50 th Anniversary of Operational Numerical Weather Prediction

50 th Anniversary of Operational Numerical Weather Prediction John Jones Deputy Assistant Administrator for Weather Services June 15, 2004 University of Maryland College Park 1

Overview ü Forecasting 60 years ago: before Numerical Weather Prediction ü Forecasting today: Model-based ü Remaining challenges for the future ü Debt to the Joint Numerical Weather Prediction Unit 2

Weather Prediction – 60 Years Ago • Forecasting was a subjective art – Based on surface observations • Forecasts of extreme events were poor beyond 12 hours June 15, 1944 3

Limits of Predictability of Public Weather Forecasts (from Cressman 1970) Even as late as the early 70’s, forecast skill for snowstorms and hurricane force winds was only 12 hours 4

Revolution in Forecasting after World War II ü Expanding Raob network ü Improved theoretical basis ü Development of computers All came together for: ü Development of Numerical Weather Prediction models ü Creation of the Joint Numerical Weather Prediction Unit in 1954 5

Forecasting Today • Based on sophisticated global and regional numerical models – Initialized with global observations, satellites, raobs, aircraft, ships, buoys, radar – Which produce accurate forecasts of extreme events 5 -7 days in advance – Including “hazards assessment” product to day 14 Commissioned/Operational IBM Supercomputer in Gaithersburg, MD (June 6, 2003) 6

Measuring Progress • Improved short range QPF – Fine scale is being improved 7

Measuring Progress • Increasing skill through day 7 – Predictions extended with improved skill 8

Major Advancement in Prediction: Extreme Events Captured 4 -7 Days Ahead ü Severe Weather – May 3 -5, 2003 Outbreaks predicted 3+ days in advance ü Snowstorms – Feb 17 -19, 2003 predicted 5 days in advance ü Hurricanes – Isabel, September 6 -19, 2003, landfall predicted with record skill 5 days in advance 9

Cressman Chart for 2000 6 day s 2 day s 1 day Time Today’s Weather Gale-Force Winds Of Hurricanes 4 day s Severe Weather Outbreaks Hurricane-Force Winds 12 hour s Heavy Snow Hurricanes 6 hour s Thunderstorms Heavy Snow 1 hour 1 Km 10000 Km Distance 10

Hurricane Isabel Thursday, 9/18/03 12 PM EDT 3 -day forecast 5 -day forecast

National Hurricane Center Atlantic Track Forecast Errors Error (nautical miles) 500 1964 -1973 400 1974 -1983 300 1984 -1993 200 1994 -2002 2003 Isabel 100 0 12 24 36 48 72 96 Forecast Period (hours) 120 12

Remaining Challenges for the Future • As we approach the NPOESS era (2012), apply global satellite data to weather, climate, ocean and ecosystem prediction • Extend forecasts to Day 14 • Apply ensemble-based approach to quantify forecast uncertainties – We look forward to working with the international community to develop and implement “super ensemble” systems 13

Our Debt to the JNWPU • All these achievements were made possible by the creation of the JNWPU • The meteorological community owes much to the original members of the Air Force, Weather Bureau and the Navy who pushed for the creation of the JNWPU • They had the guts and foresight to get the best minds working on a challenging problem • Transformed weather prediction from a subjective “art” to a mathematically-based applied science – This transformation represents one of the great intellectual achievements of the 20 th Century 14