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Highest Confidence Forecasts. Model agreement NGM=WRF=AVN Run-to-run changes (dMod/dt) very small Models trending toward agreement Example: OLD run: WRF=AVN but *not* NGM NEW run: NGM trends toward WRF & AVN Models have current weather “in hand” - PowerPoint PPT Presentation
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Highest Confidence Forecasts
• Model agreement– NGM=WRF=AVN
• Run-to-run changes (dMod/dt) very small• Models trending toward agreement
– Example:• OLD run: WRF=AVN but *not* NGM• NEW run: NGM trends toward WRF & AVN
• Models have current weather “in hand”• Parameterized processes not significant part of
feature
Lowest Confidence Forecasts
• Large model disagreement– NGM, WRF, AVN all have different solutions
• Run-to-run changes (dMod/dt) large
• Don’t have current weather “in hand”
• Parameterized processes significant part of feature
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!
When models disagree …..
NGM
AVN
ETA
KJAX 141756Z 33008KT 1 1/2SM -RA BR OVC010 15/15 A3013 60086
Which model do you go with?
15Z RADAR
MODEL TREND: Single Model
LAGGED AVERAGE FORECAST- Average of each forecast valid at same time-“Poor man’s” Ensemble
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
ENSEMBLE FORECASTS
• What are ENSEMBLE FORECASTS?– Model’s initial conditions are perturbed– Variety of solutions occur
ENSEMBLE FORECASTS
THESE ARE THE MEMBERS OF THE ENSEMBLE- Negative and Positive tweaks
ONE MODEL … MANY TWEAKS
ENSEMBLE FORECASTS: Another Approach
THESE ARE DIFFERENT MODELS- ETA, AVN, NGM, MM5, EUR, MRF, UKM, CMC
MANY MODELS … MANY DIFFERENT “PHYSICS” & IC