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GXM 40 Owner’s Manual 23
XM WX Weather Features
Fronts
The Fronts feature displays the lines indicating the leading edge of an air mass that is replacing an existing air mass. This
feature also displays pressure centers. Pressure centers are represented by a large red “L” for low-pressure centers or a large
blue “H” for high-pressure centers. Pressure centers represent an area where pressure is measured to be either the highest or
the lowest relative to the surrounding area.
Indicates a low-pressure center. A low-pressure
center is an area where the measured pressure is
lowest relative to the surrounding area. Moving
away from a low-pressure center in any horizontal
direction results in increased pressure. Winds ow
counterclockwise around low-pressure centers in
North America.
Indicates a high-pressure center. Similar to a low-
pressure center, a high-pressure center is an area
where the measured pressure is highest relative to
the surrounding area. Moving away from a high-
pressure center in any horizontal direction results
in decreased pressure. Winds ow clockwise
around high-pressure centers in North America.
Cold front
Warm front
Stationary front
Occluded front
Trough
Indicates a low-pressure center. A low-pressure
center is an area where the measured pressure is
lowest relative to the surrounding area. Moving
away from a low-pressure center in any horizontal
direction results in increased pressure. Winds ow
counterclockwise around low-pressure centers in
North America.
Indicates a high-pressure center. Similar to a low-
pressure center, a high-pressure center is an area
where the measured pressure is highest relative to
the surrounding area. Moving away from a high-
pressure center in any horizontal direction results
in decreased pressure. Winds ow clockwise
around high-pressure centers in North America.
Cold front
Warm front
Stationary front
Occluded front
Trough