ENCYCLOPEDIC ENTRY
ENCYCLOPEDIC ENTRY
A front is a weather system that is the boundary separating two different types of air. One type of air is usually denser than the other, with different temperatures and different levels of humidity.
Grades
5 - 8
Subjects
Earth Science, Geography, Physical Geography
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A front is a weather system that is the boundary separating two different types of air. One type of air is usually denser than the other, with different temperatures and different levels of humidity. This clashing of air types causes weather: rain, snow, cold days, hot days, and windy days.
Two major types of
fronts
are cold fronts and warm fronts.
Cold
fronts
often come with thunderstorms or other types of extreme
weather
. They usually move from west to east.
Cold
fronts
move faster than
warm
fronts
because cold air is
denser
, meaning there are more molecules of material in cold air than in warm air.
Strong, powerful
cold
fronts
often take over warm air that might be nearly motionless in the atmosphere. Cold,
dense
air squeezes its way through the warmer, less-
dense
air, and lifts the warm air. Because air is lifted instead of being pressed down, the movement of a
cold
front
through a
warm
front
is usually called a low-pressure system.
Low-pressure systems
often cause severe rainfall or
thunderstorms
.
Warm
fronts
usually show up on the tail end of precipitation and fog. As they overtake cold air masses,
warm
fronts
move slowly, usually from north to south. Because
warm
fronts
aren't as
dense
or powerful as
cold
fronts
, they bring more moderate and long-lasting
weather
patterns.
Warm
fronts
are often associated with high-pressure systems, where warm air is pressed close to the ground.
High-pressure systems
usually indicate calm, clear
weather
.
Fast Fact
Fronts on Weather Maps
On weather maps, cold fronts are illustrated by blue lines with sharp "teeth" pointing in the direction of the wind. Warm fronts are illustrated by red lines with rounded bumps pointing in the direction of the wind.
Credits
Media Credits
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Writers
Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Jeff Hunt
Diane Boudreau
Tara Ramroop
Kim Rutledge
Hilary Hall
Illustrators
Mary Crooks, National Geographic Society
Tim Gunther
Editors
Jeannie Evers, Emdash Editing
, Emdash Editing
Kara West
Educator Reviewer
Nancy Wynne
Producer
National Geographic Society
other
Last Updated
October 19, 2023
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