[Model Graphics Information]
John Scott's notes on Skew-T
updated 6/2005

The far left column is altitude in millibars. Here's a rough comparison:

The thin lines angled left to right are for dew points.  The thin lines angled right to left before curving upwards are dry adiabats.  The thick line (usually red) in the middle right of the chart is the predicted temps.  The middle left line (usually green) relates to dew points.  The far right column is wind direction and speed.

In a nutshell the more the actual temp line parallels the dry adiabats the better.  The conventional way to read a Skew-t is to first find out the temps at altitude from the morning balloon soundings.  Then find out what the predicted high is for the day.  Then draw a line from the high temp point (from ground level) along the dry adiabats until it meets the actual temp line.  The point in which the line intercepts the actual temp line marks the top of the lift.  Of course, you have to take into account our sink rate; you won't get that high.  An unscientific method is to just lop off 1,000ft.  A more scientific way is to determine where the difference between the drawn line and the actual temp line drops below 3 degrees Celsius.

To find out where cloudbase might be:  Find out the dew point prediction.  Draw a line left to right following those thin dew point lines.  Where the line intersects the actual temp line is where cloudbase will be -- maybe.  If it intersects above the line that you have drawn above then more than likely it will be blue.  If it intersects well below your original line then there is a good chance of overdevelopment.

But since you can now get Skew-Ts for every three hours you don't have to go through all of that.  Just look at the afternoon soundings and see how high the predicted temps parallel the dry adiabats.  To find out cloudbase potential look at how the green dew point line relates to the actual temp line.  Inverted Vs are the best (the apex of the V generally marks cloudbase levels).  If the green line follows the temp line too closely that usually means rain or overdevelopment.  If the green angles away from the temp line that usually means a blue day.