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HPC Products and Services for Forecast Operations

This presentation by the Hydrometeorological Prediction Center covers the methodology and verification of their Quantitative Precipitation Forecast, winter weather desk, and medium-range forecasts. It also discusses resolving differences between model and ensemble solutions in NCEP's modeling system.

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HPC Products and Services for Forecast Operations

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  1. National Centers for Environmental Prediction (NCEP) Hydrometeorlogical Prediction Center (HPC) Forecast Operations Branch Dan Petersen Hydrometeorological Prediction Center DOC/NOAA/NWS/NCEP Dan.Petersen@noaa.gov 301-763-8201 With assistance from Joshua Scheck and Mike Schichtel

  2. Review HPC Products HPC Quantitative Precipitation Forecast (QPF) methodology HPC winter weather desk and temperature biases HPC medium range forecasts and performance verification NCEP modeling system update Answer questions Goals of Presentation

  3. NWS OPERATIONAL FORECAST OFFICES CWSUs not depicted WFOs RFCs

  4. HPC Products and Services Model Diagnostics Discussion- RESOLVE DIFFERENCES BETWEEN MODEL AND ENSEMBLE SOLUTIONS MODEL DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 1218 PM EST SAT DEC 09 2006 VALID DEC 09/1200 UTC THRU DEC 13/0000 UTC MODEL INITIALIZATION... MODEL TRENDS... MODEL DIFFERENCES AND PREFERENCES...

  5. HPC Products and Services • National Day One Forecast Chart-highlights precipitation types and potential for heavy precipitation, excessive rainfall, severe convective storms, tropical cyclones

  6. HPC Products and Services • Short Range Fronts, Pressures, and Precipitation Type/Intensity 12/24/36/48 hours New graphics for 6 hr, 60 hr forecasts coming in 2008

  7. HPC Products and Services • Surface Analysis

  8. HPC Products and Services • Excessive rainfall • Excessive Rainfall for Day One, Two, and Three • http://www.hpc.ncep.noaa.gov/qpf/94ewbg.gif (98e,99e) • PEI745 KWBC , discussion QPFERD

  9. QPF Performed on 3 desks (Day One, Days 2/3, Medium Range) Six-hourly forecasts for Days 1 through 3 Days 4-5, Five Day Total http://www.hpc.ncep.noaa.gov HPC PRODUCTS AND SERVICES

  10. HPC Products and ServicesQPF Methodology

  11. HPC QPF Methodology GFS 48 hr forecast 850-700 mb standardized moisture flux anomalies for 12z Oct 25 2007 GFS Day Two 24 hr forecast rainfall (left) • Ingredients-Based Approach Doswell et. al. December 1996 Weather and Forecasting • Forecaster examine moisture, lift, instability diagnostics

  12. HPC QPF Methodology • Forecasters review model timing and make a decision based on the timing preference • This is the NAM 84 hour forecast for 12z Oct. 25, 2007, resulting in NAM producing rains in the southern Plains and not southeast and Appalachians Verifying low near the AL/MS border

  13. HPC analysis of 24 hr rainfall ending 12z Oct 25, 2007 (3 inch isohyet green) RFC analysis (color-filled) overlaid with GFS Day 3 forecast

  14. RFC analysis (color-filled) overlaid with HPC Day 3 Forecast RFC analysis (color-filled) overlaid withNAM Day 3 Forecast

  15. HPC QPF Methodology • Adjust for known biases • ‘Long running NAM problem of generating too little warm sector convection, leading to higher amounts in the comma head’ Verifying analysis NAM 24 hr FCST 12z 30 MAR 2007 Too Much Too Little

  16. ECMWF HPC QPF Methodology GFS Verification

  17. HPC QPF Methodology PRISM is used as an overlay but not part of the qpf blender 5 km gridded HPC QPF available in AWIPS downscaled from 32 km generated by forecaster Average November rainfall

  18. HPC QPF Blender

  19. HPC Products and Services • QPF verification

  20. HPC Products and ServicesWinter Weather Desk

  21. HPC Winter Weather Desk • Twice daily issuance of product suite based on new model guidance 9/15-5/15 • 24 hour Snow and Ice accumulation probability graphic for days 1 through 3. • Public and technical versions of low tracks graphic depicting synoptic scale surface low tracks associated with heavy snow or ice. • Heavy Snow and Ice Discussion • Intended to complement the deterministic short term snow and ice forecasts issued by local Weather Forecast Offices

  22. HPC Winter Weather Forecast Process • New model guidance arrives • HPC uses model/ensemble blender on left to generate draft graphics sent to NWS WFOs only

  23. HPC Winter Weather Forecast Process • Experimental Snow to liquid ratios multiplied by qpf to determine snow accumulations • http://www.hpc.ncep.noaa.gov/wwd/internal/slr/index.html

  24. 15 Oct 2006 – 1 May 2007 GFS RMSE HPC Snow to Liquid Ratio (SLR) Verification Roebber, QPF*10 lowest RMS error for all forecast times Experimental 2007-8 SLRs consist of a 25% blend of Roebber NAM, Roebber GFS, Climatology SLR, 10:1 ratio

  25. HPC Winter Weather Forecast Process • WFO Forecasters receive internal snow/ice accumulation graphics by 1815/0615z and comment (12planet, phone) • HPC/WFO Collaboration 1815-2015 UTC on day shift and 0615-0815 UTC on night shift WFOs may request conference call with adjacent WFOs/HPC

  26. HPC Winter Weather Forecast Process • Software reviews ensemble data and compiles editable probabilistic snow/ice graphic (right graphic prob of 8 inches) • WFO input is used to modify snow/ice probabilistic forecast • WFO may request change in accumulation

  27. HPC Products and ServicesWinter Weather DeskProbabilistic Snow Forecast

  28. Forecaster-Perceived Model Temperature Forecast Biases • NAM • Better at resolving inversions in the 850 to 700 mb layer, which cause snow to melt and refreeze in the shallow, subfreezing air below. • GFS • Persistent with a cold bias throughout layer. • East of the cyclone with a southerly component of flow, the model will be too slow to warm the inversion layer (850 mb to 700 mb).

