LINES:

For this class of graphics, solid black lines represent isohypses which are defined as lines of constant geopotential height. Here the geopotential height is for the 500 mb atmospheric pressure level normally located around 5.6 km (18,000 ft). Isohypses are drawn in thirty meter increments with the largest and smallest isobar values also labeled. Thin blue lines represent lines of equal temperature called isotherms and are drawn in four degree Celsius increments with the largest and smallest values also labeled. The intervals may be different depending on the product you are viewing therefore it is important to look at the line interval legend at the bottom right of the plot.

COLORS:

Background color represents the air temperature at 500 mb in degrees Celsius. The color-bar located at the bottom identifies the temperature for each shading of color. Thin blue lines separate regions of different temperature every four degrees.

WIND BARBS

Evenly spaced on the map are wind barbs that indicate the strength and direction of the wind at the 500 mb atmospheric pressure level.

1 kt ~ 1.15 mph ~ 1.85 km/hr

WHY IS THIS IMPORTANT?

The 500 mb height, temperature and wind field gives forecasters a representation of the middle atmosphere, a region that steers many of our surface weather systems. Features that impact surface weather such as troughs and ridges can be identified. Small disturbances that also impact surface conditions, called shortwaves, can also be located along with their intensity. Forecasters look at 500 mb maps to see if conditions are favorable for upper level weather systems to strengthen or weaken by identifying regions of warm and cold advection.