9702017H IOP16 (Flight109) on Low 39a

Aircraft Involved: P-3, UK C-130

Summary Description of Mission:

The planned primary mission was a "systematic survey" LOW 38 using the P-3 and UK C-130. The wave cyclone was expected to develop near the southwest of the MSA and move very rapidly to the northeast (055 degrees 27.4 m/s). The plan called for the C-130 and P-3 to have virtually identical tracks to insure that dropsondes were collected within the 100 km wide swath of dual-Doppler data. Leg lenths were 400 km to allow for uncertainty in the forecast track position. Six legs were planned.

Shortly after departure from Shannon the P-3 and C-130 met at the inital point of the first leg at about 0508 UTC. Just prior to joining up the C-130 relayed a message from the Ops Center that satellite imagery indicated the principal development area may be up to 40 nm farther south. Just prior to beginning the first leg, the aircraft patterns were shifted 30 nm (one-half degree) south. Rainbands associated with the frontal zone were clearly evident to the P-3s LF radar, and a "blob" of precipitation was near the forecasted track of the wave cyclone to the SW. Following the completion of Leg 1, the flight patterns were further shifted another half-degree of latitude southward to better capture the frontal band in the C-130 cross-sections. One leg 3, the P-3 descended to 1500 feet to better locate the cold front. The front was seen near 54.8N, confirming the desirability of shifting the patterns 60 nm south. On legs 3-6, the P-3 flew through a strong narrow cold frontal rainband. Reflectivities sometimes exceeded 50 dBZ. Stratiform precipitation existed to the south of the rainband. The last P-3 leg was cut about 40 nm short because of endurance limitations.

Communications and Coordination:

1. No problems with VHF. The Sat Comm e-mail system on the C-130 worked well in getting information from the Ops Center.

P-3 Equipment Problems Encountered:

1. The P-3 radar system froze once for a few minutes, no important data was missed.

2. The P-3s GPS navigation system became unreliable soon after takeoff. The P-3s primary navigation source was switched to INE #2. Apparently the GPS antenna needs repair again.

Recommendations & Evaluation:

1. Very good coordination on what appeares to be a weak cyclone development case. Several transects of a very strong narrow cold frontal rainband were made.

2. 10 "perl" patterns were completed by the P-3 in moderate to heavy precipitation associated frontal wave and stratiform precipitation near the narrow cold frontal rainband.

--Dave Jorgensen & Yvon Lemaitre