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Skew-T Log-P Diagrams

An upper air sounding from the Slidell, Louisiana, NWS site, located about 85 SM west of the accident site, depicted a moist low-level environment with saturated conditions from 500 feet AGL to 6000 feet with a capping inversion. The freezing level was identified at 14,700 feet. The wind profile indicated calm surface wind with wind from the south-southeast veering to the southwest and west through 18,000 feet. A low-level wind maximum or low-level jet was identified near 5000 feet at 215 degrees at 25 knots, with winds less than 10 knots below 1000 feet AGL.

Strega Reno Air Racing Association
Gemini Sparkle

Key Takeaways:

  • Skew-T Log-P diagrams provide pilots with a comprehensive vertical slice of the atmosphere, derived from weather balloon soundings, revealing conditions like stability, moisture, and potential for severe weather beyond surface reports.
  • These diagrams graphically represent actual temperature, dew point, pressure, and wind profiles with altitude, along with thermodynamic concepts like dry and moist adiabats.
  • They include crucial calculated parameters such as the Lifted Index and K Index for assessing atmospheric stability and thunderstorm potential, and various condensation levels (LCL, CCL) for determining cloud bases.
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Skew-T Log-P diagrams(weather.rap.ucar.edu/upper). are not the most popular weather products perhaps since, at first glance, they appear confusing and hard to interpret. The diagrams are produced from atmospheric soundings, which are measurements of the vertical distribution of physical properties of the atmosphere.

As a pilot and not as a meteorologist, I find that these nomographs provide additional information about the state of the atmosphere by vertically slicing the atmosphere. Other than low-level obscuration such as fog, “nasty” weather manifests itself in the vertical. Of course, glider pilots use them extensively since an unstable atmosphere is a glider pilot’s dream. Let’s decipher these diagrams.

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