1 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

2 HPC Winter Weather Desk Overview Internal deterministic 6-h snow/ sleet/ ZR accumulation grids & graphics Heavy Snow and Ice Discussion (QPFHSD) 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

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

4 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 HPC/WFO Collaboration via instant message, phone and/or event conference calls WWD Collaborative Forecast Process

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

6 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 Advent of WWD Accumulation Grids in GFE

7 Probabilistic snow forecast verification 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) NAM + GFS + SREF members + GEFS members

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

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

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

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

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

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

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) (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

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/ pdf –Benefits »Better tropical cyclone definition »Small incremental improvement in forecast skill

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

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

25 The NCEP Global Ensemble Forecast System (GEFS) upgrades Yuejian Zhu Zoltan Toth, Richard Wobus, Dingchen Hou and Bo Cui Global Ensemble Group Environmental Modeling Center

26 Planned Changes - Summary Effective late January, 2010 Upgrade horizontal resolution from T126 to T190 Use 8 th 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 6.5-day Extend current 5-day skill to 6-day

28 NH Anomaly Correlation for 500hPa Height Period: August 1 st – September 30 th 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 Several upcoming model upgrades –SREF (Oct 2009) –GFS (several phases) –GEFS (January 2010) WWD products generally improve upon NCEP model guidance Questions or Comments? Dan Petersen (301)

30 WWD Snow/Ice Verification Method Where model forecasts snow: Model forecast snow accumulation = model QPF * Snow Liquid Ratio where the SLR is a 4 member mean of Roebber technique 1 applied to GFS, Roebber technique applied to NAM, Climatology 2, and 10:1 1 Roebber, P. J., S. L. Bruening, D. M. Schultz, and J. V. Cortinas, 2003: Improving snowfall forecasting by diagnosing snow density. Wea. Forecasting, 18, Baxter, 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, WWD gridded forecasts compared against “Superensemble” (NAM+GFS+SREF mean+GEFS mean) Manually selected model blend P-type mask applied based on station obs. Where snow: First guess snow analysis = NPVU QPE x climatological SLR 2. The resulting first guess is adjusted by Coop, CoCorahs, and METAR observations. Model forecast P-type determined from each model’s p-type algorithm To compare skill of WWD forecasts versus models, need to convert 6-hourly model QPF forecasts into model snow and ice forecasts Where model forecasts freezing rain: Model forecast ice accumulation = model QPF 6 hourly Snow and Ice Gridded Analyses 6-hourly Snow and Ice Gridded Forecasts Where freezing rain: First guess ice analysis = NPVU QPE. This is adjusted by METAR observations.