1. Rating Snowstorms Based on Travel Impacts Ernie Ostuno National Weather Service, GRR

2. Storm Impact: Travel Conditions Recent survey found (not surprisingly) that travel impacts were the leading cause of people altering their normal routines during snowstorms

3. Two Methods of Ranking Storms Pre-Storm: Pre-Storm: – – Saffir/Simpson scale: damage potential Post-Storm: Post-Storm: – EF scale: damage assessment

4. Winter Storms: Criteria vs. Impact NWS warning criteria based on amount and rate of snow NWS warning criteria based on amount and rate of snow Impact: primarily the effect on travel conditions, which we don’t explicitly forecast Impact: primarily the effect on travel conditions, which we don’t explicitly forecast Zielinski (2002), Grumm and Hart (2001) rated winter storms based on meteorology Zielinski (2002), Grumm and Hart (2001) rated winter storms based on meteorology Kocin and Ucellini (2004) rated winter storms based on impacts Kocin and Ucellini (2004) rated winter storms based on impacts The impacts did not include taking into account some important variables The impacts did not include taking into account some important variables

5. Northeast Storms Severity Index Based on amount of snow that affects the greatest area/most population Based on amount of snow that affects the greatest area/most population Somewhat analogous to the EF-scale; tornado will likely get a higher rating if it hits a city Somewhat analogous to the EF-scale; tornado will likely get a higher rating if it hits a city Ranks 11-12 Feb 1983 higher than 6-7 Feb 1978 Ranks 11-12 Feb 1983 higher than 6-7 Feb 1978 Not accounted for: Timing, winds, temperatures, local severity Not accounted for: Timing, winds, temperatures, local severity

6. Variables Affecting Travel Impacts Snow: Amount, Rate, Timing Snow: Amount, Rate, Timing Wind: Speed and Duration Wind: Speed and Duration Temperature: Hypothermia, Road Salt Temperature: Hypothermia, Road Salt Icing: Freezing rain, rain to snow Icing: Freezing rain, rain to snow

7. Ranking Historic Northeast Snowstorms February 6-7, 1978 February 6-7, 1978 January 7-8, 1996 January 7-8, 1996 February 11-12, 1983 and 2006 February 11-12, 1983 and 2006 February 16-17, 2003 February 16-17, 2003 April 1, 1997 and April 6, 1982 April 1, 1997 and April 6, 1982 Ranking Factors : Amount of snow, winds, persistence of deep snow Societal impacts to account for: Economic disruption, travel bans Discussion point: which is more important, snow amount or wind? Drifting snow and snowfall rates are important factors in affecting travel, as well as timing What makes a storm memorable enough to mark anniversaries of it?

8. Rankings by Snow, Wind* Snow17.7…200615.5…198315.4…199615.1…197813.1…2003 *Average of BDR and BDL snow totals and peak winds ** Top ranking for each category is given 5 points, next highest given 4 points, etc., then added together. Wind is given a weighting factor of 1.5 Wind40…197837…199636…200633…200328…1983 Rank points** 2006…9.51978…9.51996…91983…5.52003…4

9. A Look at One Possibly Important Variable: Snow Depth Following some of the Big Storms Snow depth in inches (y-axis) measured each day after the storm (x-axis) Post-storm assessment ranking: 10 inches or more on the ground 5 days after = 1 point 10 inches or more on the ground 10 days after = 2 points

10. Final Ranking Rank points 1978…11.51996…112006…10.51983…6.52003…4

11. “The Old 1 to 5 Scale” Wind (mph)Snow (In)Temp (F) Wind (mph)Snow (In)Temp (F) >40… 5>12… 5 40… 5>12… 5 <15… 5 30-40… 4 8-12… 415-20… 4 20-29… 3 4-8… 320-25… 3 10-19… 2 2-4… 225-30… 2 30… 1 30… 1 *Amounts can vary based on forecast zones*

12. Graphical Forecasts Peak Wind + Snow +Temp = Impact Impact Forecast generated from graphics that are already being produced and calculated as follows: 45 % Wind + 40 % Snow + 15 % Temperature Example: Wind = 35, Snow = 10 and Temp = 20 Impact = 4(.45) + 4 (.4) + 3 (.15) = 3.85

13. Let’s Look at Some Examples Discussion points Severity vs. Impact Severity vs. Impact Timing is everything? Timing is everything? Can we forecast road conditions? Can we forecast road conditions? What about icing? What about icing? Two recent cases show the difficulties in assessing impacts

14. Winter Storm of 3 Feb 2007 High impact event with road closures, blizzard conditions and extreme cold High impact event with road closures, blizzard conditions and extreme cold Impact mitigated since it hit on weekend Impact mitigated since it hit on weekend Highly variable conditions, but frequent whiteouts in falling and blowing snow Highly variable conditions, but frequent whiteouts in falling and blowing snow

15. Lake Effect Blizzard with Whiteouts, Low Wind Chills

16. Winter Storm of 30 Jan 2008 High Impact rain to snow event with extremely poor travel conditions High Impact rain to snow event with extremely poor travel conditions Quick temperature drop with a “flash freeze” of rain into a sheet of snow covered ice Quick temperature drop with a “flash freeze” of rain into a sheet of snow covered ice Cold temperatures greatly reduced the effectiveness of road salt Cold temperatures greatly reduced the effectiveness of road salt Travel conditions were bad for several days Travel conditions were bad for several days

17. Not a lot of snow, but worst driving conditions EVER

18. Other high impact winter events: Black ice Black ice “Clear Air” drifting of snow “Clear Air” drifting of snow Localized whiteouts Localized whiteouts Localized dense fog from snowmelt Localized dense fog from snowmelt Dirt Roads icing over in thaw situations Dirt Roads icing over in thaw situations High winds after ice storms causing continued power outages High winds after ice storms causing continued power outages These are high impact events that we must anticipate and communicate better!

19. Strategy for Communicating Impacts of Winter Storms A rating system for winter storms based on impacts can help communicate how “bad” a storm will be A rating system for winter storms based on impacts can help communicate how “bad” a storm will be Existing forecast parameters can be used to calculate impacts Existing forecast parameters can be used to calculate impacts No easy way to account for so many variables No easy way to account for so many variables Each storm is different; recognize the main impacts Each storm is different; recognize the main impacts Stress major impacts in briefings/NWSChat/AFDs Stress major impacts in briefings/NWSChat/AFDs Choose wording that best conveys what the major impacts will be Choose wording that best conveys what the major impacts will be

20. In Summary Diagnose the Meteorology Assess the Impacts Describe the Event