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AVIATION TRAINING BRIGADE UNITED STATES ARMY AVIATION CENTER Fort Rucker, Alabama February 2009 File No. 2/5/9/9E-0525-3 PRACTICAL EXERCISE AVIATION WEATHER COMPREHENSIVE REVIEW DIRECTIONS TO STUDENTS: This comprehensive review covers the atmosphere and air masses, pressure and winds, atmospheric stability and clouds, frontal weather, weather hazards, weather reports, weather charts, and weather forecasts. You may use any publication or notes that you desire. However, on the exam, references cannot be used. All questions on this comprehensive review pertain to rotary-wing. If you need help, ask the instructor. 1. The lowest layer of the atmosphere is the __________ and is approximately __________ feet at the equator and ____________ feet at the poles. 2. What is the difference between dry air and natural air? ___________________________________ ________________________________________________________________________________ 3. Name the two major conditions affecting atmospheric circulation. (1) ______________________________________ (2) ______________________________________ 4. Name one semi-permanent pressure (air mass) system that causes weather over the United States. ___________________________ 5. One method of heat transfer is radiation. Define radiation. ______________________________ _____________________________________________________________________________ 6. What is the difference between convection and advection? ______________________________ ______________________________________________________________________________ 7. What is the definition of an air mass? _______________________________________________ _____________________________________________________________________________ 8. What does the air mass classification code “c” indicate? ________________________________ _____________________________________________________________________________ 9. What is the source region and temperature/moisture content of an mP air mass? _____________________________________________________________________________ 10. Is an air mass designated cPk warmer or colder than the surface? _______________________ 11. Is a cPk air mass stable or unstable? _________________ 12. Define OLR. _________________________________________________________________ 13. If the temperature is increasing with altitude it is called an ______________; Two types of these are _____________ and _____________. 1 14. Polar air masses normally move in a ___________ direction and tropical air masses in a ________________ direction in the northern hemisphere. 15. Standard mean sea level pressure in “mb” millibars is __________; in inches of mercury "Hg" ________. 16. Define an isobar and its spacing on a surface analysis chart. _________________________________________________________________________________ 17. The force that starts the wind moving is the ______________ __________ ________________. 18. Pressure gradient forces always act from ___________ pressure to ___________ pressure. 19. How are isobars used to indicate strong or weak gradient forces? _________________________________________________________________________________ 20. In what direction does the wind flow around a high pressure area in the northern hemisphere? ________________________ 21. How does the wind flow in relation to the isobars above the friction level (above 2,000’ AGL)? ________________________ 22. What force modifies gradient force and causes the wind to flow parallel to the isobars above 2,000’? _____________________________ 23. What force is evident at the surface that causes the wind to flow across the isobars? ___________ _____________________________ 24. On the following diagrams draw the gradient and surface winds. 25. Near the center of a high the air tends to SINK/RISE and in a low it tends to SINK/RISE. 26. State Buys Ballots Law. _____________________________________________________________ 27. You are crabbing left to correct for a left crosswind, where is the area of lower pressure? _____________________________ 28. Water may exist in the atmosphere in three states, they are __________, ___________, and ___________. 29. Define water vapor. ________________________________________________________________ 30. Water vapor in the atmosphere may begin to condense when the temperature/dew point spread is within ___________ degrees. 31. Define sublimation. ________________________________________________________________ 32. The dry adiabatic cooling rate is _____ degrees per thousand feet. 33. What is the moist adiabatic cooling rate? _______________ 2 34. What is the level of free convection (LFC)? ________________________________________ 35. What are the three conditions of atmospheric stability? ________, _________, and _________. 