LINES:

For this class of graphics, solid black lines represent isohypses which are defined as lines of constant geopotential height. In this case the geopotential height is for the 300 mb atmospheric pressure level normally located around 9-km or 30,000 feet. The isohypses are drawn in sixty meter (m) increments with the largest and smallest values also labeled. Thin blue lines represent lines of equal temperature called isotherms and are drawn and labeled in four degree Celsius increments.

COLORS:

Background color represents the wind speed at 300 mb in meters per second (m/s). The color-bar located at the bottom identifies the value for each shading of color.

WIND BARBS

Evenly spaced on the map are wind barbs that indicate the strength and direction of the wind at the 300 mb atmospheric pressure level.

1 kt ~ 1.15 mph ~ 1.85 km/hr

WHY IS THIS IMPORTANT?

The 300 mb wind field is important because it identifies the location and strength of the jet streams. Jet streams help forecasters determine the movement and speed of weather systems such as surface fronts. The location of jet streams are also important to air travel, specifically continental and trans-oceanic flight routes.