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March 2007 NAEFS Upgrade

March 2007 NAEFS Upgrade. Yuejian Zhu, Richard Wobus, Mozheng Wei, Bo Cui and Zoltan Toth Environmental Modeling Center NOAA/NWS/NCEP Acknowledgements: Qingfu Liu, DingChen Hou, Mark Iredell and Stephen Lord EMC Luke Lin, David Michaud, Joey Carr and Brent Gordon NCO.

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March 2007 NAEFS Upgrade

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  1. March 2007 NAEFS Upgrade Yuejian Zhu, Richard Wobus, Mozheng Wei, Bo Cui and Zoltan Toth Environmental Modeling Center NOAA/NWS/NCEP Acknowledgements: Qingfu Liu, DingChen Hou, Mark Iredell and Stephen Lord EMC Luke Lin, David Michaud, Joey Carr and Brent Gordon NCO

  2. Planned Changes - Summary • Increasing NAEFS (NCEP/GEFS) membership • 80 perturbations in cycling (see schematic plot) • Replaced operational 56 perturbations in cycling • 20 perturbed long forecasts (16-d) in each cycle • Replaced operational 14 long forecasts in each cycle • NAEFS (NCEP/GEFS) post-product • Post-process 20 ensemble forecasts instead of operational 14 ensemble forecasts for: • Bias correction • Anomaly forecast

  3. 6 hours breeding cycle Production 6 hours breeding cycle Planned Change Re-scaling Re-scaling 6hrs Next T00Z Up to 16-d 6hrs Next T00Z Up to 16-d T00Z 56m T00Z 80m Re-scaling Up to 16-d Re-scaling T06Z 56m T06Z 80m Up to 16-d Re-scaling Re-scaling T12Z 56m T12Z 80m Up to 16-d Up to 16-d Re-scaling Re-scaling T18Z 56m T18Z 80m Up to 16-d Up to 16-d

  4. GEFS configurations

  5. Early study indicated: (by Mozheng Wei) ET20/80 give most skillful probabilstic forecast when compared to 10m operation and 10m ET

  6. Planned Changes 1 • Increasing NAEFS (NCEP/GEFS) membership. • From current 14 increasing to 20 members per cycle. • Tuning initial perturbations. • Using 80 cold start initial perturbations (on Jan. 25) • From 24-h forecasts and many dates. • To have large spread of sampling • This change is intended to improve ensemble based probabilistic forecast over all and to support NAEFS (North American Ensemble Forecast System) project. • Results: • Improving probabilistic skills. • Not much improvement for ensemble mean (expected).

  7. ENS_s – operation ENS_b – large sprd ENS_d – small sprd Doted lines – 1-day spread Day-5 PAC scores Cold start from 00UTC Nov. 17 2006 Large initial spread has more skill Doted lines-spread

  8. Cold start from 00UTC Nov. 7th 2007 ENS_s – operation ENS_c – large sprd NH 500hPa ROC Different period-more runs for large initial spread (cold start) Tropical 500hPa ROC SH 500hPa ROC

  9. ENS_s – operation ENS_b – large sprd ENS_d – small sprd NH 500hPa RPSS 20m has more prob skills than 14m Tropical 500hPa ROC SH 500hPa ROC

  10. Retrospective experiments/NCO real time parallel • Retrospective experiments. • Summer period: August 22- September 24 2006 (Hurricane season). • Winter period: November 7-December 7 2006 • 20 ensemble members. • Using current GFS. • NCO real time parallel. • Starting since January 25 2007. • Full evaluations (follow up above experiments). • Summer: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/exp/ens_20m_2006_exp_h.html • Winter: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/exp/ens_20m_2006_exp_c.html • NCO real time: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/opr/prx_2007.html • Expect to implement (March 27 2007).

  11. Winter 2006 Retrospective runs Summer 2006 Retrospective runs

  12. Winter 2006 Retrospective runs Summer 2006 Retrospective runs

  13. Winter 2006 Retrospective runs Summer 2006 Retrospective runs

  14. Hurricane Track Errors (Period: 08/22-09/24/2006) Atlantic Basin East Pacific Basin ENSs-operational ensemble ENSx-retrospective runs Hours Cases 157 146 133 121 99 80 58 Cases 98 86 74 64 40 19 10

  15. NCO real time parallel NH 500hPa geopotential height NCO real time parallel NH 2 meter temperature

  16. Conclusions of the 20m experiments • Ensemble mean: • No significant different (do not expect). • No degradation (not worse – very important) • Ensemble distribution (probabilistic forecast): • Significant improvement from 20 ensemble members. • For ROC, EV, Reliability. • Not for RPSS BSS. • Initial perturbation for cold start: • Large cold start initial spread is (JIFed) • From backup perturbation based on 24h forecasts in many dates. • Giving sufficient spread in ET. • Quickly scaling down to the expected level (1-2 days). • Able to catch up large uncertainty cases. • Degrading the skills a little for short lead-time in the first few cycles. • Small cold start initial spread is • From backup perturbation based on 6h forecasts in one day. • No degradation at early cycling. • Not able to catch up large uncertainty system for longer lead-time. • Because error grows very slowly.

  17. Planned Changes 2Details for Slide 2 • NAEFS (NCEP/GEFS) Post Products • Bias corrected members of joint MSC-NCEP ensemble • NCEP • Current: 14 (perturbed forecasts) + 1 (control forecast) = 15 forecasts at each cycle • Plan: 20 (perturbed forecasts) + 1 (control forecast) = 21 forecasts at each cycle • MSC • Same: 16 (multi-model, multi-physics forecasts) + 1 (control forecast) = 17 forecasts at 00UTC and 12UTC cycle only • 35 of NAEFS variables • Bias correction against each center’s own operational analysis • Weights for each member for creating joint ensemble (equal weights right now) • Weights don’t depend on the variables • Weights depend on geographical location (low precision packing) • Weights depend on the lead time • Climate anomaly percentiles for each member • NCEP • Current: 14 (perturbed forecasts) + 1 (control forecast) = 15 forecasts at each cycle • Plan: 20 (perturbed forecasts) + 1 (control forecast) = 21 forecasts at each cycle • MSC • Same: 16 (multi-model, multi-physics forecasts) + 1 (control forecast) = 17 forecast at 00UTC and 12UTC cycle only • 19 of NAEFS variables

  18. NH Mean Sea Level Pressure NH 2 Meter Temperature NCO real time parallel: Accumulated bias (absolute values) for past one month Black – raw forecasts Red – bias corrected forecasts NH 500hPa Height

  19. Summary of Subjective Analysis • CPC • We do not see any cause for concern that an increase in the ensemble will have any negative impact on the CPC operational products.  Given that, we fully support this implementation to increase the ensemble size. • HPC • There was little improvement over the standard GFS ensemble forecast. This subjective evaluation was noted on both mass fields and model QPF. • HOC recommends implementation • OPC • Little difference noted between operational and parallel data sets. • OPC recommends implementation • AWC • While AWC supports the idea to increase the number of members in the ensemble to represent better the envelope of possibilities for various forecast parameters, we are unable to provide a more rigorous assessment due to the lack of resources to ingest the data and routinely view the available fields

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