Published: February 6,2016
The accumulated winter season severity index, or AWSSI, combines temperature, snowfall and snow depth data in a point system to rate each winter dating to 1950-1951 at dozens of locations in the U.S. The colder and snowier the winter, the higher the AWSSI score.
Winters are then categorized in one of five categories: mild, moderate, average, severe, or extreme.
"The categories are site-specific...because what constitutes a severe winter, say, in Washington D.C. or Atlanta would be considered mild in Chicago or Minneapolis," said Dr. Barbara Mayes Boustead, a co-creator of AWSSI, and forecaster at the National Weather Service in Omaha, Nebraska.
"We wanted the index to be representative, easy to compute, and be able to use readily available data," said Steven Hilberg, co-creator of AWSSI at the Midwest Regional Climate Center.
Mayes Boustead said her inspiration for this research was the "Long Winter" of 1880-1881 made famous by Laura Ingalls Wilder. "I wanted to put that winter into context - was it the 'worst' in history (for that region) and how do you define a severe winter season?"
Winter 2015-2016: Mild For Most
AWSSI
national index values for winter 2015-2016 as of Feb. 3, 2016. City
locations color-coded based on severity of winter, as shown by legend at
left.Based on those AWSSI values, we're handing out our mid-term grades.
Cities receiving an "A" have been much snowier and colder than average, the envy of The Weather Channel winter weather expert, Tom Niziol. They're the winter nerds, honor students, finalists for valedictorian, and those that do extra credit even after nailing an exam. Think Brian Johnson, played by Anthony Michael Hall, in the 1985 classic "The Breakfast Club."
Receiving a "B" grade are those few cities denoted by light blue dots, classified as "severe" winters by the AWSSI. Above average, but not extreme relative to other winters-to-date in each location.
Winter's slacker cities get an "F". They're the persistently warmest and least snowy of the bunch, setting records for the most mild winter-to-date for those locations, denoted by the red diamonds on the AWSSI map. Using the "Breakfast Club" analogy, they're John Bender, played by Judd Nelson.
According to the AWSSI calculations, most of Lower 48 states have skated by with a fairly benign winter, as shown by the sheer volume of red and orange dots in the graphic above, denoting mild or moderate winters as of February 4, 2016. These cities get a "D" grade.
"F": Record Mild Winters
These cities had a record mild pace, according to the AWSSI, so far this winter. (Note that the parameters below aren't strictly the same as those in the AWSSI, but are listed to give a general overview on the winter, so far.)| Season-to-Date Snowfall Departure | Season Snow So Far | Nov-Jan Temp Ranking | |
|---|---|---|---|
| Albany, NY | -31.1" | 5.5" | 2nd warmest |
| Burlington, VT | -26.4" | 20.4" | Record warmest |
| Sault Ste. Marie, MI | -42.3" | 42.6" | 3rd warmest |
| Wichita, KS | -9" | 0.8" | 4th warmest |
| Williamsport, PA | -19.7" | 0.9" | Tied 2nd warmest |
Couple that with a near record-warm pace since November and they firmly belong on this list.
Plot of the record low season-to-date AWSSI through Feb. 4, 2016 for Albany, New York, indicated by the black line.
Plot of the record low season-to-date AWSSI through Feb. 4, 2016 for Albany, New York, indicated by the black line.Williamsport, Pennsylvania, one-upped Albany, setting their least snowy start to the season, a snow total they typically see by November 19.
Finally, how about one of America's snowiest cities, Sault Ste. Marie, Michigan, sporting an over 3.5-foot snowfall deficit!
"C": Average Students
These cities are right about par for the course this winter, according to the AWSSI. In some cases, a city may have been quite snowy, but overall warm. In others, persistent cold makes up for a dearth of snow.| Season-to-Date Snowfall Departure | Season Snow So Far | Nov-Jan Temp Ranking | |
|---|---|---|---|
| Asheville, NC | 8.3" | 13.8" | Tied 6th warmest |
| Boise, ID | -4.4" | 10.9" | Tied 64th warmest |
| Charleston, WV | 1.8" | 21.7" | Tied 10th warmest |
| Helena, MT | -8.3" | 14.8" | Tied 60th warmest |
| Lynchburg, VA | 2.8" | 10.2" | Tied 8th warmest |
| New York City | 13.8" | 27.2" | Record warmest |
| Pendleton, OR | -7.6" | 4.1" | 57th warmest |
| Philadelphia | 11.3" | 22.9" | 2nd warmest |
| Pierre, SD | 6.4" | 22.9" | Tied 24th warmest |
| Richmond, VA | 5.3" | 12.1" | Tied 6th warmest |
| Salt Lake City | -7.3" | 29" | Tied 64th warmest |
| Sioux Falls, SD | 21.9" | 47.5" | Tied 17th warmest |
| Spokane, WA | -1.1" | 33.6" | Tied 50th warmest |
Through January 21, only 0.4 inch was measured the entire season at New York's Central Park, one of the city's least snowy starts to a season. Add what has been one of, if not the warmest, winter on record in much of the Northeast, and it sure seems winter has largely underachieved.
Interestingly, despite rather healthy mountain snowpack overall, many lower elevation cities in the West, shown in the table above, have been a little lacking in snow this season. The "average" AWSSI rating, then, is a result of the persistent cold.
"A": The Lone Honor Student
No U.S. city has had a record extreme winter, so far, according to the AWSSI calculations. So, in a sign of "grading on a curve", we'll highlight one shining example for the rest of the class to look up to: Flagstaff, Arizona.
After about 2 feet of snow this week, here's the view of the NWS Flagstaff office this morning! #azwx
Tweet above from January 8, 2016 after 30.9 inches of snow was measured at Flagstaff's Pulliam Airport in just over four days.This
northern Arizona city, at an elevation of about 7,000 feet, by the way,
has already surpassed their seasonal snowfall from each of the past
three seasons, tallying almost 6 feet of snow (71.7 inches) through
February 4, 2016.What also helped boost their AWSSI score was the persistence of snow cover. According to the National Weather Service, at least one inch of snow on the ground had persisted in Flagstaff for almost two straight months, as of February 4. This was one of the longest such streaks on record, there.
The only factor keeping Flagstaff from chalking up a record extreme start to winter has been temperatures.
While overall, the winter has featured numerous bouts of cold, the magnitude of it has not been record-shattering. For example, they've had five days with subzero low temperatures, but that's about par for the course from November through early February.
You can read the complete 2015 paper about AWSSI in the Journal of Applied Meteorology and Climatology here.
No comments:
Post a Comment