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HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes

HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes. Dan Petersen NROW Conference Nov. 4, 2009 With contributions from David Novak and Keith Brill. HPC Winter Weather Desk Overview. Internal deterministic 6-h snow/ sleet/ ZR accumulation grids & graphics.

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HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes

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  1. HPC Winter Weather Desk Operations and Upcoming NCEP Model Changes Dan PetersenNROW Conference Nov. 4, 2009With contributions from David Novak and Keith Brill

  2. HPC Winter Weather DeskOverview Internal deterministic 6-h snow/ sleet/ ZR accumulation grids & graphics Track forecasts for sfc. lows associated w/ significant winter weather • Public products of 24-h exceedance probabilities for: • Snow/Sleet: 4,8,12 in. • Freezing Rain: 0.25 in. • Probabilities computed from deterministic forecast and model spread Heavy Snow and Ice Discussion (QPFHSD)

  3. Winter Weather Desk (WWD) Forecast Process • Analysis of lift, instability, moisture, and thermal profiles of model solutions • Use model/ensemble blender to generate first guess • - Precipitation type from thermal profile of blend • - Snow-liquid ratio from Roebber technique /Climatology/ fixed ratio • Forecaster edits first guess, and sends to WFOs

  4. WWD Collaborative Forecast Process HPC/WFO Collaboration via instant message, phone and/or event conference calls • WFO input used to modify public snow/ice probabilistic forecasts • HPC input used to modify grids within GFE to produce local forecast • Results in final collaborated forecast

  5. Advent of WWD Accumulation Grids in AWIPS (snow blue-green-orange, freezing rain pink-purple) Courtesy Brian Montgomery, WFO Albany

  6. Advent of WWD Accumulation Grids in GFE Snow, freezing rain, and snow to liquid ratio grids are available in six hourly increments for ingest at WFOs. Requested at NROW 2008! Courtesy Brian Montgomery, WFO Albany

  7. Probabilistic snow forecast verification NAM + GFS + SREF members + GEFS members • Hypothesis: Probabilities for ≥12” threshold forecast over too small of area (i.e., under dispersive / too focused on a preferred solution or cluster of solutions)

  8. 2008-9 Day One Snow Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+ SREF mean +GEFS mean

  9. 2008-9 Day Two Snow Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+SREF mean +GEFS mean

  10. 2008-9 Day Three Snow Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+SREF mean +GEFS mean

  11. 2008-9 Day One Ice Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+SREF mean +GEFS mean

  12. 2008-9 Day Two Ice Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+SREF mean +GEFS mean

  13. 2008-9 Day Three Ice Accumulation Threat Scores Green: Winter Weather Desk manual forecast Blue: NAM+GFS+SREF mean +GEFS mean

  14. Verification of HPC low tracks (position at each forecast hour) Average of GFS/NAM did best through 24 hours, while ECMWF and HPC were best after 48 hours.

  15. The NCEP Short-Range Ensemble Forecast (SREF) System Jun Du, Geoff DiMego and Bill Lapenta NOAA/NWS/NCEP Environmental Modeling Center http://www.nws.noaa.gov/om/notification/tin09-29aaasref_upgrade.txt

  16. Upgrade models: WRF-NMM, WRF-ARW and RSM Increase horizontal resolution: ARW (45 km to 35 km) NMM (40 km to 32 km) RSM (45 km to 32 km) Total Membership = 21: Adding 4 WRF members Eliminating 4 Eta members Zhou cloud physics  Ferrier (3 RSM members) Ensemble Transform (ET) perturbations (10 WRF members) Increase output frequency from every 3 hr to hourly for 1st 39hr Add/fix/unify variables in SREF output radar (composite reflectivity + echo top) (aviation) unify PBL height diagnosis with critical Ri (aviation) fix cloud base (aviation) BUFR broken out into individual station time-series (SPC) Hurricane track Upgrades to the SREF system (Implemented 27 Oct. 2009) 87 h forecast

  17. SREF Plume – State College, PA Initial time: 09 UTC 23 Nov 2008 Cold WRF v2.0 Members

  18. SREF Plume – State College, PA Initial time: 09 UTC 23 Nov 2008

  19. SREF Future Plans • 2010: • Post processed output of SREF members downscaled to 5 or 2.5km • Addition of more variables to AWIPS • Addition of more ensemble products requested by users such as AFWA • Eta members discontinued

