Copyright © 2003 WGN-TV

Computer ModelsComputer Models are the Primary Source are the Primary Source of Information for All Weather & Climate of Information for All Weather & Climate

PredictionsPredictions

The Prediction ProcessThe Prediction Process

Analyze ResultsAnalyze Results

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Observe the AtmosphereObserve the Atmosphere

Identify and ApplyIdentify and ApplyPhysical LawsPhysical Laws

Create a MathematicalCreate a MathematicalModelModel

Create and Run aCreate and Run aComputer ModelComputer Model

The Prediction ProcessThe Prediction Process

Analyze ResultsAnalyze Results

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pare

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Observe the AtmosphereObserve the Atmosphere

Identify and ApplyIdentify and ApplyPhysical LawsPhysical Laws

Create a MathematicalCreate a MathematicalModelModel

Create and Run aCreate and Run aComputer ModelComputer Model

Observe the Atmosphere Observe the Atmosphere

Upper-AirUpper-AirBalloonsBalloons

SatellitesSatellites

NEXRAD NEXRAD Doppler Doppler

RadarRadar

Commercial AircraftCommercial Aircraft

AutomatedAutomatedSurface Surface

NetworksNetworks

The Prediction ProcessThe Prediction Process

Analyze ResultsAnalyze Results

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Identify and ApplyIdentify and ApplyPhysical LawsPhysical Laws

Create a MathematicalCreate a MathematicalModelModel

Create and Run aCreate and Run aComputer ModelComputer Model

Observe the AtmosphereObserve the Atmosphere

Identify & Apply Physical Identify & Apply Physical LawsLaws

F=ma

The Prediction ProcessThe Prediction Process

Analyze ResultsAnalyze Results

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pare

and

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ify

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pare

and

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Create a MathematicalCreate a MathematicalModelModel

Create and Run aCreate and Run aComputer ModelComputer Model

Observe the AtmosphereObserve the Atmosphere

Identify and ApplyIdentify and ApplyPhysical LawsPhysical Laws

Create a Mathematical ModelCreate a Mathematical Model

                                                                   

The Prediction ProcessThe Prediction Process

Analyze ResultsAnalyze Results

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pare

and

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ify

Com

pare

and

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Create and Run aCreate and Run aComputer ModelComputer Model

Observe the AtmosphereObserve the Atmosphere

Identify and ApplyIdentify and ApplyPhysical LawsPhysical Laws

Create a MathematicalCreate a MathematicalModelModel

Create Computer Model Create Computer Model

Solve highly nonlinear partial differential equations Solve highly nonlinear partial differential equations East/West WindEast/West Wind North/South WindNorth/South Wind Vertical WindVertical Wind TemperatureTemperature Water VaporWater Vapor Cloud WaterCloud Water Precipitating WaterPrecipitating Water Cloud IceCloud Ice GraupelGraupel HailHail Surface TemperatureSurface Temperature Surface MoistureSurface Moisture Soil TemperatureSoil Temperature Soil MoistureSoil Moisture Sub-Grid TurbulenceSub-Grid Turbulence

Run the Computer Model Run the Computer Model

Over the course of a single forecast, the Over the course of a single forecast, the computercomputermodel solves billions of model solves billions of equationsequations

Requires the fastest Requires the fastest supercomputers in the supercomputers in the world -- capable ofworld -- capable ofperforming quadrillionsperforming quadrillionsof calculationsof calculationseach secondeach second

Run the Computer Model Run the Computer Model

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

Richardson’s Forecast Grid – Richardson’s Forecast Grid – Predictions Done by HandPredictions Done by Hand

25 point mesh!

