Mission Summary
Hurricane Earl

980902I1 Aircraft: 43RF

Scientific Crew
Chief Scientist Peter Dodge
Doppler Scientist John Gamache
Cloud Physics Bob Black
Dropsonde Scientist Jimmy Franklin
Workstation/AXBTMike Black
Observer Rob Rogers
SRA Ed Walsh

Aircraft Crew
CockpitCAPT Jerry McKim
LCDR Tim O'Mara
CAPT Dave Tennesen
Roc Torrey
NavigatorLCDR Dave Rathbun
Flight DirectorStan Czyzyk
EngineersSean McMillan
Jim Barr
Richard McNamara
RadioDamon SansSouci

Mission Briefing:

At 1 pm EDT, 2 September 1998, we briefed the AOC flight crew for a Tropical Cyclone Windfields at Landfall research flight in Tropical Storm Earl, which at that time was forecast to reach hurricane strength and make landfall between Mobile, Alabama, and Panama City Florida. The goal of the flight was to collect flight-level, radar and GPS dropsonde data to capture the structure of the windfield in a landfalling hurricane. We were especially interested in the onshore flow because of the possibile storm s urge in the Florida Panhandle.

Pete Black started the briefing by cautioning the flight crew that there could be severe weather associated with Earl, because of the higher wind shear and the interaction with the coast . I explained our initial pattern, a figure 4 through the storm to be followed by some radial legs toward the Eglin Air Force Base WSR-88D (KEVX). Then we planned, tentatively, to fly a saw-tooth pattern through the main rainabnd east of the center and then to descend to 8000' to fly along the coast, to measure the storm surge in Apalachee Bay with Ed Walsh's surface radar. We planned to drop numerous GPS Sondes and Airborne Expendable BathyThermographs (AXBT's) to map out the onshore and offshore flow, the eye, and the main rainband and/or wind maximum. The AOC crew agreed to this flexible plan. It helped that both Stan Czyzyk and Jerry McKim had been on the Fran and Danny landfall missions in previous years.

Mission Synopsis:

We left MacDill at 1925 UTC, and reached our initial altitude of 14,000' by 1945. This flight was seperated into three modules:

  1. The initial paffern: By 2007 we had reached the wind max in the main rainband, ~200 km east of the center of the storm. Sondes and AXBT's were deployed in the band and at buoy 42039. At 2037 Stan fixed the center at 29°04.7'N, 87°09.1'W, and we proceeded west to buoy 42040 where we also dropped sonde and AXBT at 2050. We passed through the center for the second time at 2110 and headed NE to KEVX. This leg was bouncy as we flew through rainbands near the coast. John Gamache reset the LF color scale so we could more easily pick out the 50 dBZ cores; there were several and we managed to avoid them all. At 2129 we turned at the coast dropped some more sondes and AXBT's and passed through the center again at 2150, where we dropped a center sonde. As we headed the south the bouncing subsided and we were in clearer air for a while.
  2. The rainband sawtooth: After we had finished the outbound leg from KEVX at 2200 UTC, Mike and Rob designed a sawtooth pattern to measure the inflow into the main convection of the storm. The goal was to drop sondes on either side of the band, as well as in the middle. We had succesful sonde + BT drops at 2240, 2254 and 2305.
  3. The coastal survey: We began our descent to 8000' at 2311 as we headed for Keaton Beach (KTNF1).
At 2320 we started running along the coast We dropped sondes at KTNF1 at 2320, two sondes near St. Marks at 2330, and one at 2334 near Panacea. We had planned to follow the coast on around St Georges Island to sample the coast near Port St Joe and Panama City, but there was some rather strong echo near Cape San Blas (CSBF1), so we headed southeast. In fact, the TLH WSR-88D detected a Tornado Vortex Signature at 2350 in this same area. Mike suggested that we head out to buoy 42039, repeat the figure 4 through the storm and then head for EVX one more time. So thats what we did. Just southeast of Cape San Blas the aircraft flew upwind inot the wind max, just inside the rainband. Mike remarked to Jerry that this was probably the first time he had flown upwind in an "eyewall". The flight crew did an excellent job of steering us around the convection that seemed to be increasing. At 0107 we dropped a sonde just offshore of KEVX, west of Panama City. We paralled the coast for awhile, about 10-20 km offshore, and then we flew right over Gulf Shores into the mouth of Mobile Bay. After dropping a sonde in Mobile Bay, we turned at the Dauphin Island C-Man (DPIA1) and headed SE for our last pass through Earl. At 0204 Stan fixed the center at 29°33.5'N, 86°17.9'W, well east of our previous center. The Air Force remarked that the center seemed stretched out on a N-S axis. Ed Walsh noted 30' waves at 0208. We dropped the last sonde and AXBT at 0238, in the main rainband, and 0242 we climbed and headed back to Tampa. At 0311 we did a radar altimeter calibration pass over the runway for Ed Walsh, and then landed at 0317 UTC.


