Our cold winter just might be turning warmer

Last October I did my annual winter forecast for the southeast and theirs no denying I blew the temperature forecast big time! I relying on some long range modeling and teleconnections that pointed to La Nina having an influence on us with mild and dry conditions. I did though feel that much like last winter the negative N.A.O (North Atlantic Oscillation) and the negative A.O. (Arctic Oscillation) would help cancel out some of the effects of the La Nina. I just didn’t foresee how negative both indices would get. The net results of these 2 indices being negative especially the A.O, which may have been at record low readings, has resulting in the second coldest winter in the past 69 years here in Charlotte. Here is what these 2 indices do to our weather patterns across the southeast.On the left in the figure you can see the impacts of a positive A.O. on the left and a negative phase on the right. Notice how when the A.O. is negative both Europe and the eastern U.S. have really cold winters. You also will notice that Greenland and parts of eastern Canada have warm winters.
When you look at the effect of the N.A.O you have very similar impacts when this index goes negative.

             Positive  N.A.O                                                          Negative N.A.O

Looking at these 2 indices you can clearly see why we had such a brutal stretch of cold weather the past 2 months. Though notice the forecast 10-14 days out into middle and late February. You can see for the first time in almost 2 months these indices are going positive. Which will likely mean a significant warming trend for late winter. This is no grantee that we’ll be done with the cold and snow, but likely those cold episodes will be fewer and shorter lived later next month. I also should note here that climatological Charlotte has it’s biggest snows in February and March. This is due mainly to better timing of the moisture and cold air as the cold air is retreating and warmer air is coming north.

Here is where we stand today across the southeast for ranking the coldest winters in the past 69years. The numbers represent the ranking this winter for coldest mean temperatures so far, through Jan 27th, 2011. We’ll see if this late winter warm spell will be knocking us further down the list but with 2 solid months of cold it’s not likely 2-3 weeks of warmer weather in February will have much impact on the final numbers.