Use of Probablistic Weather Forecasts by Utilities AMS - “Enhancing Weather Information with Probability Forecasts” January 2002

Forecasting with Probability Factors 1960’s Utilities - Storm Warnings

Probability Forecasting Time of Beginning of Precipitation Time Probability Block Combinations 1-3 PM 40% 30% 20% 10% 3-5 PM 60% 70% 80% 90% 100% Start Time pm 4pm 4pm

Probability Forecasting Time of Beginning of Precipitation Time Probability Block Combinations 1-3 PM 60% 70% 80% 90% 100% 3-5 PM 40% 30% 20% 10% Start Time pm 2pm 2pm

Probability Forecasting Duration of Precipitation Duration Probability Combinations 3-6 Hr 60% 70% 80% 90% 100% 6-12 Hr 40% 30% 20% 10% Avg Max 12 hr 12 hr 10 hr 8 hr 6 hr

Probability Forecasting Duration of Precipitation Duration Probability Combinations 3-6 Hr 40% 30% 20% 10% 6-12 Hr 60% 70% 80% 90% 100% Avg Max 12 hr 12 hr 12 hr 12 hr 12 hr

Probability Forecasting Operational Color Code Condition Green Condition Yellow Condition Red Condition Black

Probability Forecasting Operational Color Code Condition Green - No Trouble Expected Condition Yellow - Little or Limited Effect

Probability Forecasting Operational Color Code Condition Red - Significant Trouble Condition Black - Major Storm

Probability Forecasting Operational Color Code G6Y4 Green 60%, Yellow 40% Borderline Situation No Trouble Expected

Probability Forecasting Operational Color Code Y6G4 Yellow 60%, Green 40% Borderline Situation Localized Problems Possible

Probability Forecasting Operational Color Code Y7G3 through Y10 Increasing Forecaster Confidence of Localized Problems

Probability Forecasting Operational Color Code Y9R1 through Y6R4 100% Chance of Some Trouble

Probability Forecasting Operational Color Code R7Y3 through R10 100% Chance of Trouble Increasing Confidence in Significant Trouble

Probability Forecasting Operational Color Code R6B4 through B10 Major Trouble with Increasing Forecaster Confidence

Probability Forecasting Education Forecaster Education Client Education

Probability Forecasting Example 1 Snow and Ice Warning Village of Winnetka March 1950

Probability Forecasting Example 2 Snow and Ice Warning City of Chicago January 1, 1999

Probability Forecasting Example 3 Severe Storm Warning

Probability Forecasting Example 4 Severe Storm Warning Red 7, Black 3

Probability Forecasting Conclusion Educate Forecasters Educate Clients and Potential Clients Increase Utilization