The National Weather Service has issued its predictions for the upcoming winter, and for most of the country, the outlook is for warmer than usual temperatures. The persistent drought in the Southeast is also a concern in the press release put out by NOAA. Here’s a look at the predicted temperatures from December, 2007 through February 2008:

While the greatest chances for above normal temperatures are in the southern Plains states, virtually the entire country with the exception of the Northwest is expected to be warmer than normal. Cooler than normal temperatures aren’t predicted for anywhere in the country. Part of this is due to the long-term trend towards warmer temperatures compared to NOAA’s base years of 1970-2000, and the other part is due to the La Nina conditions expected this winter, particularly in the southeast. Even though temperatures are predicted to be warmer than normal, the Weather Services says that on a nationwide basis, they should be cooler than the 2006-07 winter.

As far as the chance of precipitation goes, much of the southeast and southwest is predicted to be drier than normal, while the northwest is going to be wetter than normal, both due to the La Nina conditions. Also predicted to be wetter than normal is much of the Midwest.

The weather service stressed that this outlook isn’t a snowfall forecast for the season, claiming that it’s difficult to predict exact snowfall patterns more than two weeks out, which is true. I’m a bit surprised that NOAA used the long range outlooks they issued back on September 20th as the basis for their winter outlook, when an updated one is due out in a week, and should in theory be more accurate. Perhaps they wanted to be ‘in the lead’, prior to other forecasters making their predictions.

The Climate Prediction Center has issued their updated drought outlook for the period between October and December, 2007, and the increasing La Nina conditions have prompted forecasters to expect the drought to persist for much of North Georgia through Maryland, and removing the hope for some improvement that was in the previous outlook.

You can see the changes to the left, with the previous outlook on the top, and the current one on the bottom. The strengthening La Nina means that much of the southeast US will see warmer and dryer conditions than normal, and was a good part of the reason for the total ban on outdoor watering in North Georgia issued last week.

The warm conditions presently extend for much of the east coast for the weekend, with Atlanta’s temperatures expected to be in the 80s through next week (the normal high for this time of year is 77 degrees). Even up in Buffalo, New York, which almost a year ago suffered from a major early snowstorm is seeing temperatures more than ten degrees above normal, with tomorrow’s predicted high of 85 being 21 degrees above the normal of 64.

Upper level high pressure over Georgia is doing a good job of keeping most of the effects of some tropical low pressure in the Atlantic and Gulf of Mexico away. While Coastal Georgia extending to Augusta could see 2.5 inches of rain over the next three days, North Georgia is likely to see less than half an inch. Once whatever rain we get clears out of the Atlanta area by the end of the weekend, it’s likely to be this time text week before we get another chance at precipitation.

The Weather Service provided further confirmation to what it had been hinting at for the past several months yesterday, when it issued a news release reporting a developing La Nina condition. The expectation is that La Nina conditions will continue to develop over the next three months, and provide a wintertime La Nina weather pattern. This expectation is backed up not only by observation, but by computer modeling.

If La Nina conditions develop, what can we expect for this winter? According to statistics gathered during previous La Nina years, there is a 49% chance of less than normal precipitation in North Georgia from January through March, and a 60% chance that temperatures will be above normal. There’s only an 8 percent chance of below-normal temperatures, but there is still a 32% chance of above normal precipitation.

La Nina conditions occur when sea surface temperatures in the Pacific Ocean are below normal for more than three months in a row. It is the opposite of El Nino conditions, where equatorial ocean temperatures are above normal. The last time we had a La Nina episode was back in 2000.

This morning’s AJC front page features an article highlighting the possibility of 100+ degree temperatures this summer due to the drought. Somewhat skeptical due to their previous story predicting high temperatures, I found the article written by the Georgia’s Climatologist, David Stooksbury, who does indeed tell a tale of worsening conditions, and warm summer temperatures.

Stooksbury says that extreme drought conditions have expanded into 104 of Georgia’s 159 counties, compared to 95 counties back in early June, when tropical storm Barry brought some relief to the southeast part of the state. Barry’s benefits are fading quickly however, and Stooksbury echoes the predictions of others when he says that to break the drought conditions, we are going to need some tropical storms.

As you can see from the soil moisture anomaly map above, soil moisture levels are below 5% across much of north and west Georgia, indicating dry conditions normally seen only five times in every hundred years. Even with the rains from Barry, the southeast part of the state is seeing moisture levels expect only once out of four years.

While the lack of rain is taking its toll on your landscape, the drought is about to take a bite out of your wallet as well. Quoting Stooksbury,

“If dry conditions continue, high temperatures between 100 and 105 degrees Fahrenheit could become common in the piedmont region of Georgia. Highs between 103 and 108 could be common in the coastal plain. Even the immediate coast and the mountains could have temperatures in the middle 90s.”

So, with the best hope for drought relief being tropical weather, what’s happening with the climate? In March, NOAA predicted a change to La Nina Conditions this summer, which would point to a stronger than normal hurricane season. However, the sea surface temperatures which determine if we are in a La Nina or El Nino pattern haven’t cooled down in the central Pacific Ocean as much as predicted, and the Weather Service now says that La Nina conditions probably won’t develop until early fall.

If that’s true, then this year’s predictions of more hurricane activity than normal may be overdone. We’ll just have to hope that whenever tropical storms arrive, Georgia becomes the beneficiary of the rainfall.

The Weather Service is hinting that we may be moving into La Nina conditions as spring moves into summer. In a press release, the agency says the warm sea surface temperatures that characterize El Nino conditions are rapidly decreasing, and that cooler waters in the eastern Pacific are a sign of an upcoming La Nina episode.

If indeed we move into a La Nina cycle, the effect is likely to be a more active than normal Atlantic hurricane season this summer. Should the cool ocean temperatures persist, it could mean a warm and dry winter season next year in the Southeast. Other than the chance of increased hurricane activity, La Nina cycles don’t provide much influence on temperatures or precipitation in the summer in the Southeast.

Meanwhile, if it seems like it’s gotten a bit cooler than it has been, you are right. Last week’s temperatures were above normal, which makes the effect more apparent, but the overall weather pattern right now is similar to what we saw in early February. Of course, the increased daylight limits the cold air’s push into the south — in fact, aside from some cool nights, most of the weather effects will be north of the mid-Atlantic states. It should be warming up again soon, with expected above normal temperatures for most of next week.