4-11. Which of the following upper air characteristics is associated with the passage of a fast-moving cold front? 1. Slight backing of the wind with height 2. A  double  inversion;  the  frontal  inversion and  a  subsidence  inversion  some  distance to the rear of the front 3. Isotherms  are  well  spaced  and  cross  the front at an angle of about 30 degrees 4. Each of the above 4-12. What is a secondary cold front? 1. A fresh outbreak of very cold air to the rear of a fast-moving cold front 2. A trough of low pressure 3. The classification given to any summertime cold front 4. Any    cold    front    that    is    classified    as unimportant meteorologically 4-13. Which  of  the  following  occurrences  leads  to the formation of a cold front aloft? 1. The  mP  air  to  the  rear  of  a  cold  front crosses  a  mountain  range  and  rides  atop warm moist mT air 2. Cool  air  overtakes  colder  more  dense  air and rides up over it 3. Cold dense air overtakes cooler less dense air and forces it aloft 4. Each of the above 4-14. A   squall   line   is   an   instability   line,   but   an instability line is NOT necessarily a squall line. 1. True 2. False 4-15. Which of the following statements concerning prefrontal squall lines is correct? 1. They   form   about   50   to   300   miles   in advance of fast-moving cold fronts 2. Their speed is roughly equal to 40% of the 500-mb wind speed 3. They   are   most   common   in   spring   and summer in the United States 4. Each of the above 4-16. Which   of   the   following   weather   changes occurs  with  the  passage  of  a  prefrontal  squall line? 1. The temperature rises significantly 2. The pressure falls 3. The wind shifts cyclonically 4, The wind shifts anticyclonically 4-17. What   air   mass(es)   is/are   involved   in   the development of Great Plains squall lines? 1. mT only 2. mT and mP 3. mT and cP 4. mP and cP 4-18. What is the average speed of warm fronts? 1. 5 to 10 knots 2. 10 to 20 knots 3. 15 to 25 knots 4. 20 to 30 knots 4-19. In   the   Northern   Hemisphere,   how   are   the surface  winds  affected  before  and  after  the passage of a warm front? 1. They are generally southeasterly ahead of the  front  and  shift  to  southwesterly  after passage 2. They are strongest after passage 3. They shift in a counterclockwise direction 4-20. Where  is  nimbostratus  and  its  accompanying precipitation most frequently found in relation to the warm front? 1. Within  300  miles  of  the  front  in  the  cold sector 2. Within 300 miles of the front in the warm sector 3. 500 miles in advance of the front 4. 500 miles to the rear of the front 4-21. What is produced when the winds perpendicular  to  a  warm  front  increase  with height? 1. Strong overrunning of the warm air across the top of the retreating cold air mass 2. Pronounced prefrontal cloudiness 3. Precipitation 4. Each of the above 4-22. When overrunning occurs, and the air is moist and  unstable,  which  of  the  following  weather phenomena occurs? 1. Clear skies 2. High and mid clouds only 3. Stratus and fog 4. Thunderstorms 20