The flight went very well. The sonde and AXBT coverage provide good coverage of a rather unusual hurricane. Jimmy Franklin noted that the sondes did nott find a surface wind > 50 kts, yet at 7000' the flight-level winds were > 70 kts for much of the latter part of the flight. Mark Powell incorporated some of that flight level data in an analysis centered at 0130 that estimated the maximum surface wind to be 79 kts, 91 nmi east of the center. A preliminary surface analysis of the GPS sonde data shows similarities to a cold front! The portion of the data set that was collected in Apalachee Bay will be supplemented by wind profiler data collected by Kevin Knupp's group from the University of Alabama-Huntsville, and the WSR-88D data collected by the Eglin AFB and Tallahassee WSR-88D radars.

We now have four data sets collected over land in weak to moderate hurricanes. l still think we must be very cautious about flying in stronger hurricanes overland. It is difficult to interpret the LF display when at 14,000' because strong echo can be caused ether by convectlion or bright band echo. The Dopplerized nose radar may help in discriminating the nasty places from the merely bumpy.


The AOC crew were great. Stan Czyzyk and Dave Rathbun agreed to every change in the flight patterns that we requested, and Jerry McKim, Dave Tennesen, and Tim O'Mara moved us through some bumpy flying with a minimum of surprises. Jim Barr kept the radar running, and Sean McMillan and Richard McNamara managed to keep with our evolving plans for GPS sonde and AXBT drops.

Mike Black acted as co-LPS on this mission; he called most of the Sonde and AXBT drops, and also helped design the rainband and second figure-4 patterns. Rob Rogers also helped plan the rainband pattern. Jimmy Franklin processed and transmitted most of the GPS data. Bob Black collected some more big raindrop data; NASA will probably be interested in our cloud physics data because they did not fly below 14 000 '. Pete Black helped plan the flight, and reminded us to be careful on this hurricane flight after 21/2 weeks of continuous operation.Steve Feuer and Mark Powell's analyses and comments helped set up the first part of the flight for the briefing.


I forgot to request that we record WARDS data, so the WARDS system did not collect Dopplerized Nose radar data. There was a brief probblem with the ASDL system at the beginning of the flight. There may be a problem with the way spectral width is reorded on the data system. We did not send out our LF composites until late in the flight; we should have sent them in a more timely manner. The radar tape has numerous parity errors, which may result in significant data gaps.

Mission Data:

One second data


Table 1
Centers determined by AOC Flight Director and Navigator
Time LatLonComments
2037 29° 04' 87° 09'
2110 29° 04' 87° 08'
2150 29° 08' 87° 08' maybe a bit south of center. Sonde dropped here.
0024 29° 19' 86° 45'
0052 29° 20' 86° 43'
0204 29° 33' 86° 17'

Table 2
GPS Sondes
#Serial IDTime Lat Lon Comments
1 974940036 200206 28.5°84.5°With BT
2 974510099 200730 28.6 84.9 Rainband, signal loss
3 974530042 202222 28.8 86.0 with BT
4 981950004 205100 29.2 88.3 "
5 982630002 210243 28.6 87.5 "
6 974740026 212032 29.7 86.6 rainband, no winds
7 974510001 212130 29.7 86.6 rainband
8 973730034 213207 30.3 86.4 rainband
9 974740043 214357 29.5 86.8 rainband
10 981950051 214431 29.5 86.9 rainband
11 981810026 215018 29.1 87.1 eye
12 973730037 222918 27.3 85.8 with BT, sst = 27
13 973840061 223420 27.585.4 rainband edge
14 982640245 224005 27.9 85.2 with BT, clipped, 10% diff
15 982710012224438 28.1 85.4 rainband
16 982630012 225409 28.6 85.4 with BT, no data (late winds?)
17 973840042225607 28.785.2 rainband
18 973730042 230527 28.6 84.5 with BT, over buoy 42036
19 980410074 232205 29.8 83.6
20 973250047 233020 30.1 84.2 No LD, rainband
21 981750067233110 30.1 84.2 rainband
22 975020002 233430 29.9 84.4 rainband
23 974530061 233715 29.9 84.6 over land, rapid ws falloff
24 974510040235130 29.385.0 eyewall
25 982630004001046 28.886.0 no winds
26 973730045 001343 28.9 86.2
27 981810011 010738 30.2 86.3 rainband offshore
28 982430005 012515 30.2 87.8
29 982010104 023806 28.6 84.5 rainband, failed early
Table 3
# Time Lat Lon Comments
1 200219 28°30' 84°32'
2 202300 28°47' 86°03'
3 205100 29°10' 88°17'
4 210248 28°34' 87°29'
5 211657 29°26' 86°47' in rainband, maybe no good
6 214534 29°25' 86°55'
7 222920 27°15' 85°49'
8 224006 27°52' 85°09'
9 225409 28°36' 85°21'
10 230528 28°35' 84°26'
11 001100 28°47' 86°01' near Buoy 42039
12 002400 28°18' 86°45' Dropped in eye
13 004320 28°52' 87°07'
14 010057 29°51' 86°23'
15 014042 29°48' 87°22'
16 021732 29°36' 85°54'
17 023025 28°56' 84°55'
18 024018 28°34' 84°24'

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