Nimrod rainfall forecasting system overview


Nimrod overview
  • Operational in UK since 1997
  • Operational domain
    • Poland: 1600 x 1600 km
  • Analyses
    • synoptic reports, radar, satellite, NWP and previous Nimrod nowcast
    • 2D-VAR
  • Nowcasts
    • optimum combination of observation extrapolation & NWP
    • resolution: 4 km, 15 minute
    • range: T+6 hours
Nimrod data I/O
Nimrod radar data processing in UK


Nimrod Forecasts
  • Rainfall rate and accumulation
  • Probability of snow
  • Precipitation type


Nimrod rainfall forecast scheme
  • Identify rain objects in rain analysis
  • Identify optimum method of moving rain objects
    • Cross-correlation
    • NWP wind vector
  • Generate an extrapolation forecast using optimum vectors for each rain object
  • Merge extrapolation forecast with NWP rain forecast
    • infill missing data areas in extrapolation forecast
    • introduces growth and / or decay into forecast
    • ensures continuity between forecast products
Nimrod extrapolation and 'merged' forecasts




Dissemination
  • RAINBOW
  • Nimrod format - binary, header followed by integer or real data array
  • Text
  • GIF / PNG - monitor pages
Progress
  • Tasks completed or almost complete
    • processing of GRIB / BUFR inputs
    • processing of Meteosat-7 VIS and IR
    • processing of synoptic weather reports
    • modifications to rain analysis / forecast to run on new domain
    • Nimrod monitor
  • Tasks still to do
    • radar processing
    • NWP processing
    • heavy rain warning messages
    • precipitation type forecast