|Chief Scientist||Michael Black|
|Radar/Doppler Scientist||Chris Samsury/Stan Goldenberg|
|Cloud Physics||Bob Black|
This document is divided into 3 sections (Each section is written by the Chief Scientist):
Hurricane Fran was forecast to be near the North Carolina coast on the afternoon of 5 September and was a candidate for the electrification experiment. An HRD crew flew to Tampa, Florida the previous evening to be prepared for a late morning/early afternoon takeoff on NOAA43 from MacDill AFB. Fran was a category 3 hurricane with maximum winds of about 100 kts. Ed Bracken, a visiting graduate student from SUNY, was able to access lightning data from the NLDN network. Prior to takeoff, he sent us a fax showing the locations of cloud-to-ground (CG) lightning, relative to Fran's center. We planned to fly a figure four pattern with leg lengths of 125 nmi to survey the storm and to locate a rainband suitable for study. The lightning plot showed flashes in a rainband about 120 nmi to the east and northeast of Fran's eye.
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Takeoff from MacDill was at 1715 UTC and NOAA43 flew to the initial point at 1818 UTC, 150 nmi SW of the storm center, off the coast of South Carolina. Flying at 5,000 ft,we were in the eye at 1852 UTC and continued to the NE toward Frying Pan Shoals (33.5N, 77.6W). The LF radar showed that Fran had the remnants of a dissipating inner eyewall, surrounded by the main eyewall which was open on the south side. Maximum flight-level winds were near 110 kts on the north side. On the northernmost extent of the figure 4 pattern, the LF radar revealed a convective rainband which curved from the north side of Fran, near the coastline, around to the east and southeast sides at a radius of about 100 nmi. This would be the rainband that we would investigate later. We interrupted the pattern temporarily by flying across the band to the southeast before heading downwind on the inside of the band to a point NW of Fran's center along the N.C. coast. From there, we proceeded south along the coast and just west of the eye arriving at 1954 UTC. Heading east to the eyewall, we found a wind maximum of ~100 kts, 75 nmi from the eye. We were in the eye at 2012 UTC where the estimated surface pressure was 952 mb. Continuing to the east, a wind maximum of 115 knots was at 75 nmi radius and the last point of the figure 4, on Fran's east side was reached at 2032. NOAA43 climbed to 19,000 ft to study the rainband that spiraled around to the northeast of the center. The aircraft performed a series of sawtooth legs across the rainband while heading downwind. At 2131 UTC we reached the coastline and reversed course heading upwind along the inside of the rainband to repeat the sawtooth pattern. We were east of the storm center at 2141 UTC when we climbed to 21,000 ft and crossed the band 3 times while heading downwind to the north side of Fran's eye. We headed southwest along the coast through Fran's northern eyewall and the eye at 2240 UTC before turning in the eye and heading back to the rainband on Fran's east side. While crossing the band, we turned around, heading west to the eye, now near the coast at Cape Fear, N.C., at 0018 UTC,. The aircraft turned in the eye to head south through the open side of the eyewall and we climbed to 22,000 ft for our ferry back to Tampa. We landed at MacDill at 0154 UTC.
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Before the mission, Fran appeared to be the ideal candidate for the second landfalling hurricane electrification experiment (the first was flown in Opal of 1995). Little visible evidence of lightning was observed during the flight in either the eyewall or the rainband. While the rainband that we flew through appeared to be convective on radar, the vertical velocities observed seemed to be too weak to produce the conditions necessary to produce lightning. A preliminary analysis of the lightning data from the NLDN confirmed this; little CG lightning was observed in the eyewall or the rainband during our flight although there were some occurrences of flashes in the northern portion of the rainband near the coast. A rainband much further out at >200 nmi to the north of Fran's center contained much more lightning but, unfortunately, was not apparent on our radar and was to far away to study completely. Nevertheless, this mission provided additional data to be used in HRD's ongoing study of electrification of hurricanes.
No significant problems occurred as the equipment and crew performed well.
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