Monday, December 11, 2023

How Do You Define a "Harsh Winter"?



HOW DO YOU DEFINE A "HARSH WINTER?"

No question typifies weather subjectivity and story telling more than this one.  Ask this question and you'll get a different answer virtually every time. Here are some of responses via Twitter when I asked this question recently.  I'll analyze each one with data from Cleveland to see how often each weather occurs.  Responses are abbreviated.

TWITTER (X) RESPONSES AND ANALYSIS:    

1) Above average snow & below average temps

First, here is snowfall vs normal for each winter since 1960-61 using a running average.


Now winter temperatures vs average over the same time frame.  Again, we use a 10 year running average.


The only winters that fit each component (temps and snowfall) are:

1962-63, 1969-70, 1977-78, 1981-82, 1983-84, 1993-94, 1995-96, 2002-03, 2003-04, 2008-09, 2013-14 and 2014-15

2) Sustainable snow cover into April

Most Aprils rarely has sustainable snow on the ground.  Here are the total days with 1"+ snow cover for each winter since the late 1930s.  Most year its only one day. Only 6 winters had 3 or more days in April in the last 40 years.


Expanding snow cover days into March and April, we find 21 of the last 64 years with 10 days or more with snow cover between March 1 and April 15:


3) Less than 10 days without sunshine

Hard to quantify due to data limitations.

4) Extreme cold with no breaks

"Extreme cold" is arbitrary. So we'll go with total days with temperatures under 20 degrees.



5)  DJF - 45 days or more below freezing for highs AND Total snowfall 50"+

Nice graph showing the 45 days at/under freezing. Red box indicates years with total snowfall 50"+

Most recently:  2014-15, 2013-14, 2010-11, 2002-03, 2000-01, 1995-96, 1984-85, 1983-84, 1980-81



6) Below zero temps

Not many in recent years. Only 4 in 2017-18.  The two back-to-back super cold winters of 2013-14 and 2014-15 saw 23 combined.


7) Temps consistently below 32

Winters since 1969-70 where we had more than 14 straight days at/under 32 degrees. Date shows when the streak ended.



8) More than 4 weeks with more than 6" of snow on ground

Only 6 winters had more than 28 days with at least 6" snow over:
1962-63, 1976-77, 1977-78, 1978-79, 2008-09, 2009-10


9) DJF - half of days with snow cover

Most recently, these winters:

2014-15, 2013-14, 2010-11, 2009-10, 2004-05, 2002-03
1995-96, 1993-94, 1985-86, 1984-83, 1983-84, 1981-80
1980-81, 1978-79, 1977-78, 1976-77, 1967-68, 1963-67
1962-63, 1960-61

10)  Snow totals above normal



Filtering out the winters with at least 8" snow above normal we get these winters:




11)  Wind chills under -10

My nice chart I update each year denoting the total hours where we reach below zero wind chills. I noted the years in red where chills dropped under -10.  Last winter it occurred frequently around the holidays. In fact it was coldest period (using wind chill) since January 1994. Prior to last winter, the winter of 2012-22, 2018-19 and 2017-18 were the most recent winter with chills under -10.


The winter of 2008-09, 2006-07 and 2000-01 



12)  High temps under 20 degrees for 30% of the winter

Has never happened

13)  20 days with single digit temps & Frequent 10" snows

The only winters with ONE DAY 10" snowfalls are:


How about TWO DAY 10" snowfall?  That has happened 57 times.  Here are the occurrences in the last 50 winters:


How about 2 day 10" snowfalls AND 20 days with single digit temperatures in the same winter?




14)  5 snowfall events greater than 6"

Hard to believe but the most in one year (since 1960) is 6 and that happened in 2004-05.  Here is the list showing all winters with at least two.



15)  Below 10 degrees for two weeks

Since 1960, we've only had TWO WINTERS where we had more than 10 straight days with overnight lows at/under 10 degrees.  



16)  Consecutive days with at least 1" of snow cover

Last year we had only 15 days with at least an inch of snow cover. Second lowest since 1960-61. 


The top ten winters with snow cover since 1960-61:



17  Consecutive days under 40

Here is the list showing the top 15 winter and the date when the consecutive streak ended.



So you can see that everyone's definition of a harsh winter is different.  By checking history, many of these listed above don't occur as frequently as we would believe. There is definitely some availability bias here. That is we tend to create--in this case--a weather narrative using the most noticeable, seemly important information we have at our disposal. Yet in reality, that information can be incomplete. The the lack of super cold and snowy winters in recent years has seemed to artificially "enhance" our memories of what a rough winter used to be.  As is often the case, what we remember of winter weather from yesteryear gets blurred and sometimes exaggerated over time. If we experienced an historic weather events firsthand those indelible marks, can inflate--perhaps due to availability bias or recency bias (more recent events tend to be overemphasized)--what might have been a more benign event.

Either way, our feelings on winter are highly subjective and always filled with emotion unlike any other season. Let's see if winter 2023-24 conditions make these lists!

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