1. Weather Cloud Types A cloud is ice crystals and or tiny water droplets formed by cooling air to its dew point. Dew point is the temperature where the air is saturated with water vapor

2. Convection Currents Two objects can not occupy the same space at the same time. This goes for clouds also. This drives the clouds upward to higher less crowded regions of the atmosphere creating convection currents.

3. Compare and Contrast Cold and Warm Fronts Cold Front Fast moving 30 miles/hr Blunt nosed Dense air At the boundary there are vertical clouds w/ rain and winter snowfalls, possible thunderstorms Warm Fronts Slow moving 10 to 20 miles/hr Gently sloping Air less dense Thicken clouds far in advance of the frontal boundary. Produces a slower, steady moving, widespread rain.

4. Topographic Affect on Cloud Formation Orographic- where air travels up a mountain range cooling as it goes, and getting to its dew point rapidly and forming clouds.

5. Inversion Inversion occur when air with a temperature profile that is warmer rather than cooler above the surface. This traps cooler air which is unable to rise creates city fog, day after day. Farmers have problems with inversions because it may kill of young plants just starting to emerge.

6. Classes of Clouds We need to examine the types of clouds and the conditions in which they exist. www.mountwashington.org The original classification was done by Luke Howard (a British naturalist) about 200 years ago. This system is still used today.

7. Howard labeled the clouds by their appearance and their altitude. There are three basic types: –Stringy = cirrus –Heap = Cumulus –Layered = Stratus There are three altitudes –High = (Cirro means a curl of hair) 20,000 ft. + –Middle = Alto (6,500-20,000 ft. –Low = Surface to 6,000 ft.

8. High Clouds The altitude of cloud types will vary with latitude. Atmosphere over the warm Equator is higher than the atmosphere over the North and South Poles. In middle latitude the cloud base is approximately 23,000 ft (4 miles) in a very cold environment (well below zero). Cirro clouds form from ice crystals in high winds (not weather makers, but may indicate bad weather is on the way).

9. . Department of Atmospheric Sciences (DAS)Department of Atmospheric Sciences (DAS) at the University of Illinois at Urbana-Champaign

10. Cirrus Clouds

11. Cirrocumulus Clouds Thin patches of small, white rounded clouds arranged in long rippling rows (resemble fish scales). Forms in conditions of wind shear (when wind changes direction or speed from one height to another). Wind shear generally occurs in the front of storms (rain or snow in 12-24 hours).

12. Cirrostratus Clouds

13. Cirrocumulus Clouds http://asd-www.larc.nasa.gov/SCOOL/cloud_contest/Oct03_C3/rock_island.jpg

14. Middle Clouds (altos) Altitude of middle clouds range from 6,500’ to 23,000’ (1.5 miles to 4 miles). Composed of super cooled water droplets and small ice crystals. Temperature ranges form 32 o F to -13 o F. Usually less than ½ mile thick.

15. Middle Clouds (altos)

16. Altocumulus Appears as gray, puffy patches, that may show a wave or band pattern. Are bigger than cirrocumulus, covering more area. Edges are sharply defined since they are composed of water droplets rather than ice. Rarely cause any precipitation but may signal and an advancing cold front.

17. Altocumulus

18. http://www.capetownskies.com/9788/10_alto_cumulusm.jpg

19. Altostratus Appear gray to bluish-white composed of ice crystals and water droplets and cover the entire sky. The cloud cover is so thin that the sun or moon can be barely visible. This type of cloud usually a head of a widespread rain.

20. Altostratus http://www.weatherpictures.nl/altostratus.html

21. Low Clouds Occur between ground level and 6,500’. Composed of water droplets or if cold enough ice crystals or snow.

22. Stratocumulus clouds Stratocumulus clouds generally appear as a low, lumpy layer of clouds that is sometimes accompanied by weak intensity precipitation. Stratocumulus vary in color from dark gray to light gray and may appear as rounded masses, rolls, etc., with breaks of clear sky in between. http://www.maltaweather.info/clouds.html

23. Stratocumulus clouds http://www.maltaweather.info/clouds.html

24. Stratocumulus clouds http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

25. Stratocumulus Clouds Rule of thumb: Hold arm up. If the cloud is the size of your thumb then it’s a Altocumulus, if it is the size of your fist then it’s a stratocumulus.

