1. Air Masses, Clouds, and Fronts Frank Brody / Brian Hoeth National Weather Service Spaceflight Meteorology Group Johnson Space Center Houston, TX The “nuts and bolts” of day-to-day weather analysis and forecasting

2. 2 Weather and the Space Shuttle The Space Shuttle cannot fly: The Space Shuttle cannot fly: Through thick low cloudsThrough thick low clouds Through rain and snowThrough rain and snow Near thunderstormsNear thunderstorms Near lightningNear lightning In winds that are too strongIn winds that are too strong In strong turbulenceIn strong turbulence

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4. 4 High and Low Pressure aka “anticyclone” Sinking air Usually associated w/ fair weather aka “cyclone” Rising air Usually associated w/ clouds and precipitation Isobars: Lines of constant pressure

5. 5 Forces and Winds Forces creating wind Forces creating wind Pressure Gradient ForcePressure Gradient Force Coriolis ForceCoriolis Force Frictional ForceFrictional Force “Use the Force”

6. 6 Pressure Gradient Force The pressure gradient force results in a net force that is directed from high pressure to low pressure

7. 7 Coriolis Force

8. 8 Geostrophic Wind Clockwise around High Pressure Counterclockwise around Low Pressure Wind blows parallel to isobars (lines of constant pressure)

9. 9 Frictional Force Cause: Surface of earth is rough Effect: Slows the wind down  Coriolis force weakens, pressure gradient force becomes dominant Result: Converging winds near lows and diverging winds near highs.

10. 10 Cyclonic Circulation

11. 11 Cold Fronts

12. 12 Warm Fronts

13. 13 Stationary Fronts

14. 14 “Classic” Frontal Pattern

15. 15 Occluded Fronts Cold front and warm front merge Further lifts already rising warm air Typically associated w/ intense, mature cyclones

16. 16 How to Read a Weather Map Temperature Dew Point Weather Wind Pressure

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19. And now … It’s time for a pop quiz …

20. 20 A warm front exists when ___ air is rising over ___ air (a) cold, warm (a) cold, warm (b) hot, moist (b) hot, moist (c) warm, cold (c) warm, cold (d) cold, stable (d) cold, stable

21. 21 A warm front exists when ___ air is rising over ___ air (a) cold, warm (a) cold, warm (b) hot, moist (b) hot, moist (c) warm, cold (c) warm, cold (d) cold, stable (d) cold, stable

22. 22 At the surface, winds tend to flow ___ and ___ towards a center of a low pressure center (a) clockwise, outward (a) clockwise, outward (b) counterclockwise, outward (b) counterclockwise, outward (c) clockwise, inward (c) clockwise, inward (d) counterclockwise, inward (d) counterclockwise, inward

23. 23 At the surface, winds tend to flow ___ and ___ towards a center of a low pressure center (a) clockwise, outward (a) clockwise, outward (b) counterclockwise, outward (b) counterclockwise, outward (c) clockwise, inward (c) clockwise, inward (d) counterclockwise, inward (d) counterclockwise, inward

24. 24 The pressure gradient force results in a net force that is directed from ___ to ___ (a) high pressure, low pressure (a) high pressure, low pressure (b) low pressure, high pressure (b) low pressure, high pressure (c) left, right (c) left, right (d) right, left (d) right, left

25. 25 The pressure gradient force results in a net force that is directed from ___ to ___ (a) high pressure, low pressure (a) high pressure, low pressure (b) low pressure, high pressure (b) low pressure, high pressure (c) left, right (c) left, right (d) right, left (d) right, left

26. 26 Clouds How clouds are formed? How clouds are formed? Types of clouds Types of clouds CumulusCumulus StratusStratus CirrusCirrus NimbusNimbus Clouds by height Clouds by height High: CirroHigh: Cirro Mid: Alto Mid: Alto Low: StratoLow: Strato

27. 27 Cloud Formation Clouds form when air is cooled to its dewpoint or when the air reaches saturation. Air rises  Lower pressure  requires work  Air is cooled! Cooler air holds less water vapor  some of the vapor condenses  CLOUDS!

28. 28 Cloud Types Latin Root TranslationExample CumulusHeap Fair weather cumulus StratusLayerAltostratus Cirrus Curl of hair Cirrus NimbusRainCumulonimbus

29. 29 Clouds by Height Height in the atmosphere Prefix Cloud Base Height (ft) HighCirro Above 20,000 MidAlto Between 6,000 and 20,000 LowStrato Below 6,000

30. 30 Cirrus – “Curl of Hair” Thin, wispy clouds composed of ice crystals

31. 31 Stratus - ”Layer” Layered low clouds, sometimes patchy with poorly defined edges

32. 32Cirrostratus Stratus: “Layer” Poorly defined edges Cirro prefix: High Cloud Cirrus: “Curl of Hair” Thin, wispy clouds “Halo around the sun”

33. 33 Cumulus – “Heap” Fair weather cumulus – small heaps of scattered clouds w/ flat bottoms and round tops Altocumulus – common ahead of cold front

34. 34Altocumulus Cumulus: “Heap” Flat bottoms, round tops Alto prefix: Mid Cloud

35. 35Stratocumulus Cumulus: “Heap” Flat bottoms, round tops Strato prefix: Low Cloud StratoCumulus – Dark fluffy clouds Relatively stable air Not as menacing as it may appear

36. 36 Nimbus – “Rain” Cumulonimbus - Cumulo: “Heap” Nimbus: “Rain” Easier Translation: “Thunderstorm cloud” Nimbostratus - Widespread thick layer of cloud with poorly defined edges producing precipitation

37. 37 Got any questions or have we left you in a fog??? Thank you for coming … buh bye now!!

38. 38 Contact Info/Websites Frank Brody: frank.brody-1@nasa.gov Frank Brody: frank.brody-1@nasa.govfrank.brody-1@nasa.gov Brian Hoeth: brian.r.hoeth@nasa.gov Brian Hoeth: brian.r.hoeth@nasa.govbrian.r.hoeth@nasa.gov http://www.srh.noaa.gov/smg http://www.srh.noaa.gov/smg http://www.srh.noaa.gov/smg http://ww2010.atmos.uiuc.edu http://ww2010.atmos.uiuc.edu http://ww2010.atmos.uiuc.edu http://virtualskies.arc.nasa.gov/main/mweather.html http://virtualskies.arc.nasa.gov/main/mweather.html http://virtualskies.arc.nasa.gov/main/mweather.html http://www.srh.weather.gov/jetstream/ http://www.srh.weather.gov/jetstream/ http://www.srh.weather.gov/jetstream/ http://www.windows.ucar.edu http://www.windows.ucar.edu http://www.windows.ucar.edu

39. 39 Backup Slides

40. 40 FRICTIONAL FORCE

41. 41 FRICTIONAL FORCE