In recent seasons, I have been requested to write a seasonal outlook for North Dakota State Climatologist Dr. Adnan Akyuz for his climate bulletin that is issued quarterly. Attached below is what I wrote for the upcoming Winter Climate Bulletin that will be published shortly.
Perhaps because North Dakota?s climate has more cold days than warm days the interest in winter outlooks seem to garner the most attention. The winter of 2010-11 is expected to follow the trend of recent years with colder than average temperatures dominating much of the season. Plus, current projections would also suggest above average precipitation for much of the state as well.
Many of you have likely heard that La Nina conditions are currently occurring in the Pacific Ocean. A La Nina is the cold water equivalent to El Nino and is part of a recurring atmospheric oscillating pressure pattern between the western and eastern portions of the equatorial Pacific Ocean. A La Nina often leads to colder than average temperatures for this part of North America as it influences the upper level wind flow in such a way that arctic air frequently moves into the northern plains.
Although La Nina conditions are a good tool in forecasting probable winter conditions, it is only one of many factors in a complex array of atmospheric and oceanic interactions that influence weather patterns across the northern hemisphere. Unfortunately, several of these other factors also suggest a higher probability for colder than average temps for this entire region.
One of those other factors is a phenomenon referred to as the Arctic Oscillation (AO). The AO is a climate pattern characterized by winds circulating counterclockwise around the arctic. When the AO is in its positive phase, a ring of stronger winds circulating around the North Pole tends to keep the coldest air in the higher latitudes. In the negative phase of the AO, this belt of winds becomes weaker allowing arctic air to more readily move southward bringing bitterly cold air to the state. Although accurate forecasts of what state the AO will be in is difficult beyond a few weeks, recent weather patterns hint that the AO will, like last winter, be frequently in the negative phase.
Other factors leaning toward cold conditions are the above average early snow cover across the Northern Hemisphere, a continued quiet Sun, active volcanic activity and the current state of oceanic temperatures around the globe.
Forecasting long-term temperatures, albeit imperfect, is easier than precipitation. In our relatively dry climate, one or two storms missing or hitting us often make the difference between average and very wet conditions over the course of any three-month period. Using the past as our guide, the odds favor the winter to finish at least near average and more likely above average for precipitation during the December through February time frame for most parts of the state.
The North Dakota State climate office has links to the National Weather Service?s local 3-month temperature outlooks for the upper coming year. Those outlooks can be found here: http://www.ndsu.edu/ndsco/outlook/L3MTO.html
The latest winter outlook from the Climate Prediction Center (CPC) is predicting an above average probability of a colder than average winter with equal chances for the winter season to be either average, above average or below average for precipitation for most of North Dakota with the exception of the far western portion of the state where CPC has an above average threat for above average precipitation.
Those outlooks can be found at http://www.cpc.ncep.noaa.gov/products/predictions/.