  20. SREF Future Plans • 2010: • Post processed output of SREF members downscaled to 5 or 2.5km • Addition of more variables to AWIPS • Addition of more ensemble products requested by users such as AFWA • Eta members discontinued • 2012: • SREF run at 20 km resolution (2010 run at 32 km) • Introduction of the NAM Rapid Refresh (10-12 km, hourly update to the 24 hour forecast) • Introduction of higher resolution (3 km) nested rapid refresh for high impact events in CONUS, AK and HI

  21. The NCEP Global Forecast System (GFS) John Ward NOAA/NWS/NCEP Environmental Modeling Center http://www.nws.noaa.gov/om/notification/tin09-32gfs_changes.txt

  22. December 15 Implementation • Gridpoint Statistical Interpolation (GSI) Analysis/GFS Fall Bundle • Ingest new data types – primarily satellite • Motivation: Simulating ECMWF initialization improved GFS forecast performance ams.confex.com/ams/pdfpapers/142644.pdf • Benefits • Better tropical cyclone definition • Small incremental improvement in forecast skill

  23. March 2010 Implementation • Update Shallow convection, Deep Convection, PBL Schemes • Benefits • Significant reduction in gridpoint storms • Improvement in forecast skill (QPF, wind, temp, etc) 24 h accumulated precip ending 12 UTC 15 July 2009 Observed 72 h GFS Forecast 72 h GFSp Forecast

  24. May 2010 Implementation • GFS Resolution Increase • T382L64 (~35 km) T574L64 ( ~27 km grid spacing) • Benefits • Overall improvement in forecast skill

  25. Yuejian Zhu Zoltan Toth, Richard Wobus, Dingchen Hou and Bo Cui Global Ensemble Group Environmental Modeling Center http://www.nws.noaa.gov/om/notification/tin09-34gefs.txt The NCEP Global Ensemble Forecast System (GEFS) upgrades

  26. Planned Changes - Summary • Effective late January, 2010 • Upgrade horizontal resolution from T126 to T190 • Use 8th order horizontal diffusion for all resolutions • Improved forecast skills and ensemble spread • Introduce Earth System Modeling Framework(ESMF) for GEFS • Allows concurrent generation of all ensemble members • Needed for efficiency of stochastic perturbation scheme • Add stochastic perturbation scheme to account for random model errors • Increased ensemble spread and forecast skill (reliability) • Add new variables (28 more) • Mostly stratospheric

  27. Continuous Ranked Probability Skill Score for Northern Hemisphere (NH) 850hPa temperature Extend current 5-day skill to 6-day Extend current 5-day skill to 6.5-day

  28. NH Anomaly Correlation for 500hPa HeightPeriod: August 1st – September 30th 2007 GEFSp is better than GFS at 48 hours Parallel GEFS forecast skill at day 9 equals the GFS skill at day 7 24 hours better than current GEFS 48 hours better than current GFS

  29. Summary • WWD continues to provide critical winter weather forecast guidance and collaboration • Gridded snow and ice accumulations and SLR in AWIPS • WWD products generally improve upon NCEP model guidance • Several upcoming model upgrades • SREF (Oct 2009) • GFS (several phases) • GEFS (January 2010) Questions or Comments? Dan Petersen (301)763-8201 Dan.Petersen@noaa.gov

  30. WWD Snow/Ice Verification Method 6 hourly Snow and Ice Gridded Analyses P-type mask applied based on station obs. Where snow: First guess snow analysis = NPVU QPE x climatological SLR2. The resulting first guess is adjusted by Coop, CoCorahs, and METAR observations. Where freezing rain: First guess ice analysis = NPVU QPE. This is adjusted by METAR observations. 6-hourly Snow and Ice Gridded Forecasts • WWD gridded forecasts compared against • “Superensemble” (NAM+GFS+SREF mean+GEFS mean) • Manually selected model blend To compare skill of WWD forecasts versus models, need to convert 6-hourly model QPF forecasts into model snow and ice forecasts Model forecast P-type determined from each model’s p-type algorithm Where model forecasts snow: Model forecast snow accumulation = model QPF * Snow Liquid Ratio where the SLR is a 4 member mean of Roebber technique1 applied to GFS, Roebber technique applied to NAM, Climatology2, and 10:1 Where model forecasts freezing rain: Model forecast ice accumulation = model QPF 1Roebber, P. J., S. L. Bruening, D. M. Schultz, and J. V. Cortinas, 2003: Improving snowfall forecasting by diagnosing snow density. Wea. Forecasting, 18, 264-287. 2Baxter, M. A., C. E. Graves, and J. T. Moore, 2005: A climatology of snow-to-liquid ratio for the contiguous United States. Wea. Forecasting, 20, 729-744.

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