1. The 20101226 Blizzard Discussion 1.Summary Discussion a. Medium Range Issues (Days 4-7) b. Short-Range Issues c. Ensemble trends d. Upstream differences 2. Comments From Various Groups/Offices 3. What To Do Next? a. Science Goals b. Operational Goals CSTAR reference: http://dendrite.somas.stonybrook.edu/CSTAR/2627Dec2010.htmlhttp://dendrite.somas.stonybrook.edu/CSTAR/2627Dec2010.html

2. 00 UTC 18 Dec Model Forecasts 204 h forecast of 540 DM height valid 12 UTC 26 Dec Courtesy: David Novak

3. 00 UTC 19 Dec Model Forecasts 180 h forecast of 540 DM height valid 12 UTC 26 Dec

4. 00 UTC 20 Dec Model Forecasts 156 h forecast of 540 DM height valid 12 UTC 26 Dec

5. 00 UTC 21 Dec Model Forecasts 132 h forecast of 540 DM height valid 12 UTC 26 Dec

6. 00 UTC 22 Dec Model Forecasts 108 h forecast of 540 DM height valid 12 UTC 26 Dec

7. 12 UTC 22 Dec GFS Forecast WAVE PACKET EVOLUTION http://ferrel.msrc.sunysb.edu/Wave/Dec22_12Z/F4-12hrly.htm

8. 12 UTC 22 Dec GFS Forecast WAVE PACKET EVOLUTION

9. 12 UTC 22 Dec Run ETKF Sensi plots 22/12z GFS Forecast Courtesy: Yucheng Song

10. Forecasts from 24 Dec 2010 Courtesy: Dan Petersen Short-Range Forecast Issues

11. 00 UTC 24 Dec Forecasts 84 h forecast of 24 h accumulated precip NAM GFSECMWF Courtesy: David Novak x NYC

12. Sensitivity of cyclogenesis to initial condition e.g., 03z, Dec. 24, 2010 SREF individual members (one Eta_KF and one RSM members are very close to the observed) Courtesy: Jun Du

13. Consequently, the problem for precipitation is that the major precipitation is too far from the coast prior to Dec. 25, 2010: e.g. 03z and 09z, Dec 24, 2010 SREF >1” (liquid equiv) probability 03z, 84hr 09z, 78hr Courtesy: Jun Du and Rich Grumm

14. 1200 UTC 24 Dec forecast: F060 VT 0000 27 Dec 2010 Courtesy: Joe Sienkiewicz

15. 12 UTC 24 Dec Runs 72 h forecast of 24 h accumulated precip NAM GFSECMWF Courtesy: David Novak

16. Forecasts from 25 Dec 2010 Courtesy: Dan Petersen

17. 00 UTC 25 Dec Runs 60 h forecast of 24 h accumulated precip NAM GFSECMWF Courtesy: David Novak

18. 12 UTC 25 Dec Runs 48 h forecast of 24 h accumulated precip NAM GFSECMWF Courtesy: David Novak

19. ETKF Sensitivity valid 27/1200 UTC 24/1200 UTC One uncertainty area Near Texas/Mexico 25/0000 UTC Growing Courtesy: Yucheng Song 26/0000 UTC 26/1200 UTC

20. From Richard Grumm 06Z24DEC GFS forecast minus the 12Z24DEC Forecast at the Valid TIme

21. GFS (green), ECMWF (blue) 500 mb height 00 hr forecasts 12z 24 Dec. 2010

22. GFS (green), ECMWF (blue) 500 mb height 12 hr forecasts verifying 00z 25 Dec. 2010

23. GFS (green), ECMWF (blue) 500 mb height 24 hr forecasts verifying 12z 25 Dec. 2010

24. GFS (green), ECMWF (blue) 500 mb height 36 hr forecasts verifying 00z 26 Dec. 2010

25. GFS (green), ECMWF (blue) 500 mb height 48 hr forecasts verifying 12z 26 Dec. 2010

26. GFS (green), ECMWF (blue) sea level pressure 48 hr forecasts verifying 12z 26 Dec. 2010

27. Summary 1.A Rossby wave packet led to downstream wave amplification over NAmer., but the East Coast trough was underpredicted, especially > 3 days in advance. 2.The large shift in the models and ensembles between 0000 UTC 24 and 0000 UTC 25 Dec may have originated from small IC uncertainties/errors in the trough the central and southern central Plains. 3.Small IC differences between GFS and ECMWF at 1200 UTC 24 Dec amplified to large differences 36-48h later (GFS/GEFS appears to have done better than EC by ~12h). 4.Cyclone position was well forecast < 24-h but still mesoscale banding location issues (LI vs just west NYC). 5.Difference plots between models and run cycles is a useful tool. We need more of these plotting approaches in realtime to look at ensemble/model run to run differences.

28. Some Questions 1.What led to the large change in GEFS solutions between 0000 and 1200 UTC 24 Dec? - previous model error finally corrected? - Important observations around SPlains? - Difficultly in trough (PV) merger? 2.Was there an impact of the targeted obs over the Gulf at 0000 UTC 25 December? 3.Why couldn’t ensemble (GEFS) perts over S. Plains create some cyclone solutions closer to obs for 24/00(06z) cycles? Why did the SREF cluster offshore as well? 4.Was there a large contribution from physics uncertainty in this event?

29. Future Plans for this Event Look more carefully on how the predicted wave packets evolved in the medium range for this event using the TIGGE ensemble. Use this case to test other metrics for ensemble sensitivity (see Edmund Chang presentation). Look more carefully at what observations went into the 24/00z vs 24/12z cycles. Need a web page to show difference plots from the various model and ensembles. Others?