!
(and a lot of luck - Wisconsin Ann)
