970125H IOP7 (Flight 4) on Cold Front and Bands

Aircraft Involved: P-3, Electra, UK C-130

Summary Description of Mission:

The planned primary mission was a "phenomena investigation" of the expected wave cyclone within the advancing cold front. Frontal strenght (as measuremd by near sfc thermal contrast) was expected to be good, with some hope of upper PV support to amplify the wave. The plan was for the C-130 to depart Lyneham at 1900 UTC, the P-3 from Shannon at 2000 UTC, and the Electra at 2100. The UK C-130 departed Lyneham on schedule at 1700 UTC, tbut he P-3 was delayed by a bad engine starter until 2053 UTC. Bacause of the P-3 delay, the Electra takeoff was delayed 1 hour, but they were also delayed an additional 1 hour 45 minutes because of a bad engine starter, and eventually departed Shannon at 2345 UTC.

Upon arrival at the inital point, where the precipitation was expected by the forecast models to be the greatest, the P-3 found no precip, but a rainband was seen by LF radar 70 miles NW. That band did not contain the expected thermal contrast characteristic of a cold front, so the P-3 proceeded to another band evident on radar 60 miles farther NW. The P-3 proceeded to that band and set up a 100 mile long pattern oriented toward 040 down the middle of the band to await the Electra. The band was relatively weak, with only about 20-25 dBZ evident in the strongest cells. A good thermal contrast was noted across the band at the flight level of 5,000 ft. Following the completion of 2 legs, the P-3 set up a "box" pattern 20 nm wide by 100 km long centered on the band. Once the Electra arrived, they elected to set up patterns on the easternmost band which was apparently the surface front, as the thermal contrast and wind shift was characteristic of a cold front. As the P-3 moved its box pattern farther NE as the band apparently dissipated on its southern side. Eventually, all wind and thermal contrast across the band was lost as the cold air deepened and the entire band dissipated. Other weak and thin NE-SW oriented bands were seen spaced about 10 nm from the leading edge (where the Electra was operating) reminiscent of "roll vortices" in the cold air. These band were extremely weak and short lived. The P-3 had to break off its science work at 0313 UTC and return directly to Shannon because of a "chip light" on #3 engine, indicating the presence of metal in the oil. The P-3 landed at 0453 UTC for a 8.3 hour mission.

Communications:

1. No problems.

P-3 Equipment Problems Encountered:

1. Tail Doppler radar apparently had a problem with its I/Q signal connector until about 0155 UTC. The impact on the data is not known at this time, but could potentially ruin the data up to this point.

2. Engine #4 starter was replaced in about 45 minutes. Chip light problem on engine #3 caused premature termination of mission (by about 45 minutes). No significant data lost.

Coordination Problems

1. No problems of note.

Recommendations & Evaluation:

1. This is the second "cold frontal band" flight. It is difficult to find significant work for two Doppler aircraft on such weak bands.

--Dave Jorgensen & Frank Roux