Winter Returns With a Vengeance
If you are in the snow and ice industry, it is hard not to take note of the mild weather as of late. After a cold start to the New Year, negative temperature departures across the region have all but been wiped out. With even milder weather expected through the upcoming weekend, temperatures through the 15th will undoubtedly average above normal. However, don’t pack up your coats or plows just yet – as cold weather is expected to make a triumphant return for the second half of the month!
Just to be clear, by cold weather we don’t mean typical “middle of the winter” cold…we mean exceptionally cold – perhaps some of the coldest weather we’ve seen in the past few years cold! Although things are often far from certain in medium and long-range weather forecasting, confidence for this upcoming event is above average…with things not panning out being rather unlikely. Why all the confidence all of a sudden, you may ask? It must be that the NAO is trending negative– right? Wait, could it be the PNA will force a ridge out west and shift the cold anomalies east? Actually, the reasons for this upcoming cold shot lie outside many of the traditional tropospheric oscillations that meteorologists tend to look at. Instead, to find the key to this forecast you’d have to travel to an altitude of almost 70,000 feet above sea level – and into the stratosphere. This phenomenon is commonly referred to as a “Sudden Stratospheric Warming.”
Although many people outside the weather industry may be unaware of Sudden Stratospheric Warming Events, they are an important tool for forecasting cold outbreaks across the eastern half of North America during the winter months. In its simplest terms, quick spikes in temperature across the high altitudes of the stratosphere (~ 10 – 50 mb or 65, 000 – 75,000 feet) are statistically correlated to cold weather outbreaks across this part of the world. Such warmings have been linked to significant cold outbreaks in the past. For instance, a sudden stratospheric warming preceded major arctic outbreaks in 2004, 2006 and 2009. Another interesting fact about these events is that these “cold shots” tend to come in discrete packages around 6 and 10 days after the initial warming…then again to a lesser extent 30 and 60 days later on. With January 10th marking the peak of the warming from this event (temperatures have begun to cool slightly as of earlier this morning), expect an initial bout of cold weather near or around the 16th, with more of a significant cold shot on approximately the 20th…with the possibility of chillier than average temperatures being enhanced by early February. The attached images are 850 mb temperatures from the control run of the ECMWF Ensemble Forecasting System. Note an initial cold shot around the 15th (nothing that out of the ordinary for late January) followed by a more exceptional cold outbreak by the 21st. Should this occur, readings of this caliber at 850 mb would likely translate to surface temperatures in the single digits and teens for highs, with lows dropping well below zero for some parts of the region.
Although these cold outbreaks tend to suppress significant winter weather events, we will undoubtedly have our fair share of snow threats at some point during the time period – as it is extremely rare to have such a prolonged stretch of dry weather during the heart of winter. The most likely times for this to occur would be during the “brief reprieves” from the extreme cold. As of now, we here at WeatherWorks are highlighting a period between the 16 – 21st, and again from the 25 – 30th for an enhanced risk of a widespread significant snowfall. Additionally, chances will be increasing for several low-end events during the interim of these periods.
Interested in receiving more frequent updates on future weather events? Contact Kevin Hopler (kevinhopler@weatherworksinc.com) to inquire about our Long-Range and Winter Risk products for more information.
