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Nowcasting and Short Range NWP at the Australian Bureau of Meteorology

Nowcasting and Short Range NWP at the Australian Bureau of Meteorology. Peter Steinle Earth System Modelling Group Alan Seed Weather & Environmental Prediction Group. Rainfall Nowcasting in the BoM … Short Term Ensemble Prediction System (STEPS) Estimation & Nowcast (radar & gauge)

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Nowcasting and Short Range NWP at the Australian Bureau of Meteorology

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  1. Nowcasting and Short Range NWP at the Australian Bureau of Meteorology Peter Steinle Earth System Modelling Group Alan Seed Weather & Environmental Prediction Group

  2. Rainfall Nowcasting in the BoM … • Short Term Ensemble Prediction System (STEPS) • Estimation & Nowcast (radar & gauge) • Short forecast (radar, gauge & NWP) • NWP in the BoM … • Aust. Community Climate & Earth System Simulator (ACCESS) • Met Office Unified Modelling System • Bringing them together …. • Strategic Radar Enhancement Program (SREP) The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  3. Initializing the nowcast:Multi-radar QPE • Mosaic of Sydney area radars • 10 min, 2 km resolution • Gauge adjusted QPE for each radar • Advect images to a common time: • 1-5 min forecasts • Blend the radars: • inverse error variance as weights The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  4. 128-256-512 km 64-128-256 km 32-64-128km 16-32-64 km 8-16-32 km 4-8-16 km 2-4-8 km STEPS QPNSpectral decomposition of a rainfall field Use Fourier notch filters to isolate narrow bands of wavelengths in the field The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  5. STEPS QPN60 minute rainfall accumulation forecasts Radar accumulation Forecast – ensemble mean The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  6. STEPS QPN60 minute probability products Probability accumulation > 10 mm Probability accumulation > 20 mm The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  7. STEPS QPF: 0 – 6 hours • Melbourne, Sydney, Brisbane – 500 km domain, 2 km & 10 min resolution • Blends radar forecasts with Numerical Weather Prediction • 30 member ensemble updated every hour • 10-min forecasts of rainfall intensity out to 6 hours • Probability products for hourly accumulations for next 6 hours Probability of rain > 1 mm for 2 & 3 hour lead times, Melbourne Rainfall intensity forecast, 150 min lead time, Sydney The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  8. STEPS QPF 0 – 6 hour with NWP blending • Skill of nowcast is a function of scale and lead time • Skill of NWP is a function of scale • Decompose the NWP into components • Blend the NWP and nowcast components, weights a function of lead time and scale • Generate the ensemble by adding statistical noise that represents the error in the deterministic blended forecast for each component • Combine the components into the forecasts The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  9. STEPS QPFWeights for nowcast & NWP Blending The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  10. NWP systems • Met Office Unified Model (UM7.5,L70) • 6 hourly 4dVAR : Global, Region & TC • 4km City Systems • No Assimilation (3dVAR expt.) • 1.5km UM7.6/L70 (Experimental) • 3dVAR • + radar winds & precip(LHN) • Relocatable • Ensembles • Global & Regional EPS in research • Need deterministic high res. Global: N320 (~40km) + 4dVAR Regional 0.11o +4dVAR City: 4km ; no DA The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  11. SREP to deliver: • 4 new radars delivering QPE & F products as appropriate for radar location • STEPS blending radar nowcasts with NWP in the Capital Cities • NWP assimilating radar data operationally • Start with Latent Heat Nudging for simplicity & baseline • Begin moving to VAR soon • Rapid update cycle and relocatable domains tested and made ready for transition into operations • Prototype radar QC system ready for transition into operations The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  12. Extensive testing on Brisbane Jan2-14 2011 Hourly precipitation Radar+Gauge Analysis SREP 1.5km 6hr forecast Operational 0.05o 6hr forecast The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  13. Have STEPS & NWP…So all done & dusted??? • Apart from one or two problems… • Rainfall estimation • Systematic errors from clutter and quality control • Model calibration • Overdoes heavy precipitation in tropics • Assimilation • Large initial rainfall in the tropics • Dirty laundry time….. The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  14. QPE Errors Climatology – truth from rain gauges Melbourne Mean daily rain rate Gauge data only The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  15. QPE ErrorsClimatology – radar Systematic errors are obvious in long accumulations Blocking from hills Clutter Radar clutter rejection The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  16. Area & Volume vs Rainfall Rate (2-11 Jan) Obs 3dVAR+LHN 3dVAR only • 1.5km – too much convection & too strong • 4,5 & 6 hour forecasts • Model calibration • Latent Heat Nudging needs calibration • One of the worse events • Sydney events looked much better • 0.05o & 0.11o problems with heavy precipitation too • 3,4,5,….,14 hour forecasts • Little sensitivity to forecast length • 3dVAR / no 3dVAR similar Obs 3dVAR+LHN 0.05o (FC only) 0.11o 4dVAR The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  17. After effects from Latent Heat Nudging … Hourly precipitation Radar+Gauge Analysis SREP 1.5km 4hr forecast Operational 12km 4hr forecast The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  18. Summary • Rainfall nowcasting established • In the queue for operations • Improved radar quality control being tested • NWP “developing” • Seems better much behaved away from tropics • More extensive trials in Sydney underway • Tropical NWP still a challenge • Restrain LHN • Systems are in place • Analysis → Nowcast → NWP blend → NWP • Calibration/tuning of components ongoing The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

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