The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
University of Oklahoma School of Meteorology Seminar: 1/15/03
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Table of Contents
The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts "Forecasting snowfall is a mesoscale challenge cloaked in a synoptic-scale culture." OBJECTIVES Methodologies for Forecasting Snowfall Methodologies for Forecasting Snowfall TOP-DOWN APPROACH Steps in Producing Snow 1. THEORY: Will Ice Be Produced in the Cloud? 1. OBSERVATIONS: Will Ice Be Produced in the Cloud? Author: David Schultz Email: schultz@nssl.noaa.gov Home Page: http://www.cimms.ou.edu/~schultz
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The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
1. OBSERVATIONS: Will Ice Be Produced in the Cloud? OBSERVATIONS: SEEDER-FEEDER PROCESS OBSERVATIONS: SEEDER-FEEDER PROCESS 2. THEORY: How does ice grow in cloud? 2. THEORY: How Does Ice Grow in Cloud? Fukuta and Takahashi (1999) 2. OBSERVATIONS: How does ice grow in cloud? 2. OBSERVATIONS: How does ice grow in cloud? 2. OBSERVATIONS: How Does Ice Grow in Cloud? OBSERVATIONS: How does ice grow in cloud? NSHARP at SPC AWIPS Utility (Dan Baumgardt) 3. THEORY: How does ice grow in cloud? Fukuta and Takahashi (1999) 3. THEORY: How does ice grow in cloud? Convective snow environments
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The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
4. THEORY: How does ice grow in cloud? Enhancing growth through turbulence Enhancing growth through turbulence 5. Hydrometeor-altering environments Summary of Top-Down Microphysics Approach for Snow Even if you were able to predict the liquid equivalent perfectly Density can vary by a factor of 2-9, depending on crystal shape Apparent density will decrease, then stabilize as crystal grows Density will decrease as snowflakes increase in size, but it is not a simple relationship Factors Affecting Snow Ratio Factors Affecting Snow Ratio NWS snow-density vs temp. table Roebber et al. (2003): Improving Snowfall Forecasting by Diagnosing Snow Density, Wea. Forecasting, in press. Histogram of snow ratios for 1650 snowfall events Histogram of snow ratios for four different cities in the northeast U.S.
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The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
Properties of Snow Ratio Climatology of Snow Ratio Snow Ratios for Lake Effect Forecasting Snow Ratio How are we doing now? The Fall Velocity of Snow and Why It Matters Colle et al. (1999) Idealized MM5 2-D Simulation What do we need to do to forecast snow better?: Observations The Promise of Polarimetric Radar Satellite imagery enhancement What do we need to do to forecast snow better?: Research What do we need to do to forecast snow better?: Numerical Weather Prediction Cloud Microphysics . . . The Ultimate Limitation? Acknowledgments
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The Challenges of Accurate Snowfall Forecasts: Implications for Observing Strategies and Future Research Efforts
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OBJECTIVES
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Methodologies for Forecasting Snowfall
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Methodologies for Forecasting Snowfall
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TOP-DOWN APPROACH
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Steps in Producing Snow
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1. THEORY: Will Ice Be Produced in the Cloud?
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1. OBSERVATIONS: Will Ice Be Produced in the Cloud?
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1. OBSERVATIONS: Will Ice Be Produced in the Cloud?
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OBSERVATIONS: SEEDERñFEEDER PROCESS
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OBSERVATIONS: SEEDERñFEEDER PROCESS
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2. THEORY: How does ice grow in cloud?
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2. THEORY: How Does Ice Grow in Cloud?
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2. OBSERVATIONS: How does ice grow in cloud?
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2. OBSERVATIONS: How Does Ice Grow in Cloud?
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OBSERVATIONS: How does ice grow in cloud?
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3. THEORY: How does ice grow in cloud?
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3. THEORY: How does ice grow in cloud?
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Convective snow environments
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4. THEORY: How does ice grow in cloud?
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5. Hydrometeor-altering environments
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Summary of Top-Down Microphysics Approach for Snow
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Even if you were able to predict the liquid equivalent perfectly
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Factors Affecting Snow Ratio
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Factors Affecting Snow Ratio
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NWS snow-density vs temp. table
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Roebber et al. (2003):Improving Snowfall Forecasting by Diagnosing Snow Density, Wea. Forecasting, in press.
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Properties of Snow Ratio
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Climatology of Snow Ratio
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Snow Ratios for Lake Effect
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Forecasting Snow Ratio
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How are we doing now?
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The Fall Velocity of Snow and Why It Matters
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Idealized MM5 2-D Simulation
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What do we need to do to forecast snow better?:Observations
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The Promise of Polarimetric Radar
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What do we need to do to forecast snow better?:Research
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What do we need to do to forecast snow better?:Numerical Weather Prediction
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Cloud Microphysics . . . The Ultimate Limitation?
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Acknowledgments
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