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.


  • 1. Weather Theory Made Easy

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. The Atmosphere Composition 78% Nitrogen 21% Oxygen 1% Inert Vertical Structure Troposphere Tropopause Stratosphere Mesosphere & thermosphere 4. Variations Diurnal Seasonal Variation with Latitude Topographic Altitude Temperature 5. Atmospheric Pressure Measurement Barometer Mercurial Aneroid Variation Altitude Temperature Pressure Depiction on Chart Isobars 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. Wind Convection Pressure Gradient Force Corriolis Force Friction Global Circulation Patterns Jet Stream 8. Land & Sea Breezes Sea Breeze Land Breeze Mountain/Valley Winds Valley Winds Mountain Winds Katabatic Winds Wind Shear Local/Small Scale Winds 9. Moisture Water Vapor Relative Humidity Dewpoint Change in State Evaporation Condensation Freezing & Melting Sublimation & Deposition 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. 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. 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. 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. 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. Lapse Rate The decrease in temperature with increasing altitude Approx. 2C/1000 16. Resists any upward OR downward development Unstable may grow into a vertical or convective current Atmospheric Stability 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. 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. Moistures Role in Stability Unsaturated 3C/1000 Unstable Normal 2C/1000 Stable Saturated 1.1 to 2.8C/1000 Unstable 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. What causes variations in altimeter settings between weather reporting points? 1. Unequal heating of the Earths surface 2. Variation of terrain elevation 3. Coriolis force 0% 0% 0% Countdown 20 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. 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. The development of thermals depends upon ___________. 1. A counterclockwise circulation of air 2. Temperature inversions 3. Solar heating 0% 0% 0% Countdown 20 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. Temp & moisture content of the underlying surface Tropical oceans & large deserts Middle latitudes are poor regions Source Regions 27. Classifications Temp Polar Tropical Moisture content Continental Maritime 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. Fronts Boundaries between air masses 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. 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. Cumulus Clouds Turbulence Showery Precipitation Gusty Winds Good Visibility Speed Will Dictate the Weather 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. Fast Moving Cold Front 35. Slow Moving Cold Front Much shallower frontal slop 36. Occurs when warm air overtakes cooler air Move at much slower rates Frontal slope is very gradual Warm Fronts 37. Generalizations Stratus clouds Smooth air Steady precipitation Poor visibility 38. Occurs when two air masses are equally balanced A mix of both air masses may be present for several days Stationary Fronts 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. Weather Hazards 41. Thunderstorms 3 conditions necessary Unstable lapse rate High moisture content Some form of lifting action 42. 3 stages Cumulus or building stage Continuous updrafts Mature stage Rain at the surface Dissipating stage Downdrafts Anvil top Thunderstorms 43. Types of T-Storms Air Mass Convection on hot summer days Frontal Collision of 2 AMs Orographic Mountainous areas Converging Air flow from 2 active storms Squall lines 44. Turbulence Lightning Microburst Hail Hazards 45. Dos & Donts 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. 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 Cant Avoid 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. 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. Wake Turbulence Caused by wing tip vortices Cup in a cup 50. Icing Rime Ice Tiny rain droplets or drizzle Milky in color Clear Ice Large water droplets Cumulous clouds Above the freezing level 51. Restrictions to Visibility 52. Fog Gets its name by how its formed Radiation or ground Advection Upslope Steam 53. Haze Airborne dust particles Smoke Combustion materials Smog Smoke & Fog mixed Haze, Smoke, Smog 54. Cooling from aloft tends to make an air mass more 1 2 50%50% 1. Stable 2. Unstable Countdown 20 55. When an air mass is warmed from below, its stability is 1 2 50%50% Countdown 20 1. Increased 2. Decreased 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. 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. 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. 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. 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