A
mesohigh (sometimes called a "bubble high")
is a mesoscale high-pressure area that forms beneath
thunderstorms. While not always the case, it is usually associated with a mesoscale convective system.
In the early stages of research on the subject, the mesohigh was often referred to as a "thunderstorm high".
Formation
A mesohigh forms underneath the
downdraft in a
squall line and is associated with the
cold pool of a thunderstorm. It is largely formed by
hydrostatic phenomenon, specifically the
evaporation of falling precipitation.
As precipitation, primarily
rain, falls in the downdraft, it evaporates in the
Dew point air, leading to cooling in the downdraft due to an absorption of
latent heat. The cooling of the air leads to an increase in the pressure as the air becomes denser.
While not the primary mechanism behind the mesohigh, melting or
Sensible heat of
hail can also lead to increased pressure in the mesohigh.
An additional source of increased pressure is hydrometeor loading, the weight of precipitation increasing the speed of the downdraft, leading to increased pressure as the air converges at the surface.
See also
