Mission Summary
20090818N2 Aircraft 49RF
TDR flight about Hurricane Bill 2009

Aircraft Crew (49RF)
Aircraft CommanderJohn Logenecker
Co-pilotKristie Twining
Flight DirectorPaul Flaherty
Flight DirectorJessica Williams
Data StationJohne Hill
AVAPS Operator"Mean" Joe Greene
AVAPS OperatorCharles Lynch
Scientific Crew (49RF)
Dropsonde ScientistMike Black
Dropsonde ScientistBob Black

Mission Plan :

At 1500 UTC on 18 August, Hurricane Bill was located near 15.9°N, 51.2°W, or about 550 miles to the ENE of our base in Barbados and was forecast to gradually strengthen during the next 24-36 h to a major hurricane while moving to the WNW at about 15 kt. The G-IV would fly a research mission in the immediate environment of Bill, concurrent with a NOAA P3 research mission flying a rotating figure 4 mission in the core. This was a follow on mission to the one that took off near 0800 UTC and would be one of several back-to-back missions. The planned takeoff time was 2000 UTC and the jet would fly a starfish pattern (Fig. 1) in the periphery of Bill and releasing 25-30 dropsondes along the flight track with a higher concentration of drops in the dry air to the west and NW of Bill.

Figure 1: Planned flight track for the 090818N2 Bill mission.

Figure 2: Water Vapor imagery of Hurricane Bill at 1700 UTC.

Figure 3: Visible satellite image of Hurricane Bill at 1715 UTC.

Mission Summary :

Take off Landing
Barbados19:52 UTC Barbados02:38 UTC

Takeoff was at 1952 UTC and we headed NE to our first drop just to the north of Barbados and to the SW of the CDO of Bill at 14° N, 58.4° W (see Fig. 3). We were still climbing and had reached an altitude of 7974 m (379 mb). As seen if Fig. 4, the environment on the south side of Bill was very dry above the pronounced temperature inversion near 900 mb. There was also a low-level jet of about 30 kt near 700 mb (Fig. 5). This sonde was characteristic of the environment on the south and west sides of Bill, although the depth of the dry layer and the height of the low-level jet differed some by location.

As we flew around to the north side of Bill, the environmental air got progressively more moist and the jet was either absence or not as pronounced. An example of the air mass on Bill's north side is in Figs. 6 and 7. Here, we dropped into a stratiform rain area and the entire sounding was moist. Also, the winds at this location were blowing pretty steadily out of the east at 35-40 kt.

The G-IV continued flying the starfish pattern and found that the environmental air on the east side of Bill was similar to that in the north, being relatively moist and without a distinct wind maxima. We released our last drop, number 29, at 0214 UTC and headed back to Barbados where we landed at 0238 UTC.

Figure 4. Skew-T diagram of dropsonde data ~ 150 nmi south of Bill.

Figure 5. Vertical profile of wind speed and direction from sonde data ~150 nmi south of Bill.

Figure 6. Skew-T diagram of dropsonde data ~ 150 nmi north of Bill.

Figure 7. Vertical profile of wind speed and direction from sonde data ~150 nmi north of Bill.

Problems :

There were three dropsondes that had partial failures, one that lost winds and another two that had missing or faulty PTH data. Another 4 were noted as fast falls so that the wind data from these is unreliable. The number of data failures and fast falls is unusually high and should be investigated.

Michael Black

Mission Data :

Drop plots
150 mb
200 mb
250 mb
300 mb
400 mb
500 mb
700 mb
850 mb
925 mb
1000 mb
surface mb

Page last updated September 18, 2009
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