Information Shown on Composite Weather Maps:
North Pacific and North American Overviews

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Upper-Air Maps (500 and 300 millibars)

1. Contours of geopotential height (that is, the height above sea level of a constant-pressure surface, in this case shown at intervals of 60 meters).
   The analyses come from either the eta or aviation (AVN) forecast model initializations performed twice daily by the National Centers for Environmental Prediction (NCEP--formerly the National Meteorological Center, NMC).

   [Note: The domain of the eta-model extends only a modest distance into the eastern Pacific, whereas the AVN model domain covers the globe. However, the eta-model output typically arrives several hours earlier than the AVN model output, so in the interests of timeliness, the eta model output is shown for a few hours every day before the more extensive AVN output replaces it.]

2. A gray-scale infrared satellite image from the GOES-West satellite (for the North Pacific view), or a composite of that image plus an image from the GOES-East satellite (for the North American view), recorded as near as possible to the time of the analyses in (1) above.
3. Plots of weather data recorded by balloon-borne rawinsondes launched at the same time as the analyses in (1) above. The weather data include:
   • wind speed (in knots) and wind direction;
   • temperature and dew-point temperature (both in degrees Celsius); and
   • geopotential height (in meters above sea level).

Surface and Sea-Level Map

1. Contours of sea-level pressure (at intervals of 4 millibars).
   The analyses come from the eta-model initialization (twice daily, for 00Z and 12Z) or aviation (AVN) model initialization (four time daily, for 00Z, 06Z, 12Z, and 18Z) performed by the National Centers for Environmental Prediction (NCEP--formerly the National Meteorological Center, NMC).

   [Note: The domain of the eta-model extends only a modest distance into the eastern Pacific, whereas the AVN model domain covers the globe. However, the eta-model output typically arrives several hours earlier than the corresponding AVN model output, so in the interests of timeliness, the 00Z and 12Z eta model output is shown for a few hours every day before the more extensive AVN output at those hours replaces them.]

2. A gray-scale infrared satellite image from the GOES-West satellite (for the North Pacific view), or a composite of that image plus an image from the GOES-East satellite (for the North American view), recorded as near as possible to the time of the analyses in (1) above; and
3. Plots of surface weather data, recorded at the same time as the analyses in (1) above. The weather data include:
   • wind speed (in knots) and wind direction;
   • cloud cover;
   • temperature and dew-point temperature (both in degrees Fahrenheit);
   • present weather (represented symbolically); and
   • sea-level pressure (in millibars, coded).