Copyright © 2003 WGN-TV Computer Models are the Primary Source of Information for All Weather & Climate Predictions

The Prediction Process Analyze Results Compare and Verify Observe the Atmosphere Identify and Apply Physical Laws Create a Mathematical Model Create and Run a Computer Model

The Prediction Process Analyze Results Compare and Verify Observe the Atmosphere Identify and Apply Physical Laws Create a Mathematical Model Create and Run a Computer Model

Observe the Atmosphere Upper-AirBalloons Satellites NEXRADDopplerRadar Commercial Aircraft AutomatedSurfaceNetworks

The Prediction Process Analyze Results Compare and Verify Identify and Apply Physical Laws Create a Mathematical Model Create and Run a Computer Model Observe the Atmosphere

Identify & Apply Physical Laws F=ma

The Prediction Process Analyze Results Compare and Verify Create a Mathematical Model Create and Run a Computer Model Observe the Atmosphere Identify and Apply Physical Laws

Create a Mathematical Model

The Prediction Process Analyze Results Compare and Verify Create and Run a Computer Model Observe the Atmosphere Identify and Apply Physical Laws Create a Mathematical Model

Create Computer Model

n Solve highly nonlinear partial differential equations n East/West Wind n North/South Wind n Vertical Wind n Temperature n Water Vapor n Cloud Water n Precipitating Water n Cloud Ice n Graupel n Hail n Surface Temperature n Surface Moisture n Soil Temperature n Soil Moisture n Sub-Grid Turbulence Run the Computer Model

n Over the course of a single forecast, the computer model solves billions of equations n Requires the fastest supercomputers in the world -- capable of performing quadrillions of calculations each second Run the Computer Model

Computer Weather Prediction Began with a Vision in the early 1920s -- L.F. Richardson’s “Forecast Factory”

Richardson’s Forecast Grid – Predictions Done by Hand 25 point mesh! One Level Grid Spacing = 250 km

The Vision Becomes Reality… ENIAC

ENIAC Versus Today n Weighed 30 tons n Had 18,000 vacuum tubes, 1,500 relays thousands of resistors, capacitors, inductors n Peak speed of 5000 adds/second and 300 multiplies/sec n A 1.2 GHz Pentium IV processor is 500,000 times faster than the ENIAC n A desktop PC with 1 Gbyte of RAM can store 5 million times as much data as the ENIAC

n Done on ENIAC: 1.2 million times slower than my laptop n Numerically integrated one equation at one altitude n 736 km grid spacing n 24 hour forecast took 24 hours to compute! n Forecast below up due to lack of smoothing of data – but rerun today, it was ok! 450 Miles 1950: The First Computer Weather Forecast Model

…And Things Have Been Improving Ever Since

Supercell Storms – The Big Tornado Producers! n Occur most often during spring n Isolated and very intense n Updraft rotates in the vertical direction n Can last for a few hours

Structure of a Supercell Storm Updraft Downdraft

Schematic Diagram of a Supercell Storm (C. Doswell)

Structure of a Supercell Storm

A Supercell on NEXRAD Doppler Radar n Hook Echo

Starting with Simulation

Early Contour Plot of Horizontal Wind from 3-D Simulation Courtesy R. Wilhelmson, University of Illinois

Early “Animation” of a 3-D Simulation Courtesy R. Wilhelmson, University of Illinois

3-D Structure Based on Trajectories Courtesy R. Wilhelmson, University of Illinois

Pipe Cleaner Perspective! Courtesy R. Wilhelmson, University of Illinois

Computer-Generated Pipe Cleaners! Courtesy R. Wilhelmson, University of Illinois

Where Does the Rotation Come From? Courtesy NCAR

To the Dome!!

Today’s State-of-the-Art Computer Forecast

The Real Atmosphere

Why the Lack of Detail in the Model? This Thunderstorm Falls Through the Cracks

A Foundational Question... explicitly predict this type of weather? Can computer forecast technology...

The Billion Dollar Question: Will Computer Models Ever Be Able to Predict Tornadoes?

Current: Warn-on-Detection NSSL Warn on Forecast Briefing March 5, 2007, Courtesy R. Schneider Hazard Based Tornado Warning n 30% Developing Thunderstorm

Vision: Warn-on-Forecast Developing thunderstorm Most Likely Tornado Path T=2120 CST T=2150 T=2130 T=2140 T=2200 CST 70% 50% 30% NSSL Warn on Forecast Briefing March 5, 2007, Courtesy R. Schneider Most Likely Tornado Path T=2120 CST T=2150 T=2130 T=2140 T=2200 CST 70% 50% 30%

Hurricanes vs Tornadoes?

What May be Impossible to Predict!