December 17, 1946: Heavy snow is reported along with strong wind across northern Minnesota. Duluth has winds up to 62 mph.
Thunder & Lightning in mid-December? It's Complicated
So this is what December is supposed to feel like. The first half of December was nearly 14F warmer than average in the Twin Cities with 7 nighttime lows at or above 32F. Remarkable.
What's really going on? It's over-simplistic to point to only El Nino. Yes, that's a huge signal, but so is the additional warming of the atmosphere and oceans, which will make 2015 the warmest year on record, worldwide by a very wide margin.
But the Arctic Oscillation (AO) is another big factor in our persistent warmth; a strong positive value reflecting unusually low pressure over the Arctic region. When this happens the dreaded polar vortex tends to stay over far northern latitudes, with fewer intrusions of Siberian air into the USA. We've seen a positive phase most of autumn; no signs of an imminent shift that would divert polar air into Minnesota.
Until and unless that happens we'll see more slop-storms with temperatures near freezing; more neutered cold fronts. Enjoy 20s today and Friday, but Pacific air blows more 30s into town next week; 40F possible by next Wednesday.
Snow? Maybe a cosmetic coating Monday morning.
Can I interest you in a beige Christmas?
* Image credit above: NASA GISS and Hot Whopper.
Monthly Frequency of Thunder at MSP. As you can see, at least since 2000, reports of thunder/lightning at KMSP are exceedingly rare, with no reports the last 15 years from January into mid-February. I wonder if that will change too. Graphic: Iowa Environmental Mesonet.
Image credit: "Polar vortex variations: high pressure (cold breaking into the US) on the left, low pressure (cold trapped to the north) on the right." NOAA.
Positive Phase of AO (Arctic Oscillation). We've witnessed a consistently positive phase of the AO since mid October, a trend which is forecast to continue into early January, possibly longer. Source: NOAA.
Map credit: NASA GISS
Photo credit above: "Cherry blossoms are seen on the street in Washington DC on Tuesday due to the warm weather." Photograph: Bao Dandan/Xinhua Press/Corbis.
Temperature Anomaly Map: Climate Reanalyzer.
Map source: Wikipedia.
Map source: NOAA SPC.
FRIDAY: Coldest day in sight. Partly sunny, windchill near 0F at times. Winds: NW 10-15. High: 19
SATURDAY: Patchy clouds, not as harsh. Wake-up: 9. High: 29
SUNDAY: Intervals of sun, thawing out again. Wake-up: 26. High: 36
MONDAY: Light snow tapers to flurries. Coating possible. Wake-up: 29. High: 32
TUESDAY: More clouds than sun, fairly mild. Wake-up: 26. High: 36
WEDNESDAY: Marchlike, risk of a passing rain shower. Wake-up: 28. High: near 40
Will Global Warming Heat Us Beyond our Physical Limits? National Geographic asks the question, based on new research; here's the intro: "If greenhouse gas emissions are not reduced, rising temperatures and humidity wrought by global warming could expose hundreds of millions of people worldwide to potentially lethal heat stress by 2060, a new report suggests. The greatest exposure will occur in populous, tropical regions such as India, Southeast Asia, the Middle East, and Africa. But even in the northeastern United States, as many as 30 million people might be exposed at least once a year to heat that could be lethal to children, the elderly, and the sick, according to the new study..."
Photo credit above: "In India last May, temperatures rose to 120°F (50°C), killing more than 2,300 people—and melting this street in New Delhi". Photo: Harish Tyagi, EPA.