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Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC)

Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC). Great Lakes Operational Meteorological Workshop Dan Petersen, Wallace Hogsett , Faye Barthold , Mike Bodner , and Keith Brill. Presentation Outline.

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Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC)

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  1. Upcoming Changes in Winter Weather Operations at the Weather Prediction Center (WPC) Great Lakes Operational Meteorological Workshop Dan Petersen, Wallace Hogsett, Faye Barthold, Mike Bodner, and Keith Brill

  2. Presentation Outline New ensemble membership of probabilistic snow/freezing rain forecasts for the 2014-15 season Experimental winter weather ‘watch recommender’ Experimental Days 4-7 Winter Weather Forecasts

  3. Previous Models/Ensembles Used to Compose Snow/Ice Probability Forecasts 32-member ensemble: WPC deterministic forecast 21 Short Range Ensemble Forecast (SREF) members GFS Global Ensemble Forecast (GEFS) Mean, 5 GEFS members ECMWF, ECMWF Ensemble Mean Canadian Global (GDPS) snowfall/freezing rain forecasts

  4. 24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014 Forecast Observed SREF Mean 87 hr precipitation forecast (left), Climate Prediction Center Analysis of observed precipitation (right)

  5. 24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014 Forecast Observed GFS 84 hr forecast (left), Climate Prediction Center Analysis (right)

  6. 24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014 Forecast Observed ECMWF 84 hr forecast (left), analysis (right)

  7. 24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014 Forecast Observed NAM 84 hour forecast (left), Climate Prediction Center Analysis (right)

  8. Weather Prediction Center 24 Hour Probability of Snow 12z 03 Mar to 12z 04 Mar 2014 The SREF, NAM further north axis of QPF results in northward expansion of probabilities in PA/NJ/NY/southern New England)

  9. Run to Run Changes result in lower forecast confidence-03 Mar 2014 Later run (left) decreases precip across southern NY/New England SREF Forecast 6 hour precipitation valid 18z 03 Mar 2014 (15z run left, 09z run right) http://eyewall.met.psu.edu/rich/compare/

  10. Run to Run Changes result in lower forecast confidence-17 Mar 2014 The high probability of QPF over PA/northern NJ/Long Island NY too high and not calibrated (courtesy Rich Grumm and Jeff Tongue) - 14 Mar runs of the SREF probability of 12.5 mm of precip 09z cycle 14 Mar 15z cycle 14 Mar 03z cycle 14 Mar - 14-16 Mar runs of the SREF probability of 12.5 mm of precip 21z cycle 14 Mar 09z cycle 15 Mar 09z cycle 16 Mar

  11. 2014-15 Models/Ensembles Used to Compose Snow/Ice Probability Forecasts http://www.wpc.ncep.noaa.gov/pwpf/about_pwpf_products.shtml Need to include more datasets has resulted in the addition of 25 ECMWF ensemble members For the 2014-15 season: 57-member ensemble including • WPC deterministic forecast • 25 ECMWF Ensemble members (transition to 0.5 degree resolution during 2014-15 season) • 21 SREF members • GFS • GEFS Mean, 5 GEFS members • ECMWF, ECMWF Ensemble Mean • Canadian Global (GDPS) snowfall/freezing rain forecasts

  12. 2014-15 season: Experimental Winter Weather ‘Watch Recommender’ Goal: provide maps of where the snow/freezing rain accumulation probabilities of watch/warning criteria exceed 50 percent for use in watch decisions Maps of 12/24 hour forecasts will be posted on password protected winter weather page

  13. Methodology + = Probability of exceeding warning criteria WPC Snow Probability 12-hr warning criteria ≥ 50% ? Probability of exceeding warning criteria Highlight areas of >50% on map Step #1 – Compute probability of exceeding snow/ice accumulation thresholds and compare to local warning criteria to determine the probability of exceeding watch/warning criteria Step #2 – If probability of exceeding watch/warning criteria ≥ 50%, area on map is highlighted Step #3 – Produce map summarizing where >50% probability of exceeding watch/warning criteria occurs at any time during the 3 day period

  14. Probability of exceeding 12-hr criteria ending 12Z 3/12 Example – 12 March 2014 Probability of exceeding 12-hr criteria ending 18Z 3/12 Summary map-all areas where >50% chance of exceeding 12 hr criteria anytime during 72 hrperiod ending 00 UTC 3/15 Probability of exceeding 12-hr criteria ending 00Z 3/13 Probability of exceeding 12-hr criteria ending 06Z 3/13 ‘Watch Recommender’ is a tool to assist in collaboration between WPC and WFOs Probability of exceeding 12-hr criteria ending 12Z 3/13

  15. Example – 7 March 2014 Red highlights areas where probability of exceeding 24 hr freezing rain criteria >50% Blue highlights where probability of exceeding 24 hr snowfall criteria>50%

  16. Experimental Days 4-7 Winter Weather Forecasts Forecast Components: WPC QPF and international ensembles WPC QPF-2 day QPF divided into 24 hour components WPC Day 6-7 48-hr QPF Day 6 24-hr WPC QPF Day 7 24-hr WPC QPF

