River Ensemble Forecast Comparisons Meteorological Model Ensemble Forecast
River Ensemble Forecast Comparisons Meteorological Model Ensemble Forecast Service (MMEFS) v Meteorological Ensemble Forecast Processor (MEFP) Spring Runoff 2019 Erick Boehmler, NERFC erick. boehmler@noaa. gov National Oceanic and Atmospheric Administration’s National Weather Service 1 Northeast RFC Norton, Massachusetts
MMEFS Processing = forcings = runoff = users Ops GEFS (21 members, 1 -15 days) Hydrologic Models (CHPS) National Oceanic and Atmospheric Administration’s National Weather Service Ensemble Flow Forecasts 2 NWS / External User Apps. Northeast RFC Norton, Massachusetts
MEFP Processing = forcing = runoff = users Legacy GEFS forecasts (15 days) Sampled Climatology (Day 16 – 90) Meteorological Ensemble Forecast Processor (MEFP) Hydrologic models (CHPS) • Correct forcing bias • Merge in time • Downscale (basin) (MEFP forcing also available to users) National Oceanic and Atmospheric Administration’s National Weather Service 3 Ensemble flow forecasts NWS and external user applications Northeast RFC Norton, Massachusetts
MMEFS AND MEFP DIFFERENCES MMEFS MEFP OPERATIONS GEFS FORCINGS “Legacy” GEFS FORCINGS ENSEMBLE FORCING VARIABLE TRACES INCLUDING THE MEAN ENSEMBLE MEAN FORCING VARIABLES 21 ENSEMBLE TRACES BY KALMAN FILTER 59 ENSEMBLE TRACES BY STATISTICAL DISTRIBUTION OF HISTORICAL ERRORS NO MERGE OF METEOLOGICAL MODEL FORECASTS CAPABLE OF MERGING MET MODEL FORECASTS LITTLE BIAS REDUCTION IN FORCING VARIABLES REDUCES BIAS IN FORCING VARIABLES National Oceanic and Atmospheric Administration’s National Weather Service 4 Northeast RFC Norton, Massachusetts
Streamflow Results - Reduction in Bias Maximum bias reduction (All flow data) Maximum bias reduction (top 5% flow) Bias = abs(Relative Mean Error) National Oceanic and Atmospheric Administration’s National Weather Service 5 Northeast RFC Norton, Massachusetts 5
MMEFS Forecast Graphic Ensemble of 19 of 21 river hydrographs over 7 days represented between high and low line plots About 25% of river level forecasts are above the orange shaded range About 50% of river level forecasts are within the orange shaded range Graphic represents 21 river forecast hydrographs generated with Global Ensemble Forecast System precipitation and temperature forecasts applied to river forecast models twice each day National Oceanic and Atmospheric Administration’s National Weather Service 6 Northeast RFC Norton, Massachusetts
Hydrologic Ensemble Forecast Service (HEFS) Short-range Probabilistic Forecast Hydrograph Ensemble of 57 of 59 river hydrographs over 10 days represented by the entire shaded area About 5% of river level forecasts are above the tan shaded range About 10% of river level forecasts are above the green shaded range About 25% of river level forecasts are above the blue shaded range About 50% of hydrographs are within the blue shaded range Graphic represents 59 forecast hydrographs generated with Global Ensemble Forecast System precipitation and temperature applied to river forecast models once each day
MMEFS and MEFP Comparisons • Two high runoff time-lines selected • May 28 – Apr 7 and Apr 18 – 28, 2019 • MMEFS – GEFS expected value flow plots from river forecast software, CHPS • MEFP – HEFS short-term probability forecast graphics from AHPS • Each type of ensemble graphic contains river flow / stage observations after the fact • HEFS graphics also include the latest deterministic river forecast National Oceanic and Atmospheric Administration’s National Weather Service 8 Northeast RFC Norton, Massachusetts
Advances with MEFP • Forcing variables bias correction • Historical errors in forcing variables drive variance in ensemble members • Reduced bias in forcings are reflected in river flow forecasts • Over-correction possible in some circumstances National Oceanic and Atmospheric Administration’s National Weather Service 9 Northeast RFC Norton, Massachusetts
Snow Water Equivalent Conditions – Mar 28 National Oceanic and Atmospheric Administration’s National Weather Service 10 Northeast RFC Norton, Massachusetts
SWE Percent of Normal – March 28 National Oceanic and Atmospheric Administration’s National Weather Service 11 Northeast RFC Norton, Massachusetts
Sacandaga River at Hope, NY 3/30 – 4/1: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 3/30 – 4/1: Ensemble range is on target with observed 12 Northeast RFC Norton, Massachusetts
Hudson River at North Creek, NY 3/30 – 4/1: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 3/30 – 4/1: Ensemble range is on target with observed 13 Northeast RFC Norton, Massachusetts
Lamoille River at Johnson, VT 3/30 – 4/1: Some forecast hydrographs above flood level National Oceanic and Atmospheric Administration’s National Weather Service 3/30 – 4/1: Forecast hydrograph range remains below flood level 14 Northeast RFC Norton, Massachusetts
Otter Creek at Center Rutland, VT 3/30 – 4/1: Forecast hydrograph range remains above observed National Oceanic and Atmospheric Administration’s National Weather Service 3/30 – 4/1: Forecast hydrograph range includes observed 15 Northeast RFC Norton, Massachusetts
Mettawee River at Middle Granville, NY 3/30 – 4/1: Forecast range mostly contains observed National Oceanic and Atmospheric Administration’s National Weather Service 3/30 – 4/1: Forecast range mostly underestimates observed 16 Northeast RFC Norton, Massachusetts
Snow Water Equivalent Conditions – April 18 National Oceanic and Atmospheric Administration’s National Weather Service 17 Northeast RFC Norton, Massachusetts
Sacandaga River at Hope, NY 4/18 - 25: Observed stage / flow within interquartile range National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Ensemble range nearly all below observed 18 Northeast RFC Norton, Massachusetts
Hudson River at North Creek, NY 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Ensemble range is mostly below observed 19 Northeast RFC Norton, Massachusetts
Lamoille River at Johnson, VT 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Observed crest within ensemble interquartile range 20 Northeast RFC Norton, Massachusetts
Passumpsic River near Passumpsic, VT 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Observed crest within ensemble interquartile range 21 Northeast RFC Norton, Massachusetts
Saco River near Conway, NH 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Observed crest within ensemble interquartile range 22 Northeast RFC Norton, Massachusetts
St. John River at Fort Kent, ME 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Observed crest within ensemble interquartile range 23 Northeast RFC Norton, Massachusetts
Aroostook River at Washburn, ME 4/18 - 25: Ensemble range mostly above observed crest National Oceanic and Atmospheric Administration’s National Weather Service 4/18 – 27: Observed crest within ensemble interquartile range 24 Northeast RFC Norton, Massachusetts
MEFP Improvements Summary • Bias correction in forcing variables • Historical errors in forcing variables drive variance in ensemble members • Reduces bias in river flow forecasts • SNOW 17 melt bias impact remains • Over-correction possible after previous meltrunoff periods National Oceanic and Atmospheric Administration’s National Weather Service 25 25 Northeast RFC Norton, Massachusetts
Example of national HEFS product AHPS short-range probabilistic product See: http: //water. weather. gov/ahps/ National Oceanic and Atmospheric Administration’s National Weather Service 26 Northeast RFC Norton, Massachusetts
- Slides: 26