Height Contours 500 hPa:
In case of a Comma the 500 hPa height shows a marked trough. Sometimes even an isolated low. The Comma is situated at the leading edge or near the trough line.
Temperature Advection 700 hPa:
The Comma is often found in the cold air advection behind frontal zones.
Isotachs 300 hPa:
Commas are situated at the cyclonic side of the polar jet. There may also be a left exit region of a jet streak which can further enhance the Comma cloud due to a PVA maximum situated in this left exit.
PVA 500 hPa:
A weak PVA maximum is superimposed over the Comma cloud.
Height of PV = 2 units:
Severe deepening of stratospheric air indicating the cyclogenesis is often seen just behind the Comma.
Curvature Vorticity 500 hPa:
A maximum of curvature vorticity indicating the ongoing cyclonic rotation is observed over the Comma cloudhead.