Mission Summary
9909151 Aircraft 43RF
XCDX/Air-Sea Interaction

Mission Briefing: On Wednesday 15 September N43RF was tasked to do a single plane XCDX/Air-Sea Interaction experiment into Hurricane Floyd while it passed E of Jacksonville, FL with a takeoff from Tampa International at 1830 UTC recovering back in Tampa (this mission was almost scrubbed the night before because of equipment problems during the surveillance flight, but AOC was sure they could fix those in time to get this mission off). The plan called for three rotated figure-4 patterns at 8,000 ft altitude with 120 nm legs with AXBT and GPS sonde drops on the ends of the legs, 75 nm from the center, near any C-MAN or buoys (see Table 3), and in the eyewall on all cardinal directions. Three drops were also planned in the eye on the first and fourth, and sixth (last) passes through the center. We also planned two legs along the coast on the NW side of the storm where the radial legs were abbreviated for storm surge mapping and to collect some off-shore flow GPS sondes to augment the windfields at landfall experiment on the next flight. There were also three instrumented towers and a DOW (see Table 1) along the coast that we hoped to overfly. Unfortunately, no synoptic drops are available for this mission as N49RF was tasked to do a synoptic surveillance mission in Hurricane Gert.

Mission Synopsis: Takeoff was delayed till 1945 UTC to allow the AOC engineers to work on the main and radar data system problems from the previous flight. The delay was exacerbated by the fact that the planes were at Tampa International because of cross winds the night before. The delay worked to our advantage as it gave us more possible overlap with the Windfields at Landfall mission scheduled for an 0300 UTC takeoff later that night. The delay also worked to NHC's advantage as it put our mission in between the two AFRES missions, providing data at a critical time <12 h before landfall. The AOC engineers did a phenomenal job and we only took off a little over an hour later than originally scheduled.

We took off at 1948 UTC and tracked to an IP 120 nm SW of the storm center. We reached the IP <45 min later (2030 UTC) descending to 8,000 ft. After dropping a sonde we tracked NE to the center (Fig. 1) running the TA radar in F/AST so the flight director (Damiano) could get a good fix. The LF radar showed the radar eye was still very large (60-70 nm diameter) with the strongest reflectivities N of the center extending >200 nm from the center (Fig. 2). The S eyewall reflectivity was fairly weak, but it still appeared closed, with the same major band from the day before extending 100-160 nm from the center. We dropped our first eyewall sonde (see Table 4) followed by the first AXBT (which failed, attached log) SW of the center at 2053 UTC with surface winds of 63 kt which agreed fairly well with the SFMR estimates. At 2059 UTC we fixed the center (see Table 2) dropping a sonde and AXBT (SST 28.1°C, MLD 90m). The sonde had very little wind (peak winds of 8 kt) and a central pressure of 950 mb (18 mb higher than the day before). We continued tracking NE doing an eyewall drop and AXBT (SST 27.8°C, MLD 90 m) on the NE side of the storm at 2104 UTC with a peak wind of 104 kt well above the surface. We hit our turn point 100 nm NE of the center at 2130 U TC dropping a sonde and then tracked W to a C-MAN FBLS 1 (Folly Island, SC) roughly 100 nm NW of the center passing over and dropping a sonde on buoy 41004 at 2147 UTC. The second leg of the first figure-4 started at 2202 UTC roughly 100 nm NW of the center along the SC coast. This run to the center we set the radar in normal scan mode for EVTD and instructed the flight director to not making any major track changes. As we approached we dropped two AXBTs outside the eyewall to sample the Gulfstream (see attached log). We did an eyewall drop and AXBT on the NW and SE side of the center, but we passed about 10 nm SW of the circulation center at 2225UTC. We dropped two more AXBTs on the outbound leg to the SE reaching a point 120 nm SE of the center at 2252 UTC where we dropped a GPS sonde only. Unfortunately, the eyewall was too large to do an EVTD analysis so one was sent back to NHC.

