5th Annual Winter Forecast
The winter of 2011-2012 forecast was a challenge in that the previous few winters have begun to display an overall change in the northern hemisphere patterns. These are shifts from what we’ve seen in the 2000’s – 1990’s and resemble the 1960’s. The challenge is determining whether this is a long term cycle or something more short term. Obviously this is what makes long range forecasting an extreme challenge.
The QBO is currently reversing to a negative or easterly phase as we head into late fall and winter. The easterly phase of the QBO is seen to be more favorable for -AO and blocking schemes. The eastern momentum of the -QBO can weaken the strength of the polar vortex and lead to SSW events over the poles. As far as timing this winter’s -QBO with past winters, many of the all time great winters such as 1995-1996 and 2002-2003 were entering a negative phase late in the year preceding winter.
2011 has seen a moderate to strong La-Nina this past winter fade back to ENSO neutral conditions. Over the last few months we have seen a weak La Nina begin to develop once more and will likely see this continue through 2011 into early 2012. The discrepancies currently surrounding ENSO seem to be whether this will trend into a moderate La-Nina or if it will simply hold serve and remain weak or perhaps fade back to neutral by late winter.
Earlier in the fall sub-surface data as well as the CFS model were hinting at a solid moderate La-Nina developing this winter. However, as we have progressed through fall the much more reliable suite of statistical and dynamical models continue to show a weak La-Nina with the potential of neutral conditions by late winter. This combined with the overzealous CFS leads me to assume we will see a weak la-nina winter with the outside chance of neutral conditions by February.
The PDO has seen a strong negative shift in recent months. This bears no surprise given the solid cold pool developing over the gulf of Alaska. This is also in conjunction with the warming over the western and central North Pacific. With the continuing La-Nina and recent string of -PDO months (16), as well as factoring in the cyclical nature of the oscillation, I see nothing to convince me this winter will not average negative once again.
The AO and corresponding NAO continues to be the hardest oscillation to predict. The phenomena is not understood as well as the PDO and ENSO. However, we can view past data and see it does tend to run in long term positive and negative cycles. The main reason the winters of the 60’s rest in historical lore (at least in the southern mid-Atlantic) depend on this one oscillation. The provided link below can give you a graphical picture of this.
The most recent winter-time declines in the AO has been historic in nature and has no precedence since the 1970’s. This to me seems to signal the start of a new cycle in the oscillation downward. How long this lasts and the year to year variance is what makes long term forecasting very hard.
The best research into forecasting the AO seems to be matching the sunspot min/max cycles vs. the positive/negative QBO cycles as mentioned above.
The analogs this year seemed to fall into place faster than last year for me. These are mainly determined using an ENSO-PDO-NAO statistical and graphical SST analysis. I generally do not go before 1960 due to limited northern hemisphere SST graphics.
The primary analog I narrowed down to this year was 1962-1963 with secondary analogs of 1967-1968 and 2008-2009. These years seemed to fit what I look for in a year long comparison, as well as falling into line with the expectations I have for the future ENSO/PDO/AO evolutions.
In general my analysis leads me to believe we will see a winter that is gradually taken over by the NAO. The analogs I reviewed lead to the cold peaking in February over the east coast, with perhaps the best chances of snow in January. There were mixed signals for December, some very warm and very cold. At this time I am leaning towards a colder December due the fall pattern being a closer match to the colder December analogs. However, I am the least confident on December. My confidence does increase, however, as we go through January and February.
This year I am trying to present my thoughts in a more pattern specific layout. I am trying to “put a little sugar on it” to quote Deion Sanders. This should make it more user friendly and possibly help display my pattern thoughts as well as the intricacies and changes month by month I foresee. In the past I have only used precipitation and temperature.