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), 
             Ron Gelaro (NRL), 
             Gerald Desroziers (METEO-FRANCE),
             Diana Baertels (NOAA),
             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 
 others 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.