The second figure-4 started at 2311 UTC ( Fig. 3). We turned inbound to the W and dropped a GPS sonde tracking W to the center. We dropped two more AXBTs outside the E eyewall and a combo (GPS sonde and AXBT) in the E and W eyewall and an AXBT in the eye (#14) at 2340 UTC. We finished the outbound leg with a combo drop 60 nm W of the center and then a GPS sonde drop at 0008 UTC 120 nm W of the center. We tracked SE to a point 120 nm S of the center reaching it at 0040 UTC, dropped a GPS sonde and tracked N to the storm center. We dropped 3 AXBTs on the inbound leg the last one 60 nm S of the center. We dropped an eyewall sonde S of the center at 0103 UTC and a center drop at 0109 UTC. The eyewall sonde had very little wind all the way to the surface and a mean boundary layer wind of 0 kts and a 951 mb central pressure. We proceeded N to the coast dropping 2 GPS sondes in the N eyewall and at the endpoint 100 nm N of the center near KLTX (see table 3) at 0134 UTC. Also on this leg we dropped our last two AXBTs in the N eyewall and 60 nm N of the center.

After completing the first two figure-4s we decided to leave out the last figure-4 out, in favor of a third leg along the coast N of the storm to capture the storm surge as the center was only 75nm offshore (the N eyewall was only 45 nm off shore). After the second figure-4 we tracked SW along the beach mapping the surge with Ed Walsh's scanning radar altimeter (SRA) dropping GPS sondes in the offshore flow near Folly Island (FBLS1) and in a heavy rainband near Savannah, GA. (Fig. 4). From there we tracked to the center over buoy 41004, then from the center NE on a radial toward the WRS-88D KMHX (Moorehead City, NC) and C-MAN CLKN7 (Cape Lookout, NC) passing over C-MAN FPSN7 (Frying Pan Shoals). From there we tracked WSW along the coast for SRA mapping of the storm surge from CLKN7 to a point due S of the WSR-88D KLTX (Wilmington, NC) passing very close to the 3 instrumented towers and the DOW (see Fig. 4). From there we flew a radial from KLTX to the center, departing the storm to return to MacDill AFB.

Accomplishments:

WOW!! After the mission the previous day this mission was pure heaven. The only major change from the plan was leaving the last figure-4 out, adding a third leg along the coast N of the storm to capture the storm surge as the center was only 75 nm offshore (the N eyewall was only 45 nm off shore). This extra leg allowed Ed Walsh and the AOC crew to get some experience trying to fly along the coastline in the dark and a lot of heavy rain. This portion of the mission was joy to experience as the navigator (Rathbun) and pilots (McKim and Kenul) worked closely with Ed to have the plane weave back and forth across the beach keeping all turns <10° so the SRA beam stayed near the beach.

We managed to get GPS sondes at the extremities of the pattern on all the legs providing a very good mapping of the edges of the vortex. Overall the GPS sondes worked nearly flawlessly, the one exception being when the CNN reported picked up the Airphone on the coastal run at the end of the first figure-4 causing us to lose signal completely on 2 sondes (one a backup of the first) and partially on a third over C-MAN FBLS 1 (Folly Island, SC). The AXBT drops also were very good, with 17/22 providing excellent SST and MLD info as the storm interacted with the Gulf Stream as it approached landfall. The Doppler radar data on the last coastal leg would be excellent for comparison with the two WSR-88Ds and the DOW which started recoding near the time of our overpass.

Problems:

Thanks to the phenomenal job the AOC engineers (Terry Lynch, Jim Barr, and Richard McNamara) did after all of the problems we encountered during the previous mission, no major problems were encountered. The main data system worked nearly flawlessly, the radar data system suffered only a few brief hangups (the TA reflectivity was still 6-8 dB low), and the AVAPS and HAPS communications were great! The only disappointment was caused by a CNN reporter using the Airphone without permission causing us to lose signal completely on 2 sondes (one a backup of the first) over C-MAN FBLS 1 (Folly Island, SC) and partially on a third when we were on our first coastal run.

Frank Marks

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