Mission Summary
Danielle
980829I1 Aircraft 43RF

Mission Briefing:

At 2000 UTC on 29 August Hurricane Danielle was projected to be a 25.5° N and 71° W, moving WNW at 11 kts. We briefed the N43RF crew for the Vortex Motion and Evolution Experiment (p. 19 in HFP) with a take off at 1800 UTC from Opa Locka in Miami. The initial point (IP) in the pattem was 160 nm SSW of the center. Flight-level was planned to start at 18,000 ft outside 50 nm radius from the center, climbing as high as possible throughout the mission. Inside 50 nm radius flight level would be 16,000 ft to avoid pstatic effecting the GPS-sonde antenna.

Mission Synopsis :

Take off occurred at 1820 UTC and we proceeded to the IP (2005 UTC). Radar revealed that Danielle was trying to form an eyewall with a radius of 25 nm. The developing eyewall was on the SE corner of a large hook shaped principal rainband curving around the center from 200 nm SE of the center through 150 nm N of the center to 50 nm NW of the center. The principal band contained active convective cells all along its length. Initially, the eyewall was characterized by an opening to the NW, with a large anvil over the inner 50 nm radius. Scatterers were confined to the convection SW, S, SE, and E of the center at all levels and at low and high levels to the NW. During the mission the NE comer of the developing eyewall slowly wrapped around the center, and by the last pass through the center convection was growing all around the center.

The first coordinated dual-Doppler pattern was from 2029-2130 UTC. N43RF ran the Doppler radar with single PRF (1600) scanning perpendicular to the track on all of the radial legs to produce an EVTD analysis, while N42RF ran the Doppler radar in dual-PRF (2100/1400) and F/AST on all legs. The EVTD was completed showing over 80 kt winds at 1 km in the NW side of the storm and transmitted for the first time back to NHC (it was received and given to the hurricane specialist). The center at 1 km altitude was found WNW of the flight level center at 16,000 ft. Peak winds of 70 kts were found at flight level in the SE quadrant. The EVTD-derived hodograph showed the storm was embedded in a flow with a low-level (600-850 mb) E jet with mean winds of 10 kts. The hodograph showed the winds dropped off both above and below these levels.

The second coordinated dual-Doppler pattem was from 2252-2344 UTC. On this Fig-4 N42RF ran their Doppler radar with single PRF (1600) scanning perpendicular to the track on all of the radial legs to produce an EVTD analysis, while N43RF ran the Doppler radar in dual-PRF (1600/1050) and F/AST on all legs. N42RF ran an EVTD and successfully transmitted their first analysis to NHC. Again the center at the surface was found WNW of the flight-level center at 16,000 ft. Peak winds of 70 kts were found at flight level in the SE quadrant. At the end of the outbound leg 160 nm N of the storm the radar system crashed taking 9 min to be restarted. Fortunately, very little scatterers were present in this part of the pattern and no data was lost.

The third coordinated dual-Doppler pattern was from 0105-0201 UTC. As on the last coordinated Fig-4 N42RF ran their Doppler radar with single PRF (1600) scanning perpendicular to the track on all of the radial legs to produce an EVTD analysis, while N43RF ran the Doppler radar in dual-PRF (1600/1050) and F/AST on all legs. The first leg was very well coordinated with both planes passing through the eye at the same time (visual confirmation), and 3-min after the AFRES WC-130 and 1 -min after the NASA DC-8. The second leg was not as well coordinated as N42RF cut their downwind leg short to avoid intense convection, thereby getting to the center 5 min ahead of us.

AXBTs on the first leg showed peak SST 160 nm WSW of the center of 28.2°, remaining above 27° through the center to 50 nm NE of the center. The coldest SST was 25.7° 160 nm SSE of the center in the wake of both Bonnie and Danielle. SSTs in the precipitation within 100 nm E of the center were typically hovering near 26-26.5°, while SSTs 160 nm N of the center were over 28°.

We had one GPS-sonde failure out of 38 total drops on the 75 nm ring E of the center inbound to the second coordinated Fig-4. We also had one bad AXBT at the 100 nm ring on the same leg and another at the 100 nm ring W of the center.

We had 6 penetrations.

Evaluation :

Overall the experiment went very well as we completed the whole pattern as planned. With the addition of the DC-8 dropsondes from 35,000 ft in the core and the presence of the G-IV dropsondes surrounding the storm, this experiment should provide an unprecedented data set to match the inner vortex onto it environment for use in studies of vortex interaction. The presence of the DC-8 dropsonde themmodynamic data will provide an excellent opportunity to derive the potential vorticity structure of the vortex. The evolution of the eyewall as it formed during the mission, combined with the missions the next day should provide an excellent opportunity to study the vortex evolution.

The coordination with N42RF was pretty good during the coordinated dual-Doppler legs in the core. We typically passed through the center within 1 min of N42RF. On the next to last leg we passed though the eye at the same time as N42RF, 2 min after the AFRES WC-130 and 1 min after the NASA DC-8. The worst coordination occurred on the last leg when N42RF crossed the eye 5 min ahead of us. The GPS sondes perfommed very well, with only one complete sonde failure out of 38 total drops. 3-4 other dropsondes had partial failures. The radar data system also performed well, with only one outage along the downwind leg 160 nm N of the center, where we had no scatterers. The AXBTs also worked real well with 13 good sondes out of 15 total.

Most of the data systems worked very well. We did have a few problems:

1. 2D-P was not working for almost the whole flight. 2D-C was very noisy for most of the flight, but did seem to be getting some good images.
2. Radar system crashed at 0011 UTC and was down for 22 min while we were traversing downwind 160 nm N of the storm. However, no significant data was lost as there were few scatterers.
3. Two AXBTs failed: one had no launch signal and the second had no data.
4. One total failure of the GPS sondes (D16). 3-4 had partial winds in the boundary layer.

Frank Marks
3 September 1998

Return to Danielle mission listing.
Return to Danielle main page.