36. If the OLR is 4C/1000’ the air will be _________ (stable/unstable) and if the OLR is 1C/1000’ the air will be __________ (stable/unstable). 37. The two basic categories of clouds are ______________ and ________________. 38. Which of the above categories would produce the most violent flight conditions? ___________________ 39. Interpret the following cloud abbreviations. (1) Cu ______________ (2) Cb ______________ (3) St ______________ (4) Ns ______________ (5) Sc ______________ (6) Ac ______________ (7) As ______________ (8) Cs ______________ (9) Cc ______________ (10) Ci _____________ 40. Which of the clouds in the previous question would have bases below 6,500 feet? ____________________________________________________________________________ 41. Define a front. ________________________________________________________________ 42. The four discontinuities across a frontal surface are: (1) _______________________________ (2) _________________ (3) _______________________ (4) ______________________ 43. Which, of the above discontinuities, would indicate to a pilot that the front has been penetrated while in flight? _________________________ and __________________________________________ 44. What is the primary cause of frontal weather? ________________________________________ 45. Define a cold front and give its typical direction of movement. _____________________________________________________________________________ 46. If you take off in the cold air behind a cold front and climb through the frontal surface, what will happen to the free air temperature? _______________________________________________________ 47. The typical width of the severe weather band with a cold front is ______ miles and it move at an average speed of ________ knots. 48. If a cold front is moving at a speed of 45 knots, what weather situation may form ahead of the front? _______________________________ 49. Define a warm front including its slope and direction of movement. _____________________________________________________________________________ 50. Warm front weather occurs _____________ (ahead of/behind) the surface front and may extend for ___________ miles. 51. State the cloud sequence in order if you are approaching a stable warm front from the cold air side. _____________, _______________, _______________,__ _____________, _______________ 52. Probably the most important element in flight planning for flight in a warm front is ____________________________________________________. 53. Define a stationary front. ________________________________________________________ 54. The stationary front has weather similar to a _____________________ front. 3 55. The winds associated with a stationary front __________________ (parallel/cross) the front. 56. In an open wave, if the air behind the cold front is the coldest of the air masses involved, a __________ type occlusion may form. 57. Identify the following frontal symbols. 58. The most violent frontal weather that pilots should probably not attempt to penetrate are the ___________ front, the _________ front, and the pre-frontal ___________ ____________. 59. Name the three atmospheric conditions necessary for all fog formation. (1) ____________ (2) ______________ (3) ________________ 60. For radiation fog, one additional factor is required, this is _____________ _________________. 61. What weather condition may cause radiation fog not to form, yet this same condition may also delay its dissipation? ________________ 62. What type fog may form when warm moist air flows over a colder surface? _________________ 63. The type of fog produced by adiabatic cooling is called ____________ fog. 64. In mountainous areas, what type of fog may form as a result of cold mountain air moving down slope? ___________ _____________ 65. Name the three conditions necessary for a thunderstorm to form. (1) ______________ (2) ______________ (3) _______________ 66. The two major types of thunderstorms are ____________________ and __________________. 4 67. Thermal convective and orographic thunderstorms are two examples of which of the above type? _______________ 68. Which of the two major types of thunderstorms are the most dangerous to flying? ______________ 69. The three stages in the life cycle of a thunderstorm are: (1) ______________ (2) _____________ (3) _____________ 70. Which of the above stages is the most dangerous and when does its cycle begin? ___________________________________ 71. The ______________ stage of a thunderstorm has only updrafts and the _____________ stage has only downdrafts. 