The main purpose of this ongoing blog will be to track planetary extreme, or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials).😉
Main Topic: Our Melting and Disappearing White Christmases
Dear Diary. What a difference a year makes. Last Christmas was quite cold across the United States and very gloomy due to COVID19. Just check out my diary from one year ago:
This year there is much more hope in association with the vaccine because there are plenty of vaccines and Pfizer has just come out with a pill that is about 88% affective against the disease. Also, it won’t be seasonably cold for many. We could be looking at the warmest Christmas, temperature average wise, on record:
In truth though, it would be much better for our environment and even livelihood if we consistently had that cold and snowy Christmas from 2020. I can see a scenario in which flora started to peek out of the ground way too early across the South shortly after New Year’s, creating some havoc. For one, in my home state of Georgia, the peach crop would be imperiled since it requires many hours below freezing during the winter for trees to properly germinate.
Then, there are adult kids and real kids all wishing for that magical white Christmas. As a climatologist, I know that these are slowly decreasing with time due to global warming. As far south as my hometown of Atlanta, though, white Christmases were never truly part of the holiday tradition. Still, back in colder times, Atlantans didn’t have to drive too far into the Appalachians to see white stuff on the ground around Christmas. Snow cover looks pretty measly this Christmas Eve except in higher elevations of the West:
Here is this year’s Washington Post article on rarefied White Christmases:
Capital Weather GangAnalysis
Climate change is shrinking the odds of a white Christmas, this year included
Rising temperatures have been eating away at the chances for snowfall for Santa in much of the United States, and the forecast is for mild weather again.
A dusting of snow on a Christmas decoration on Dec. 16, 2020, in Leesburg, Va. (Mark Miller/The Washington Post)
By Jason Samenow Weather editor December 18, 2021 at 9:50 a.m. EST
The unforgettable lyric to Irving Berlin’s classic holiday song may need a rewrite: “I’m dreaming of a warm Christmas, unlike the ones I used to know” …
Exceptionally mild weather dominating the Lower 48 this month shows little sign of meaningful change through the Christmas holiday. This means rather underwhelming chances for a white Christmas in many parts of the United States, a state of affairs to which we probably should become accustomed.
Our warming climate appears to be eating away at white Christmas chances, newly available data shows.
This week, the National Oceanic and Atmospheric Administration released white Christmas probabilities across the United States, basing them on the most recent 30 years of climate data that revealed broad decreases compared to just a decade ago. The changes “are consistent with the reality of long-term warming,” NOAA wrote.
The observed changes have been rather subtle, but “more areas experienced decreases in their chances of a white Christmas than increases,” the agency said. NOAA’s criterion for a white Christmas is one inch of snow on the ground on the morning of Dec. 25.
How have white Christmas chances changed in our nation’s cities in the past decade? We analyzed NOAA’s white Christmas data in the 25 biggest cities, from Seattle to D.C., and, unsurprisingly, found declines in most of them:
- 18 of the 25 cities saw their chance of a white Christmas decrease; Denver and Columbus saw the largest drops (six percentage points). D.C.’s odds of a white Christmas plummeted from around 8 percent to just a little over 4 percent.
- Four cities’ chances were unchanged (Minneapolis, Indianapolis, Portland and Dallas)
- Three saw their chances increase, but only by one or two percentage points (New York, Philadelphia and Raleigh)
(Boston — which was among the 25 cities — had incomplete snowfall data, so we substituted Providence, R.I.)
Our results are consistent with an analysis from CNN, which found 64 percent of the 2,000 locations in NOAA’s database exhibited decreases in their white Christmas chances.
The Associated Press, using an analysis from the University of Arizona, also described a marked falloff in Christmas snow between the 1980s and 2010s. In the 1980s, 47 percent of the country had snow on the ground on Dec. 25, with an average depth of 3.5 inches. But, by the 2010s, the snow cover extent was just 38 percent, with an average depth of 2.7 inches.
Maps from NOAA help illustrate the white Christmas decline in parts of the country by comparing the periods 1981-2010 and 1991-2020.
“The easiest one [decline] to spot with the naked eye is the expansion of the dark gray area, where the chances of a white Christmas are less than 10%,” NOAA wrote. “The gray area shifted noticeably northward across the South, and upslope along the ocean-facing slopes of some of the West Coast mountain ranges.”
The probability of a white Christmas in the period 1981-2010 compared to 1991-2020. (NOAA, adapted by Jason Samenow)
Rising temperatures are the probable reason for the most noticeable declines in southern areas because that circumstance increasingly favors rain rather than snow.
This year’s grim white Christmas chances
Temperature differences from average over the past 20 days over the Lower 48. (WeatherBell)
The Lower 48 has already seen three bouts of record-breaking warmth this month, with many areas on track for their warmest December on record. Accordingly, snow cover is considerably below normal across the country. As of Saturday, about 29 percent of the nation has snow cover compared to a more typical value of 37 percent. Only four years since 2003 have had less extensive snow cover than this one.
Computer models for the period around Christmas project a fourth burst of warmth that will probably greatly limit snow potential and melt away previous snow cover in a number of areas.
Temperature difference from normal predicted on Christmas morning from the European modeling system. (WeatherBell)
While the specifics are subject to change, the temperature forecast for Christmas over the Lower 48 looks much like it has so often this month. Model simulations show a high likelihood of milder than average weather over much of the country, with abnormally warm weather in the central states, especially the Southern Plains. Chillier-than-normal conditions are isolated to the very north central U.S. and perhaps parts of California.
The European modeling system’s simulation of snow cover on Christmas morning only shows at least an inch of snow in northern New England, the northern Great Lakes and Upper Midwest, and Mountain West. The Mountain West will, by far, be the most wintry part of the country, especially in the Cascades and Sierras, where a succession of storms will have unloaded massive amounts of snow.
Predicted snow depth on Christmas morning from the European modeling system. (WeatherBell)
A number of places that typically have white Christmases, such as large parts of Iowa, Wisconsin and even southern Minnesota, which recently experienced tornadoes, may well awaken to bare ground on Dec. 25.
Welcome to the new normal.
By Jason Samenow is The Washington Post’s weather editor and Capital Weather Gang’s chief meteorologist. He earned a master’s degree in atmospheric science and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association. Twitter
Notes from the lucky “few” with snow, and other related items:
Here are some of Friday’s “ET’s”:
Here is more climate and weather news from Friday:
(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity. In most instances click on the pictures of each tweet to see each article. The most noteworthy items will be listed first.)
Now here are some of today’s articles and notes on the horrid COVID-19 pandemic:
(If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.)
Guy Walton “The Climate Guy”