Second G4 Flight in support of FASTEX IOP 18 Takeoff: 16:24 GMT (Goose Bay, Labrador) Landing: 21:23 GMT (Shannon) Duration: 5 hr Purpose This flight immediately followed the previous G4 flight that took off in Shannon in the morning. This flight, in spite of the fact that it was basically a return to Shannon, constitutes a separate mission. The purpose was to essentially redo the subjective and objective targets that were sampled on the first mission but catch the targets in mid Atlantic. L44 was traveling very fast and it was necessary to turn around immediately at Goose Bay rather than lay over to the next day when it would have been too late. L44 was expected to be in the MSA by then. Leaving immediately meant that the storm would not be really in mid Atlantic but this was the best compromise. At the time of mid flight, forecasts had the low southeast of the tip of Greenland and still east of Labrador with a central pressure of 978, down from 983 on the outbound of the two missions. The jet off Labrador was of course still there and the jet on the eastern side of the Atlantic had moved somewhat to the east with the surface wave center just east of the Ireland Coast. Since we made a decision on the outbound mission to conserve sondes, we expected to have enough left as we approached the Irish coast to try a cross section across the dramatic jet we passed on the way out. The number would depend on the failure rate and the need to replace the failures on the earlier legs. In fact by the time we reached 25 W on the return we had almost 14 sondes left and a total of 11 were use to create this cross section. In addition we expected to be able to drop from high levels and in fact did from 37,000 ft on this one cross section. Description of the Flight. The turn around in Goose Bay went well with the refueling and we left the service area on time. We were however, delayed in taking off by ATC by about half an hour due to concerns about the dropsondes. This delay required a modification in the original flight plan which would have taken us to 52 N 30 W and instead we had to go from 57 N 45 W to 53 N 25 W and then directly to Shannon. There had been some hope of getting as far south as 50 N at 30 W to better sample objective targets but the late takeoff and crew duty day considerations required the more direct route. After takeoff, we climbed to 26,000 (or 27,000: notes not clear) and all drops before 25 W were from this altitude. First part of the flight was in clear skies with beautiful views of the snow covered Labrador, the ice at the edge of the coast and the ice flows off shore. By 17:07 GMT we could see towering convective clouds ahead (52.1 N 51.1 W). First drop occurred after 50 W around an 17:15 GMT. The first three drops to the turn point were separated by about the equivalent of 1.5 degrees of latitude. At 51.6 N and 48.3 W we passed over what appeared to be a semi-circular hole in the clouds with higher convective clouds to north, west and south and none to the east. There were puffy cumulus and stratocumulus below the aircraft. It was clear at flight level. The turn point was reached at 17:32 GMT. During this leg we reached ground speeds of about 600 knots due to an almost 80 ms tail wind that was parallel to our track. After the turn point the track was directly north again almost along the same south-north leg we flew on the way into Goose Bay but one degree further west. The purpose was to again sample the strong PV feature in this region. Drop frequency was again increased to an spacing equivalent to better than one degree of latitude. This time as we flew north, we only found a single jet that was very well defined with a very sharp cyclonic shear to the north. Slightly north of the jet we passed over a very strong edge of the cirrus (which was below us) at 17:55 GMT and 53.6 N 45.0 W. To north of our position when we passed over the edge of the cirrus, higher clouds could be seen that appeared to be associated with deep convection. At the northern end of the flight track, flight level winds went to zero then switched into the east. At the surface, as indicated by the sondes, we remained west of the low center and lowest surface pressure was 985 mb. We reached the turn point at 18: 24. From the turning point at 57 N 45 W the track was east southeast toward 53 N 25 W. From here the drop frequency was again reduced to the equivalent of about 1.5 degrees of latitude. This track took us just very slightly to the north of the surface low at 56 N 36 W with a central pressure of 975 mb (about what was forecast on the 12 hour prog). Flight level winds slowly veered first from the east and then to southwest by the end of the leg. Speeds slowly increased to about 40 ms. It became dark about two thirds of the distance along this leg and over the part that was in sunlight, clouds included layers of stratocumulus and cirrus and some towering cumulus scattered along the flight track. Last sonde along this track was at 30 W due to ATC considerations. The purpose of these sonds was to sample objective targets. The turn point was reached at about 20:00 GMT at which point we climbed to 37,000 feet for our final series of drops. These drops were at a frequency of the equivalent of better than one degree of latitude. At flight level (37,000) winds varied in speed only slightly and backed from west southwest to southwest. The sondes indicated we were clearly above the jet level and cross sections indicate that we had a strong shear zone on the cold side of the jet, with a nearly vertical front that extended from the jet to the surface. Final sondes indicated that they were east of the front with northerly winds on one side and southerly on the other. After the final sonde at 12 W and at 20: 59 GMT we descended for our landing at Shannon. Overall assessment of the Flight. We were somewhat disappointed that we could not get as far south at 30 W as we originally planned. This would have provided better coverage of the objective targets. The last cross section however was a bonus and provided both verification of the surface wave and as well as targets for this system that would verify after it was north of the MSA. The south- north section at 45 west was regarded as very successful in that we reached the center of the upper level low and PV anomaly. Sonde success rate was as high as the earlier mission. We dropped a total of 35 sondes and only 3 failed. All three were replaced after failure.