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Weather Forecasting

Weather Forecasting. Acquisition of Weather Information. 10,000 land-based stations, hundreds of ships and buoys; four times a day, airports hourly Upper level: radiosonde, aircraft, satellites United Nations World Meteorological Organization, 175 countries

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Weather Forecasting

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  1. Weather Forecasting

  2. Acquisition of Weather Information 10,000 land-based stations, hundreds of ships and buoys; four times a day, airports hourly Upper level: radiosonde, aircraft, satellites United Nations World Meteorological Organization, 175 countries World Meteorological Centers: Melbourne, Moscow, Washington D.C. NCEP, US NWS ASOS

  3. Weather Forecasting Tools • Topics: Watches, Warnings, and Advisories • Advisories: potential hazardous conditions; wind, wind chill, heat, urban and small stream, snow, dense fog (likely) • Watch: atmospheric conditions favoring hazardous weather over a region in time, actual location and time not known; flash flood, severe thunderstorm, tornado, hurricane (more likely) • Warning: imminent or occurring hazardous weather over a region in time; high wind, heat, flash flood, severe storm, tornado, hurricane, winter storm, blizzard, gale, storm (very likely)

  4. Weather Forecasting Tools High speed data modeling systems (AWIPS): communication, storage, processing, and display Doppler radar Satellite imagery Forecast charts Soundings Meteograms Wind profiles

  5. Fig. 9-1, p. 247

  6. Fig. 9-2, p. 247

  7. Fig. 9-3, p. 249

  8. Fig. 9-4, p. 250

  9. Weather Forecasting Tools • Satellite Observations • Geostationary, polar orbiting • Visible light provides a black and white picture of clouds • Infrared approximates cloud temperature which infers height • Satellites measure many other variables: sea surface temperatures, ozone, upper level features, snow cover, land cover

  10. Fig. 9-5, p. 250

  11. Fig. 9-6, p. 251

  12. Fig. 9-7, p. 251

  13. Fig. 9-8, p. 252

  14. Fig. 9-9a, p. 252

  15. Fig. 9-9b, p. 252

  16. Fig. 9-10, p. 253

  17. Fig. 9-11, p. 253

  18. Fig. 9-12, p. 254

  19. Weather Forecasting Methods • 1950s maps, charts plotted by hand • Numerical weather prediction • Solves equations using gridded data • Final chart called analysis • 24 hr forecast for the N Hemisphere requires millions of calculations • Resolution • Guidance/ rules of thumb

  20. Fig. 9-13, p. 255

  21. Fig. 9-13a, p. 255

  22. Fig. 9-13b, p. 255

  23. Fig. 9-14, p. 255

  24. Weather Forecasting Methods • Why Forecasts Go Awry • Assumptions • Models not global • Regions with few observations • Cannot model small-scale features • All factors cannot be modeled • Ensemble Forecasts: • Spaghetti model, robust • Observation: Weathercasters • Chroma key or color separation

  25. Fig. 9-15, p. 257

  26. Weather Forecasting Methods • Other Forecasting Techniques • Persistence • Trend • Analogue • Statistical • Weather type • Climatological

  27. Table 9-1, p. 259

  28. Fig. 9-16, p. 260

  29. Fig. 9-17, p. 261

  30. Weather Forecasting Methods • Types of Forecasts • Now cast <6 hrs • Short range 12-65 hrs • Medium range 3-8.5 days • Long Range >8.5 days • Accuracy and Skill • 12-24 hrs most accurate, 2-5 days good • Skill = more accurate than a forecast utilizing persistence of climatology

  31. Fig. 9-18, p. 262

  32. Fig. 9-18a, p. 262

  33. Fig. 9-18b, p. 262

  34. Weather Forecasting Using Surface Charts Movement of Weather Systems • Mid-lat cyclones move in same direction and speed as previous 6 hrs • Lows move in direction parallel the isobars in the warm air ahead of the cold front • Lows move toward region of greatest pressure drop

  35. Table 9-2, p. 265

  36. Weather Forecasting Using Surface Charts • Forecast Data collected… • Augusta GA • Washington DC • Chicago • Memphis • Dallas • Denver

  37. Fig. 9-20, p. 266

  38. Fig. 9-21, p. 267

  39. Stepped Art Fig. 9-22, p. 267

  40. Isobars • Isobars: lines of constant pressure • A line drawn on a weather map connecting points of equal pressure is called an isobar

  41. Fig. 9-23, p. 269

  42. El Nino & La Nina • Affects sea surface temperature in the equatorial Pacific Ocean-El Niño is characterized by unusually warm temperatures and La Niña by unusually cool temperatures • A strong El Niño is often associated with wet winters over the southeastern US, as well as drought in Indonesia and Australia • A strong El Niño can last a year or more before conditions return to normal and can occur every 3 to 7 years

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