We have a potential for severe weather Thursday. Has a tornado ever touched down in a snow-covered area?
— Kevin Kutz, McHenry
We posed your question to two tornado experts from NOAA’s Storm Prediction Center in Norman, Okla. — director Russell Schneider and warning coordination meteorologist Greg Carbin.
They felt that in most cases, a layer of cold, stable air over the snow cover would inhibit tornado formation, but with very strong low-level winds and high surface-based moisture, it is possible.
They cited two examples: In 2011, an EF3 tornado struck Merrill, Wis., when area lakes were still frozen and snow cover had been present a few days earlier. Two tornadoes, an EF3 and EF1, also occurred in southeast Wisconsin on Jan. 7, 2008 along the south edge of the snowpack.
I have lived in Indiana all my life and have never seen robins so early. Do you have any clue why they came back with all this snow? I think they are confused.
— Northern Indiana resident
Dear Indiana resident,
It’s not at all unusual to see robins in the Midwest during the winter. They are hardy birds. You might have seen Canadian robins wintering here, or “locals” who chose to stay.
In the summer, robins can be found across almost all of North America — north even to Alaska and the shore of the Arctic Ocean. Surprisingly, most of the U.S., including the Midwest, is wintering territory for some Canadian robins. Locally, most (but not all) of our “summer” robins migrate to Southern states for the winter, but some will remain in the area if they are able to find berries, seeds and dormant insects.
Why has the snow been light and fluffy this year? It seems that we usually get heavy, wet snow in the Chicago area.
— Wayne Bessette
Most of this season’s snow came from clipper systems from the northwest. These storms originate in the Canadian Prairie Provinces and typically produce a dry snow with a snow-to-water ratio of 15-20-to-1 (an inch of water yields 15-20 inches of snow) with temperatures in the teens or 20s.
In most winters, a couple of the city’s snowstorms arrive from the south or southwest. They are loaded with Gulf moisture and deliver the snow in a much warmer environment with temperatures around freezing. These storms often originate in the Texas Panhandle or along the Gulf Coast and produce a heavy, wet snow with a snow-to-water ratio more like 5-10-to-1.
What is the longest period that Chicago has remained below freezing?
Neal Plano, Amy Pokras, Tim Stewart, Herschel Weller
Dear Neal, Amy, Tim and Herschel,
The city’s record for continuous below freezing temperatures was established during the brutal winter of 1976-77. Chicago weather historian Frank Wachowski reports that the mercury dropped below 32 degrees at 10:15 pm December 27, 1976 and remained there through 10am February 9, 1977; a total of 43 days 11 hours and 45 minutes. During that spell the city logged 17 days below zero; the coldest day was January 16th, with a high of minus 7, and a low of 19 below zero. The subfreezing spell ended with a flourish of warmth, with the high on February 9th peaking at 42 degrees. By February 11th, the temperature climbed to 52 degrees, and on February 23rd it soared to 60.
I see Chicago’s weather records as those officially observed since late 1870. Are there earlier records?
— Wayne Callham, Chicago
Chicago’s official weather records date back to Nov. 1, 1870, but there is a smattering of information from 1820 to 1836 when observations were taken at Fort Dearborn. A few observations were also taken at the Mechanics Institute in 1844, and nearly continuous readings were taken by Smithsonian observers from 1859 until late 1870, when the Army Signal Corps began documenting the city’s official weather history. Many of those early observations, which consisted mostly of temperature data, were compiled by professor Henry A. Hazen and published in his 1893 book “The Climate of Chicago.” Journals, diaries and newspapers also provide valuable insight.
Tom, we’ve just endured the 10th coldest (15.7 degrees) and third snowiest (33.7 inches) January in Chicago’s weather history. How many other Januarys share this top-10 dual distinction?
Frank Casalino, Grayslake
There are only two other January’s that fit the bill- 1918 and 1979 and both were colder and snowier than this year. January 1918 ranks not only the city’s snowiest January but also Chicago’s all-time snowiest month logging 42.5 inches. It also is the sixth coldest with an average temperature of 13.3 degrees. January, 1979 tallied 40.4 inches of snow to qualify as the city’s second snowiest January (and month) and its average temperature of 12.4 degrees places it as the fifth coldest. Prior to this year, January 1982 was the 10th snowiest (21.1 inches) and fourth coldest (12.2 degrees) but no longer ranks as one of the top 10 snowiest.
I see we’re having a full moon on Valentine’s Day. When was the last time this happened? When is the next time?
—Philip Schwimmer, Chicago
It’s been a while since there’s been a Valentine’s Day full moon in Chicago. The last one occurred 46 years ago, in 1968. However, there will be four more this century — occurring in 19-year intervals, in 2033, 2052, 2071 and 2090. Triton College astronomer Dan Joyce tells us that the probability of a full moon on Valentine’s Day is the same as it is every other day of the year: occurring an average of twice in any 59-year period. For a while, a full moon will occur on a specific date every 19 years, but since the period of repetition is 18.61 years and there is a leap day added every four years, it eventually lapses into a longer repetitive period.
Why is it that the Aurora (or is it the entire Fox Valley?) area seems to be so much colder in the winter than anywhere else in Chicagoland?
The unusually cold temperatures you refer to are not representative of Aurora or other locations in suburban or outlying Chicagoland. Retired meteorologist Jim Allsopp explains: “The weather observation is taken at the Aurora airport, which is actually in Sugar Grove, about eight miles west of downtown Aurora. It is a rural setting, and it is not representative of temperatures in the city of Aurora. The airport sits in a low area. Because cold air is more dense, it settles into low spots on clear, calm nights. These weather observations provide necessary information for aviation operations and are not intended for other purposes.”
Saturday’s snowfall was the season’s 35th day of measurable snow (0.1 inch or more). Are we approaching any record?
— Connie Blasing, Lockport
We’ve had a lot of snow and a lot of snowy days this winter, but are a long way from tying or breaking the record for most days of measurable snowfall. So far this season the city has logged 35 days with measurable snow, the most of any season dating back to 1884-85 with the exception of 1961-62, which produced 53. This season’s to-date snow total of 62.1 inches has already beat 1961-62’s full-season total of 58.9 inches; that season had a lot of days with minor snowfall. In the 11-day period During the 11-day March 4-14, 1962, the city had 10 days of measurable snow, with 0.6 inch or less on nine of them
With the below normal winter we are having, what is the possibility of an above normal summer? Is there any connection?
-Joe Szwiec, Glenview
Historical temperature data reveal no connection. As of Feb. 10, this winter’s average temperature (from Dec. 1 through Feb. 10) as recorded at Midway airport stood at 19.9 degrees. A computer search of 85 years of Midway temperature data (1928-2013) identified seven winters with comparably cold average temperatures during that period. Summer temperatures (from June through August) following those seven cold winters revealed no reliable temperature trends. Three of those summers brought near-normal temperatures, one summer ran significantly warmer than normal and three were somewhat cooler than normal.