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Hurricane Research 

IFEX daily log

Wednesday, July 6, 2005

Dennis had become a strong tropical storm by the morning of 7/6. It was practically a hurricane at the 09 UTC advisory. Deep convection was evident around the core of the system, primarily on the east and the north side of the system. For today's mission, a butterfly pattern was planned for the P-3 (N43RF) and the ER-2. The plan called for an IP 75 nm southwest of the center of the storm, proceeding to the northeast, and then executing the butterfly pattern from there, finishing on the southeast side of the storm. The ER-2 would be offset by 12 nm during all of the radial legs, and would be stacked during the downwind legs. The TA radars on the P-3's would operate in F/AST scanning mode on the radial legs and continuous mode on the downwind legs. After the pattern was complete, or perhaps during the pattern while the aircraft was on the east side of the storm, the aircraft would search for an area to execute either the convective burst module (if a convective burst was seen to be occurring) or the microphysics module (if no convective burst is evident but stratiform rain is present), in coordination with the ER- 2. This mission would mark the second day of coordinated flights within a developing tropical cyclone. N42RF had a down day today, in anticipation of a tasked mission out of Key West for a 06 UTC July 8 fix (takeoff at 03 UTC) into Dennis on the night of July 7.

The plan called for a 1 PM LT takeoff for N43RF and a 2 PM LT takeoff for the ER-2. However, there were some AOC crew issues (stolen passports) that delayed the takeoff of N43RF until 4 PM LT. The ER-2 still took off at 2 PM, however, because the weather conditions at the airport at the time of takeoff were expected to deteriorate after that time. Because of this delay, the ER-2 would arrive at the IP much earlier than the P- 3, so the modified plan called for the ER-2 to conduct bowtie patterns around the core of the system until the P-3 could arrive at the IP and the coordination could begin. Enroute to the IP, it was recognized that it would take too long to conduct the full pattern, so a modified pattern was planned that called for the P-3 and the ER-2 to meet 75 nm south of the center and conduct a south-north leg, with the ER-2 stacked with the P-3. At the IP, the coordinated run began. There were several bands of convective and stratiform rain on the south side of the system. During the inbound portion of the leg, the P-3 climbed from its pattern altitude of 14,000 ft to 19,000 ft. The flight-level temperatures ranged from +3 to -5 during this ascent. The TA radar was operating in continuous mode. The actual portion of the flight track that was exactly coordinated with the ER-2 was in heavy precipitation south of the center. The aircraft then completed their leg, descending back to 14,000 ft while passing to the north of the center where convection was not as widespread.

On the return leg, the P-3 TA radar remained in continuous mode and it flew a stacked mission with the ER-2 again, climbing to 19,000 ft and returning again . Once again excellent coordination was achieved, and it is anticipated that valuable data was obtained on these legs with the coincident aircraft combining their Doppler radar measurements and the microphysical probe measurements collected concurrently across the melting level. The coordination with the ER-2 only occurred for half of this second leg. From that point the ER-2 returned home, while the P-3 continued its pattern, with the TA radar now running in F/AST mode. All of the octants were covered except for the northwest and west legs

In summary this was an excellent mission that collected valuable coincident data that should be very useful for microphysical studies. The coordinated portion of the pattern essentially accomplished a modified version of the microphysics module in the 2005 HFP by providing measurements of the vertical distribution of hydrometeors across the melting level and having concurrent looks at reflectivity fields from the TA radar at vertical incidence and the ER-2 EDOP. The two substantive differences between the pattern performed here and the one envisioned in the HFP are that the actual pattern flown was not in the same location, contrary to that spelled out in the HFP, and the pattern was flown in a strong tropical storm/weak hurricane, whereas the one in the HFP is intended for a genesis situation. While the lack of a truly vertical profile is not ideal, it still provides a look at the vertical distribution of hydrometeors in the hurricane environment. Reflectivity from the TA radar, EDOP, and LF radars can be used to assess the degree of horizontal variability to determine the representativeness of the profiles. Future patterns should be attempted that are restricted in the horizontal direction and provide a look at true vertical profiles, however. As for the measurements in a hurricane vs. a pre-depression, there may be differences in these fields. But these measurements are more than what was collected during all of CAMEX-4. Furthermore, they can serve as a benchmark for comparison with comparable measurements in pre-depressions, if and when such measurements are taken.

Rob Rogers
HRD Field Program director

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