1. The Challenge of Convective Forecasting “Predictability does not necessarily imply ability to predict” ASP/MMM Colloquium July 10-21, 2006 Morris Weisman NCAR/MMM Introduction/Motivation

3. “Weather prediction is the principal reason for the support which we are given by our fellow citizens…… I believe it is time for convective- storm scientists to apply our knowledge to this purpose and to subject our products to its discipline…… ……..The task is not trivial…..” Doug Lilly, Q. J. of the Royal Meteor. Soc., 1990 Numerical prediction of thunderstorms—has its time come?

5. Initialized 05 Nov 2005 00 UTC Reflectivity forecast Composite NEXRAD Radar

6. Reflectivity forecastComposite NEXRAD Radar 06 Nov 2005 31 h valid 07 UTC08 UTC (tiff)

7. Evansville Tornado ??? Well, actually from Greg Thompson’s Web page

9. Terrain-following hydrostatic pressure vertical coordinate Arakawa C-grid, two-way interacting nested grids (soon) 3 rd order Runge-Kutta split-explicit time differencing Conserves mass, momentum, entropy, and scalars using flux form prognostic equations 5 th order upwind or 6 th order centered differencing for advection Multiple physics combinations (many converted from MM5), Noah and RUC land-surface submodels WRF-ARW Mass Coordinate Core

10. WRF Model Physics “Plug-compatible” interface defined for physics modules Physics options implemented in WRF: – Microphysics: Kessler-type (no-ice) Lin et al. (graupel included),WSM6 NCEP Cloud3, Cloud5, Ferrier – Cumulus Convection:New Kain-Fritsch, Grell Ensemble Betts-Miller-Janjic – Shortwave Radiation:Dudhia (MM5), Goddard, GFDL – Longwave Radiation:RRTM, GFDL – Turbulence:Prognostic TKE, Smagorinsky, constant diffusion – PBL: MRF, MYJ, YSU – Surface Layer:Similarity theory, MYJ – Land-Surface:5-layer soil model, RUC LSM Noah unified LSM, HRLDAS

11. Idealized WRF Simulations PBL LES,  x = 50 mDensity current,  x = 100 m Supercell thunderstorm,  x = 1 km Mountain wave,  x = 20 km Baroclinic wave,  x = 100 km 5 min10 min15 min (Chin-Hoh Moeng)

12. WRF Realtime Convective Forecasting May 1 – July 31 4 km 00 UTC -- 36h 2003, 2004, 2005

13. 00Z 10 June – 13Z 11 June 2003

14. Real-time WRF 4 km BAMEX Forecast Composite NEXRAD Radar Reflectivity forecast Initialized 00 UTC 9 June 03

15. Real-time WRF 4 km BAMEX Forecast Initialized 00 UTC 10 June 03 Reflectivity forecastComposite NEXRAD Radar

16. Realtime WRF 4 km BAMEX Forecast Composite NEXRAD Radar30 h Reflectivity Forecast Missed Valid 6/12/03 06Z = MCS “position” Correspond

17. 1 10 100 km Cumulus Parameterization Resolved Convection LES PBL Parameterization Two Stream Radiation 3-D Radiation Model Physics in High Resolution NWP Physics “No Man’s Land”

18. 4 km? 2 km? BAMEX OBS, Reflectivity 100m? How much resolution do we need?? George Bryan NCAR/MMM (Thursday morning) What does it take to simulate convection??

19. ARW2BREF NMM4ARW4 0500 UTC 29 April 2005: 1 km model reflectivity, NEXRAD BREF

20. Power Spectra for 3 h Precipitation 12Z forecasts, 15-18 Z accum precip, valid 4 June 2002 (From Mike Baldwin and Matt Wandishin, NOAA/NSSL)

21. NEXRAD CompositeReisnerSchemeSB2004 Scheme WSM-6 Scheme Lin, et al. Scheme 4 km WRF-ARW 12 h reflectivity forecast, Valid 10 June 2003 12 Z Column Max Reflectivity (dBZ) Does microphysics matter at all??? Axel Seifert (DWD), Friday morning

