Download Description of an Occluded Front

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BLM 15-9
CHAPTER 15
REINFORCEMENT
Description of an Occluded
Front
Goal • Increase your understanding of occluded fronts.
What to Do
Fill in the blanks to complete the following paragraph. Use the diagram below, the information in your textbook,
and your class notes to help you. Note: The thickness of a cloud refers to the distance between the top and bottom
of the cloud. TROWAL is a Canadian acronym that is gaining international acceptance. It stands for a Trough Of
Warm Air aLoft.
warm air
cumulonimbus
cirrus
altostratus
cool air
cold air
nimbostratus
An occluded (1) _______________________ (also known as a TROWAL) is formed when a
(2) _______________________ front catches up to a (3) _______________________ front, and forces all of the
warm, (4) _______________________ air off the ground. Since the cool air is (5) _______________________ than
the warm air, the motion of the cold front is (6) _______________________ and the occluded front may last for
several days. Clouds in an occluded front are a (7) _______________________ of those in warm and cold fronts.
(8) _______________________ clouds at the lowest region of the front cause (9) _______________________ to fall.
Due to the nature of the front, this precipitation begins before the cold front reaches the
(10) _______________________ air and continues until after the temperature has (11) _______________________ .
Thus a change in temperature while the rain or snow continues to fall is one sign that an
(12) _______________________ front has passed. Ahead of the front, the (13) _______________________
are the same as for a warm front — high (14) _______________________ clouds forming a layer of
(15) _______________________ clouds that can thicken into nimbostratus or even (16) _______________________
clouds as the air is forced up rapidly, then some (17) _______________________ altocumulus or
(18) _______________________ clouds as the front moves past. An occluded front often brings a period of
(19) _______________________ rain.
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