METEOROLOGIST JEFF HABY
CIFK stands for Convective Instability of the First Kind. Convective instability is a situation in which
thunderstorms will occur when air rises through unstable air. One factor that promotes instability is
warming air near the surface. Another factor is cooling air aloft in the middle troposphere. Very warm
air under cold air is an
unstable situation. Think of a pot of boiling water. The air rises from the
stove toward the ceiling since warm air rises through the surrounding cooler air since the warmer air is
less dense. CIFK only deals with the temperature profile. CIFK becomes more significant as the air near
the surface warms (i.e. daytime heating,
warm air advection) and the air aloft cools (i.e.
cold air advection, adiabatic lifting).
CISK stands for Convective Instability of the Second Kind. Not only does a changing temperature profile lead to
more or less instability. Instability is also influenced by the
moisture profile. Instability will increase
further when the dewpoint near the surface increases. The addition of moisture makes the air
less dense near the surface but more importantly releases more
latent heat when air rises and
condenses into precipitation. Air that is less dense and is warmer due to latent heat release will
produce a more significant convection.
Severe thunderstorms often have an environment with warm and
humid air near the surface with cool air aloft.
In conclusion, instability is influenced by the temperature and moisture profile. The three factor
that will increase instability are warming air near the surface, cooling air aloft and increasing
dewpoints near the surface.