One of our favorite weather blogs that we love to follow here at OpenSnow is the Wasatch Weather Weenies. The Wasatch Weather Weenies discuss the weather and climate of the Wasatch Front and Mountains in Utah, western United States, and beyond.

Participants include aspiring and old-school atmospheric scientists, weather enthusiasts, powder snobs, and poor souls enrolled in classes taught by University of Utah Atmospheric Sciences Professor Jim Steenburgh. Many posts feature content or insights enabled by the support of the National Science Foundation, Office of Naval Research, and the NOAA/National Weather Service. 

Yesterday featured a blog post about one of the most important large scale modes of climate variability, the Arctic Oscillation. In a definition taken directly from the National Climate Data Center, the AO is a climate pattern characterized by winds circulating counterclockwise around the Arctic at around 55°N latitude. When the AO is in its positive phase, a ring of strong winds (the jet stream) circulating around the North Pole acts to confine colder air across polar regions ("bottling-up"). This belt of winds (the jet stream) becomes weaker and more distorted in the negative phase of the AO, which allows an easier southward penetration of colder, arctic airmasses and increased storminess into the mid-latitudes ("buckling").

Source: NOAA

The author of yesterday's blog post, Peter Veals, decided to take a brief look at the Arctic Oscillation Index and its potential impact on monthly snowfall in the Wasatch of Utah. Peter looked at the correlation of the monthly mean AO Index and monthly snowfall at the Snowbird SNOTEL site. He plotted the the AO Index versus total monthly SWE (snow water equivalent) at Snowbird for the period 1991-2014. The red line is the best fit line or the line that best represents the data on a scatter plot.

Source: Wasatch Weather Weenies

Peter's results were not encouraging. Below are the R-squared values for each month. A value of 1 would indicate a perfect fit for the line of best fit. 

November: 0.03

December: 0.16

January: 0.01

February: 0.12

March: 0.00

April: 0.16

In other words, the AO Index has no correlation to snowfall at Snowbird in November, January, and March, and a very slight correlation for the rest of the winter. So as you can see, the AO overall is not of much use for predicting snowfall in the Wasatch on the monthly scale.

Peter went on to explain that while medium-range weather forecasting (out to 10 days) has become increasingly skilled in the computer age, seasonal prediction is still in its infancy. Also, the Arctic Oscillation is calculated over the entire Northern Hemisphere, and there are other climatic oscillations such as the Pacific Decadal Oscillation (PDO) that capture more of the conditions that impact western North America. 

As you can see below in the observed & ensemble mean forecasts, the Arctic Oscillation is currently in the negative phase but is trending towards the positive phase. 

Source: NOAA - Climate Prediction Center

Will the forecast hold and keep colder arctic airmasses and increased storminess "bottled-up"? Remember, this is only one teleconnection and for the Wasatch of Utah, it's a weak one at that. 

Sam Collentine | OpenSnow