Most of October was very warm. In fact, it was the fourth warmest on record by average temperature in Colorado Springs and Pueblo. We only started seeing flakes flying right around Halloween. But now - only a week later - we're living in a snow globe. So what gives? As with most weather patterns of this scale, a lot of it comes down to a meteorological concept called teleconnections. A teleconnection is a large-scale semi-permanent weather pattern that changes slowly leading to changes in our storm tracks, temperatures and more.
For us, a pattern near Alaska called the Pacific North American Oscillation (or PNA) is typically one of the most important. In this case, it is a factor (and something to talk about another time)..but something less common is happening too.
With this storm system...a pattern called the Madden-Julian Oscillation (MJO) is at play. The MJO is a pattern of higher rainfall and moisture that sometimes develops in the Indian Ocean...about 11,000 miles from us here in Colorado! This enhanced rainfall pattern then moves east over the Pacific Ocean over a couple of months and eventually changes the shape of the jet stream over the U.S. That's happening now - and we're getting more storms as a result. The complexity here is that the MJO is a tropical weather pattern. So it's not directly enhancing rainfall and snow for us. Instead, it's disrupting big wind circulations that transport air from the tropics, up to the mid-latitudes...where we live. That's how it ends up changing our jet stream - and in some cases enhancing storm energy in the middle atmosphere. Also adding to the fun: the MJO isn't always active. It does impact our weather a few times a year, but it's not a constant part of U.S. weather science.
The second thing we need for lots of snow is cold air from the Arctic. So let's talk about another big weather pattern. The Arctic Oscillation. The A-O... for short... measures whether pressure over the Arctic is higher or lower than usual. Right now… it's lower than usual. And when that happens… high pressure can sit over the eastern U.S., like it's doing now.
Putting these ideas together… our jet stream is very wavy right now… and we have a lot of energy coming in from the Pacific. As cold air surges south from the Arctic… low pressure is pulling in wet air from the Gulf of Mexico… and high pressure over the central U.S. is gumming up the works and keeping storms spinning over us. It's a perfect recipe for a lot of snow.
As of today… Colorado Springs is in second place for the most snowfall in the first 10 days of November on record. To achieve the snowiest November on record, we need at least 26.3 inches of snow in the Springs. We'll be in the running.
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