Sounding Parameters

Using a program to pull sounding data from the U Wyoming archive, I was able to isolate certain characteristics of each case sounding. I focused on three primary supporting features of high wind events:

• Low level cross-mountain flow
• Critical level where cross-mountain flow drops to zero
• Inversion or stable layer aloft

To produce quantitative data, I averaged the sfc-850mb wind for cross-mountain flow, yielding an average direction, average speed, and the component crossing the mountain from the southeast. I calculated the height of the critical level by the level at which the component of the wind cross the mountain dropped below 5kt. I tested for the existence of an inversion layer between 850mb and 500mb, and determined the height of the bottom of the inversion as well as the vertical depth of the inversion.

These six variables were then compared to the magnitude of the wind report in each event. The inversion and critical level data was promising: The stronger events more frequently had an inversion present, with the bottom at a lower height than for weak events, and the depth of the inversion larger than for weak events.

The critical level was also generally at a lower height for strong events and higher, or not present at all during weak events.

Interestingly, the cross-mountain flow shows a small negative correlation to the magnitude of the wind event, which I'm not sure what to make of ... weaker events tended to have stronger low level cross-mountain flow...