The Winter Solstice is still 47 days away (December 21, 2018) and there are three main factors that will be driving the pattern. A weak to moderate “central-based” (Modoki) El Nino, a positive PDO (also known to some as the “warm blob” of water south of Alaska) and a Solar Minimum are increasing the odds of several big snow events across the National Capital Region this Winter.
I expect at least two significant snow events this Winter across the DC Region:
Current Sea Surface Temperature Anomalies:
The current sea surface temperatures depict weak El Nino conditions with the warm water extending well into the central Pacific. “Central-based” El Nino events are referred to as “Modoki” and in the past have been a “cold signal” for the Winter temperatures across the eastern United States. El Nino in general, favors a more active southern storm track increasing our odds of Nor’easters coming up the coast.
Also of note (in the map below) is the warmer than average sea surface temperatures south of Alaska which is referred to in Meteorology as a positive Pacific Decadal Oscillation (+PDO). This warmer water tends to shunt the northern branch of the jet stream northward across Alaska forcing a trough of low pressure to develop across the eastern United States and allowing for arctic air to drop southward out of Canada.
Weak to moderate El Nino conditions are forecast to continue through the upcoming Winter:
Solar Minimum Cycle:
Several studies have suggested that solar minimums during winter may have a correlation with snowy winters across the DC Area. The last solar minimum occurring during winter was in 2009-2010.
December through February Temperature Anomalies (departure from average) during past Modoki El Nino Events:
December through February Precipitation Anomalies (departure from average) during past Modoki El Nino Events:
Breaking down the analog package into individual months (December, January and February) we get the following trends:
December 2018 (Looking cooler than average with precipitation near to slightly below average):
January 2019 (Looking cooler than average with above average precipitation): Excellent pattern for a big snowstorm around DC!
February 2019 (Looking much colder than average with average precipitation): Decent pattern for several snow events around DC!