highest confidence forecasts
DESCRIPTION
Highest Confidence Forecasts. Model agreement CMC=NAM=GFS Run-to-run changes (dMod/dt) very small Models trending toward agreement Example: OLD run: NAM=GFS but *not* CMC NEW run: CMC trends toward WRF & GFS Models have current weather “in hand” - PowerPoint PPT PresentationTRANSCRIPT
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Highest Confidence Forecasts
• Model agreement– CMC=NAM=GFS
• Run-to-run changes (dMod/dt) very small• Models trending toward agreement
– Example:• OLD run: NAM=GFS but *not* CMC• NEW run: CMC trends toward WRF & GFS
• Models have current weather “in hand”• Parameterized processes not significant part of
feature
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Lowest Confidence Forecasts
• Large model disagreement– ECMWF, WRF, GFS all have different
solutions
• Run-to-run changes (dMod/dt) large
• Don’t have current weather “in hand”
• Parameterized processes significant part of feature
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When models disagree …..
• In a 12-36 hr. fcst, lean toward model/s that has “best” handle on current weather!
• Lean toward a model whose run-to-run change is small, especially if other models are trending toward it
• Lean away from a model if it is showing its bias!• Take consensus!
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When models disagree …..
Rainfall forecast:Cape Canaveral, FL
Postpone a launch?
CMC
NAM
AVN
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When models disagree …..
CMC
AVN
NAM
KJAX 141756Z 33008KT 1 1/2SM -RA BR OVC010 15/15 A3013 60086
Which model do you go with?
15Z RADAR
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MODEL TREND: Single Model
Is the Trend a useful forecast technique?
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MODEL TREND: Single Model
Is the Trend a useful forecast technique?
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MODEL TREND: Single Model
Is trend any help at all in this case?
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MODEL TREND: Single Model
LAGGED AVERAGE FORECAST- Average of each forecast valid at same time-“Poor man’s” Ensemble
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MODEL TREND
Trending toward New York City?
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MODEL TREND
Trend = Bust-o-matic
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MODEL TREND
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Interpreting Model Trends: What’s Legitimate ??
• Least significant if associated with “parameterized” situation
• 3-model run trend stronger signal than 2-model trend• Hierarchy of model run-to-run trends
– 24 ->12 hours most significant– 60-> 48 hours least significant
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MODEL CONFIDENCE: Utilizing Trend & Agreement
MOST CONFIDENT!
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MODEL CONFIDENCE: Utilizing Trend & Agreement
TRENDING TOWARD AGREEMENT
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MODEL CONFIDENCE: Utilizing Trend & Agreement
TRENDING TOWARD AGREEMENT
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MODEL CONFIDENCE: Utilizing Trend & Agreement
TRENDING TOWARD AGREEMENT
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MODEL CONFIDENCE: Utilizing Trend & Agreement
TRENDING TOWARD AGREEMENT
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MODEL CONFIDENCE: Utilizing Trend & Agreement
TRENDING TOWARD AGREEMENT
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MODEL CONFIDENCE: Utilizing Trend & Agreement
What’s a forecaster to do? Suggestions???
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MODEL CONFIDENCE: Utilizing Trend & Agreement
LEAST CONFIDENT!
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ENSEMBLE FORECASTS
• What are ENSEMBLE FORECASTS?– Model’s initial conditions are perturbed– Variety of solutions occur– Ensembles on e-wall
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ENSEMBLE FORECASTS
THESE ARE THE MEMBERS OF THE ENSEMBLE- Negative and Positive tweaks
ONE MODEL … MANY TWEAKS
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ENSEMBLE FORECASTS
EACH MEMBER IS RUN OUT IN TIME- Provides “unique” solution
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ENSEMBLE FORECASTS
ENSEMBLE MEAN IS “most likely” SOLUTION averaged over ALL cases
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ENSEMBLE FORECASTS
HOW CONFIDENT ARE WE IN THE ENSEMBLE MEAN?
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ENSEMBLE FORECASTS
IS THE ENSEMBLE MEAN more likely than the CLUSTERS?
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ENSEMBLE FORECASTS
Which solution is LEAST likely?
MEM 1
MEM 2ENSEMBLE
MEAN
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ENSEMBLE FORECASTS: Another Approach
THESE ARE DIFFERENT MODELS- WRF, GFS, NGM, MM5, EUR, MRF, UKM, CMC
MANY MODELS … MANY DIFFERENT “PHYSICS” & IC
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ENSEMBLE FORECASTS
What’s the better approach?
MULTI-MODELCONSENSUS
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ENSEMBLE FORECASTSMany “perturbations”, Many People
What’s the better approach?
Many “perturbations”, One YOU
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ENSEMBLE FORECASTS
• Variance measures forecast reliability– Measures “robustness” of a model solution– How much confidence in model forecast
• Ensemble mean is “most accurate” averaged over all cases
• Member clustering can be useful
• TARGETING OBSERVATIONS
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OPTMIZING MODEL OUTPUT
• MODEL AGREEMENT– Agreement of different models on same
solution = POWERFUL• Confidence high if models converge on solution• Confidence low if models diverge
• MODEL TREND– Run-to-run changes of a model
• Confidence higher if run-to-run changes are small• Confidence lower if run-to-run changes are large