500 mb Plot

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The 500 millibar (mb) map plots a variety of information collected by weather balloons and represents atmospheric conditions at an altitude of approximately 5,500 meters (18,000 feet). The map displays:
  • The air temperature (degrees Celsius) in red
  • The dew point temperature (degrees Celsius) in green
  • The height of the 500 mb level (decameters) in black. For example, "558" means 5,580 meters.
  • Winds (knots) – The wind barb is an "arrow" that depicts the wind speed and direction. The "feathers" of the arrow indicate the wind speed while the blank end of the arrow indicates the direction the wind is blowing toward.
Also shown on the map as brown lines are contours of the height of the 500 mb level (decameters). These are at intervals of 60 meters.

This map is updated twice a day.