9702023H IOP18 (Flight 12) on Low 44

Aircraft Involved: P-3

Summary Description of Mission:

The planned mission was a single aircraft survey of Low 44 for model validation and structure determination. The dropsonde system will be utilized as the C-130 will not investigate this system. Flight level will be as high as possible. The proposed flight pattern will consist of a modified "figure 4" survey that will include a leg segment through the cold front, and two legs through the "bent back" region the the northwest and southwest regions of the low center. Three passes through the low center are planned. 26 dropsondes were available for the pattern.

The P-3 departed SNN about 15 minutes ahead of the scheduled 1100 UTC departure to insure getting ahead of the rapidly eastward advancing cold front. Five sondes were deployed on the first leg through the cold front. Once through the cold frontal rainband, the relative humidity dropped to less than 6% at 20,000 ft altitude as the aircraft traversed the dry slot. The second leg cut northward through the approximate location of the sfc low center. Five sondes were deployed on that leg. Based on the sonde data, the 6th turn point (that was to go back to the low center) was shifted northward by 48 nm. The next two legs to the low center deployed 6 and 4 sondes, respectively. There was little precipitation evident on the "bent-back" side of the low.

Communications and Coordination:

1. No problems

P-3 Equipment Problems Encountered:

1. The LF radar appeared very noisy at times.

Recommendations & Evaluation:

1. 25 sondes were deployed, 23 were perfect, 2 failures. Apparently an excellent case of a mature, deep, cyclone. Lowest sfc pressure was about 955 mb.

2. 3 "perl" patterns were completed.

--Dave Jorgensen & Yvon Lemaitre