1. Nowcasting Trends Past and Future By Jim Wilson NCAR 8 Feb 2011 Geneva Switzerland

2. Father of Nowcasting Sydney 2000 His Disipiles

3. Nowcasting definition – description of the current state of the weather in detail and the prediction of changes in a few hours WHAT IS NOWCASTING Originally defined by Browning for the 1 st Nowcasting Conference in 1981 as: O-6 hr forecasting by any method spatial scale of no more than a few kilometers (1-3 km) with frequent updates (5-10 min) Heavy emphasis on observations

4. Original Objectives of Nowcasting Working Group  Promote nowcasting (Forecast Demonstration Projects)  Encourage numerical modelers to work on the nowcasting time and space scales  Train forecasters in nowcasting techniques.

5. The following discussion relates to nowcasting convective storms

6. a) AutoNowcaster b) SPROG c) NIMROD f) Verification e) TITAN d) GANDOLF Sydney 2000 Forecast Demonstration  Extrapolation  Blending  Expert System  Verification Knowledge of convergence line location required to improve over extrapolation

7. Country SystemForecast Period Spatial Resolution Output Products China Hong Kong SWIRLS 0-6h2kmQPF 0-1hLightning; hail; downburst/wind gust; mesocyclone/tornado; and precipitation probability China BMB Beijing- ANC 30 and 60 min1kmInstantaneous reflectivity, likelihood of initiation > 35 dBZ, convergence line location and forecast position, (considering a wind fx product for venues) Canada CARDS 0-6hLocation, intensity and track of storm cell; QPF; hail size; gust; downburst; mesocyclone Australia STEPS 0-6h2kmQPF and precipitation probability China GRAPES 0-6h1kmPrecipitation; wind; temperature; humidity; and various diagnostic parameters for severe weathers (wind gust, hail, tornadoes, flash-flood, etc.). USA NIWOT 1-6h1kmInstantaneous reflectivity, (considering QPF) USA Forecast VDRAS 0-2h4kmWind, temp? Australia TIFS 0-3hLocation, intensity and track of storm cell; threat area Beijing 2008 Forecast Demonstration Project Participating Systems  Extrapolation  Blending  Expert System  Verification Blending techniques did not improve over extrapolation (did not have radar data assimilation) Forecaster with conceptual models of local storm evolution produced the best nowcasts.

8. There is now some evidence that high resolution numerical models that assimilate radar data can improve over extrapolation in the 3-6 hr time period

9. Original Objectives of Nowcasting Working Group  Promote nowcasting (Forecast Demonstration Projects) NWG has conducted two FDP’s and two Nowcasting Symposiums (Toulouse, France and Whistler, Canada) Success - Nowcasting now part of most meteorological conferences  Encourage numerical modelers to work on the nowcasting time and space scales Partial Success – Some good progress  Train forecasters in nowcasting techniques. Four WMO sponsored nowcasting training workshops (Sydney, Brasilia, Pretoria, Palm Cove). Plus double that for other sponsors. Success – but only a start, not a priority, observation skills weak

10. Summary of present status of nowcasting  Radar echo extrapolation – some work to improve, but little more possible 1.0

11. Summary of present status of nowcasting  Radar echo extrapolation – some work to improve, but little more possible  Data – utilizing all data sets essential  Numerical models – high resolution data assimilation essential and then only better for 3-6 hr period. Much effort still required.  Forecaster role – Best nowcasts include a forecaster with conceptual models of local storm evolution and access to automated tools

12. Rules for Storm Initiation With Boundary Cloud growth, IR cloud top temp decrease

13. Rules for Storm Initiation With Boundary Boundary moving into field of cumulus (convective rolls) Cloud growth, IR cloud top temp decrease

14. Rules for Storm Initiation With Boundary Colliding boundaries particularly if cumulus present Boundary moving into field of cumulus (convective rolls) Cloud growth, IR cloud top temp decrease

15. Rules for Storm Dissipation Boundary moving away from storm

16. Rules for Storm Dissipation Storms not organized, not large (<10 km), not with boundary 10 km

17. Rules for Storm moving from Mountains to Plains Mountains Plains Organized with gust front Cumulus or storms on plains Modified sounding unstable Move storms to Plains if:

18. Rules for Storm moving from Mountains to Plains Mountains Plains Unorganized, no gust front Modified sounding stable Dissipate Storms if: No Cumulus No cumulus on plains

19. What is needed to improve nowcasts 1) Improved understanding of physical processes on the micro- and mesoscales 2) High resolution observations of boundary layer winds and three-dimensional temperature and moisture fields

20. High resolution wind field from VDRAS

21. What is needed to improve nowcasts 1) Improved understanding of physical processes on the micro- and mesoscales 2) High resolution observations of boundary layer winds and three-dimensional temperature and moisture fields 3) Major improvements in numerical models on the nowcast time and space scales

22. Future: Require commitment of weather services or private companies to provide nowcasts. In U.S. see a trend toward private companies. Aggressive training of forecasters. 0-2 hr – Expert System with human input (possible exception is blending for strongly forced synoptic situations blending) Need to develop local conceptual nowcast rules 2-4 hr – blending (extrapolation, expert system and models) 4-6 hr – blending with heavy weight toward the model

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