Hurricane Emily

Operational Synoptic Flow Experiment
(930828I Aircraft 43RF)

Scientific Crew

Chief Scientist -- R. Burpee

Doppler Scientist -- F. Marks

Dropwindsonde Scientist -- J. Franklin

Workstation -- J. Griffin

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

Mission Briefing

Vortex Interaction experiment, 42RF at 5000' doing Doppler pattern, and 43RF as high as possible doing ODW pattern. Both aircraft take off from Bermuda at 1800Z, 42RF set to return to MIA, and 43RF returns to Bermuda. Coordinate with AF aircraft so tha t 42RF will give center pressures to the AF in exchange for them not dropping sondes from 10 kft. NHC requests that 42RF get a 2100Z fix.

Mission Synopsis

Took off from Bermuda at 1800Z. 43RF starts pattern 160 nm N of center, while 42RF starts 40 nm W of center. 43RF at their IP 160 nm at 1856Z. The first ODW failed and 42RF reports radar problems again. 43RF reached 50 nm radius at 1919Z and 42RF poin t 40 nm W of center, starting coordinated fig 4. 42RF fixed the center at 1921Z and then headed for area outside the eye NE of the center to fix radar. 43RF continued pattern to W after coordinated fig 4 trying to get good ODWs. 43RF didn't get PMS dat a on first leg because I forgot to have the operator start it up.

On the first coordinated pattern storm looked like it might have double eyewall structure so we starting thinking about options if ODWs kept failing and 42RF TA radar didn't work. Decided to make decision point the same as the one we used the day before, the beginning of the second coordinated fig 4 pattern. Meanwhile, Joe Griffin completed a radar composite and sent it over ASDL after a little glitch in the ASDL computer was repaired. James decided that the ODW failures had compromised the mission as f ar as he was concerned and that we should investigate options if 42RF TA came back up. James suggested attempting ODW/LOD2 intercomparison to SW of center on final turn before fig 4 (2121Z). Also set up monitoring of omega signal on both aircraft to try to resolve the problem.

42RF TA radar repaired at 2115Z and they do fix at 2129Z on their way to the coordination point 40 nm NW of center. John Gamache suggests we do at least one coordinated fig. 4 together with both TA radars working. Start coordinated pattern at 2152Z, 43R F tracking 050 deg and 42RF tracking 140 deg. Center appears to have tilt from NW to SE with increasing altitude. No longer and indication of double eyewall, although eyewall has radar echo only on N semicircle. Radar eye appears to have contracted, wit h intense cells in NE corner, extending downwind. Finished coordinated pattern at 2248Z, 43RF SSE of the center and 42RF WSW of center. 42RF climbed to 18 kft after fixing the center to drop ODW as a test of signal strength. At 2249Z 42RF departed for MIA and 43RF headed for Bermuda.

James compared omega signals with 42RF during ferry. 43RF transmitted a second LF composite just before landing. 43RF landed in Bermuda at 0000Z.

Mission Evaluation and Problems

Similar problems to those experienced the day before. 43RF had many problems with the ODWs, while 42RF had no TA radar until the start of the second coordinated fig 4. 43RF completed almost half the pattern (to the end of the second coordinated Fig 4), while 42RF made one pass at 5000' then loitered NE of center to repair the radar.

42RF managed to get the TA radar repaired around 2110 UTC and fixed the center at 2130Z. Starting at 2200Z we did the coordinated fig 4 with both TA Dopplers for 3-D mapping. 43RF also managed to get an ODW/LOD2 intercomparison at the last drop SW of ce nter. Mission was a marginal success. One lesson that was learned was that the Vortex-interaction experiment is very susceptible to failure if only a few drops are compromised. We need to re-evaluate the plan to build in better flexibility.

Two LF composites transmitted via ASDL to NHC, and the EVTD looked real interesting (shallow circulation with hint of double wind maxima in earliest time period). Coordinated Fig 4 should help John Gamache evaluate the GPS effects on Doppler analysis. OD W/LOD2 intercomparison should be useful to Jimmy Franklin.


  1. 42RF TA radar problems for the first 1.5 h of mission. Jim Roles got it working in time for last coordinated fig 4 pattern. If we hadn't canceled the mission we could have continued to use the radar system.

  2. 43RF had numerous ODW failures, compromising the flight. Dropped 9 sondes and 6 were failures. The main culprit appears to be weak omega signals being received on 43RF. During the mission we monitored the omega signal on both aircraft for 1.5 h a nd 42RF did a test drop to see if the signal strength was the problem or it was the 43RF receiver. Evaluation of the signal test suggests the problem is on 43RF. Interesting sidelight is that the LOD2/ODW intercomparison worked well till the ODW lost si gnal near 850 mb, while the LOD2 continued to report omega winds. Al Goldstein is working to try to trouble shoot ODW system by next mission.