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

3. 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

4. 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

5. Observe the Atmosphere Upper-AirBalloons Satellites NEXRADDopplerRadar Commercial Aircraft AutomatedSurfaceNetworks

6. 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

7. Identify & Apply Physical Laws F=ma

8. 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

9. Create a Mathematical Model

10. 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

11. Create Computer Model

12. 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

13. 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

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

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

16. The Vision Becomes Reality… ENIAC

17. 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

18. 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

19. …And Things Have Been Improving Ever Since

20. 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

21. Structure of a Supercell Storm Updraft Downdraft

23. Schematic Diagram of a Supercell Storm (C. Doswell)

25. Structure of a Supercell Storm

26. A Supercell on NEXRAD Doppler Radar n Hook Echo

27. Starting with Simulation

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

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

30. 3-D Structure Based on Trajectories Courtesy R. Wilhelmson, University of Illinois

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

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

33. Where Does the Rotation Come From? Courtesy NCAR

34. To the Dome!!

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

36. The Real Atmosphere

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

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

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

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

44. 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%

45. Hurricanes vs Tornadoes?

46. What May be Impossible to Predict!