72. What is the recommended flight procedure for scattered air mass thunderstorms? ___________________ 73. The three types of ice an aircraft is subject to are: (1) __________, (2) _______________, (3) __________________. 74. Ice formed by small supercooled water droplets is called _____________. 75. The temperature range for rime ice in stratus clouds is ____________ and in upper cumulus clouds is _____________. 76. The type of ice formed from large supercooled water droplets is called __________________. 77. The temperature range for clear ice in clouds is ______________. 78. The most hazardous icing condition is known as ___________ ___________ and would be found under a warm front during the winter months. 79. What are the two most important conditions necessary in the formation of aircraft icing? (1) _______________ (2) _______________ 80. The three types of clouds that may form in a mountain wave condition are: (1) _______________ (2) _____________ (3) ________________ 81. Of the three types of clouds listed above, which would be the best visual indicator of a mountain wave? ____________________ 82. For helicopter flight, what is the most dangerous condition with a mountain wave? __________________________________________________________________________________ 83. What is the recommended flight procedure for crossing a mountain range if a wave condition is suspected? ________________________________________________________________________________ METAR KOZR 201255Z 18004KT 1/2SM R06/1800FT DZ FGHZ FEW000 BKN003 OVC030 25/23 A2991 RMK DZB40 FG FEW000 SLP101 SPECI KPNS 201455Z 30015G30KT 2SM +TSRA SCT010 BKN015 OVC030 29/28 A2994 RMK TSB30 RAB35 CIG014V016 SLP279 NOTE: Use the above reports to answer questions 84-93. 84. What is the ceiling at OZR? _______________________ 85. What is causing the obscuration at OZR? ______________________ 5 86. How much of the horizon is being obscured at OZR? ______________________ 87. Is any precipitation occurring at OZR and if so when did it start? ________________________________________________ 88. What is the temperature/dew point spread at OZR? _____________ 89. What is the RVR at OZR? ___________ 90. SPECI at PNS indicates it is what type report? ____________ 91. What is the ceiling reported at PNS? ______________ 92. Which of the two stations has the lowest altimeter setting? __________ 93. At what time did the rain begin at PNS? ___________ CST. 94. The valid time for Aviation Terminal Forecast (TAF) is ________ hours. 95. 99 on a winds aloft forecast chart would indicate _________________________. 96. In the diagram on the right (from a winds aloft forecast chart), the wind and temperature in the northwest section are _______________________, and in the northeast section are ___________________. 97. The lowest altitude covered on a winds aloft forecast chart is ___________________. 98. Surface analysis charts are issued how often? ________________ 99. The source of data used on a surface analysis chart is obtained from __________________. 100. According to the station model on the right, write the following: (1) Sky condition ___________________. (2) Temperature/dew point ___________. (3) Precipitation ___________. (4) Wind ____________. (5) Station pressure 3 hours ago _____________. NOTE: Use the diagram on the right to answer questions 100-105. 101. The wind direction and speed at position # 1 is _________ at _________ knots. 102. What weather hazard to flight symbol is shown at position # 3? _______ 6 103. If flying at position # 4, what type aircraft icing situation would you be encountering? ______________________________ 104. Position # 5 is showing what weather symbol? __________________ 105. At which position, # 2 or # 3, would the weather be improving most rapidly? ___________ 106. The purpose of the weather depiction chart is ________________________. 107. Shaded areas on the weather depiction chart, that may be outlined in red, indicate what kind of weather? ___________________________ Unshaded areas outlined in blue? ________________________ 108. Define the weather conditions that constitute-IFR __________________________ MVFR _________________________ VFR __________________________ 109. Indicate the following sky condition symbols used on the weather depiction chart. 5 6 110. On the weather depiction chart, the visibility is normally shown to the left of the station model. If this is not shown, what does this mean? ____________________________________________________________ 111. The symbol on the right would be classified as ______________ (IFR/MVFR/VFR) category of weather on a weather depiction chart. 112. The weather depiction chart is issued every _________________ and the data to make up the chart is obtained from _______________________. 