  17. Experimental Days 4-7 Winter Weather Forecasts Forecast Components Probability of Winter Precipitation > 0.10” Ensemble Probability of Frozen Precipitation Probability of WPC QPF >= .10 Forecasters edited probability of winter precipitation for individual models/ ensemble members and means

  18. Multi-ensemble Precipitation Type Future Work GEFS ECMWF GEFS+ECMWF • Expand precipitation type guidance to include all GEFS, ECENS and CMCE members • Add ensemble QPF mean from other ensemble systems (ECMWF, Canadian) Future Work Thermal Probability Fields for all 3 Guidance sets

  19. Experimental Days 4-7 Winter Weather Forecasts 24 hr snow ending 00z 13 Mar 2014 www.nohrsc.noaa.gov

  20. Examples of Experimental Days 4-7 Winter Weather Forecasts Red contours WPC probability of 0.10” liquid equivalent frozen precipitation Color filled graphic observed liquid equivalent precipitation (scale on left) Day 7 forecast verifying 00z 13 Mar 2014

  21. Examples of Experimental Days 4-7 Winter Weather Forecasts Red contours WPC probability of 0.10” liquid equivalent frozen precipitation Color filled graphic observed liquid equivalent precipitation (scale on left) Day 6 forecast verifying 00z 13 Mar 2014

  22. Examples of Experimental Days 4-7 Winter Weather Forecasts Red contours WPC probability of 0.10” liquid equivalent frozen precipitation Color filled graphic observed liquid equivalent precipitation (scale on left) Day 5 forecast verifying 00z 13 Mar 2014

  23. Examples of Experimental Days 4-7 Winter Weather Forecasts Red contours WPC probability of 0.10” liquid equivalent frozen precipitation Color filled graphic observed liquid equivalent precipitation (scale on left) Day 4 forecast verifying 00z 13 Mar 2014

  24. Summary: WPC Winter Weather Desk Updates Snow and ice accumulation probabilities have been updated to incorporate 25 members of the ECMWF ensemble Winter Weather ‘Watch recommender’ has been developed to match watch/warning criteria and produces maps of locations where the probability of the criteria being exceeded is >50% Initial testing of days 4-7 winter weather outlooks has begun and more testing is forthcoming for 2014-15 Future: NWS proposal to expand winter weather desk to 24 hour/day operations

  25. Questions or Comments? Dan.Petersen@noaa.gov WPC Forecast Operations Branch (301) 683-1530

  26. Future Improvements • Timing • Output from watch recommender currently available at the very end of each WWD shift • Warning Criteria • Currently using estimates for Western Region, much of Southern Region • Not accounting for terrain

  27. Experimental Days 4-7 Winter Weather Forecasts Probability of WPC QPF >= .10 Forecast Components Probability of WPC QPF >= 0.10” ●WPC 24-hr QPF is used as a mean The 24-hr QPF from each of the 20 GEFS members and 50 ECENS members are used as a variance to compute a cumulative distribution function (CDF) of the WPC QPF reaching or exceeding 0.10” (top right image) Ensemble Probability of Frozen Precipitation Frozen Precipitation Component ●An ensemble probability of frozen precipitation is generated using the precipitation type fields for snow, sleet and freezing rain in each of the GEFS members (middle right image) ●Probability of winter precipitation >= 0.10” is derived from multiplying ensemble probability of frozen precipitation by the probability of the WPC QPF >= 0.10” (Bottom right image) Probability of Winter Precipitation > 0.10”

  28. Updates, Plans, and Applications 2014 NCEP Ensemble Users workshop: http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/6th_User_workshop.shtml SREF upgrade: http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S1-02-SREF2014.pdf ECMWF upgrade: http://www.emc.ncep.noaa.gov/gmb/ens/WkShopOct13/program/pdf/S4-04-RB_2014_03_NCEP_WSensUsers.pdf QPF Object oriented verification: http://www.wpc.ncep.noaa.gov/verification/mode/mode.php#page=page-1

  29. Impetus to Change Ensemble Membership in Probabilistic Snow Forecasts http://www.nohrsc.noaa.gov Analysis of Observed 24 Hr Snow ending 00z 04 Mar 2014

  30. Winter Weather Desk Forecast Snowfall Accumulation Ending 00z Tue 04 Mar 2014

  31. 72 Hr 50th Percentile Snowfall ending 00z Tue 04 Mar 2014

  32. observed DCA Forecast SREF mean snow 12.4 inches observed 7 inches

  33. observed DCA Forecast experimental SREF mean snow 11.7 inches observed 7 inches

  34. 24 Hour Forecast Liquid Equivalent Precipitation Valid 12z 04 Mar 2014 NAM B 84 hr forecast (left), Climate Prediction Center Analysis (right)

  35. http://www.srh.noaa.gov/ridge2/snow/index.php?site=dtx

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