|LIMITING FACTORS FOR CONVECTION
METEOROLOGIST JEFF HABY
A convective limiting factor is a factor that prevents convective thunderstorms from occurring. This writing takes a look at several factors
that can prevent convective storms.
Relatively cold air in lower troposphere: Solar radiation warming of the ground surface is often an important ingredient for convection. If
the lower troposphere is too cold, this can prevent convection. This can occur from a thick cloud deck that limits solar radiation, nighttime
when there is no solar radiation, and a cold front that brings in cold air and stabilizes the lower troposphere.
A strong capping inversion: A strong capping inversion is relatively warm air aloft that prevents convection from the lower troposphere from
penetrating the inversion layer. If the cap holds strong even with daytime heating of the ground surface, convection will not occur. Forecasters
note how strong the cap is and compares that to the lifting mechanisms and solar heating in order to determine if the cap will prevent
storms from occurring.
Lower troposphere too dry: Updrafts need moisture to be unstable. If moisture is low, the rising parcels of air will be too stable to cause
convection if a cap (and in many cases even a weak cap) is in place. The latent heat from rising saturated air helps the rising parcels
to be more unstable. Forecasters look at dewpoints at the surface and the moisture profile in the lower troposphere to assess how moisture
will add or subtract from the convective potential.
High pressure dome: Being near the center of a synoptic high pressure dome can greatly limit the convective potential. This is because
the air is sinking and stabilizing. These high pressure systems help produce a capping inversion, help dry out the atmosphere and make
the atmosphere stable.