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Michael J. Brennan Science and Operations Officer Hydrometeorological Prediction Center

What’s New at NCEP? An Update on the HPC Winter Weather Desk and Recent Changes to the NCEP Model Suite. Michael J. Brennan Science and Operations Officer Hydrometeorological Prediction Center 9 th Northeast Regional Operational Workshop 8 November 2007. Outline. HPC Winter Weather Desk

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Michael J. Brennan Science and Operations Officer Hydrometeorological Prediction Center

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  1. What’s New at NCEP? An Update on the HPC Winter Weather Desk and Recent Changes to the NCEP Model Suite Michael J. Brennan Science and Operations Officer Hydrometeorological Prediction Center 9th Northeast Regional Operational Workshop 8 November 2007

  2. Outline • HPC Winter Weather Desk • 2006–2007 Verification • What’s new for 2007–2008 • NCEP Model Upgrades • SREF • NAEFS • Hi-Res Window • New Uncertainty Guidance

  3. HPC Winter Weather DeskOverview • Internal deterministic 24-h snow/sleet and freezing rain accumulation graphics for days 1–3 • PRISM-adjusted for Intermountain West • 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 • Track forecasts for sfc. lows associated w/ significant winter weather • Heavy Snow and Ice Discussion (QPFHSD)

  4. HPC Winter Weather Desk2006–2007 Verification – Snow/Sleet HPC adjustments show largest improvement over model guidance for snow > 12” D1 D2 D3

  5. HPC Winter Weather Desk2006–2007 Verification – Freezing Rain HPC Adjustments show most improvement for FZRA amounts <0.10” Day 3 D1 Day 2 D2 D3

  6. 15 Oct 2006 – 1 May 2007 GFS Root Mean Square Errors Forecast Hour (from 00Z or 12Z) HPC Winter Weather Desk2006–2007 Verification Snow-Liquid Ratio • Roebber method had lowest RMSE for computation with GFS model • 10:1 ratio second lowest RMSE at all lead times

  7. HPC Winter Weather Desk2006–2007 Verification Low Tracks (Associated with “significant winter weather” only) • HPC low track forecast RMSE ranges from 85 nm at F12 to 140 nm at F72 • HPC shows most improvement over GFS and NAM after 36 h • Best guidance at most times is GFS/NAM blend • SREF Mean also performs well (best at F12 and F72)

  8. HPC Winter Weather DeskNew for 2007–2008 • Grid spacing of non-PRISM-adjusted snow/ice grids decreased from 40 km to 20 km • QPF from Canadian model now available in winter weather precipitation blender • Addition of ECMWF pending receipt of 6-h QPF • CoCoRAHS snow data will be used in verification

  9. HPC Winter Weather DeskNew for 2007–2008 • Based on 2006-2007 verification, HPC Snow-Liquid Ratio will be equal blend of: • 10:1 ratio • Roebber method computed from NAM • Roebber method computed from GFS • Climatological SLR • Computed every 6-h through forecast period • Maps on internal WWD webpage show resultant 6-h SLR values

  10. NCEP Model Suite Changes

  11. Hi-Res Window (HRW) Upgrade 12 km 4 km Black dots represent water points in model (Chesapeake Bay) • Code upgraded to official public version of WRF distributed by NCAR • WRF-NMM: • Decreased horizontal grid spacing from 5.2 km to 4.0 km • Added local NCEP changes made to NAM • WRF-ARW: • Decrease horizontal grid spacing from 5.8 km to 5.1 km • No CP scheme used • Generate new post-processed fields: • Simulated GOES satellite fields • Improved simulated radar reflectivity • Available through TOC and ftpprd • Limited fields available on NCEP models website

  12. HRW “Large” Domains • Large Domain Schedule: • 00/12Z: East-Central CONUS • 06Z: West-Central CONUS • 18Z: Alaska • 1 hurricane run cancels ARW runs on large and small domains • 2 or 3 hurricane runs cancel both ARW runs and NMM run on large domain • 4 hurricane runs cancel all runs • Small domains: • Hawaii (00/12Z) • Puerto Rico (06/18Z) East-Central CONUS Alaska West-Central CONUS