One Level

Grid Spacing = 250 km

The Vision Becomes Reality… ENIACThe Vision Becomes Reality… ENIAC

ENIAC Versus TodayENIAC Versus Today

Weighed 30 tonsWeighed 30 tons Had 18,000 vacuum tubes, 1,500 Had 18,000 vacuum tubes, 1,500

relays thousands of resistors, relays thousands of resistors, capacitors, inductorscapacitors, inductors

Peak speed of 5000 adds/second Peak speed of 5000 adds/second and 300 multiplies/secand 300 multiplies/sec

A 1.2 GHz Pentium IV processor is A 1.2 GHz Pentium IV processor is 500,000 times faster than the 500,000 times faster than the ENIACENIAC

A desktop PC with 1 Gbyte of RAM A desktop PC with 1 Gbyte of RAM can store 5 million times as much can store 5 million times as much data as the ENIAC data as the ENIAC

Done on ENIAC: 1.2 Done on ENIAC: 1.2 million times slower million times slower than my laptopthan my laptop

Numerically integrated Numerically integrated one equation at one one equation at one altitudealtitude

736 km grid spacing736 km grid spacing 24 hour forecast took 24 hour forecast took

24 hours to compute!24 hours to compute! Forecast below up due Forecast below up due

to lack of smoothing of to lack of smoothing of data – but rerun today, data – but rerun today, it was ok!it was ok!

450 Miles

1950: The First 1950: The First ComputerComputer Weather Weather Forecast ModelForecast Model

……And Things Have Been And Things Have Been Improving Ever SinceImproving Ever Since

Supercell Storms – The Big Supercell Storms – The Big Tornado Producers!Tornado Producers!

Occur most often during springOccur most often during spring Isolated and very intenseIsolated and very intense Updraft rotates in the Updraft rotates in the verticalvertical direction direction Can last for a few hoursCan last for a few hours

Structure of a Supercell Structure of a Supercell StormStorm

Updra

ft

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ndraf

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Schematic Diagram of a Supercell Storm (C. Doswell)

Structure of a Supercell Structure of a Supercell StormStorm

A Supercell on NEXRAD Doppler A Supercell on NEXRAD Doppler RadarRadar

Hook Echo

Starting with SimulationStarting with Simulation

Early Contour Plot of Early Contour Plot of Horizontal Wind from 3-D Horizontal Wind from 3-D

SimulationSimulation

Courtesy R. Wilhelmson, University of Illinois

Early “Animation” of a 3-D Early “Animation” of a 3-D SimulationSimulation

Courtesy R. Wilhelmson, University of Illinois

3-D Structure Based on 3-D Structure Based on TrajectoriesTrajectories

Courtesy R. Wilhelmson, University of Illinois

Pipe Cleaner Perspective!Pipe Cleaner Perspective!

Courtesy R. Wilhelmson, University of Illinois

Computer-Generated Pipe Computer-Generated Pipe Cleaners!Cleaners!

Courtesy R. Wilhelmson, University of Illinois

Where Does the Rotation Come Where Does the Rotation Come From?From?

Courtesy NCAR

To the Dome!!To the Dome!!

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

The Real AtmosphereThe Real Atmosphere

Why the Lack of Detail in the Why the Lack of Detail in the Model? Model?

This ThunderstormFalls Through the Cracks

A Foundational QuestionA Foundational Question

. . . explicitly predict this. . . explicitly predict thistype of weather?type of weather?

Can computer forecastCan computer forecasttechnology. . .technology. . .

The Billion Dollar The Billion Dollar Question: Will Question: Will

Computer Models Ever Computer Models Ever Be Able to Be Able to PredictPredict

Tornadoes?Tornadoes?

Current: Warn-on-Detection

NSSL Warn on Forecast Briefing March 5, 2007, Courtesy R. Schneider

Hazard Based Tornado Warning

30%Developing Thunderstorm

Vision: Warn-on-Forecast

Developing thunderstormMostLikelyTornadoPath

T=2120 CST

T=2150

T=2130T=2140

T=2200 CST

70%

50%

30%

NSSL Warn on Forecast Briefing March 5, 2007, Courtesy R. Schneider

MostLikelyTornadoPath

T=2120 CST

T=2150

T=2130T=2140

T=2200 CST

70%

50%

30%

Hurricanes vs Tornadoes?Hurricanes vs Tornadoes?

What May What May be be

Impossible Impossible to Predict!to Predict!