Lee wave lenticular clouds in southern Nevada
GOES-11 visible channel imagery (above) showed a nice example of lee wave “lenticular clouds” immediately downwind of the Spring Mountains (whose highest peak is Mt. Charleston at 11,918 ft or 3362 m) just to the northwest of Las Vegas, Nevada (Google maps) on 14 September 2007. The vertical motions associated with lee waves can cause moderate to severe turbulence which is a hazard to aviation, but on this particular day there were no pilot reports of turbulence noted in the immediate vicinity of the lenticular cloud formations (McCarran International Airport is located about 20 miles or 50 km southeast of the Spring Mountain range, and no lenticular clouds were seen on the satellite imagery directly over the Las Vegas metropolitan area or the airport itself).
Such lee waves are generated when strong atmospheric flow encounters a barrier to the flow — in this case, the axis of a strong southwesterly jet stream was located over the region, as indicated by an AWIPS image of RUC80 model 250 hPa wind fields overlaid on GOES-11 water vapor channel imagery (below). The lenticular clouds associated with this lee wave were seen to dissipate later in the day as the strongest jet stream winds propagated northeastward away from the region.
In order for these types of stationary lee wave clouds to form and be maintained, there often needs to be a stable layer located at altitudes above the top of the terrain obstruction. In this case, the 12 UTC rawinsonde data from Desert Rock, Nevada (below) did indeed indicate the presence of a shallow stable layer between about 600 and 650 hPa (with a 50 knot wind speed maximum at the 650 hPa level).
