Where's Winter? The Storm Team explains
Scroll down for an in-depth video from Dave Longley
(WSYR-TV, Syracuse) -- Where is winter? It seems like an obvious question, given the paltry snow and the consistent bouts of warmth over the past couple of months. We found that on average this winter, the longest stretch of days that we went between 50° was...nine. To me, that was truly incredible. I also feel it’s a sign of the inability of cold to stay locked in here across Central New York.I’m no expert in global circulation patterns. In the words of Don Henley, “I make my living on the evening news.” I love the day-to- day forecasting of the weather, and while I do keep an eye on the longer range and global weather patterns, what I present here are just my observations on what I think is happening. Frankly, I don’t know of anyone who knows specifically why this winter's been so warm, and I’m sure this winter will be a source of plenty of research in the years to come.
As Jim Teske stated in his blog, we’ve seen winters like this before, both in terms of warmth and lack of snow. If you look at the top 5 least snowiest winters in Syracuse, we get about one of these winters once a decade. The exception to that rule is the decade of the 70s.
One factor that I think got us off and running to the warmth this winter, was the hot summer over the Continental US. The drought in the south-central US helped build a surplus of heat, which had to be dissipated. That energy just doesn’t disappear, so I wonder if perhaps that helped keep us warm through November and December? Anytime the wind blew from the south, it would seem that we would tap into some of that warmth.
Yes, we’re dealing with a moderate La Nina. In fact, word came in just this afternoon (Thursday, February 9) that the La Nina will totally dissipate by late Spring. Again, La Nina is a pool of anomalously cold water in the equatorial Pacific Ocean that affects the jet stream circulation across the world. While La Nina likely plays some role in this winter’s weather, as we go through the winter, mechanisms farther north in latitude tend to take over control of our weather. Face it, we’re a long way away from the equator, and as time goes on, things like the magnitude of the arctic oscillation tend to dominate our weather more.
What is the arctic oscillation or AO? The arctic oscillation looks at the surface pressure pattern between the arctic and mid-latitude portions of the northern hemisphere. It can have two phases...positive or negative. In the positive phase, the surface pressure over the high latitudes is high. This causes the reservoir of bitter cold air to remain primarily locked over the polar region. Ask the people of Alaska just how cold this winter has been. With the cold locked to our north, milder, Pacific air can dominate the weather in the lower 48 and southern Canada, keeping temperatures mild.
Image courtesy of NASAI’ve attached a map showing the surface temperature anomaly for December and January. The area of yellow represents an area of above to much-above normal air that has dominated the weather over Canada and much of the US. We’re included in that above normal area.
When the arctic oscillation is negative, the air pressure in the polar regions is lower. Thus, it’s harder for the bitter cold to remain locked up at the north pole. The cold air drives southward, usually across the eastern half of the US. Sometimes, the jet stream can get blocked up to where we can see a consistently cold and snowy pattern set up for several days or weeks. The map shows the surface temperature anomalies for December and January of LAST year, and you can clearly see the area of blue, or abnormally cold air showing up in Canada, and the eastern US. Also, the area of red, or unusual warmth showing up just west of Greenland is an indication of the “blocking” of the jet stream and the position of the upper level ridge.
The differences between last winter and this winter are pretty remarkable. Here’s another tidbit: We measure the strength of the arctic oscillation, what follows is the plot of AO from December 2009 vs. December 2010 vs. December 2011. Thanks to Stu Ostro from the Weather Channel for providing this image on his Facebook page. You might remember just how cold and snowy December 2010 was. We had over 70” of snow in Syracuse, making it the snowiest December on record. Notice how low the AO was. That’s about as low as we’ve ever seen it. We feel this low AO contributed to snowstorms along the east coast and the unusual cold and snow as far south as Florida. You might remember the Boxing Day snowstorm that clobbered NYC in December of 2010.
Compare that to the AO plot from this December, where the index was strongly positive. We had very little snow and unseasonably warm air for the end of 2010.
It’ll be interesting to see how all this unfolds over the next couple of weeks. The AO has been trending negative, and the cold air has been moving around. This has resulted in 400 deaths in Europe. We’re also expecting a brief visit from the cold this coming weekend. The problem is that the overlying jet stream circulation is one that doesn’t favor this cold pattern settling in for an extended period of time. As has been the case so often this winter, the cold can get in here, but it doesn’t stick around long.
What does this mean for Spring? Good question. We don’t portend to have all the answers, but we will take a stab at all that’s given on NewsChannel 9 on Thursday, February 23.
"Where's Winter" Video: Storm Team Chief Meteorologist Dave Longley
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