1 Appendix

2 For the Encore: NYC Blizzard (Dec 25-27, 2010)

3 Radar/HPC Surface Analysis December 25-28, 2010

4 H L L 1200 UTC 25 December 2010 H H L L UTC 26 December 2010 H L 1200 UTC 26 December 2010 H L L L 0000 UTC 27 December 2010 NYC Blizzard Dec 25 – 27, 2010

5 Snowfall Totals

Guidance from 12Z December 22 - Wednesday Forecast uncertainty led to inaction that increased the overall impact of the storm Observed – Blue ECMWF – Red GFS - Green

7 Guidance from 12Z December 24 - Friday Observed – Blue 12Z ECMWF – Red 12Z GFS – Green 00Z ECMWF - Brown

Surface Analysis Seven day forecast Valid 12Z December 27, 2010

Surface Analysis Six day forecast Valid 12Z December 27, 2010

Surface Analysis Five day forecast Valid 12Z December 27, 2010

Surface Analysis Four day forecast Valid 12Z December 27, 2010

Surface Analysis Valid 12Z December 27, 2010 Forecast Issued 24 December 2010 Three day forecast

Surface Analysis Two day forecast Valid 12Z December 27, 2010

Surface Analysis One day forecast Valid 12Z December 27, 2010

15 3 days prior SREF/GEFS Forecasts for Dec 26, 2010: NYC Blizzard 2 days prior 1 day prior

Favorable Jet-Streak Circulation Pattern Radar Simulation of Snow Bands* 16 Short Term Forecasts Point to Potential Heavy Snowfall in NYC and Surrounding Areas * 4km NMMB will be operational for next winter

Model Forecasts: 250 MB Coupled Jets (00Z Mon Dec ) GFS 24 Hour Forecast *

HPC SFC MapObserved Radar NAM 4km Reflectivity 18 Z Dec Z Dec Z Dec 27 * * * * * * 18hr fcst 24hr fcst 30hr fcst

Model Forecast: Simulated Reflectivity 33 hour Reflectivity Loop (03 UTC 26 Dec to 12 UTC 27 Dec) NAM (run on 00Z Dec 26) Simulated Reflectivity experimental 4 km NMMB model (to become operational this summer) *

December 26-27, Potential for major east coast storm highlighted 5 days in advance Low confidence about model predictions – especially track forecasts – until late December 24 Blizzard warning issued for NYC at 4PM Saturday, December 25 (14 hours prior to onset) By December 24-25, special effort made to reach out to Emergency managers and airline industry prior to onset of heavy snow in Northeast corridor/NYC Airline industry takes action Snow emergency not declared in NYC NYC/NJ/West CT gets buried by 2+ feet of snow with 50+ mph winds

Airlines/airports are prepared for crippling event –Cancel thousands of flights –Attempt to mitigate impact on national and international flight operations –Fully recover in 3-4 days NYC does not declare snow emergency despite blizzard warning – results in major gridlock within city Impacts: Forecast for December

New York City Report: Preliminary Review of the City’s Response to the December 2010 Blizzard - Report and Recommendations 22 From Introduction – “On December 26, 2010, a blizzard struck New York City and surrounding areas. Though earlier forecasts had called for only a light to moderate snow falls, the National Weather Service issued a blizzard warning at 3:55 PM on December 25th. At that time, between 11 and 16 inches of snow were predicted, along with high winds and low visibility. Even this forecast underestimated the storm’s ferocity. ” Third of six key problems – “Insufficient and delayed deployment of City assets. The weather forecast for the storm got significantly worse rather quickly, culminating in a blizzard warning issued at 3:55pm on Christmas Day. Due to the late change in the forecast, as well as the fact that DSNY has adeptly handled large snowfalls so many times previously without assistance, agencies that are not typically involved in snow removal—such as the Taxi and Limousine Commission --were not mobilized expeditiously.”