Long range forecasting can be very difficult whether it is looking two weeks out or up to a whole season out, but meteorologists look for clues in the larger weather pattern to help. One of those clues is looking at recent remarkable weather that has occurred and what has followed those particular events. For example if the Mid-Atlantic or Northeast had a wet month, does that mean the next month is wet or dry? Some times the answer is obvious. Other times not so much.
The Pennsylvania State Climatologist office at Penn State did a recent study looking back at December 2020. The remarkable features that were noted include a wet Northeast, a dry upper Midwest, and a warm Northern Rockies weather pattern. A list of similar December weather patterns were compiled. The list included the Decembers of 1896, 1900, 1939, 1954, 1957, 1962, 1979, 1986, 1993, 1997, 2002, 2003, and 2014.
The next step is then to average the conditions of the Januarys that followed the analyzed Decembers. The results that followed demonstrate a two notable pieces of the forecast puzzle for this January. Conditions should turn colder than average, which we have not achieved yet. However, model forecasts do show colder trends after the next 7-10 days. The other result from this analog study is a drier Ohio Valley and Mid-Atlantic, including Pennsylvania. This result could suggest that our weather does turn cold enough for wintry weather, but the storm track may not exactly line up.
There is one other thing to consider. January 2015 featured a strong cold spell caused by the movement of very cold, Arctic air southward into the United States. This movement of Arctic air was caused by a disruption of the polar vortex (for more on what the polar vortex is, check out Adis Juklo’s story: https://www.abc27.com/weather/what-is-stratospheric-warming-and-how-does-it-affect-our-weather/). We could see a similar pattern over the next 2-3 weeks develop for parts of the United States with direct impacts from much colder air. We will wait to see how the rest of this month plays out!