Cross-section P

Strong upward motion (minimum omega) is found within the zone of the cold front, where in the satellite image the wave is seen in the cloud band. Upward (ascending) motion is the strongest at about 700 hPa and is nicely correlated to the highest IR and WV pixel values (orange lines in the cross-section). Behind the front pozitive omega values can be found, indicating downwarn (descending) motion. Another region with upward motion is found in the left-hand side of the cross-section. Looking at the satellite image, it is clear that this ascending motion causes convection behind the front (convective clouds can bee seen behind the front).

Jet streak is seen to the left of the highest peak in IR pixel values, in the region just behind the frontal zone. This is the expected position, since the jet usually flows parallel to the cold front with the maximum along the rear edge of the frontal cloud band. Here the height of the jet streak is about 300 hPa. Notice also how the maximum wind lowers down to about 900 hPa with values higher than 20 m/s, indicating strong surface wind connected to the passage of this front.

There is positive vorticity behind the frontal zone, with a maximum at about 350 hPa. Negative vorticity values are found ahead of the front, in the region og the highest IR signal. Maximum or negative votrticity is at 300 hPa.

Very strong cold advection is found behind the cold front. There is warm advection ahead of the front, but also above the front in the upper troposphere.

Positive vorticity advection preveals in this cross section, mainly behind the frontal zone, with maxima at about 250 and 300 hPa. The right-hand maximum, the one at 250 hPa, is the one connected to the wave development on the front.