113. The radar summary chart is issued every ______________ and its main purpose is to _______________. 114. The following symbols on a radar summary chart indicate-- TRW 7 AVIATION TRAINING BRIGADE UNITED STATES ARMY AVIATION CENTER Fort Rucker, Alabama February 2009 File No. 2/5/9/9E-0525-2 PRACTICAL EXERCISE ANSWER SHEET AVIATION WEATHER COMPREHENSIVE REVIEW 1. troposphere, 60,000, 25,000 18. high, low 2. natural air contains water vapor and condensation nuclei 19. closely spaced isobars indicate a strong/steep gradient; widely spaced isobars indicate a weak/flat gradient 3. (1) uneven heating, (2) rotation of the earth 20. clockwise 4. North American High (CP) or Bermuda High (MT) or Siberian High (MP) 21. parallel 5. transfer of heat by electromagnetic waves 22. coriolis 6. Convection is the transfer of heat vertically via a gas; advection is the transfer of heat horizontally via a gas. 23. friction 24. 7. a large body of air whose physical properties (temperature and moisture) are horizontally uniform 8. The air mass was formed over land (continental). 9. Maritime Polar (Atlantic or Pacific Oceans), cold/moist 25. sink, rise 10. colder 26. In the northern hemisphere, with your back to the wind the area of lower pressure will be to your left. 11. unstable 12. observed lapse rate, the actual change in the air temperature with an increase in altitude 27. ahead of you 13. inversion, nocturnal, frontal 29. moisture in the form of an invisible gas 14. southerly, northerly 30. 2C 15. 1013.2; 29.92 31. changing water vapor directly to ice or ice to water vapor 28. liquid, vapor, solid 16. a line connecting points of equal barometric pressure corrected to MSL; every 4 mb 32. 3C 17. pressure gradient 33. 1.5C 8 34. altitude at which the temperature inside a rising parcel of air is the same as the ambient (outside) temperature 57. (1) warm (2) open wave (3) cold (4) stationary (5) cold occluded (6) warm occluded 35. stable, unstable, and conditionally unstable 58. cold, occluded, squall line 36. unstable, stable 59. (1) high moisture content; (2) condensation nuclei; (3) a cooling action 37. cumulus, stratus 60. light wind (2-5 knots) 38. cumulus 61. overcast sky (greenhouse effect) 39. (1) cumulus (2) cumulonimbus (3) stratus (4) nimbostratus (5) stratocumulus (6) altocumulus (7) altostratus (8) cirrostratus (9) cirrocumulus (10) cirrus 62. advection 63. upslope 40. Cu, Cb, St, Ns, Sc 64. valley fog 41. the boundary line between air masses of different densities 65. (1) unstable air (2) lifting action (3) moisture 66. (1) air mass (2) frontal 42. (1) temperature (2) dew point (3) pressure (4) wind direction 67. air mass 43. temperature, wind shift 68. frontal 44. lifting of warm moist air by cold air 69. (1) cumulus (2) mature (3) dissipating 45. the leading edge of an advancing mass of cold air; northwest to southeast 70. mature; when precipitation begins to fall 71. cumulus, dissipating 46. it will decrease, increase, decrease 72. circumnavigate by at least 20 nautical miles 47. 50, 25 73. (1) rime (2) clear (3) frost 48. squall line 74. rime 49. the trailing edge of a retreating cold air mass with an average slope of 1:200 and moves northeast 75. 0C to -20C, -10C to -20C 76. clear 50. ahead, 400 to 600 77. 0C to -10C 51. Ci, Cs, As, Ns, St 78. freezing rain 52. fuel requirement to reach an alternate airfield 79. (1) visible moisture (2) at or below-freezing temperatures 53. any front that is moving less than 5 knots 80. (1) lenticular (2) cap (3) rotor 54. warm 81. lenticular 55. parallel 82. clear air turbulence and downdrafts on the lee side of the mountain 56. cold 9 83. Cross at a 45 angle and as high as practical above mountain elevation. Remain clear of clouds. 108. IFR--ceiling less than 1000’ and/or visibility less than 3 miles MVFR--ceiling 1000’ thru 3000’ and/or visibility 3 thru 5 miles VFR--ceiling over 3000’ and visibility over 5 miles 84. 300’ broken 85. fog and haze 86. 1/8 to 2/8 (FEW000) 109. (1) overcast (2) scattered (3) totally obscured (4) few clouds (5) broken (6) clear 87. yes, moderate drizzle, 1240Z 88. 2C 110. visibility is greater than 5 miles 89. 1800’ 111. MVFR 90. special 112. 3 hours, METAR reports 91. 1500’ broken varying 113. hour, depict areas of precipitation 92. OZR 114. (1) cell movement (2) tops of echo 44,000’ (3) thunderstorm and rain showers 93. 0835 94. 24 95. light and variable 96. 290 at 25 knots, temperature 2C, 070 at 15 knots, temperature 6C 97. 6000’ MSL 98. every three hours 99. METAR reports 100. (1) overcast (2) 16/10 (3) rain (4) NE at 20K (5) 1011.5 mb 101. SE at 25 knots 102. thunderstorm 103. freezing rain 104. hail showers 105. 2 106. to depict areas of IFR, MVFR, and VFR weather 107. IFR, MVFR 10