G4 Flight in support of FASTEX IOP 15
 Low 38: Primary cyclone
 Date: February 15, 1997
 (report prepared by Jean-Pierre Cammas)


 Ferry flight to Saint-Johns (New Foundland):
 Take-off Time Shannon (approx): 1200Z, February 13, 1997
 Landing Time Saint Johns (approx): 1700Z

 Targetting flight nearby Saint-Johns:
 Take-off Time Saint-Johns (approx): 2100Z, February 13, 1997
 This flight was cancelled due to mechanical problems with
 the aircraft.

 Subjective flight from Saint-Johns to Shannon:
 Take-off Time Saint-Johns (approx): 0300Z, February 15, 1997
 Landing Time Shannon (approx):      0930Z, February 15, 1997
 Flight Duration: 6h30mn

 Scientists: Melvin Shapiro (NOAA/ETL),
             Ron Gelaro (NRL),
             Gerald Desroziers (METEO-FRANCE),
             Diana Bartels (NOAA/NSSL),
             Jean-Pierre Cammas (LA/CNRS, not in the aircraft
                                 during this mission, proposed
                                 and designed the flight plan
                                 at Operations Center, Shannon)

 Purpose:

 The purpose of this flight was to document actual structures of
 a primary mature cyclone over the Central Atlantic, Low 38. The
 other MSA aircraft flights were scheduled to take-off right after
 the G4 landing in Shannon with flights focused on precipitation
 features in the occluded portion of the mature low on its
 northeastern part. In order to get the best coverage of the
 system, the G4 flight plan was designed to sample the northwestern
 back-bent surface front, the low center and its southwestern part,
 the upper-level potential vorticity anomaly and the apex of
 the warm sector with surface frontal structures on the eastern
 part of the low.

 Description of the flight:

 The entire track has been flown at FL260. About 29 dropsondes were
 sent on the GTS. Seven dropsondes were launched across the north
 part of the bent-back surface front, a nice easterly low level jet
 was observed (> 35 ms-1). With about 5 dropsondes, the next
 north-south leg sampled a cross-section across the low center
 observed as a warm and humid core, as well as across the
 potential vorticity maximum aloft. Mid-tropospheric dryness is
 observed on the south part of this leg. The third leg involved 5
 dropsondes in the northwesterlies south of the bent back surface
 front. Strong low level winds were observed (35-40 ms-1).
 The last zonal leg involved about 15 dropsondes across features
 east of the low center (dry intrusion, cold front, apex of warm
 air and warm front, southerly upper-level jet). Wind speeds
 in excess of 60 ms-1 were observed with the dropsondes (400 hPa)
 when crossing the jet core. The upper-level frontal zone and the
 surface cold front were well resolved by the dropsonde sampling.


 Overall assessment of the flight:

 Very good data on the mature phase of a primary cyclone. Focus was
 put first on the northhwestern bent back surface front, the
 surface low center and the lowest tropopause part. The flight
 ended with a nicely sampled cut across the dry intrusion, the
 cold front, the apex of warm air and the warm front, and the
 southerly upper-level jet.