HOW DOES THE WINTER RATE IN YOUR CITY....?

February 22, 2018

If it seems like this has been a good old average winter, you're right...at least according to the accumulated winter season severity index. The AWSSI was designed and developed to measure the relative severity of the winter season based on the intensity and persistence of cold weather, the frequency and amount of snow, and the amount and persistence of snow on the ground.

As you can see above most of the central Midwest (especially my area) is currently experiencing an "average" winter based on the index. At the bottom of the post I have included the scores for some major Midwest Cities.

 

Here's the goals of the index which is based on a point system.

  • Objectively index winter conditions

  • Use commonly available data—max/min temperature, snowfall, and snow depth or precipitation

  • Create a historical database of AWSSI for any location with daily temperature, snow, and precipitation data

  • Allow comparisons of season to season severity at one location in the context of the climatology of that location or between locations

  • Use as a baseline to scale subjective impacts such as those to snow removal, commerce, and transportation

  • Apply to multiple users and their needs

     

    Here's how the AWSSI accumulates points over a winter.

  • Objectively index winter conditions

  • Use commonly available data—max/min temperature, snowfall, and snow depth or precipitation

  • Create a historical database of AWSSI for any location with daily temperature, snow, and precipitation data

  • Allow comparisons of season to season severity at one location in the context of the climatology of that location or between locations

  • Use as a baseline to scale subjective impacts such as those to snow removal, commerce, and transportation

  • Apply to multiple users and their needs

     

    Daily scores are calculated based on scores assigned to temperature, snowfall, and snow depth thresholds. The daily scores are accumulated through the winter season, allowing a running total of winter severity in the midst of a season as well as a final, cumulative value characterizing the full season. Accumulations of the temperature and snow components of the index are computed separately and then added together for the total index. This allows comparison of the relative contribution of each to the total score.

The AWSSI has been processed for 52 locations across the continental U.S. to provide a variety of locations in different climate regimes for analysis. The AWSSI is calculated for each season from 1950‐1951 to 2012‐2013. The seasonal data is then subject to quality control, and seasons missing data that would contribute 5% or more of the seasons AWSSI are removed . Averages and standard deviations are calculated for running accumulations of daily temperature and snowscores as well as the total AWSSI.

Quintiles of AWSSI scores were determined for each location. Descriptive categories were assigned to each quintile as follows:

Here's the limitations of the AWWSSI index

  • Does not include wind (e.g. wind chill, blowing snow)

  • Does not include mixed precipitation or freezing rain explicitly (a precip‐only version of AWSSI may help address impacts of these events)

  • Thresholds have been set with impacts in mind and are subject to adjustment in the future as analysis continues.

Here's some cities with moderate winters to date:

Severe winters are indicated in these cities, including Chicago.

A moderate winter is indicated in Minneapolis.

These scores may yet go up, especially in the upper Midwest where tonights GFS showed this for snowfall the next 10 days. 

That's a wrap for now. No matter how good or bad your winter is from here on out, April is just 37 days away. Dang, I have to start mowing the yard again. Roll weather...TS

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© 2019 Terry Swails