Experiences with 0-36 h Explicit Convective Forecasting with the WRF-ARW Model Morris Weisman (Wei Wang, Chris Davis) NCAR/MMM WSN05 September 8, 2005

Composite NEXRAD Radar 00 UTC 6/10/ UTC 6/11/03

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

WRF Real-time Forecasts: 2004, 2005  4-km from 0000 UTC - 36 h  Version 1.3 ( )  Eta initial and boundary conditions (40 km)  Physics: Lin et al. (5 cat.) microphysics (WSM6) YSU PBL (first-order closure) Noah LSM (HRLDAS)  2000 km X 2000 km domain / 2800 km X 2600 km domain  5.0h (6.5h) on 128 (192) IBM Power-4 processors

Real-time WRF 4 km Forecast Composite NEXRAD RadarReflectivity forecast Initialized 00 UTC 9 June 03

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

Consider the h forecast challenge (i.e., the next diurnal cycle). How does the 4 km WRF-ARW ‘’guidance’’ compare to the 12 km operational ETA?

Radar 03 GMT May 30, GMT 27 hr 06 GMT prec. 30 hr 4 km WRF- ARW 12 km ETA

Overall Forecast Good: OK: Bad: WRFRADAR

How well does 4-km WRF represent the climatological behavior of convection? (e.g., diurnal cycle, episodes)

Longitudinal 1 hr Precip. May 10-31, 2004 Stage IV WRF

Diurnal Average Frequency: May 10-July Stage IV4 km WRF

12 km ETA4 km WRF Stage IV Diurnal Average3 hr Precip.

Initialized 04 June UTC Reflectivity forecast Composite NEXRAD Radar

24 h forecast Valid 00 UTC 06/05/05 4-km ARW 2-km ARW 4-km NMM Nexrad

ARW2BREF NMM4ARW UTC 29 April 2005: 1 km model reflectivity, NEXRAD BREF

Progress 4 km WRF-ARW simulations exhibit:  A surprising ability to forecast mesoscale convective systems (MCS) out to 36 h ( strongly controlled by 12-km ETA forcing)  A demonstrated skill at depicting MCS mode ( bow echoes, mesoscale convective vortices, supercell lines)  A more accurate depiction of diurnal cycle and precipitation episodes  An ability to spin-up convective systems within 3-4 h from a cold start.

QPF problematic (too much convective precip) Stratiform regions appear too small (microphysics?) Convective systems often fail to decay (BL evolution?) Initialization (data assimilation) Verification methods Challenge:

WRF-ARW 2005 real-time forecasts can be found at: Also archived at:

24 hr precipitation verification Valid 6/10/03 12 UTC OBS 10 km WRF4 km WRF12 km ETA

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

4 km WRF 12 h Reflectivity Forecast NEXRAD CompositeReisnerSchemeSB2004 Scheme WSM-6 Scheme Lin, et al. Scheme Valid 10 June Z Column Max Reflectivity (dBZ) (Axel Seifert, 2004)

Reisner LinWSM-6 SB h Surface Theta

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

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

Sounding comparison: 24h forecast valid 00Z 28 April at OUN ARW4 NMM4 Good in PBL, but CIN layer is washed out PBL too shallow and moist, but CIN layer looks good Model Raob Model Raob

24 h Reflectivity Forecast valid Z Radar 4 km WRF-ARW 2 km WRF-ARW 4 km WRF-NMM

Diurnal Average (2003) 4 km10 km

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”

CAT 3: severe, well organized (> 1 in) CAT 2: some organization ( in) CAT 1: weak, disorganized (<.25 in) Convective Mode/Intensity WRFETA