50th Anniversaryof Operational Numerical

Weather Prediction

John Jones Deputy Assistant Administrator for Weather Services

June 15, 2004

University of MarylandCollege Park

Overview

Forecasting 60 years ago: before Numerical Weather Prediction

Forecasting today: Model-based

Remaining challenges for the future

Debt to the Joint Numerical Weather Prediction Unit

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

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

1 Km 10 Km 100 Km 1000 Km 10000 Km

6 hours

1 hour

1 day

2 days

4 days

6 days

12 hours

Thunderstorms

WindsHurricane-Force

HeavySnow

Gale-ForceWinds

Of Hurricanes

Distance

Revolution in Forecasting after World War II

Expanding Raob network

Improved theoretical basis

Development of computers

All came together for:

Development of Numerical Weather Prediction models

Creation of the Joint Numerical Weather Prediction Unit in 1954

• 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

Forecasting Today

Commissioned/Operational IBM Supercomputer in Gaithersburg, MD (June 6, 2003)

Commissioned/Operational IBM Supercomputer in Gaithersburg, MD (June 6, 2003)

Measuring Progress

• Improved short range QPF– Fine scale is being improved

Measuring Progress

• Increasing skill through day 7– Predictions extended with improved skill

Major Advancement in Prediction: Extreme Events Captured 4-7 Days Ahead

Severe Weather – May 3-5, 2003 Outbreaks predicted 3+ days in advance

Snowstorms – Feb 17-19, 2003 predicted 5 days in advance

Hurricanes – Isabel, September 6-19, 2003, landfall predicted with record skill 5 days in advance

Cressman Chart for 2000

Severe Weather Outbreaks

Hurricanes

Heavy Snow

Today’s Weather

1 Km 10 Km 100 Km 1000 Km 10000 Km

6 hour s

1 hour

1 day

2 day s

4 day s

6 day s

12 hour s

Thunderstorms

WindsHurricane-Force

HeavySnow

Gale-ForceWinds

Of Hurricanes

Distance

Tim

e

Thursday, 9/18/0312 PM EDT

3-day forecast

5-day forecast

Hurricane Isabel

12 24 36 48 72 96 120

Forecast Period (hours)

0

100

200

300

400

500

Err

or

(nau

tica

l m

iles

)

1964-19731964-1973

1984-19931984-1993

1974-19831974-1983

1994-20021994-2002

IsabelIsabel

20032003

National Hurricane Center Atlantic Track Forecast Errors

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

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 20th Century