Garmin GPSMAP 640 Manual page 8

Marine Mode: Using XM WX Weather and Audio
Weather Fronts and Pressure Centers: Surface analysis
Weather Maps
Weather fronts appear as lines that indicate the leading edge of an air
mass.
Front Symbol Description
Cold front
Warm front
Stationary front
Occluded front
Trough
Pressure-center symbols often appear near weather fronts.
Pressure- Description
Center
Symbol
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 flow counterclockwise around low-pressure centers in
the northern hemispheres.
Indicates a high-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 flow clockwise around high-pressure
centers the northern hemispheres.
4
City Forecasts
City forecasts appear as weather symbols
Symbol Table. The forecast is viewed in 12-hour increments for the next
48 hours.
Weather Symbol Table
Symbol Weather Symbol
Fair (sunny,
hot, clear)
Partly Cloudy
GPSMAP 640 XM WX Satellite Weather and XM Satellite Radio Supplement
as defined by the Weather
➊
➊
Weather
Rain (drizzle, sleet, showers)
Cloudy