Mission Plan :
At 1500 UTC on 03 August, Hurricane Guillermo was located at 13.7°N, 110.8°W, moving towards 275 degrees at 11 kt, with maximum estimated sustained winds of 135 kt. The short term forecast was for continued westward motion.
The VME mission called for both NOAA aircraft to fly coordinated, pre-determined flight patterns, collecting flight-level, Doppler radar, and GPS dropwindsonde data within 160 nm of the center of Guillermo. Planned takeoff times were 1700 UTC for N43RF, and 1640 UTC for N42RF, to allow both aircraft to reach their respective initial positions (IPs) near 1830 UTC. The VME pattern was to be rotated relative to the pattern in the HRD Field Program Plan, such that N43's IP would be north of the center, and N42's IP would be located east of the center. Six eye drops from N43RF were planned, on each pass of each coordinated figure 4. Altitude was 17-18.3 kft, depending on icing conditions.
Most or all of the sondes had their RH sensors preheated to remove contaminants within 48 h of the mission. Several sondes had one of the two RH sensor heaters disabled to examine the effectiveness of the heaters.
N43RF was to run its radar in FAST mode, while N42RF scanned in planes during the coordinated parts of the pattern.
Mission Summary :
||Puerto Vallarta, Mexico||16:59 UTC
||Puerto Vallarta, Mexico||02:45 UTC
The mission began with N43RF's takeoff from Puerto Vallarta at 1659 UTC. The IP (160 nm N of the center) was reached at 1839 UTC. Drop/leg times in the pattern are summarized in the attached figure. Drop times in green, tan, and red indicate drops that were good, partial, and fail, respectively. The final position was reached at 0106 UTC, for a total pattern time of 6:27. This total time includes some circling in the eye on the last pass to try to get a better eye drop (the radar was not working at this time). N43RF recovered in Puerto Vallarta at 0245 UTC.
Mission Evaluation and problems :
Overall: Outstanding. This data set exceeds even the one from the day before in coverage and quality. Dropsonde failures were scattered, leaving no major gaps in coverage. There were enough scatterers that FAST wind sets will supplement the dropsonde failures, as well as provide winds above flight level.
Aircraft coordination: Very good. All coordinated legs were run within about 1-2 min of each other.
Radar: Very good. There was only one significant failure. The radars went down at 0015 UTC, during the second half of the last figure 4. N42RF may have switched to FAST mode at this point.
Dropsondes: Performance was very good, although a bit more altitude for the drops would have been nice. 31 of 40 sondes had good winds, 3 more were partial. There were 5 successful eye drops. It is now clear that p-static is a problem near and above the melting level.
Workstation: 31 TEMPDROP messages were transmitted. None were received at NCEP because they weren't looking for the UZPN13 KWBC header. Copies of 5 messages were converted to KNHC at OSO and were received at NCEP. The dropwindsonde scientists were able to keep up with the high data rate, but there was no time for any radar transmissions. During drop D6 communication between the AVAPS and workstation failed. It was restored for drop D9. Drops D6-D8 and E2 were retrieved from floppy from the AVAPS. Towards the end of the flight the ASDL system refused to accept any more messages. There may have been a backlog of data waiting to get off the airplane.
Oct. 18, 1997