970110H IOP1 on Low 8a

Summary Description of Mission:

The planned primary mission was the "Lawnmower" or systematic survey of the precipitation zone and dry intrusion region to the south of developing low 8a. The P-3 was at 5,000 feet, the UK C-130 at 26,000 feet, and the Electra at either 10,000 or 15,000 feet. The Electra varied its altitude to try to correct for a data system problem that was evidenced by unrealistic winds. The Shannon aircraft (N42 and 308D) departed slightly late (10 minutes). The UK C-130 departed on schedule. As a consequence of the late departure coupled with a slight detour to overfly buoy 62105 near 56N, 14.2W, and a pearl performed by the Electra over the buoy to investigate the scatterometric properties of ELDORA, the Doppler aircraft began their patterns about 25 minutes behind the C-130. Although the P-3 arrived only a few minutes late, it performed 5 pearls over the initial starting point to wait for the Electra, which had to travel about 50 extra miles to get to its IP than the P-3. Once started, the P-3 and Electra flew very highly coordinated patterns (to within 5 minutes). The C-130 orbited between its flight legs 1 and 2 for about 30 minutes to allow the P-3 and Electra to catch up. All aircraft were very well coordinated (to within 3 minutes) on subsequent legs. Tail radar on P-3 performed flawlessly.

Precipitation pattern and location of precipitation was nearly exactly as forecasted by the mid-day run of the UKMO and HirLAM limited area models. The skill shown by these LAMs was quite amazing to these observers. Flight tracks for all aircraft were designed based on the 18h forecast of surface pressure and precipitation. No adjustments in the flight tracks was necessary following takeoff. Precipitation was encountered as soon as N42 decended at its IP. The precipitation structure seen on the LF radar was nearly the classic "cloud head" structure, but with no cold frontal rainband to the southeast. Precipitation intensity at times reached 45 dBZ in isolated cells within the band. Passes 2, 3, and 4 by the P-3 revealed lower estimated surface pressure on the west side (down to 985 mb) near the forecasted location (and forecasted intensity of 986 mb). P-3 legs 3 and 4 were south (behind) the comma head in the dry intrusion zone. Very little radar information was missed after the Electra departed due to the rapid motion northward of the precipitation.

Communications and Coordination:

1. VHF comms between the aircraft was perfect. Need to work on distinguishing scientist-to-scientist comms from pilot-to-pilot comms. Often hard to distinguish when the C-130 pilot was needing to talk to the P-3 or Electra pilot or needing some scientific info provided by the mission coordinator. One solution might be for the originating caller to properly identify who he/she needs to talk to, e.g., "P-3 scientist to METMAN scientist".

2. HF comms worked intermittently to ATC and virtually not at all to the Ops Center. The C-130 apparently had better HF comms and often would relay information from the other aircraft to ATC.

P-3 Equipment Problems Encountered:

1. The scatterometer seems to have a heat related problem. After about 2 hours into the flight it started losing sensitivity when the cabin temps rose appreciably. When the cabin temps lowered, it started working again.

2. Lower fuselage radar had a number of problems in starting. Took about an hour to get it stabilized. It also had a problem with tilt stabilization, first a left to right asymmetry in tilt, then a fore to aft asymmetry. After several hours of tinkering, the engineers seemed to get it working fine.

Coordination Problems

1. Trouble syncronizing start of first leg between the three aircraft. Didn't properly account for time required for buoy overflight and extra time for the Electra to get to its IP (10 minutes), largely due to the fact that the Electra IP was 50 miles further south than the P-3 IP.

Recommendations:

1. Have the aircraft with the largest ferry distance take off first.

2. Modify the flight track preparation program to account for the buoy overflights.

3. When trying to re-syncronize flight legs of different aircraft, work with leg mid-point time (rather than start time) to better allow for different wind conditions at each level (Sid Clough suggestion via radio).

4. Flight crew would like to see positions expressed as degree and minutes rather than decimal degrees.

--Dave Jorgensen & Yvon Lemaitre