IRFP-01
Metro Review
b. Formation
(1) Forms when cold front contains air warmer than the “cold
air side” of the warm front; cool air from the overtaking cold
front slides under the warm air and over the cold air
between the warm front airmasses
(2) Produces warm and cold front systems aloft, with the warm
front extending to the surface
(3) Forms predominantly over water
c.
Wind changes
(1) Before passage, wind flows parallel to the front from higher
to lower pressure
(2) Behind warm front, wind flows perpendicular to the front,
following prevailing wind in same direction as front
III. Meteorological phenomena and hazards 21.1.1.4
A. Thunderstorms
1. Types
a. Air mass thunderstorms
(1) Convective air mass
(a) Generated by solar convection within unstable, moist
air mass
(b) Generally isolated and scattered over wide area
(2) Orographic air mass
(a) Generated when unstable and moist air mass is lifted
over hills or mountains
(b) Usually scattered among individual mountain peaks,
but can cover larger areas
b. Frontal thunderstorms
(1) Cold front
(a) Generated by cold air sliding under moist warmer air,
forcing it aloft—resulting in violent thunderstorms
(b) Usually narrow bands—50 to 100 miles along the front
(8-97) Original
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