970122H IOP5 on Frontal Wave3
Summary Description of Mission:
The planned primary mission was the systematic survey ("Lawnmower" pattern) on an active portion of frontal wave cyclone expected to become stationary within the MSA. The P-3 and Electra departed SNN near 0900 UTC to enter the pattern about 0944 UTC. The C-130 departed Lyneham about 0800 UTC. The flight patterns were designed to be highly coordinated in time and space. The C-130 was supposed to fly 450 km legs, with 96 km "caps" on the end. Both the P-3 and Electra had 450 km legs. The P-3 was at 5,000 ft, Electra 2,000 ft, and the UK C-130 at 26,000 ft. The patterns were designed to have the C-130 fly between the P-3 and Electra, which were spaced 100 km. Leg spacing between succesive legs was 140 km, which allows for some overlap of the radar coverage between the set of three "lawnmower" legs. In addition, the G-IV was supposed to take off at 1000 UTC for a test flight and they were supposed to organize a dropsonde release near one of the C-130 drop points to intercompare sonde performance. All aircraft took off on schedule and began the patterns within a few minutes of each other. After one leg, the C-130 reported problems with its dropsonde system that precluded any more sondes after about 1848 UTC. The G-IV had a single flight leg alone the C-130s track and dropped sondes after about 1125 UTC. After that run of three drops, the G-IV departed the area for wind calibrations. During the second run, the P-3s LF radar revealed that the fontal orientation was near 030 instead of the 010 predicted by the UKMO LAM model. The front, as represented by the LF radar echoes, was apparently moving eastword at about 20 knots. Due to anticipated endurance by the Electra, legs 2 and 3 were shortened by about 5 minutes by trucating the end point at about 13 30N. Further savings of flight time was obtained by shortening Electra legs 3 and 4 by about 90 miles, as the frontal band was well west of the planned end points. P-3 legs were also shortened to match the Electra patterns. Shortening legs 2-4 enabled the Electra to complete its leg 4 to the planned position of 47 37N, 14 10W. Following the departure of the Electra from the area at 1422 UTC, the P-3 continued with the original flight pattern from points 9 to 10 to the SW buoy and return. Along the way the P-3 executed many "perl" patterns in moderate to heavy stratiform precip.
The weather system consisted of an original cold front oriented about 010 which extended down into the wave cyclone south of about 50N. On the P-3 legs 4 and 5 (south of 50N) flew though what appeared to be a "triple" point with extensive stratiform precipitation to the NW. There was considerable mesoscale organization to the rainbands embedded within the stratiform region. Temperature contrast across the "front" at 5,000 feet was only 3-5 degrees C, but the wind shift was from southerlies to southwesterlies to northerlies west of the front. During several crossings, it appeared that the strongest convective cells were 15-20 nm ahead of the most prominent wind shift and temperature drop. That zone farther west was marked by a "thin" line of enhanced reflectivity on the LF radar. Very rarely did the convective cells exceed 40 dBZ on either the LF or TA radars.
Communications:
1. VHF comms between the aircraft was nearly perfect, even in the static charging region with the precipitation.
P-3 Equipment Problems Encountered:
1. The P-3 GPS system went out about 1424 UTC, and the INE was used in its place to navigate the turn points.
2. Radars worked very well, with only an occasional crash which was recovered in a few minutes, and even the scatterometer seemed to function normally.
Coordination Problems
1. No problems of note.
Recommendations & Evaluation:
1. Very good mission from an execution point of view. Coordination of leg start times was easily accomplished with the aid of the P-3 navigator. Leg lengths and new way points were easily calculated by the navigator, who did the calculatons for both P-3 and Electra.
2. The major disappointment was the loss of the UK C-130 dropsonde system during the first leg.
3. The major part of the rain region appeared to be sampled by the P-3 on its last 3 legs and the Electra on its last leg. It may have been too far south to effectively cover as the NOTAM area only extended to 47N.
--Dave Jorgensen & Yvon Lemaitre