Aviation Weather Theory Made Easy

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Part 1 of 3, most pilots loose the basics when they start flying due to numerous reasons. Whatever your reason, don't let not coming to this seminar be one of them. This three part series will fill in the memory gaps and show you how easy it can be to understand weather systems.

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Aviation Weather Theory Made Easy

  1. 1. Weather Theory Made Easy
  2. 2. The basics of aviation weather, including the cases of carious weather phenomena and how they can affect the safety of flight. For more information on aviation weather, refer to Aviation Weather for Pilots(AC 00-6A) Aviation Weather Services (AC 00-45G) Internet Communications of Aviation Weather and NOTAMS (00-62) Introduction
  3. 3. The Atmosphere • Composition – 78% Nitrogen – 21% Oxygen – 1% Inert • Vertical Structure – Troposphere – Tropopause – Stratosphere – Mesosphere & thermosphere
  4. 4. Variations Diurnal Seasonal Variation with Latitude Topographic Altitude Temperature
  5. 5. Atmospheric Pressure • Measurement – Barometer • Mercurial • Aneroid • Variation – Altitude – Temperature • Pressure Depiction on Chart – Isobars
  6. 6. Pressure Systems Highs H surrounded by L Lows L surrounded by H Ridge Elongated are of H Trough Elongated are of L Col Neutral area between 2 H or 2 L Atmospheric Pressure
  7. 7. Wind • Convection • Pressure Gradient Force • Corriolis Force • Friction • Global Circulation Patterns • Jet Stream
  8. 8. Land & Sea Breezes Sea Breeze Land Breeze Mountain/Valley Winds Valley Winds Mountain Winds Katabatic Winds Wind Shear Local/Small Scale Winds
  9. 9. Moisture • Water Vapor – Relative Humidity – Dewpoint • Change in State – Evaporation – Condensation – Freezing & Melting – Sublimation & Deposition
  10. 10. Super-Cooled Water? Exist at temps below freezing Freeze upon impact with an exposed object Condensation Nuclei Microscopic particles Serves as a place for condensation to form Salt, dust, by-products of combustion Moisture
  11. 11. Clouds/Cloud Formation • Formation – Air moving over a cold surface – Air stagnating over a cold surface – Expansion cooling of upward moving air • Classification – Fog – Low Clouds – Middle Clouds – High Clouds – Clouds with Extensive Vertical Development
  12. 12. Low Clouds Almost entirely of water Super cooled water, snow, ice Surface to ±6,500’ Middle Clouds Primarily of water Most is Super cooled Bases range from ±6,500’ to ±23,000’ Classification
  13. 13. Classification • High Clouds – Almost entirely ice crystals – Base range 16,500 to FL450 • Clouds with Extensive Vertical Development – Super cooled water above the freezing level – Tops may be ice crystals – Base range from 1,000 to above 10K
  14. 14. Particle Growth Via added condensation or sublimation Via collision of particles Precip vs. Cloud Thickness To produce significant precip, 4000’ thick Thicker the cloud, heavier the precip Precipitation
  15. 15. Lapse Rate The decrease in temperature with increasing altitude Approx. 2˚C/1000’
  16. 16. Resists any upward OR downward development Unstable may grow into a vertical or convective current Atmospheric Stability
  17. 17. Temperature Inversion An increase in temperature with an increase in altitude Lapse rate is inverted Usually confined to shallow layers of air Visibility is often restricted
  18. 18. Unequal heating of the Earths surface Overlying air heated unevenly Warm air pushed aloft Lapse rate will determine the rest Temperatures Role in Stability
  19. 19. Moistures Role in Stability Unsaturated • 3˚C/1000’ • Unstable Normal • 2˚C/1000’ • Stable Saturated • 1.1˚ to 2.8˚C/1000’ • Unstable
  20. 20. Every physical process of weather is accompanied by or is the result of a _____________. 1. Movement of air 2. Pressure differential 3. Heat exchange 0% 0% 0% Countdown 20
  21. 21. What causes variations in altimeter settings between weather reporting points? 1. Unequal heating of the Earth’s surface 2. Variation of terrain elevation 3. Coriolis force 0% 0% 0% Countdown 20
  22. 22. The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. The difference is direction is primarily due to? 1. Stronger pressure gradient at higher altitudes 2. Friction between the wind & the surface 3. Stronger Coriolis force at the surface 0% 0% 0% Countdown 20
  23. 23. Convective circulation patterns associated with sea breezes are caused by? 1. Warm, dense air moving inland from over the water 2. Water, absorbing & radiating heat faster than the land 3. Cool, dense air moving inland from over the water 0% 0% 0% Countdown 20
  24. 24. The development of thermals depends upon ___________. 1. A counterclockwise circulation of air 2. Temperature inversions 3. Solar heating 0% 0% 0% Countdown 20
  25. 25. Air Masses • What is an air mass? – Large body of air with fairly uniform • Temperature • Moisture content – Forms when air remains stationary and takes on the characteristics of the underlying surface
