Author of report: Mike Douglas

Mission Number: 030118I

Type of Mission: cold front/LLJ/MCS

Start time of Mission(UTC): 2003/01/18 15:07

End time of Mission(UTC): 2003/01/18 21:52

Flight was called to investigate a cold-frontal-type feature that was forecast to advance from the south. A major MCS developed over northern Argentina during the previous night - this complicated the interpretation of the feature but it was decided to proceed with the flight. The aircraft took off into northwesterly 25 kt winds at Santa Cruz, but almost immediately to the south found southerly winds while porpoising to a point just north of the Argentina border. The aircraft turned eastward, continuing to porpoise and the data described a weak cyclonic flow over western Paraguay. Turning northward the aircraft moved through relatively warm, unstable air to the eastern point of the standard Santa Cruz-Puerto Suarez transect, and turned westward to Viru-Viru. Winds gradually became northwesterly along this track but only reached about 20 kts. Since there was no major convection organized at this time over western Paraguay the flight turned northeastward to make two more cuts across the LLJ before landing in Santa Cruz. Winds were at times from the WSW over the eastern part of this transect. One cell was passed that reached about 20 km height. The aircraft landed in a storm environment at Viru-Viru, with 35 kt winds from the south at 900mb level. However, the winds at the surface were nearly calm.