Forecasting
Upper-Air Weather Maps Explained: 500 mb, 700 mb, 850 mb, and Jet-Level Charts
What upper-air maps show, why meteorologists use pressure levels, and how upper-level patterns guide storms, temperatures, and precipitation.
Quick answer: Upper-air maps show the atmosphere above the surface at pressure levels such as 850, 700, 500, and 250 mb.
Why pressure levels
Meteorologists use pressure surfaces because they follow the atmosphere better than fixed heights in many analyses.
Each level highlights different features: low-level temperature, moisture, lift, steering flow, and jet streams.
Common levels
850 mb is useful for low-level temperature and moisture. 700 mb can show lift and dry layers. 500 mb shows troughs and ridges. 250 or 300 mb shows jet streams.
No level tells the whole story alone.
Forecast use
Upper-air maps help explain why surface weather changes.
A storm at the ground often depends on support from the atmosphere above it.