  26. 26. Temp & moisture content of the underlying surface Tropical oceans & large deserts Middle latitudes are poor regions Source Regions
  27. 27. Classifications • Temp – Polar – Tropical • Moisture content – Continental – Maritime
  28. 28. As it moves from its source region, it begins to change Warming from below can cause instability Cooling from below may result in stability May also cause poor visibility from fog and low clouds Modification
  29. 29. Fronts Boundaries between air masses
  30. 30. Change in temp May be abrupt or gradual Change in wind direction or velocity Always shifts to the right in the Northern Hemisphere Change in pressure Usually a drop as you approach it Always reset your altimeter Frontal Passage Detection
  31. 31. Cold Fronts Hugs the ground as it moves due to gravity Forces warmer less dense air aloft Movement is usually in an easterly direction
  32. 32. Cumulus Clouds Turbulence Showery Precipitation Gusty Winds Good Visibility Speed Will Dictate the Weather
  33. 33. Fast Moving Cold Fronts Moved along by intense high pressure system Surface friction causes a steep frontal slope Wide difference between temp & moisture between the two masses Squall lines will precede if the air is moist and unstable. Usually 50 to 300 miles ahead.
  34. 34. Fast Moving Cold Front
  35. 35. Slow Moving Cold Front • Much shallower frontal slop
  36. 36. Occurs when warm air overtakes cooler air Move at much slower rates Frontal slope is very gradual Warm Fronts
  37. 37. Generalizations • Stratus clouds • Smooth air • Steady precipitation • Poor visibility
  38. 38. Occurs when two air masses are equally balanced A mix of both air masses may be present for several days Stationary Fronts
  39. 39. Frontal Occlusions • Occurs when a fast moving cold front catches up to a slow moving warm front • The difference in temperature determines the front that is produced (warm or cold front occlusion)
  40. 40. Weather Hazards
  41. 41. Thunderstorms • 3 conditions necessary – Unstable lapse rate – High moisture content – Some form of lifting action
  42. 42. 3 stages Cumulus or building stage Continuous updrafts Mature stage Rain at the surface Dissipating stage Downdrafts Anvil top Thunderstorms
  43. 43. Types of T-Storms • Air Mass – Convection on hot summer days • Frontal – Collision of 2 AM’s • Orographic – Mountainous areas • Converging Air flow from 2 active storms • Squall lines
  44. 44. Turbulence Lightning Microburst Hail Hazards
  45. 45. Do’s & Don’ts DO NOT • Take off or land in the face of a storm • Fly under a storm • Fly in a cloud mass without airborne radar • Trust the outward appearance of a cloud DO • Avoid by 20 miles • Clear the tops by 1000’ for each knot wind • Circumnavigate the area for 6/10th coverage • Avoid lightning areas • Regard tops of 35K or higher as hazadous
  46. 46. Tighten your seatbelt & secure loose items Plan & hold your course for minimum time through the storm Plan to enter below the freezing level Pitot heat & carb heat on Set power to establish Va Turn up flight deck lighting Turn off autopilot If You Can’t Avoid
  47. 47. During Penetration • DO keep you eyes on your instruments • DO maintain maneuvering speed • DO Allow the aircraft to “Ride the Waves” • DO Maintain Course for a minimum time through the storm
  48. 48. Can take place at any altitude Can be caused by wind shear, convection currents, & obstructions to airflow Often found near the jet stream CAT
  49. 49. Wake Turbulence • Caused by wing tip vortices • Cup in a cup
  50. 50. Icing • Rime Ice – Tiny rain droplets or drizzle – Milky in color • Clear Ice – Large water droplets – Cumulous clouds – Above the freezing level
  51. 51. Restrictions to Visibility
  52. 52. Fog • Gets its name by how its formed – Radiation or ground – Advection – Upslope – Steam
  53. 53. Haze Airborne dust particles Smoke Combustion materials Smog Smoke & Fog mixed Haze, Smoke, Smog
  54. 54. Cooling from aloft tends to make an air mass more… 1 2 50%50% 1. Stable 2. Unstable Countdown 20
  55. 55. When an air mass is warmed from below, its stability is… 1 2 50%50% Countdown 20 1. Increased 2. Decreased
  56. 56. Transition zone between two different air masses… 33% 33% 33% 1 2 3 1. Frontal zone 2. Trade wind 3. Trough Countdown 20
  57. 57. This will always change when flying across a front… 33% 33% 33% Countdown 20 1. Wind Direction 2. Type of precipitation 3. Stability of the air mass
  58. 58. Cold fronts in the US generally move to the… 1. East-Northeast 2. East-Southeast 3. West-Southwest 4. South 0% 0% 0% 0% Countdown 20
  59. 59. What type of front generally produces the most violent flying weather? 1. Warm 2. Cold 3. Fast-moving cold front 4. Stationary 0% 0% 0% 0% Countdown 20
  60. 60. What type of cloud is associated with fast-moving cold fronts? 1. Cirrus 2. Altostratus 3. Altocumulus 4. Cumulonimbus 0% 0% 0% 0% Countdown 20
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