  29. Model Bias Example 1 – Topeka, Kansas F24 GFS and NAM Soundings Valid 1200 UTC 14 Jan. 2007

  30. Model Bias Example 1 – Observed Topeka, Kansas Sounding 1200 UTC 14 Jan. 2006

  31. Model Bias Example 2 – Norman, Oklahoma F06 GFS and NAM Soundings Valid 1800 UTC 20 Jan. 2007

  32. Model Bias Example 2 – Observed Norman, Oklahoma Sounding 1800 UTC 20 Jan. 2007 • Norman had 0º C and rain in the hours surrounding 1800 UTC. • The nose of the inversion was about 2º C • Both models were slightly cold at F06, but the NAM was above freezing from 785 hPa to 730 hPa • It took only 6 hours for the GFS bias to result in a -2º C error in the inversion layer

  33. Precipitation Type Output Bias ‘Dominant’ precip type among NCEP, revised NCEP, NCEP microphysical algorithm, Ramer, Bourgouin In case of ties, ZR>SN>IP>R NCEP algorithm output favors freezing rain in isothermal near freezing soundings (observed weather was snow on 09z 11/03)

  34. Model/SREFMean 48 hr Temperature PerformanceJune 2007-August 2007 SREFMean had lower RMS errors than GFS over summer 2007 in the east-can this last thru the winter?

  35. Model/SREFMean 48 hr Temperature PerformanceDecember 01 2006-February 28 2007 Over winter 2006-7, NAM had highest temperature errors 850-150 mb, GFS lowest errors

  36. Model/SREF Mean 84 hr Temperature PerformanceJune 01 2007-August 31 2007

  37. Model Temperature PerformanceCase- 700 mb Observations 10/12/07 00z Verifying low over eastern PA and -6 to -8 temperatures northern VA into PA/WV

  38. Model Temperature Performance10/12/07 00z NAM 66 hr forecast NAM forecast low near PA/WV border with minus 9C core over WV

  39. Model Temperature Performance10/12/07 00z GFS 66 hr forecast GFS forecast low further east over central PA allows freezing air to reach mid Atlantic coast, with no area of -9C forecast

  40. Model/SREFmean 48 hour Height rms error 6/01/07-8/31/07 NAM higher height errors extend thru the column 850-250 mb

  41. Winter Weather Desk verification 2006-7 Winter qpf verification mid Atlantic and Appalachian mountain region Snowfall threat scores over US east of the Rockies Note high GFS/NAM bias above 1.5 inches HPC outperformed NCEP models/ensembles most in 12-21 inch range

  42. HPC Products and Services-Winter Weather Desk Low Tracks Graphic http://www.hpc.ncep.noaa.gov/wwd

  43. HPC Products and ServicesLow track verification 2006-7 Lowest RMS error-blend of NAM/GFS

  44. HPC Products and ServicesMedium Range Desk Black (i.e., absence of color) implies high confidence (i.e., absence of uncertainty). Mixtures of red, green, and blue indicate relative amounts of uncertainty due to independent sources.

  45. HPC MEDIUM RANGE PRODUCTS Model Diagnostics Desk Prelim Day 3-7 Frontal Progs 0900 UTC Prelim PREEPD 0900 UTC Medium Range Pressure/Fronts Prelim Day 3-7 500 mb Progs 1130 UTC Updated Day 3-7 Frontal Progs 1315 UTC Updated PREEPD 1400 UTC Tropical Hotline Call (seasonal) Noon ET Final Day 3-7 Fronts 1900 UTC PMDEPD (Final) 1930 UTC Medium Range Temps/PoPs/QPF Hawaiian 1-7 Day Discussion 1130 UTC Morning Day 4/5 and 1-5 QPF 1200 UTCPrelim Day 3-7 Min/Max/PoPs 1400 UTC Prelim Medium Range Grids 1500 UTCFinal Day 3-7 Min/Max/PoPs 1900 UTC Final Medium Range Grids 2000 UTC Afternoon Day 4/5 and 1-5 QPF 2300 UTC MEDIUM RANGE DESK TWO FORECASTER TEAM SHIFT HOURS 1030-1930 UTC EVERY DAY OF THE YEAR 288 daily members of model/ensemble height field forecasts

  46. HPC DAY 3-7 500 MB PROGS HPC DAY 3-7 FRONTS HPC DAY 4/5 QPF HPC DAY 1-5 QPF

  47. HPC Products and Services-Medium range Forecast Desk • Blender for sea level pressure/ 500 mb forecasts

  48. HPC Medium Range Temperature/Probability of Precip Blender

  49. HPC Medium Range Available Models/ensembles Overlay of ECMWF/GFS/ensemble 500 mb height forecasts (left) HPC can now access ECMWF ensemble mean 200-500/700 mb Heights , 850 mb height/temp/wind , sea level pressure forecasts from both 00z and 12z cycles

  50. HPC Days 3-7 Minimum Temperature Verification

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