About This Product
The 850 millibar (mb) map plots a variety of information collected by weather balloons and represents atmospheric conditions at an altitude of approximately 1,500 meters (5,000 feet). The map displays:
- The air temperature (degrees Celsius) in dashed contours at 2°C intervals. Temperature contours are red above freezing (0°C) and blue if at or below freezing.
- The height of the 850 mb level (decameters) in black contours at 3-decameter (30-meter) intervals. For example, "154" means 1,540 meters.
- Winds (knots) – Wind barbs are displayed in a grid. 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. In addition, wind speeds above 25 knots are contoured in 5-knot intervals and shaded blue, or shaded purple if above 50 knots.
This map is updated hourly. For more details, visit the NWS Storm Prediction Center's Mesoscale Analysis website.