This document is divided into 3 sections (Each section is written by the Chief Scientist):

• Mission Briefing
• Mission Synopsis
• Mission Evaluation

Mission Briefing

The VME mission called for both NOAA aircraft to fly coordinated, pre-determined flight patterns, collecting flight-level, Doppler radar, and Omega dropwindsonde (ODW) data within 160 nm of the center of Iris. Planned takeoff times were 2100 UTC for N43RF , and 2130 UTC for N42RF, to allow both aircraft to reach their respective initial positions (IPs) at 2300 UTC. The takeoff times were also set to ensure that the ODWs would be released after local sunset, when Omega signal propagation quality improves. A t the projected IP time, Iris was forecast to be at 24.0N 62.5W. Estimated IP locations were 21.33N 62.5W for N43RF, and 24.0N 64.87W for N42RF. The VME pattern was to be flown as drawn in the HRD Field Program Plan, with changes made only to the specific ODW channel frequencies to be used for each drop, due to a shortage of channel 2 (404.5 MHz) sondes.

Mission Synopsis

N43RF then headed outbound to a point 160 nm ESE of the center, releasing an ODW at 100 nm radius (0018 UTC). At 0032 UTC the aircraft turned north, made another drop, and headed to a point 160 nm ENE of the center. This point was reached at 0102 UTC. Th e aircraft turned inbound (track 240) and made drop #8. After drop 9 was made at 0116 UTC, the aircraft descended to 589 mb (14000 ft PA) for the storm penetration, to minimize exposure to graupel and electrical discharges. CP "B", 50 nm ENE of the center , was reached at 0127 UTC, simultaneous with N42RF. The center was marked at 0137, one minute before N42's mark at 0138 UTC. The end of the third TDD leg was reached at 0151 UTC, and the aircraft turned downwind towards a point 50 nm SSE of the center. Dr op #10 was held for three minutes (0154 UTC) so that it could be dropped in a relatively clear location between rainbands. At 0204 the aircraft turned inbound (track 330) for the fourth TDD leg and made drop #11, reaching the center at 0216 UTC. Unfortuna tely, the drop in altitude resulted in a slower ground speed, and N42 reached the center at 0206, 10 min before N43. The fourth TDD leg ended at 0230Z, where drop #12 was made 50 nm NNW of the center.

Outbound, the aircraft ascended to 465 mb before making drop #13 100 nm out at 0242 UTC. The northernmost point of the pattern, 160 nm N of the center, was reached at 0252 UTC, and drop #14 was made at 0254 UTC. This ODW was backed up at 0259 UTC. Drop # 15 was made 160 nm WNW of the center at 0322 UTC, when the aircraft again turned inbound (track 120). After drop #16 at 0335 UTC, the aircraft descended to 14000 ft PA, and reached CP "C", the start of the fifth TDD leg at 0347, one minute after N42 reach ed their CP "C". At 0358 UTC the center was marked with a wind less than 1 kt, and the TDD leg ended at 0410 UTC, 50 nm ESE of the center. Drop #17 was made at 0412 UTC in a clear slot between rainbands. The sixth and final TDD leg started at 0424 UTC fro m a point 50 nm NNE of the center, after which drop #18 was made at 0428, delayed 4 minutes for clearer weather. The center was reached at 0437 UTC. At 0445 UTC N43 had passed the eyewall and began to climb. Drop #19 was made at 0449 from 513 mb (ending t he last TDD leg). On the last outbound heading, drop #20 was made at 0503 UTC from 446 mb, and the pattern's final position (FP) was reached at 0514 UTC, where drop #21 was made. The mission concluded with a landing in Barbados at 0619 UTC.

Mission Evaluation and Problems

Aircraft coordination: The initial long range radar fix was misleading, so the IP was off by about 30 nm. After the first penetration, pattern navigation points were well estimated. Due to the lower than anticipated flight level, N43 was several mi nutes late on the fourth and sixth TDD legs.

Radar: Good overall. There were some gaps in the reflectivity distribution early in the mission, and there was not a lot of very deep convection. By the end of the mission, however, coverage improved. Coverage should be adequate for a comprehensiv e Doppler-derived wind field, although there may be some altitude limitations. Only one significant radar failure, from 0430-0446 UTC, when the radar system froze during the last penetration. The sixth TDD leg will be lost as a result. There were also que stions about the tail radar's reflectivity being low during the third and fourth TDD legs.

ODWs: Satisfactory. Preliminary evaluation of the real-time ODW printouts follows. PTH failures are not considered mission-critical. For winds, failure of inner-ring ODWs are not considered mission-critical unless middle ring ODW also fails and D oppler targets are not present along that radial. Some of the missing data may be obtainable from N42 or recoverable in postprocessing. The most significant failures are drops 20-21, where no winds were taken below 700 mb in the outer portion of the SW qu adrant of the storm. If more channel two sondes had been present (LPS oversight), more of the failed sondes could have been backed up. However, there were no mission-critical failures, as enough sondes worked to allow reasonable interpolations over the mi ssed drops.

Workstation: 14 ODW messages and 4 lower fuselage composites were transmitted. This mission is very demanding on the workstation, and it is virtually impossible to get out all the desired messages with only one keyboard/terminal.

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