Vertical Cross Section Cloudspiral: 1st March 2004:06UTC

Isentropes
The VCS line at this point of time crosses the cloud area north of the W-E oriented frontal cloud band exactly in this area where the first signs of developing cloudiness of the “growing cloud spiral” can be noticed. There exists a small scale curl at the western boundary of the N-S oriented cloud field. The question which can be answered with the relevant parameters is if there is already a baroclinic zone in this area.

The VCS was laid from position A to B.

Temperature Advection
The isentropes show a downward inclined zone at about 71N03W. It is a shallow zone from about 600 hPa downward but it does not show a clear increased gradient compared to the surroundings. The TA field shows intensive CA in the western part which is overflown by WA from the eastern part. There is a part in the VCS where CA is from the surface up to about 800 hPa and WA above.

This supports the diagnosis of a thickness ridge cloudiness under WA which was based on appearance in satellite imagery, thickness and TA in 700 hPa. But it indicates also that there is a baroclinic boundary in the cloud area under consideration.

Convergence
There is very distinct convergence zone connected to the downward inclined isentropic zone (the baroclinic boundary) as well as with the cloud area in the thickness ridge in front of it.