26. Stratus Cloud Fog on the ground. A uniformly grey cloud, horizon to horizon. May cause mist or drizzle, but not rain. Simply, fog is a cloud near the ground. A cloud is an area of condensed water droplets (or ice crystals in the upper atmosphere). The same processes that produce clouds high above the ground can produce clouds near the surface.condensed

27. Stratus Cloud

28. Nimbostratus Nimbostratus are dark, low-level clouds, with a ragged pattern and less uniform at its base, accompanied by light to moderately falling precipitation. Low clouds are primarily composed of water droplets since their bases generally lie below 6,500 feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain ice particles and snow. Sun is blocked out completely. Associated with Scuds- drifts of ragged cloud fragments.

29. Nimbostratus

30. http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

31. Vertical Clouds Cumuliform (Cumulus, Cumulus congestus, Cumulonimbus) These are the charging bulls of clouds. They travel upwards at a rate approximately 100 miles/hr compared to 1 mile/hr on other clouds. Because of their speed they may form in a matters of minutes.

32. Vertical Clouds Cumulus Form on warm, clear afternoons. Are big, bright, sharply defined white pillows with dark undersides, with flat bases. Develop in updrafts of air. Are commonly called fair weather cumulus. Generally last less than an hour.

33. Vertical Clouds http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

34. Vertical Clouds http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

35. Vertical Clouds Cumulus Congestus- Form in warm, humid, unstable conditions, producing closely packed, high towering cumulus clouds and produce showers.

36. Vertical Clouds http://www.weatherpictures.nl/congestus.html

37. Vertical Clouds Cumulonimbus Forms when a Cumulus Congestus continues to surge into the high atmosphere, 8 to 10 miles, forming a flat anvil shaped top. May form as individual storms or squall lines, will also bring lightning and torrential downpours, possible tornadoes. Big ones are called supercells.

38. Vertical Clouds http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

39. Vertical Clouds http://epod.usra.edu/archive/epodviewer.php3?oid=122368

40. Special Clouds Lenticular Caused when moist air to form when traveling over the tops of mountains. Can be seen for miles downwind of mountains as standing waves (hold their shape). Have been responsible for many reported UFO.

41. Lenticular http://www.cloudman.com/

42. Special Clouds/ Billow Cloud Billow Cloud-Look like ocean waves. This cloud shows the boundary between layers of different temperatures.

43. Billow Clouds http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

44. Special Clouds/ Banner Cloud Banner clouds occur at the top of a mountain that drapes away in the downwind direction.

45. Special Clouds/ Banner Cloud http://hsu.as.ntu.edu.tw/cyber_course_II/chapter7/cloud/Wind%20shear.jpg

46. Special Clouds/ Pileus Cloud Occur when moist air that pushes over the top of a cumulus towering cloud, creates a fuzzy cap cloud.

47. Special Clouds/ Pileus Cloud http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

48. Special Clouds/ Mammatus Mammatus Clouds occur under cumulus or cumulonimbus clouds, and are the result of sinking bags of air. Note there is no rotation of a mammatus cloud.

49. Special Clouds/ Mammatus http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

50. Special Clouds/ Mammatus http://www.bom.gov.au/info/skypix/cloud1.shtml

51. Special Clouds/ Contrails A contrail, also known as a condensation trail, is a cirrus-like trail of condensed water vapor often resembling the tail of a kite. Contrails are produced at high altitudes where extremely cold temperatures freeze water droplets in a matter of seconds before they can evaporate.cirrus-like Contrails form through the injection of water vapor into the atmosphere by exhaust fumes from a jet engine. If the surrounding air is cold enough, a state of saturation is attained and ice crystals develop, producing a contrail.

52. Special Clouds/ Contrails http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml

53. Special Clouds/ Contrails http://hsu.as.ntu.edu.tw/cyber_course_II/chapter7/cloud/Wind%20shear.jpg

54. Reference http://ww2010.atmos.uiuc.edu/(Gh)/guides /mtr/cld/cldtyp/home.rxml For photos references given for each individual photo.