1. Winter storm forecast at 1-12 h range
Develop a method to initialize mesoscale models with radar data to capture snowband initiation and dissipation.
Implement the above into the Weather Support to Decision Making (WSDM) automated winter weather nowcasting system.

2. Approaches The numerical forecasting system
adapted from NCAR/ARMY RTFDDA system
based on MM5 and observational nudging
suitable for case studies and real-time operations
Assimilating Level II radar data
(available in real-time from NSSL)
3D mosaic reflectivity from multiple radars
raw radial velocity from individual radars

3. NCAR/ATEC RTFDDA 1-3.3 km fine mesh; highly re-locatable
Continuously nudging observations at the stations
3 hourly cycles
Currrently assimilating:
Surface stations, rawinsonde, metar, ship/buoy reports, mesonet, aircraft reports, profiler and satellite wind, special range observations, …
MM5*
OBS
ETA/AVN
Analysis
Forecast

4. Realtime Radar Observations
1 km horizontal resolution
21 levels extending to 17 km
- 3D mosaic reflectivity over CONUS
- raw radial velocity from individual radars
(available in real-time from NSSL)

5. Using radar data with RTFDDA
Assimilating 3D mosaic reflectivity
Convert Z to rain/snow mixing ratio QR on the model grid
Nudge the QR field on the model grid
Add the latent heat associated with QR on the model grid
Assimilating radial velocity observations
Perform volume-velocity-processing (VVP) analysis using observations from radars on the 10 km grid
Assimilate VVP wind vectors using observational nudging

6. Activities in 2004-2005 (1) Case studies:
On assimilating 3D radar reflectivity (converted to QR) and adding back latent heating
Radial velocity analysis and impact of assimilating VVP wind
(2) Real-time system development:
software for data transfer, conversion, quality control, interpolation, and assimilation, and system automation
integration of the model forecast product with WSDM display
(3) Real-time tests
Winter 2004 for NYC, and winter 2005 for Illinois
Summer 2005 for Illinois-Indiana
assimilated 3D mosaic reflectivity data (QR and latent heat)

7. Winter 2005 Operation – MM5 Domain
30km, 10km and 3.3km nested grid
12 h forecast every 3h cycle
January – March 2005

8. Winter 2005 Operation – Display

9. Summary of Results The 3D radar reflectivity assimilation scheme
blends qr observations into MM5 analyses, and improves the skills for 0-3 h precipitation forecasts.
produces little improvement in qr forecasts beyond 3 hour
improves temperature forecasts in the 3-9 h range.
An improvement of the wind forecast is needed.
Assimilating VVP vectors from multiple radars
showed positive impact in some case studies
need to spatially and temporally filter the VVP wind

10. a small positive effect
Winter Storm Dec , 2002
RADAR OBS
RTFDDA + QR NUDGE
RTFDDA: NO QR NUDGE
4 hour forecast
RADAR OBS
analysis hour
RTFDDA: NO QR NUDGE
RTFDDA + QR NUDGE
a small positive effect

11. Statistical Verification – surface T and RH
T Bias
RH Bias
T RMS
RH RMS
Bias and RMS errors in the 6-9 h forecast of T and RH. Each value is a 7 week-long average for the hour of the day.
Red: Parallel run with radar data nudging. Blue: Control run.

12. Statistical Verification – surface WS and DIR
WS Bias
DIR Bias
WS RMS
DIR RMS
Bias and RMS errors in the 6-9 h forecast of Ws and Wd. Each value is a 7 week-long average for the hour of the day.
Red: Parallel run with radar data nudging. Blue: Control run.

13. An Example of VVP Wind Vectors

14. Impact of assimilating VVP wind winter storm on January 13, 2005
4h forecasts valid at 6Z of Jan. 13
No Radar
Reflectivity only
Reflectivity + VVP

15. Summer Case Study and Operation
6 h forecast every 3 h cycle
May 15 – August 31, 2005

16. Impact of assimilating reflectivity convective storm July 13, 2004
3h forecasts valid at 23Z of July 13
With Reflectivity
(and latent heat)
Observation
No Reflectivity

17. Furure Work System development and evaluation
Statistical verification of the previous real-time tests
Further develop and test the wind analysis scheme
(2) Real-time operations in summer and winter
Winter test is going on for Denver January-March 2006
Summer test is planned for May-August 2006
(3) Product design and display
develop model forecast products that suits aviation users’ needs
integrate model products with WSDM nowcasting system
(4) System upgrade – transition to WRF