A Winter of Ups and Downs
Since November the weather pattern has been one of extremes. There have been major fluctuations between very warm and very cold as well as periods of wet and dry.
Whether it was the very warm weather we experienced at times in November or the severe cold waves in December and early January, the extremes have affected all 50 states and all of North America. Instead of one pattern setting up shop and sticking around, it has been a roller coaster of up and down with temperature and precipitation extremes.
This past week has been a good example. It began with a severe outbreak of Arctic air that sent temperatures past -40F in portions of the Central Rockies along with snow moving into the Deep South and Mid-Atlantic states.
Rain, freezing rain and snow moved in the Pacific Northwest with flooding and heavy rains in California and into the interior west. Even places like Boise, ID which usually enjoy temperate winters have had record cold and snowfall.
Is there any particular reason for the rollercoaster ride this winter? The answer is yes, partially due to a unique set of large scale weather patterns working together.
It has been observed that if there is no major overriding climatic pattern (such as a strong El Nino or strong La Nina, etc.) then there is the possibility of highly variable weather patterns.
The graph below shows the amount of variability in a winter season correlated with major climatic patterns.
This winter we are in a very weak La Nina weather pattern (cooler Pacific Ocean). As you can see in the graph, when we are in neither an El Nino or a La Nina (also known as a La Nada) we can have a rollercoaster winter season. So far, this winter season this has been the case. In years when we are in either a strong El Nino or La Nina, the weather patterns are likely to be more stable.
With no major shifts in the current weather pattern expected in the coming months, be prepared for more rollercoaster rides this winter.