|BURST POINT SERIES:|
METEOROLOGIST JEFF HABY
Instability can be increased by increasing low level temperatures, increasing low level moisture or cooling in the middle levels of
the troposphere. Warming temperatures and increasing dewpoints have been covered in previous topics. The cooling temperatures aloft
is the main focus of this writing.
Cooling temperatures aloft can be described as a cold pool aloft, cold air advection aloft or a lifting mechanism that is cooling the
air aloft such as dynamic lifting or evaporative cooling. These processes help weaken the cap aloft and enhance instability. Where
the cap weakens the most and where the greatest cooling occurs aloft will be a location that a rising thermal from the surface will
have the easiest time breaking the cap. This can be a burst point for initial thunderstorm development.
The three ingredients for thunderstorms are lifting, adequate moisture and instability. Cooling aloft will increase instability and
make it easier for a rising parcel of air to break the cap and develop into a thunderstorm. Thus, not only are surface conditions
important but what is occurring aloft can be very significant also in determining where convection will develop first. Lifting
aloft and cooling aloft are important to examine right along with surface temperatures and dewpoints.