1. January 10-11 2009: The Winter Storm that “Clipped” the Tri-State Patrick Maloit Richard Castro NOAA/NWS Upton, NY

2. Overview Warning Decision Making Process Warning Decision Making Process 12z cycle 9 January12z cycle 9 January 00z cycle 10 January – what changed00z cycle 10 January – what changed 12z cycle 10 January – what changed12z cycle 10 January – what changed What Actually Happened ? What Actually Happened ?

3. Warning Decision Making Process How soon is too soon for a warning? How soon is too soon for a warning? Is the event on a weekend?Is the event on a weekend? Once a watch/warning is up, how much do you change it? Once a watch/warning is up, how much do you change it? How much and what has changed from the previous thinkingHow much and what has changed from the previous thinking

4. Warning Decision Making Process Looking at the data Looking at the data Are the features well captured by the observational network? Are the features well captured by the observational network? Model comparison/confidence Model comparison/confidence All about similarities and differencesAll about similarities and differences

5. 12z Cycle on Friday January 9, 2009

6. Water Vapor, and 500 mb Heights and Vorticity 12z 9 Jan 2009

7. GFS/ECMWF/NAM 500 Hgt 12z 9 Jan Fri 12z Jan 9 Sat 0z Jan 10

8. GFS/ECMWF/NAM 500 Hgt 12z 9 Jan Sat 12z Jan 10 Sun 0z Jan 11

9. GFS/ECMWF/NAM 500 Hgt 12z 9 Jan Sun 12z Jan 12

10. GFS/ECMWF/NAM MSLP 12z 9 Jan Fri 12z Jan 9 Sat 0z Jan 10

11. GFS/ECMWF/NAM MSLP 12z 9 Jan Sat 12z Jan 10 Sun 0z Jan 11

12. GFS/ECMWF/NAM MSLP 12z 9 Jan Sun 12z Jan 12

13. ECMWF 500 MB Hgt/Vort and 300 mb PV - 12z 9 Jan Sat 12z Jan 10

14. ECMWF 500 MB Hgt/Vort and 300 mb PV - 12z 9 Jan Sun 00z Jan 11

15. ECMWF 500 MB Hgt/Vort and 300 mb PV - 12z 9 Jan Sun 12z Jan 11

16. GFS/ECMWF/NAM 850 Hgt 12z 9 Jan Sun 00z Jan 11 Sun 06z Jan 11

17. GFS/ECMWF/NAM 850 Hgt 12z 9 Jan Sun 12z Jan 11

18. GFS/ECMWF/NAM 850 Temp 12z 9 Jan Sun 00z Jan 11 Sun 06z Jan 11

19. GFS/ECMWF/NAM 850 Temp 12z 9 Jan Sun 12z Jan 11

20. NAM Time/Hgt - LGA 12z 9 Jan

21. NAM Time/Hgt - JFK 12z 9 Jan

22. GFS/ECMWF/NAM 24 Hr QPF 12z 9 Jan Sun 12z Jan 11

23. The Afternoon Forecast – 9th Already had Watch in effect for entire CWA The fact it was a weekend necessitated going to Warnings this package Thermal Profile was warning/advisory line delineator

24. Snowfall Forecast pm of 9th

25. The Afternoon Forecast – 9th Winter Storm Warnings – –All of Southern Connecticut, The Lower Hudson Valley, Northeast New Jersey, Nassau County, Northern Suffolk County, NW City Boroughs (including Queens) Winter Weather Advisories – –Southern Suffolk County and Brooklyn + Staten Island

26. 00z Cycle on January 10, 2009

27. Water Vapor, and 500 mb Heights and Vorticity 00z 10 Jan 2009

28. GFS/ECMWF/NAM 500 Hgt 0z 10 Jan Sun 12z Jan 11

29. GFS/ECMWF/NAM MSLP 0z 10 Jan Sun 12z Jan 11

30. GFS/ECMWF/NAM 850 Hgt 0z 10 Jan Sun 00z Jan 11 Sun 12z Jan 11

31. GFS/ECMWF/NAM 850 Temp 0z 10 Jan Sun 06z Jan 11

32. GFS/ECMWF/NAM 850 Temp 0z 10 Jan Sun 12z Jan 11

33. The Morning Forecast – 10th Based on thermal profiles, adjusted all Long Island and NYC, as well as Southern NE NJ Zones to an Advisory Warmer thermal profile also resulted in slight decrease in amounts

34. Snowfall Forecast am of 10th

35. The Morning Forecast – 10th Winter Storm Warnings – –All of Southern Connecticut, The Lower Hudson Valley, Northern Northeast New Jersey Winter Weather Advisories – –NYC, Long Island, Southern Northeast New Jersey