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Weather Forecasting Elisabeth (Lis) Cohen

Weather Forecasting Elisabeth (Lis) Cohen. Motivation. Foxtrot Comic Strip. What will the weather be tonight?. Our Forecasting Steps. 1 – Cloud and Rain Observations 2 – Pressure Systems 3 – Current Observations 4 – Computer Models 5 – Predict & Verify. Why focus on clouds?.

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Weather Forecasting Elisabeth (Lis) Cohen

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  1. Weather Forecasting Elisabeth (Lis) Cohen

  2. Motivation Foxtrot Comic Strip

  3. What will the weather be tonight?

  4. Our Forecasting Steps 1 – Cloud and Rain Observations 2 – Pressure Systems 3 – Current Observations 4 – Computer Models 5 – Predict & Verify

  5. Why focus on clouds? • Rain/Snow producers • Heating and Cooling • Indicator of weather • Come in interesting shapes

  6. Common Cloud Types

  7. Photo: WBZ-Mos Cloud Levels • High Cumulus • Size of top of thumb at arms length • Low Cumulus • Size of fist at arms length

  8. Cloud Levels • High Stratus • Sun and Moon easily seen • Low Stratus • Sun and Moon difficult to see

  9. Three Cloud LevelsHigh Clouds Sign of moisture high up in the atmosphere. (Storms possible in 6-24 hours).

  10. Three Cloud LevelsMiddle Clouds Possible marker of afternoon thunderstorm when clouds seen in the morning are growing or are very tall.

  11. Cloud LevelsLow Clouds Can form drizzle like precipitation

  12. Cloud LevelsLarge Vertical Development Often indicative of thunderstorms and heavy rain.

  13. Cold Front Warm Front Cold and Warm Front Clouds Frontal Movement

  14. Cloud Levels

  15. Satellites Monitor one area constantly, as it remains stationary with respect to an observer on earth’s surface Scan from north to south

  16. Click here for: Satellite loop of the United States Are the clouds moving in your direction? When will they reach you?

  17. Wavelengths of Light Radio Microwaves Infrared Visible Ultraviolet X Rays Gamma Rays Wavelength Increases

  18. High and Low Clouds in Infrared Image Infrared Image Appears Gray Satellite Appears White Infrared Energy Infrared Energy High Cloud Cold Warm Low Cloud Earth Surface

  19. Visible image Infrared image

  20. How RADAR works USA Today Weather Book Jack Williams

  21. Click here for: Infrared Satellite loop of the United States Are the clouds moving in your direction? When will they reach you?

  22. Click here for the : Radar Map of the United States Where is the rain moving? Is it getting heavier or lighter? Look at the scale

  23. Clear During the Day Relatively Warmer Air Cooler Air All Solar Energy Received = Warmer

  24. Low Clouds During the Day Some Solar Energy Received = Cooler

  25. Clear at Night

  26. Clear at Night Ground radiatively cools at night and the energy is lost to space. The ground can get very cool on these nights.

  27. Cloudy at Night

  28. Cloudy at Night The ground radiately cools at night. Some of that radiation is absorbed by the clouds and reradiated in all directions. Some of that radiation reaches the ground and keeps warms the ground. This keeps it warmer at night.

  29. What clouds are outside now? Click on the image to check the clouds in Colorado.

  30. Ingredients for Cloud Formation • Condensation Nuclei • Moisture • Cooling / Lift

  31. Surface Weather Map General Rules • Low- • cloudy skies • Sucks air • Lousy • High- • mostly clear • blows air • Happy

  32. Click here to see the: United States Surface Weather Map Where are the highs and the lows? Are their lows close by that might be associated with clouds?

  33. Warm Air Cold Air Winds Moving Air Masses

  34. During the Day… Temperatures decrease with height, in this layer of the atmosphere. Temperature

  35. At Night….Air at the ground is often cooler than the air above it. Temperature

  36. Winds at Night Relatively Warmer Air Cooler Air

  37. Local Observations • Past and Current • Wind Speed • Wind Direction • Temperature • Humidity

  38. Click here for: Surface Observations in Denver (Mesowest data)find your city on the map

  39. Click here for: Computer model forecast for United States Weather 6 hours from now

  40. Climate Normals for Boulder

  41. Helpful Hints

  42. Your Forecast

  43. Thank you! Questions? Lis Cohen eac26@cornell.edu or liscohen@met.utah.edu

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