Posted at 4:24 PM on January 9, 2012
by Paul Tosto
Filed under: Weather
Meteorologist Paul Huttner is a smart voice on Minnesota weather matters. He's been writing about the warm, weird winter on his blog. And this afternoon he answered some Frequently Asked Questions.
Q: Why has winter been so warm?
A: There may not be one specific reason. The jet stream has stayed unusually far north in Canada so far this winter. One reason is the so called Arctic Oscillation. It's been in a strong "positive phase" this year which means stronger westerlies and Pacific air masses for Minnesota.
Last year it was strongly negative, which allowed cold air and an undulating jet stream to blast us with snow. I've posted on this many times in Updraft. Here's the latest.
Q: Will the mild winter so far have any effect on Minnesota's spring, summer or fall?
A: No. Weather records show no credible correlation between winter weather and the following summer.
Q: Did forecasters predict this kind of winter? If not, what's changed between the prediction and reality?
A: Most foresters (NOAA, Star Tribune, Accuweather etc.) predicted a colder than average winter. They did this based on a forecast of continued La Nina conditions, which have weakened. MPR predicted a near average winter overall, but mentioned the possibility of the mild decadal trends overriding the cold for a milder than average winter.
From my late October post.
Decadal Trends: Our changing winter climate?Q: Is this a sign of future winter patterns in Minnesota?
Juxtaposed over the technical and dynamic factors that may control winter weather are so called decadal trends, which lean strongly in favor of milder winters with less snowfall for Minnesota.
Some facts from the past decade include:
-- 7 of the past 10 winters have featured significantly below average snowfall in the metro, (70% bias toward less than average snow in the past 10 years)
-- In those years the average winter snowfall has been 33.6"
(Roughly 22" below the 30 year average of 55.9"!)
-- 6 of the past 10 winters have featured above average temperatures
(60% bias toward milder than average winters the past 10 years)
The bottom line is, winters are trending milder in Minnesota, and while averages are made up of extremes on both ends, you can't ignore the background trend when looking at the potential for two colder and snowier than average winters in a row.
Variable: Decadal trends in winter temps and snowfall in Minnesota
Potential effect on Minnesota winter: Milder winters temps (especially at night) and a apparent bias toward lower winter snowfall totals.
Trend for 2011-'12: Increased odds for a milder winter with less snow than 2010-'11
A: Probably. As I said above, the decadal trends strongly favor milder winters in Minnesota.