P1 (orographic precipitation).

P2 (PV streamers).

P5 (Foehn in a large valley).

The Electra and P3 flew in support of P1 and the Merlin flew in support of P5. PV streamers (P2) were measured by the wind profilers.

23 October: The MC2 and SM models indicated intense early-morning precipitation over the Lago Maggiore area. Television news in Italy reported flooding on the Ligurian Coast during the day. The 500 mb flow over northern Italy was southwesterly, but the trough was broad and did not extend sharply to the south. The Milano soundings at 0000 UTC and 0600 UTC showed stable air at low levels. Infrared satellite imagery showed the frontal cloud band moving rapidly across northern Italy between 0200 and 1500 UTC. In connection with the frontal passage across the region, an area of moderate stratiform precipitation appeared on radar at about 0330 UTC. From this time until about 1200 UTC the stratiform precipitation moved rapidly across the area of radar coverage and across the Po Valley into northeastern Italy.

The P-3 flew through this region on the way to a dropsonde point in the Ligurian Sea. Both the P-3 and the Electra followed the stratiform precipitation area across northern Italy. On a northbound leg at 1005 UTC the P-3 radar showed stratiform precipitation with local terrain enhancement in the reflectivity field and flow toward and over the rugged terrain in the Doppler velocity field. The observed precipitation during this mission was more stratiform than forecast, and there was less over the mountains than over the Po valley. The POC directed both aircraft eastward to catch the precipitation maximum using the P-3’s lower fuselage (LF) radar to set up patterns. In this region, the LF indicated the most intense stratiform precipitation.

During its P5 flight over the Rhine Valley, the Merlin encountered medium to strong turbulence near the mountain ridge. This flight provided good information during a transition period between two cases of foehn. It can be studied as a situation corresponding to the end of one foehn event or as corresponding to the beginning of another one.