Winter Forecast 2012-2013
First and foremost, I hope that everyone is doing better in the wake of Hurricane Sandy. Our entire area has been through a very rough time in the last month, and while most people’s lives are gradually restoring to normal, I know that many others are still struggling a great deal.
Winter Forecast 2012-2013
I was going to post a winter forecast of one line: “More snow than last year.”
Although this would have a good probability of verifying considering we only had 7 inches last year (and we’re more than halfway there already!), I didn’t think people would appreciate that forecast. So let me begin.
This year’s forecast is a remarkably difficult one, much more so than last year. What makes it so difficult is the fact that one of the most predictable long range indices, ENSO state, which has a significant impact on the large scale North America pattern, is on vacation this year. The El Nino which was expected to develop just in time for winter did not verify, so instead we have a neural or transitioning state of ENSO. This makes it harder to find analog years and ultimately make the long term prediction.
Even so, there are some different things that I have used to help us evaluate the current state of the atmosphere in an attempt to predict its future state.
I used several assumed conditions to create analogs. First, I went back and found similar winters where the Oceanic Nino Index (ONI) was near neutral because we don’t want an El Nino or La Nina year to skew the data. I then used current sea surface temperature anomaly plots along with CFS model predictions to highlight an area of anomalous ridging which I expect to be persistent over the north central Pacific. I compared this with some of these past years.
I like how the CFS shows this ridging persistent throughout the winter, dropping it slightly to the south and east. This is consistent with averaged placement of SST anomalies.
It is the strongest anomaly we see looking back during the past two months:
Even if we look way at the end of the current GEFS cycle, we still see that ridging continue to pop up in the central Pacific:
The placement of this ridge has allowed for a negative PNA pattern to persist much of the time, and this will likely continue through much of the winter.
Now on to the QBO index. We are currently in a strong negative state of the QBO. Analogs of past seasons with a strong negative QBO indicate above normal levels of high latitude blocking.
We have recently seen abnormally strong blocking and it looks to continue in the near future.
So I only chose years with stronger blocking.
All in all, I found eight analog years, but I waited them differently based on how well they fit with my current ideas.
Surface Temperature Anomalies:
All things considered, I think this winter will feature slightly above normal temperatures along with near to just slightly below average snowfall. This means that while I expect a harsher winter than last year, I wouldn’t go overboard based on the expected large scale pattern. We will see some very cold shots, but there will be a tendency for moderation. The mean storm track will likely be to our west, which will mean occasional disappointment for many snowlovers. But I would expect one or two major snowstorms which will require everyone to stay on guard. December will likely be on the warm side with closer to normal temperatures in January and February. The overall pattern will support a –PNA, along with a –AO/–NAO couplet.
Stay safe and let’s have a great winter!