The primary method I apply in making long-range weather forecasts (short-term climate outlooks) is called the analog method. Its premise being what's past is prologue. Or put another way, similar past conditions should result in similar future conditions, or what has usually happened in the past may be expected to happen in the future. I also apply other techniques with lesser weighting. This year, due to a number of unprecedented or close to historic ocean-sun-atmosphere signals finding solid analog years has been especially problematic. Stronger La Nina years have a lot of variability, so I could not be shocked by a half way decent snow, nor at all surprised if there turns out to be nary a flake. Remember, Atlanta's 30-year "normal snowfall" is only 2 inches. So it doesn't take much to go above average even in a warmer winter, but it also means not getting much is par for the course, so expecting accumulating snow in the deep south is foolhardy in most years.
When it comes to forecasting the future using analogs, it is important to remember: Similar does not mean the same, and usually is not always--analogs or "look-backs" are predictors of the future, but we can not expect them to tell the future with precision-- they provide a guide to expectations, a guide but not a road map. We find close matches to the past to predict the future, but we don't find exact matches. The number of natures outcomes is too infinite to allow for a perfect prog. The full explanation of methods, techniques and research results are reserved for my private paying clients. This is a simplified version for your enjoyment.
What about this winter?
Much warmer than last winter and much less snow than last winter, closer to the long-term average. But the changeability and volatility means there should be some excitement this winter! The greatest change from last winter will be the lack of persistent and consistently cold weather all season long. It also looks like some extreme swings where there will periods where the cold does get our attention, but also periods where a warm spell really gets noticed for more tee times than in most winters. Frequent snows like last year are unlikely to repeat.
Another front-loaded winter, off to a fast (early) start but fades down the stretch: so a bit cool start and end, warmest in the middle.
Odds of a MAJOR snow or ice storm quite small but not zero. Slightly better odds of ice problems than snow but still low odds.
A drier than normal winter--below normal precipitation--with less than normal snowfall.
Temps averaging above normal, but not ALL golf weather either due to changeability and volatility.
Above normal risk of severe thunderstorms in November, January and March.
So not QUITE a "year without a winter", but in comparison with last winter it may almost seem that way.
At least one or two cold waves with lows in the teens or colder is still likely in the midst of a generally warmer winter.
In terms of snow and sleet, out of the 15 past moderate or strong La Nina winters in Atlanta only ONE was above average (by one inch). So the odds overwhelmingly favor less snow than last year's official 5.3 inches, at best near-average. Temperature-wise weaker La Ninas can give us cold, but in the past the stronger La Nina winters are almost never colder than normal December through February, but some past LA NINA years have had remarkable brief cold shots.
In terms of freezing rain (ice storm) Atlanta averages a 20% chance in any given year or one in every five winters on average. Out of the past 15 moderate or strong La Nina winters only 13% or two had a major ice storm, but a few had minor icing. But the odds are against getting even a minor ice storm, as 60% of past La Nina winters had zero ice accumulation.
So at this point preliminary indications are that the odds are high that this winter will NOT be colder than normal and will NOT have a significant snow or ice storm.
Only 2 of the 15 La Nina years analyzed had significant ice, none had significant snow, and only 1 of the 15 was cold.
Of course La Nina is just one factor looked at, the full analog list of past years with at least some significant similarity to antecedent conditions to this year are:
1889, 1892, 1903,1904, 1909, 1911, 1916, 1924, 1933, 1942, 1948, 1949, 1950, 1951, 1952, 1954, 1955, 1956, 1957, 1959, 1962, 1963, 1964, 1965, 1966, 1968, 1969, 1970, 1971, 1973, 1974, 1975, 1976, 1977, 1978, 1980, 1983, 1984, 1988, 1989, 1993, 1995, 1996, 1998, 1999, 2000, 2003, 2005, 2007, 2008, 2009.
Out of these, this is the list of some of the better matches:
1904, 1916, 1942, 1949, 1950, 1952, 1954, 1955, 1964, 1966, 1970, 1971, 1973, 1974, 1975, 1984, 1988, 1993, 1995, 1998, 1999, 2000, 2003, 2007.
The main drivers of the winter climate are expected to be: rapid onset moderate to strong La Nina following a strong El Nino, a cold PDO, warm AMO, low solar cycle, and west QBO.
The fine-tuned analog lists shows a December through February temperature pattern for Atlanta of between 0.38 F and 1.12 F degrees above-normal, with rainfall between one-half inch and 1.42 inches below normal. Snowfall at least 0.6 inches below normal or between half an inch and 1.4 inches.
IF there is snow it's more likely to be early or late. The highest snow amount in analog years was 4.8 inches in 1959 and 4.5 in 1933. There was at least a dusting of snow in 74% of the analog years in either winter or spring, ranging from November to March.
The known wild cards for this winter? If the NAO is more negative than I expect (blocking pattern) the winter will be much colder than I am forecasting. If the La Nina ends up being more west based than I am expecting, then the winter will be much warmer than I am forecasting with frequent golf weather. See the maps and charts of the winter forecast here.