Comma Cloud Pattern
Two uses for the term "comma cloud" in relation to
(1) traditional meaning refers to cloud
associated with mature midlatitude cyclonic storm systems.
(2) west coast meaning refers to a
single air-mass area
of enhanced clouds associated with an upper level cyclonic
Both literally shaped like a comma.
Comma-shaped with a head, tail, and socalled dry-slot
west of tail.
Associated with synoptic scale weather features of a
16 March 1998
Comma cloud pattern is essentially created by so-called
circulations of midlatitude storm systems:
Dry slot region forms from "dry conveyor belt." Dry
tropospheric and lower stratospheric air descends behind
Example of Comma Cloud
a Midlatitude Cyclone:
01 Feb. 2006 Unenhanced IR of comma cloud pattern associated
occluding low pressure center.
01 Feb. 2006 Enhanced IR of comma cloud pattern
with occluding low pressure center.
Dry slot region shows up in satellite water vapor imagery:
Non-frontal Single Air Mass Enhanced Clouds (West Coast
West Coast meteorologists use the term comma cloud to refer
non-frontal areas of enhanced cloudiness associated with an
vorticity maximum, often well behind the front in the cold
mass. They are much smaller than the classical frontal
Click on this loop
non-frontal comma cloud behind a more classical comma
cloud feature approaching the west coast of the U.S.
This "comma" forms as a propagating upper-level vorticity
maximum moves over an area of open cell convection.
environment in the positive vorticity advection area ahead
vort-max allows for deeper convection and higher, colder
Monteverdi (1976) asserts that these single air-mass
associated with an average of 30% of the annual
precipitation at San
Monteverdi, John P.
The Single Air Mass Disturbance and Precipitation
Monthly Weather Review