METEOROLOGIST JEFF HABY
While instability release is like a basketball rising from the bottom of a swimming pool, lifting is caused by air
being forced to rise. Forced lifting is like picking up a bowling ball from the ground or doing
a bench press. The object will not rise until a force causes it to rise. It is lifting not caused by
the air rising on its own.
Without enough lifting, parcels of air can not be lifted to a point in the troposphere where they can rise
on their own due to positive buoyancy.
Instability, if it is present, can not be released without the
proper amount of forced lifting for the individual situation.
1. Frontal boundaries,
dry lines and
outflow boundaries (low level convergence)
2. Low level Warm Air Advection
3. Upslope flow
4. Low pressure system (synoptic and mesoscale)
5. Differential heating along soil, vegetation, soil moisture, land cover boundaries (low level convergence)
6. Low level moisture advection
7. Differential Positive Vorticity Advection,
jet streak divergence (upper level divergence)
8. Gravity wave
PRECIPITATION FROM LIFTING
Dynamic precipitation is also known as stratiform precipitation. Dynamic precipitation results from a
forced lifting of air. These forcing mechanisms include processes that cause
low level convergence
and upper level divergence. As unsaturated air rises the
relative humidity of the air
will increase. Once the air saturates, continued lifting will produce clouds and eventually
precipitation. Dynamic precipitation tends to have a less intense rain rate than
convective precipitation and also tends to last longer. While stratiform rain is the product of lifting, convective
precipitation is the product of both lifting and instability release.
Lifting is assessed on the forecast models by examining the
700 mb upward vertical dynamic motion prog
and surface prog. It
is also important to examine constantly updated surface charts for lifting mechanisms that occur on a time and space
domain that the models have a difficult time resolving (especially in thunderstorm situations).