We appear to have a VERY DIFFERENT winter on the way compared to the last. Last winter was exceptionally mild and snow-less for almost the whole country. This winter may be far more conventional if my in-house statistical and analog work pans out. The lack of a strong ENSO signal makes this years forecast more difficult than usual.
The primary methodology I use in making long-range outlooks, which give the AVERAGE of weather changes for a 30-90 day period, is called the analog or “analogue” system, as opposed to using computer simulations or pure statistical odds. You look at a number of key parameters and try to match past climate for similar conditions with the idea that what’s past is prologue. It works when the signals used to choose analog years remain stable or change only slowly. If there is a sudden flux then the system will fail, as I will have the wrong analogs. In other words when I choose analogs for the future I HAVE to make educated ASSUMPTIONS. And we all know what can happen when you assume, but in predicting it is unavoidable.
A note about the analog forecasting method used: Like when investing in a mutual fund, it’s best not to assume that past performance is any guarantee of future results. Past results just give us a guide that may or may not perform well in any given season, but long term results have proven to be better than a mere guess or climatology. IF weather history repeats itself based on the signals we have now, we would expect similar weather this winter to those in the past that had similar signals. Of course, similar is not the same as exact.
Over 24 complex global factors assessed in making this winter outlook:
(1) Strong warm +AMO more Atlantic energy input
(2) Strong cold –PDO (but some weakening) lower Pacific energy input
(3) Weak El Nino that is biased toward the central Pacific
(4) Possible La Nada or neutral ENSO
(5) El Nino with a cool October in much of the USA
(6) Temperatures northwest of Hawaii (to a large degree part of the PDO) maybe trending less warm. If it evolves colder, that is if the PDO weakens, it improves the chances of the +PNA favored eastern trough.
(7) Relative warm pool NW of Hawaii currently favors a mild SE winter
(8) Stratospheric warming - enhanced probability with continued low solar cycle, east -QBO, and low Arctic sea ice:
(9) Easterly -QBO years favor stratospheric warming events especially in low solar periods; we are heading toward a solar max but at low levels.
(10) Low solar output (sunspot low despite heading toward max in cycle) and low geomagnetic activity but uptick in UV activity per 11-year cycle. (There are multiple sun spot cycles of varying lengths)
(11) Volcanism: global cooling trends following 2009 volcanic eruption
(12) Atlantic Ocean warm-cool-warm pool tripole favoring –NAO/AO and Greenland high latitude blocking periods.
(13) “West based” El Nino vs region 1+2 based
(14) MEI ENSO measure flip and weak ONI and region 3.4
(15) Weak El Nino after multiple La Ninas
(16) Constructed Sea surface temperature anomalies analog model
(17) Summer US weather pattern and summer NAO pattern matches
(18) Hurricane season matches
(19) WPO/EPO index tracking (Siberian Sea-Bering Straits and Gulf of Alaska blocking)
(20) Perusal of global climate computer model projections
(21) Arctic sea ice coverage, Hudson Bay and Gulf of St. Lawrence low ice, Northern Hemisphere snow cover amount and trends Eurasia/North Canada.
(22) Month to month, month to season and season-to-season persistence charts
(23) Jet stream cycle patterns for October and November
(24) Colder stratosphere compared to record warm near-space atmosphere last winter
It is the RELATIONSHIPS and INTERACTIONS of all of the above that determine the long-term weather over the course of seasons.
The initial total analog years listed below is adjusted for “best fits” for the final forecast.
1894,1904,1911,1914, 1915,1916,19171939,1944, 1951,1952,1953,1957,1958,1960,1961,1962,1963,1964,1965,1966,1968,1969,1970,1972,1973,1976,1977,1978,1979,1981,1983,1986,1987,1989, 1990,1991,1993,1994,2000,2001,2002,2003,2004, 2005,2006,2008,2009, 2010,2011.
BEST FIT ANALOGS FOR NOW: 51,52,53,57,62,63,65,66,68,69,70,72,76,77,79,84,86,94,02,04,06,09
No two ENSO winter seasons are exactly the same, and weak El Nino winters in particular can be vastly different lowering confidence in the long-range forecast compared to strong El Nino or strong La Nina winters. What is more difficult about the progression of the current ENSO state is that in the 63 years of keeping stats on El Nino/La Nina this one so far is unique. In those 63 years we’ve never seen an El Nino form in summer and fade in September.
Given a weak EL Nino or possibly neutral, the strong cold north Pacific Ocean or negative phase of the Pacific Decadal Oscillation and the warm Atlantic tripole or positive Atlantic decadal oscillation are expected to be the more significant climate drivers of the winter season.
Research has shown that REGARDLESS of the Pacific Ocean ENSO condition, a negative AO/NAO winter will be cooler than normal, as will a winter with a negative east QBO. Unfortunately, the NAO/AO (a measure of North Atlantic jet stream blocking or lack thereof) can only be reliably predicted a couple weeks in advance at a time. Months in advance --like must be done to make a winter outlook --we can only make our best guess of the NAO/AO based on the above listed signs. The AO in the winter of 2009-10 was the most negative on record since we began tracking it in 1950 whereas last winter the AO was the most positive on record! Such a big wild card can toss our best long-range outlook efforts under the bus due to the “Black Swan” effect.
As you and I know, there is nothing carved in stone or certain about ANY seasonal outlook. There are many variables which impact seasonal weather that are NOT completely understood. So weigh my research with that in mind. But history HAS been known to be a bell-weather of potential seasonal weather trends and this will be an interesting one to monitor. Given the climate extremes of the most recent decade the most unexpected outcome for this winter might be perfectly “normal” or average, since the nation has seen so little run of the mill weather in recent years.
MY PRELIMINARY OUTLOOK FOR GEORGIA FOR WINTER 2012-2013:
Near-normal to a little below-normal temperatures, but not persistently or consistently cold all winter, but a couple significant arctic blasts.
Cooler than last year.
Above-average odds of snow and/or ice.
The accompanying maps may not match exact as I subjectively adjust analog results to some extent