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Click here for latest 500 mb Data chart from website	Click here for latest Analyzed 500 mb map from website

The map on the left is constructed from data collected at a pressure value of 500 mb (about half of sea level pressure) from the network of rawinsonde stations across the conterminous U.S. The data are plotted in an upper air station model where the forward end of the wind barb is at the upper air station site. For a description of the upper air station model, click here.

Analysis lines:

• contours (blue, solid) - lines of equal altitude of the 500-mb value, interval of 60 meters based on 6000, and
  
• isotherms (red, dashed) - lines of equal temperature, interval of 5 C, based on 0.

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Click here for latest 300 mb Data chart from website	Click here for latest Analyzed 300 mb map from website

Analysis lines:

• contours (blue, solid) - lines of equal altitude of the 300-mb value, interval of 120 meters based on 9000, and
  
• isotachs (brown, dashed) - lines of equal wind speed, interval of 20 kts, based on the odd tens of 30 kts or greater.

On these upper air maps, altitude at which the chosen pressure occurs is given in meters, coded to conserve space on the map. One needs to add one or more digits to decode the actual altitude from the station model.

Upper air charts are typically drawn for "surfaces"of constant pressure, that is, assembled from data collected twice daily by rawinsondes at that particular pressure value. The routine pressure values for which upper air maps are displayed by the DataStreme Atmosphere homepage are: 850 mb, 700 mb, 500 mb, 300 mb. Additional data are collected including so-called mandatory levels from each rawinsonde measurement profile (if sufficient altitude is achieved): 1000, 925, 850, 700, 500, 400, 300, 250, 200, 150, 100, 85, 70, 50, 40, 30, 25, 20, 15, 10 mb.