Forecast Information; Viewing Forecast Information For Another Time Period; Viewing A Marine Forecast Or An Offshore Forecast; Weather Fronts And Pressure Centers - Garmin GPSMAP 800 series Owner's Manual

Color Marine Weather
Group
Dark Visibility
Gray
White Winter

Forecast Information

The Forecast chart shows city forecasts, marine forecasts,
warnings, hurricane warnings, METARS, county warnings,
weather fronts and pressure centers, surface pressure, and
weather buoys.
Viewing Forecast Information for Another Time
Period
1
Select Weather > Forecast.
2
Select an option:
• To view the weather forecast for the next 12 hours, select
Next Forecast or , and to view forecasts up to 48 hours,
in 12-hour increments, select Next Forecast or again.
• To view the weather forecast for the previous 12 hours,
select Previous Forecast or , and to view previous
forecasts, up to 48 hours ago, in 12-hour increments,
select Previous Forecast or again.

Viewing a Marine Forecast or an Offshore Forecast

1
Select Weather > Forecast.
2
Pan the chart to an offshore location.
The Marine Forecast or Offshore Forecast options appear
when forecast information is available.
3
Select Marine Forecast or Offshore Forecast.

Weather Fronts and Pressure Centers

Weather fronts appear as lines that indicate the leading edge of
an air mass.
Front Symbol
Pressure-center symbols often appear near weather fronts.
Pressure- Description
Center
Symbol
Indicates a low-pressure center, which is a region of
relatively lower pressure. Moving away from a low-
pressure center results in increased pressure. Winds
flow counterclockwise around low-pressure centers in
the northern hemisphere.
Indicates a high-pressure center, which is a region of
relatively higher pressure. Moving away from a high-
pressure center results in decreased pressure. Winds
flow clockwise around high-pressure centers in the
northern hemisphere.

City Forecasts

City forecasts appear as weather symbols. The forecast is
viewed in 12-hour increments.
SiriusXM ®
Weather Subcategories
Dense Fog, Dense Smoke, Dust Storm,
Smog
Arctic Outflow, Avalanche, Blizzard,
Blowing Snow, Cold Wave, Extreme
Cold, Flash Freeze, Freeze, Freezing
Drizzle, Freezing Fog, Freezing Rain,
Frost, Hard Freeze, Heavy Freezing
Spray, Heavy Snow, Ice Storm, Lake
Effect Blowing Snow, Lake Effect Snow,
Sleet, Snow, Snow and Blowing Snow,
Snow Squall, Snowfall, Wind Chill,
Winter Storm, Winter Weather
Description
Cold front
Warm front
Stationary front
Occluded front
Trough
Symbol Weather
Partly cloudy
Cloudy
Windy
Thunderstorms
Smoke (dusty, hazy)

Viewing Sea Conditions

The Sea Conditions chart shows information about surface
conditions, including winds, wave height, wave period, and
wave direction.
Select Weather > Sea Conditions.

Surface Winds

Surface wind vectors appear on the Sea Conditions chart using
wind barbs that indicate the direction from which the wind is
blowing. A wind barb is a circle with a tail. The line or flag
attached to the tail of the wind barb indicates the wind speed. A
short line represents 5 knots, a long line represents 10 knots,
and triangle represents 50 knots.
Wind Barb Wind Speed
Calm
5 knots
10 knots
15 knots

Wave Height, Wave Period, and Wave Direction

Wave heights for an area appear as variations in color. Different
colors indicate different wave heights, as shown in the legend.
The wave period indicates the time (in seconds) between
successive waves. Wave period lines indicate areas that have
the same wave period.
Wave directions appear on the chart using red arrows. The
direction of each arrow pointer indicates the direction in which a
wave is moving.
Viewing Forecast Sea Conditions Information for
Another Time Period
1
Select Weather > Sea Conditions.
2
Select an option:
• To view forecasted sea conditions for the next 12 hours,
select Next Forecast or , and to view forecasts up to 48
hours, in 12-hour increments, select Next Forecast or
again.
• To view the forecasted sea conditions for the previous 12
hours, select Previous Forecast or , and to view
previous forecasts, up to 48 hours ago, in 12-hour
increments, select Previous Forecast or again.

Viewing Fishing Information

The weather Fishing chart shows present water temperature,
present surface pressure conditions, and fishing forecasts.
Select Weather > Fishing.

Surface Pressure and Water Temperature Data

Surface-pressure information appears as pressure isobars and
pressure centers. Isobars connect points of equal pressure.
Pressure readings can help to determine weather and wind
conditions. High-pressure areas are generally associated with
fair weather. Low-pressure areas are generally associated with
clouds and the chance of precipitation. Isobars packed closely
Symbol Weather
Fair (sunny, hot, clear)
Rain (drizzle, sleet, showers)
Foggy
Snow (snow showers, flurries,
blizzard, blowing snow, sleet,
freezing rain, freezing drizzle)
Wind Barb Wind Speed
20 knots
50 knots
65 knots
23