He retired in 2011 to Star Valley in Wyoming and runs the Star Valley Weather Blog.
He has just posted a detailed analysis of the recent Teton Village Balloon Accident showing it was caused by a microburst.
It's worth a look and is a good reminder of the dangers of microbursts not just for airplanes, but other aviators.
The interesting aspect of the sounding and discussion presented on the Star Valley blog is that I associate an environmental lapse rate that is nearly dry adiabatic in profile as being unstable for lifting of moist, near saturation parcels. But, it is likely even more unstable for sinking parcels where water droplets are evaporatively cooling the parcel.
ReplyDeleteThe issue for downdrafts is a bit different as it is the dewpoint depression and potential for evaporation that leads to negative buoyancy. A deep, well-mixed boundary layer with a dry-adiabatic lapse rate can lead to strong downdrafts for this reason. Precipitation into such a layer results in cooling and strong negative buoyancy. A measure of maximum downdraft speed potential is a quantity known as Downdraft Convective Available Potential Energy (DCAPE), which is the downdraft equivalent of Convective AVailable Potential Energy (CAPE).
DeleteJim