Skew-T from March 13

14 March 2014  2115Z

Below is a “Skew-T” plot derived from a radiosonde sounding at 1200Z on March 12. This plot occurred just a few hours before the surface analysis forecast shown in the post of March 13. Just a few points to underscore with this plot.

Notice that the temperature line (red) and dew point line (blue) overlap from approximately 925 mb to approximately 625 mb. Such overlap indicates that the atmosphere is completely saturated between these levels. Given the vertical distance of this saturation, it is termed a deep layer. Pilots flying between these altitudes would be in IMC conditions the whole way. If temperatures are below freezing (as they are above 700mb), icing lurks in the clouds for the unsuspecting.

The wind barbs to the right show that between these two pressure altitudes, velocities ranged from approximately 45 kts to 65 kts out of the southwest.

A temperature inversion is noted between 950 mb  and 850 mb. That is, the temperature line, which begins at 7 degrees C at 950 mb. extends upward and to the right to approximately 10 degrees C at 850 mb. Under “normal” conditions, the temperature should decrease with altitude, not increase as is occurring here. Temperature and dew point is spread maximally at approximately 500 mb, 18,000’ indicating a layer or clearer skies.

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