Mission Summary
20080722H2 Aircraft 42RF
3-D Doppler Winds Operational Mission
Tropical Storm Dolly flight 2008

Scientific Crew (42RF)
Lead ScientistRob Rogers
Doppler ScientistJohn Gamache
Dropsonde ScientistKathryn Sellwood

Flight Crew (42RF)
PilotsMark Nelson
Carl Newman
Flight DirectorJack Parrish
NavigatorJoe Bishop
Flt. Eng.Dewie Floyd
Data TechTerry Lynch
Jeff Smith
Elec. TechDamon SanSouci

Mission Plan :

This was another combination EMC 3-D Doppler winds/NHC fix mission with an AXBT module for HRD into Hurricane Dolly. The plan called for the aircraft to fly a butterfly pattern at 8000 ft altitude, setting up an IP 100 nm northeast of the center (Fig. 1). Once north of the storm (after reaching point 4 in Fig. 1), the aircraft would fly an SFMR module where we would track directly to the coast, dropping four sondes across the bathymetry gradient near the coast in onshore flow, then down south to fly along the coast, dropping two sondes, and then once the aircraft reaches offshore flow, fly perpendicular out from the coast, dropping four more sondes. At that point the aircraft would return to a point northwest of the storm and finish the butterfly pattern. Within the primary pattern, the aircraft would release combination GPS/AXBT drops at the turn points and midpoints on the radials, and on the first and third points through the center. If possible, we would also drop AXBT's at coincident points from the previous flight.

Mission Summary :

Takeoff from Tampa was at 2037 UTC July 22. Dolly was located in the western Gulf of Mexico, approaching the Texas/Mexico border at this time (Fig. 2). The storm had intensified to a hurricane prior to takeoff. Infrared satellite imagery (Fig. 3) showed that deep convection surrounded the center. Cloud top temperatures as low as -70°C surrounded the circulation center. Enhanced gradients in the cloud tops on the southwest side of the storm, however, suggested that outflow was restricted on this side of the storm and Dolly was experiencing some southwesterly shear. Areas of deep convection were also evident in the microwave imagery both in the inner core in an outer band on the southeast side of the storm (Fig. 4).

Figure 5 shows the actual flight track. The butterfly pattern was flown successfully, as was some of the SFMR module. On the way to the storm we encountered deep convection in outer bands well-removed northeast from the storm center. At one point we hit an 8 m s-1 updraft in one of these cells. During the first pass through the eyewall was open on the northeast side. Lower-fuselage radar showed vigorous convection on the northwest side, however, and mammatus was seen in the eye over the aircraft. Peak flight-level (surface) winds of 70 (60) kt were on the southwest side of the storm during this pass. The sea-surface temperature at the center was 28°C. The ratio of surface to flight-level winds, and its variation from the northeast to the southwest side of the storm, suggested that the storm was tilted toward the northeast, which was consistent with the presentation on IR imagery (cf. Fig. 3). The relationship between the flight-level and surface center, however, indicates that flight-level center was displaced to the west or southwest of the surface center. By the time we were flying the next inbound leg, from the south, the intense eyewall convection seemed to have rotated a bit to be located on the west side, and the northeastern eyewall appeared to have filled in. The radar presentation did not show a closed center, but rather a band of convection spiraling out from the center, beginning on the west side of the eyewall and wrapping around the north, east, and south sides. Convection was most prevalent at the leading tip of this band (on the southwest side), with a transition to more stratiform precipitation downwind. Peak flight-level (surface) winds once the entire flight was completed of 72 (74) kt were measured on the northwest side of the storm. Extrapolated minimum sea-level pressure was 980 hPa on the last pass; the pressure from a GPS dropsonde was 982.4 hPa, though the winds 8 m above the surface for this drop were 16 kt, indicating the center was slightly displaced from the drop location. Because of time constraints due to the long ferry to the storm (approximately 2.5 h), we were not able to extend the along-coast leg down to where the surface flow became offshore. Also, because the storm was still relatively far offshore, we did not encounter very strong winds in the onshore component (SFMR winds were only about 25 kt on this leg). Figure 6 shows the location of some of the drops during this module (circled in the figure). Some of the AXBT drops were also coincident with drops from previous days' missions (Fig. 7), though the flight immediately prior to this one is not included in this figure.

Overall the mission was successful. The pattern was flown generally as planned, though the northwest leg had to be shortened because of the proximity to land. Good Doppler coverage and radar analyses were produced on all legs. Most of the GPS drops worked, except for the one along the coast on the SFMR module, possibly because of interference from land. All of the AXBT's worked. The storm was strengthening while we were out there, though not rapidly. Dolly showed asymmetries in the convection and the wind fields, with eyewall convection mostly on the northwest and west side. Peak flight-level and surface winds were located on the north and northwest side. The SST and oceanic mixed-layer depth were high (28 C and 40 m). The lack of symmetric convection in the eyewall and the size of the eye (about 30-40 nm in diameter) were possible reasons for the lack of rapid intensification during this time. Convection in the northwestern eyewall did extend to 18 km, though, so there was deep convection present.

Problems :

There were only limited problems today. There was a total of 20 GPS sondes dropped, of which two failed (no launch detect) and 14 AXBT's all of which worked.

Robert Rogers

Mission Data

1 second listing | NetCDF listing

Flight Data

Flight track

Temperature and Moisture

Wind and Atlitude

Flight track

Page last updated August 4, 2008
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