|WIND SHEAR AND SUPERCELLS
METEOROLOGIST JEFF HABY
Can speed shear ever be too high? You would think that the higher the speed shear with height, the greater the
chance would be for
supercells to develop in an
unstable environment. This is true in some cases, but not in
others. A few times when I was in Oklahoma I ran into cases where the wind shear was too high. The developing
storm broke the cap and began to climb into the mid-levels of the atmosphere. But, the mid and upper level
winds were so strong that it blew the top off the developing storm (basically shredded it in half, not just
tilted it, but chopped it).
When speed shear is very high, very high
CAPE is also needed.
An intense updraft
(i.e. 100 miles per hour) is less likely to be chopped in half than a weaker updraft. The size of the updraft
is also important. Large intense updrafts are less likely to be chopped in half. Updrafts in a high speed
shear environment can be described as "survival of the fittest updraft" since only the strongest and largest
updrafts can handle extreme speed shear; These updrafts can become monster storms. If the CAPE is marginal and
the speed shear is extreme (e.g. CAPE = 400 J/kg, PBL wind = 20 knots, 700 mb wind = 90 knots, 500 mb wind = 120
knots, these days may result in no storms (no updraft can take it, they are shredded to pieces).