Flight 990913I mission summary
|Lead Project Scientist||Dr. Hugh Willoughby
|AXBT Scientist||Dr. Liz Ritchie
|Workstation Scientist||Paul Leighton
|Dropsonde Scientist||Neal Dorst
|Guest||Dr. Kristine Katsaros
Planning: Flight 9909131 into Hurricane Floyd was an
eXtended Cylone Dynamics eXperiement (XCDX) mission with added
oceanographic observations. It originated and terminating at
Miami International Airport. HRD participants were: Hugh
Willoughby, Neal Dorst, Paul Leighton, Kristina Katsaros, and
Liz Ritchie (Naval Postgraduate School). Because the hurricane
was about 400 nmi from Miami, the normal six-sided "butterfly"
pattern was replaced with a rotating figure foi with nominal
130 nmi legs. The plan was to deploy GPS dropsondes at the
endpoints and midpoints of the radial legs with center drops
on the first and last passes through the center and eyewall
drops on the middle two passes. Some of the drops,
predominantly on the right side of the track would be augmented
by AXBTs. Chosen mission altitude was 12,000 ft.
Operations: N43RF took off from Miami at 1738 UT on
13SEP99, arrived at its initial point south of the center at
1916, and approached the eye at 12,000 ft on a nominal
due-north track. Because the (malfunctioning) lower fuselage
radar presentation showed low reflectivity and did not provide
useful guidance, we used winds and the nose radar to find the
center. Initially the eye was closed ~20 nmi in diameter. We
reached the center at 1942 UT 70 nmi east of San Salvador Is.
in the Bahamas, and observed a 923 mb MSLP of by dropsonde.
The eye was well defined, clear overhead and undercast with
broken stratocumulus. SMFR data showed an outer wind maximum
at 60 nmi radius. Maximum surface winds were about 80 kt in
the outer eyewall and 110 kt in the inner. We continued beyond
the eye on the same track to a point north of the center and
turned southwest to a point west of the center. The data system crashed during the outbound leg
from 1959 to 2009.
Two AXBT's on the downwind leg reported 28.8° and 28.7°C
SST ahead of the storm. The nominal track on the second
penetration was due east, perpendicular to the first
penetration. We reached the center at 2113 and deployed
eyewall drops on entrance and exit. We continued beyond the
eye to a point 103 nmi the east of the center and turned
downwind to the north-northwest in order to rotate the second
figure 4 by 45°. An AXBT 60 nmi from the center on the
outbound leg reported a 26.3°C SST. The third penetration was
from northeast to southwest. AXBTs on this leg showed SSTs of
26.1° and 26.8°C behind and to the right of the storm's
motion. We reached the center at 2236 and again deployed
eyowall drops. On exit through the southwest eyewall, we
encountered moderate turbulence in a 17 m/s updraft. At a
point ~100 nmi out we turned downwind to the east to pass
south of the center to the start of the final penetration from
southeast to northwest. As we broke out of the eyewall into
the eye we saw the new moon low over the western eyewall and
bright stars overhead. We reached the center 30 nmi NW of San
Salvador at 0021 UT on the 14th and observed a 923 mb MSLP by
dropsonde. N43RF recovered at Miami International at 0153.
Equipment: Airplane worked well, but instrumentation
problems compromised the mission. The LF radar never observed
realistic reflectivities, apparently due to AFC problems.
Handshaking problems between AVAPS and the workstation
prevented transmission of all but the first three dropsondes.
Ten minutes downtime on the main data system cost us uniform
spatial coverage. Eight of ten AXBTs worked, and all of the
GPS sondes worked, at least partially.
Critique: Floyd was essentially in a steady state
during an eyewall replacement after an episode of rapid
deepening on the previous day. Average storm motion during the
flight was 11 kt toward 290° This is a unique data set,
compromised by equipment problems.
Return to Floyd mission listing.
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