Whats 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 –2006–2007 Verification –Whats new for 2007–2008 NCEP Model Upgrades –SREF –NAEFS –Hi-Res Window New Uncertainty Guidance

HPC Winter Weather Desk Overview 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)

HPC Winter Weather Desk 2006–2007 Verification – Snow/Sleet D1 D2 D3 HPC adjustments show largest improvement over model guidance for snow > 12

HPC Winter Weather Desk 2006–2007 Verification – Freezing Rain Day 2 Day 3 HPC Adjustments show most improvement for FZRA amounts <0.10 D1 D2 D3

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

HPC Winter Weather Desk 2006–2007 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)

HPC Winter Weather Desk New 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

HPC Winter Weather Desk New for 2007–2008 Based on 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

NCEP Model Suite Changes

Hi-Res Window (HRW) Upgrade 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 Black dots represent water points in model (Chesapeake Bay) 12 km4 km

HRW Large Domains East-Central CONUS West-Central CONUS Alaska 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)

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 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

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 SREF Probability of 24-h QPF > 2 with TS Noel Experimental HPC/SPC SREF-based Winter Weather Impact Graphics

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 NCEPs Gridpoint Statistical Interpolation (GSI) analysis scheme Available on NDFD page graphical/sectors/ graphical/sectors/ Used for NAEFS downscaling 2-m T 10-m WND

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 –10 th, 50 th (median), and 90 th 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

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

NAEFS Uncertainty Information Mean10 th percentile 90 th percentileMedian (50 th percentile)

HPC Alaska Desk Working with EMC to provide additional uncertainty information medium range guidance for Alaska WFOs –HPC deterministic forecast mode –10 th and 90 th percentile probabilities computed from downscaled NAEFS and adjusted with HPC forecast for Min/Max T & wind speed 9010 Mode 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

Looking Ahead... NOAA Center for Weather and Climate Prediction (NCWCP) College Park, Maryland 268,762 ft 2 building will be new home for NCEP, NOAAs Satellite and Information Service, and Air Resources Laboratory Scheduled to be complete early 2009 Construction Progress as of 23 October

Questions/Comments?

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HPC Winter Weather Desk 2006–2007 Verification – 4 and 8 Snow Probabilities HPC Probabilities show good separation between forecast probability ranges and observed frequency for 4 and 8 snow amounts for days 1–3 4 in. 8 in.

HPC Winter Weather Desk 2006–2007 Verification – 12 Snow Probabilities HPC has tendency to over-forecast 12 probabilities on days 1–2, especially on 00 UTC cycle

HiResWindow WRF Configurations (No Parameterized Convection) WRF-NMMWRF-ARW Horizontal Grid Spacing (km) Vertical Levels35 Sigma-Pressure 35 Sigma PBL/TurbulenceMYJYSU MicrophysicsFerrierWSM3 Land-SurfaceNOAH Radiation (SW/LW)GFDL/GFDLDudhia/RRTM

NAEFS Uncertainty Information NAEFS bias corrected 500-mb height (216-h forecast) Ensemble mean (white) 10 th percentile (cyan) 90 th percentile (red)