METEOROLOGIST JEFF HABY
tornadoes is a function of 4 primary factors which are vegetation cover, rainfall rate in immediate
vicinity of tornado, time of day, and air quality.
Large trees restrict the viewing of tornadoes. In the Southeast U.S. and
other regions with large trees, tornadoes can not be seen beyond the canopy of the trees. Regions with small trees
or few trees make tornado observation significantly better. Examples of regions with small or few trees include the
high plains and the western Great Plains.
The type of
supercell associated with a tornado
is important in determining
the visibility through rainfall. LP (low precipitation) supercells provide the greatest visibility due to the lack
of rainfall in the immediate vicinity of the tornado. HP (high precipitation) supercells commonly have rain-wrapped
tornadoes. Often an observer can not tell the difference between a rain-wrapped tornado and a heavy rain curtain
until the tornado or rain curtain is right on top of them. Many motorists have been killed by rain-wrapped tornadoes.
Classic supercells are in between LP and HP. Rainfall may wrap into the tornado in a Classic supercell situation,
but not as much as in a HP situation. Classic supercells will have a
hook echo on Doppler radar while HP supercells
look more like a kidney bean.
The time of the day is critical for tornado observation (specifically day versus night).
Obviously, nighttime tornadoes are more difficult to view than daytime tornadoes. There tend to be more daytime
tornadoes in the high and Great Plains than in the Eastern and Southeastern U.S. This is often because storms and
storm complexes form in the west and move east.
Preexisting visibility is the forth factor. Examples of preexisting
visibility include smoke, haze, steam fog, and pollution.
Visibility of tornadoes is maximized when there is no
vegetation, the supercell is an LP or Classic supercell, a daytime occurrence, and little preexisting visibility
problems. Tornado observation is minimized by tall trees, HP supercells, nighttime tornadoes, and pre-existing
obstructions to vision. The best place to view a tornado at a considerable distance is in the Great and High
Plains, while the Southeast U.S. is generally more difficult. In comparing Oklahoma to Mississippi, tornado
chasing in Oklahoma often gives a much better terrain and environment to chase tornadoes. Many of the tornadoes
in Mississippi occur at night and are associated with HP supercells, not to mention the continuous forest
More people are killed by low visibility tornadoes for several reasons, a few are:
more difficult to spot in the field, rain hides the dangerous tornado, and darkness hides the tornado. HP
supercells, night time supercells, and supercells in a forested environment are best monitored using the NWS
Doppler radar (and other radars) along with what trained spotters can pick out under the adverse circumstances.
Although the tornado is hidden or partially hidden from surface observers, the radar can pick out a circulation
that may indicate a tornado (strong
gate to gate shear, strong