22. 4 km WRF 12 h Precipitation Forecast NCEP Stage 4 Data ReisnerSchemeSB2004 Scheme WSM-6 Scheme Lin, et al. Scheme Valid 10 June 2003 12 Z Total Precipitation (mm) (Axel Seifert, 2004)

23. Reisner LinWSM-6 SB2004 12 h Surface Theta Cold Pools??

24. Are we properly representing the structure and evolution of the PBL?? Jack Kain (NSSL) PBL observations and forecasting issues: Friday afternoon Bjorn Stevens (UCLA), PBL theory and parameterization: Monday Morning Fei Chen (NCAR/RAL), Land surface modeling: Monday Afternoon

25. Sounding comparison: 24h forecast valid 00Z 18 May at DDC ARW4 NMM4 Too dry in PBL, too moist above; Where is the PBL top? Good forecast… Model Raob Model Raob MYJ YSU (Jack Kain, NSSL)

26. Sounding comparison: 24h forecast valid 00Z 24 May at DDC ARW4 NMM4 Good forecast… PBL too shallow, cold, & moist… clouds just broke up! Model Raob Model Raob MYJ YSU (Jack Kain, NSSL)

27. Black Contours: Surface Mixing Ratio Colors: Surface Volumetric Soil Moisture (b) 4-km HRLDAS fields (a) 40-km EDAS soil fields Similar large-scale heterogeneity in OK EDAS is wetter along the TX dryline drywet Land Surface Sensitivities: (19 June 2002 IHOP, Stan Trier)

28. Trier, Chen and Manning, 2004. Coarse resolution soil moistureHigh resolution soil moisture 3 hour precip.

29. Theoretical Predictability Limits?? Thunderstorms (~10 km): ~ 1h Convective Systems (300 km): ~12 h Subsynoptic waves (~1200 km): ~1.5 days Lorenz, 1969 Atmos. Energy Spectrum Predictability Limit for given scale Scale (km) Error spectrum at given time Rich Rotunno (NCAR/MMM) Tuesday morning (wk 2)

30. What can data assimilation offer us?? Chris Snyder, (NCAR/MMM) Fundamentals of data assimilation, Tuesday morning David Dowell (NCAR/MMM-RAL) Ensemble Kalman Filters, Wednesday morning Jenny Sun (NCAR/MMM-RAL) The VDRAS system, Thursday morning

31. Three hour forecast (4DVar data assimilation system, Juanzhen Sun) Observed reflectivity (KVNX radar) IHOP case, June 12, 2002

32. EnKF assimilation of KOUN NEXRAD data (50 ensemble members) Dowell et al. 2004

33. What is the future for Mesoscale Observations? Howard Bluestein (OU) Thursday morning (wk 2)

34. Sensitivity studies indicate that moisture is the key observable for improved short range forecasts of hazardous weather. REFRACTIVITYGPS PRECIPITABLE WATER WATER VAPOR DIAL LIDAR

35. POLARIMETRIC RADAR OBSERVATIONS Particle discrimination

36. So, will we ever be able to predict this…. ….hours,days in advance??? Lou Wicker (NSSL) Tuesday afternoon (wk 2)

37. Hurricane Frances Reflectivity near Landfall Melbourne Radar 48 h forecast from 4 km WRF valid at 00Z Sept 5 Chris Davis (NCAR/MMM), Wednesday (wk 2 )

38. Convective storms/systems Morris Weisman (NCAR/MMM)

39. X 0600 UTC 10 June, 2003 11 June, 2003 0540 UTC 10 June, 2003 Upscale Growth of Convection Chris Davis (NCAR/MMM) Bow echoes MCV MCSs

40. Synoptic and mesoscale influences…… Lance Bosart (SUNY), Howard Bluestein (OU), Stan Trier (NCAR/MMM), Steve Weiss (SPC)

41. Colloquium Goals: What are our current capabilities related to convective NWP in the 0-36 h range? What are our current limitations? (numerics, physics, observations, assimilation techniques,computer capacity…i.e.,where do we need research?)  What can we hope to achieve? e.g., predictability!!!