970112H IOP2 on Low 11/12a

Summary Description of Mission:

The planned primary mission was the cold frontal rainband study on an active portion of the cold front extending from an open wave that is being tracked as Low 11. The approach of Low 12 from the west is expected to lead to the further development of the cyclone, but after the aircraft mission. The initial P-3 altitude was 5,000 feet, the UK C-130 at 26,000 feet, and the Electra at or below 3,000 feet. The UK C-130 departed Lynehame at 10 UTC, followed by the P-2 at 12 UTC, and the Electra at 13 UTC. All aircraft departed on schedule. The P-3 overflew the buoy at 51.05N, 13.33W, to calibrate its scatterometer and SFMR on the way to its intial point (IP) at 51.0N, 18.5W. The initial point was chosen to coincide with the forecasted precipitation maximum from the UKMO LAM at 15 UTC. A cold frontal rainband was found by LF radar as the P-3 approached its IP. Coordinated patterns were set up via the VHF radio with the C-130 and the Electra. There were two rainbands evident on the LF: an easternmost one associated with a pre-frontal line, and a westernmost one about 25 nm to the west that was apparently associated with the surface position of the front. The width of each line varied from very thin (>5 nm) to ~20 nm. The P-3 executed a short "survey" of the region west and north of the IP to insure that that IP region was the location of the strongest band. Based on that survey the C-130 track was set up (the planned flight track was not changed), and the Electra was vectored to the correct position to begin the extensive investigation. The P-3 focused its patterns on the westernmost band, while the Electra focused on the pre-frontal band. Each aircraft flew a "box" pattern centered on its respective band. Band orientation was about 020. Each box was 25 nm by 100 nm. The westernmost north-south leg of Electra was coincident with the easternmost P-3 north-south leg, so there was nearly continuous Doppler data throughout the 200 nm domain. As the bands dissipated on the southern side and propagated east at near 10 miles per hour the boxes were progressively shifted further north and east. The P-3 accomplished 4 complete boxes. The Electra also completed at least 4 of the boxes followed by a series of smaller boxes centered on a small part of the band that exhibited the most linear character. Following the departure of the Electra, the P-3 executed a "survey" pattern to the north (to 56N, 15W), then back to 54N, 16W to map the northern extent of the frontal band. The band seemed to weaken north of about 54.5N, so it appears that the aircraft worked the best target.

The strength of the bands was relatively weak (30-35 dBZ) but the linear character and their persistence made them easy to set up patterns and coordinate the changes required by the continued decay on the southern end and the eastward propagation.

The precipitation pattern and location of precipitation was nearly exactly as forecasted by the mid-day run of the UKMO and HirLAM limited area models. No change was necessary to the IP or the pre-determined C-130 tracks.

The C-130 executed a series of 4 legs centered on the IP and spaced every 25 nm, dropping 5 sondes per leg.

Communications:

1. VHF comms between the aircraft was nearly perfect, even in the static charging region with the precipitation.

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 continues to have its problems. It went totally out after about an hour of the mission. Apparently the same problem as the last flight. Also took about 20 minutes after take-off to get the antenna to spin.

Coordination Problems

1. Only coordination problem of note was the C-130 tracks were identified differently than the original plan prepared at the Ops Center. Took a little while to understand the new nominclature.

Recommendations & Evaluation:

1. Very good mission from an execution point of view. Rainband was well organized, albeit a little weaker in reflectivity that we expected. Perhaps the weakness is a trait of FASTEX cold frontal bands.. The model guidance continues to direct the aircraft to good locations with excellent timing.

2. Need to work a bit on standardizing the flight leg identifications for the C-130.

--Dave Jorgensen & Yvon Lemaitre