  13. Short Range Ensemble Forecast System (SREF) Upgrade • 21 members • 10 Eta • 6 WRF • 5 RSM • Bias corrected output for all parameters except QPF • Same BC methodology used for GEFS/NAEFS • Decay function weights last 50-60 days most heavily • 4 new aviation forecast parameters • Icing • Clear Air Turbulence • Low-Level Ceiling • Flight Restriction • Parallel evaluation: 2 Oct. • Implementation: 11 Dec. • Bias-corrected SREF output will eventually replace current output in AWIPS SREF Mean BC 500-mb hght (magenta) SREF Mean 500-mb hght (red) Magnitude of bias correction for 87-h 500-mb height forecast

  14. SREF Probability of 24-h QPF > 2” with TS Noel Experimental HPC/SPC SREF-based Winter Weather Impact Graphics Short Range Ensemble Forecast System (SREF) Upgrade • Next SREF upgrade – tentatively scheduled for the 3rd quarter of FY08 • Upgrade the WRF members to the latest version • Increase the resolution of all members to as close as 32 km as possible given computational resources • Eta members already running at 32 km

  15. Real Time Mesoscale Analysis (RTMA) • 5 km NDFD resolution hourly analysis of T, Td, wind, sfc. pres. • First Guess: downscaled RUC (NAM) as first guess for CONUS (AK, Hi, PR) • Uses ‘all’ sfc obs within +/- 12 min of analysis time • Data assimilated with 2-D version of NCEP’s Gridpoint Statistical Interpolation (GSI) analysis scheme • Available on NDFD page http://www.weather.gov/forecasts/graphical/sectors/ • Used for NAEFS downscaling 2-m T 10-m WND

  16. North American Ensemble Forecast System (NAEFS) Upgrade • Combined NCEP and CMC ensemble system • 40 members, available twice daily (for now) • Bias corrected output using same methodology as SREF • Output includes • Ensemble Mean, Spread, Mode • 10th, 50th (median), and 90th percentile probabilities • Anomalies compared to NCEP/NCAR reanalysis • Downscaled output to 5-km NDFD grid using RTMA • 2-m T, 10-m wnd, sfc. pres. • Parallel evaluation: 25 Oct. • Operational implementation: 4 Dec. NAEFS Ensemble Mean MSLP and Spread 90-h forecast of Noel from 00 UTC 31 Oct

  17. NAEFSDownscaling NAEFS Ensemble Mean Bias Corrected & Downscaled 2-m Temperature (F) (5km) NAEFS Ensemble Mean Bias Corrected 2-m Temperature (F) (1°)

  18. NAEFSUncertainty Information Mean 10th percentile 90th percentile Median (50th percentile)

  19. HPC Alaska Desk Mode 10 90 • Working with EMC to provide additional uncertainty information medium range guidance for Alaska WFOs • HPC deterministic forecast  mode • 10th and 90th percentile probabilities computed from downscaled NAEFS and adjusted with HPC forecast for Min/Max T & wind speed • Remaining issues • How to downscale for max/min T occurring at widely varying times? • Quality of RTMA over Alaska (for downscaling and verification) • Potentially very large spreads for temperature, wind speed – is 10/90 best range? • Desk will begin issuing experimental products in December • Opportunity to try new things – if successful may be transitioned to CONUS medium range

  20. Looking Ahead... NOAA Center for Weather and Climate Prediction (NCWCP) College Park, Maryland 268,762 ft2 building will be new home for NCEP, NOAA’s Satellite and Information Service, and Air Resources Laboratory Scheduled to be complete early 2009 Construction Progress as of 23 October

  21. Questions/Comments? Michael.J.Brennan@noaa.gov

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