WHAT IS AN AIR MASS THUNDERSTORM?
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METEOROLOGIST JEFF HABY
Thunderstorms require an
unstable troposphere, adequate
moisture and enough lift to
realize the unstable air. An air mass thunderstorm is in reference to a relatively
weak thunderstorm that usually does not last much longer than an hour, moves slowly and does
not produce
severe weather. Another term that means the same as an air mass thunderstorm
is a garden variety thunderstorm. Air mass thunderstorms tend to occur within a
maritime tropical air mass.
The wind shear is weak and this is why the air mass storms
are not severe, do not last long and do not move quickly. The main threats from
an air mass thunderstorm are
lightning and brief heavy rain. The instability tends
to be weaker with air mass thunderstorms. For example, the
CAPE value for
an air mass thunderstorm will often be more than half as less as CAPE values
associated with severe thunderstorms. Since wind shear is less in the air
mass thunderstorm environment, the
Helicity values are often less than those
associated with severe thunderstorms. The lifting mechanisms that generate
air mass thunderstorms tend to be weaker. While a severe thunderstorm may have lifting
from a strong approaching cold front, strong
upper level jet streak or a strong
low level convergence boundary, the lifting for an air mass thunderstorm tends to
be more subtle such as lifting generated by daytime heating and weak low level
convergence. Because of this air mass thunderstorms tend to occur in the
afternoon hours. Air mass thunderstorms are common in the summer along and
near the Gulf coast states and in other areas where the conditions are right for them
to occur.
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