The Mount Washington Valley has been slammed by extremely cold arctic air for well over one week. Maximum temperatures have remained in the 20s while morning low readings have dipped into the single digits. Strong winds have also persisted during this time, which has resulted in a wind chill factor of up to -20 degrees. The recent bout of arctic air is not only a record breaker, but is also assisting to produce enhanced snowfall and Nor'easter occurrences in much of the northeastern United States.
For those of you who yearn for cold and snowy weather, you can partly thank a powerful and mighty low-pressure system that is located far away from our lives. Referred to as the polar vortex, this system is one of the main elements that contribute towards North Conway's worst winter weather. During the autumn months, a strong disturbance in the jet stream develops into an intense circulation of cold air over Canada. This low-pressure system often moves very slowly and (at times) is stationary during the winter months.
The polar vortex always develops a series of frontal boundaries that continuously spin around its center. These fronts act as barriers between warm and frigid air. It is important to realize that the position of the low-pressure system is extremely crucial for its affect upon our lives. For instance, if the Polar Vortex were to be centered over Hudson Bay, much of the arctic air would affect the upper Midwest. Any shift eastward would bring the chill towards the northeastern portion of the United States. The position of other low or high-pressure systems can also affect how far south the arctic air reaches.
El Nino's can influence the significance of the Polar Vortex. During October, a broad high-pressure system developed a ridge across the western United States. This blocked a prominent Pacific Ocean airflow from affecting North America. At the same time, a large trough (area of low-pressure) developed across the eastern portion of the United States. The presence of the Western ridge aided to slightly shift and position the Polar Vortex to produce cold bouts of chill across the eastern United States. At the same time, a somewhat weak El Nino became strong enough to affect our weather by producing a stormy pattern with Nor'easters. This resulted in a very snowy and cold November.
The Pacific jet stream is expected to soon become prominent across the United States after one more plunge of arctic air. This jet stream developed because of cold air across eastern Asia. It then slid into the Pacific Ocean where it merged with an enhanced subtropical jet stream because of El Nino. On the edge of this stream of Pacific airflow, a series of storms will develop and weaken the western United States ridge. This will then translate into repositioning the Polar Vortex and the melting of snow cover, which in turn modifies our air towards average conditions. However, before the end of December, we may very well see another series of arctic fronts blasting their way into North Conway.