# Presentation: 664255

## 50th Anniversaryof Operational NumericalWeather Prediction

- John Jones Deputy Assistant Administrator for Weather ServicesJune 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

**Notes:**
At end of WWII, forecasts were based almost entirely on 6-hour surface data and a few Pibal observations
Forecasts were based on surface analysis, subjective reasoning and forecaster experience
Map is Daily Weather Map valid 2:30 am, Eastern War Time, Thursday, June 15, 1944
Very little forecast skill beyond 12 hours – especially for extended events

## 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

**Notes:**
This chart from a paper Cressman wrote while he was NWS Director
In the 1960’s to the early 70’s, as models were introduced, forecasting remained a subjective art with restricted skill
Forecasters did not trust the models which often missed the big event
Events such as hurricanes and snowstorms were only forecast out to 12-24 hours at synoptic scales

## 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

**Notes:**
Raob network designed initiated and implemented in 10 year period from 1945 – 1954
After WWII, when commercial aviation “exploded”, upper-air observations were needed to assure safe flights and assess new theoretical approaches (baroclinic instability)
Representing the bullet “improved theoretical basis” is picture is of Jule Charney - one of the dominant figures in atmospheric science in the three decades following World War II.  Much of the change in meteorology from an art to a science is due to his scientific vision and his thorough commitment to people and programs in this field. In 1948, headed up meteorology group in von Neuman’s Electronic Computer Project being funded by the Office of Naval Research.
Theoretical basis improvements included baroclinic instability theory, balanced equations and quasi-geostrophic basis for synoptic analysis.
Computer picture is of IBM 7094 – used at NMC in the early 60’s
First models were created through the meteorology group established within von Neuman’s Electronic Computer Project under Charney and von Neuman
A successful forecast of the 1950 Thanksgiving Day storm (in 1953) lead to decision to create the JNWPU. Norm Phillips will address this in his keynote banquet address on Wednesday evening and there is a poster by the registration desk highlighting this achievement.
George Cressman was the first (and only) director of the JNWPU
The IBM 701 (1955) was capable of 1000 operations/sec.

## 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

- 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**

**Notes:**
Receives Over 116 Million Global Observations Daily
Sustained Computational Speed:  450 Billion Calculations/Sec
Generates More Than 5.7 Million Model Fields Each Day
Global Models (Weather, Ocean, Climate)
Regional Models (Aviation, Severe Weather, Fire Weather)
Hazards Models (Hurricane, Volcanic Ash, Dispersion)
Upgraded 2.5x by October 1, 2004
Backup for operational side: Fairmont, WV installation Fall’04

## Measuring Progress

- Improved short range QPF
- Fine scale is being improved

**Notes:**
These maps illustrate the improvements in horizontal resolution for modeling from 1966 to the most recent Eta resolution improvement to 12km in 2001, by showing the terrain resolution.  The change in the ability to resolve terrain features is dramatic.
It also shows how the ratio of the 48hr precipitation threat score (a measure of the accuracy of the forecast, the higher the better) to the 24 hour score in 1999.  The goal is to double the 1999 one day skill by 2005. In other words, the two day forecast should be as skillful as the 1999 one day forecast, and the chart shows the progress through 2003.

## Measuring Progress

- Increasing skill through day 7
- Predictions extended with improved skill

**Notes:**
Anomaly Correlation: Measures the ability of a numerical forecast to represent the general weather patterns of high pressure ridges and low pressure troughs, and the locations and strengths of fronts and major storms.
Anomaly correlation is universally accepted as a standard score by international weather modeling centers and the World Meteorological Organization.
Has a maximum value of 1.0 (corresponding to a perfect depiction of the location of all major weather systems) 
Score above 0.6 is considered useful skill by the international modeling community. 
This graph shows the day at which the forecast at 500 mb loses useful skill (AC value goes below 0.6)
This score is currently approaching 7.5 days.
In 2001, this value shows there was a basis for making official 7 day forecast by the NWS..

## 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

**Notes:**
The improvement in prediction of extreme events is one of the major advancements in forecasting that numerical weather prediction has helped to achieve.  
Three examples:
The major outbreaks of severe weather and tornados of May 4, 2003 through out the central U.S. were predicted more than 3 days in advance
February 17-19, 2003, a major east coast snowstorm inundated many northeastern states with up to 2 feet of snow.  The storm was predicted 5 days in advance.
Hurricane Isabel’s landfall was predicted with great accuracy five days ahead.  2003 was the first year for official 5 day hurricane track forecasts. They had been performed on an experimental basis for the two previous seasons.
The following slide will show the new “Cressman chart” representing the new forecast skill
The next slide will illustrate the skill of the Hurricane Isabel forecasts

## Cressman Chart for 2000

**Notes:**
Refigured Cressman chart circa 2000
Hurricanes – on order of 100km, 5 days in advance
Heavy snow – on order of 120 km, 5 days in advance
Severe weather outbreaks 3 days, 150 km

## Hurricane Isabel

**Hurricane Isabel**

## National Hurricane Center Atlantic Track Forecast Errors

**National Hurricane Center**** Atlantic Track Forecast Errors**

**Notes:**
Track forecast errors in nautical miles for Atlantic hurricanes for various time periods, showing how accuracy has improved over the years. 
The yellow line is for all the storms from the 2003 season (first season with official 5 day forecasts) and the white line shows the error associated with Isabel, itself.  
Isabel’s five day skill is equivalent to the entire 2003 season’s three day skill.

## 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

**Notes:**
Day 14 represents an accepted theoretical limit for weather forecasts
A goal of THORPEX is to attain “useful skill” in operational weather forecasts out to day 14
Super ensembles will use forecasts from met centers around the world to create 200+ member ensembles to provide the most accurate forecast with the best estimate of certainty

## 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

**Notes:**
The notion of NWP being one of the “great” (if not the greatest) intellectual achievements comes from papers by James Baker (former Under Secretary of Commerce of Oceans and Atmosphere) and is written in a review article by Uccellini published by the AMS in 1999.