|Chief Scientist||M. Black|
|Doppler Scientist||C. Samsury|
|Cloud Physics||R. Black|
J. Lawrence (UHouston)
This document is divided into 3 sections (Each section is written by the Chief Scientist):
Early morning on the 4th revealed that Opal's MSLP dropped from 933 to 916 mb in 2 hours and winds were up to 60 m/s while Opal was moving NNE at ~10 m/s. AOC crew were alerted and Jack Parrish arranged for an 1500 UTC takeoff. Radar imagery seen on TV n ews reports showed that Opal had a small (~12 km diameter) inner eyewall surrounded by a large moat region with rainbands encircling the moat region in the west, north, and eastern quadrants at ~ 160-180 km radii. Cloud-to-ground lightning displays showed some eyewall strokes and large number of strokes in the rainband on the east side of the storm. The structure of Opal appeared to be ideal for the electrification experiment. We were informed that the proposed NOAA-42 flight (winds at landfall) was not g oing to happen as the second HRD crew was still in Miami.
In the pre-flight briefing it was decided that we would conduct a figure 4 survey pattern at 14,000 ft (500 mb) flying first through the rainband east of the center to an initial point (IP) 130 km to the south of the eye. Afterwards we would work the r ainband module before returning to the eyewall.
After climbing, we headed west to work the rainband with a series of 30 degree turns across the band as we headed downwind to a point NW of the center. At 1839 and 1847 we made successful ODW drops on the inside and outside of the band, respectively. Fr om 1905 to 1930, the passes through the band north of the center were within Doppler range of the VLPS WSR-88D.
We broke off from the rainband (which by now was virtually all stratiform rain) to fly back to the hub cloud that made up the eyewall. From a point NW of the center, we headed SE, dropping an ODW in the moat region at 1953 and entered the hub cloud at 1 946 before making a center fix at 1958. At this time, the eyewall (hub cloud) was approaching the coast near Pensacola, well within range of the WSR-88D. We decided to fly a saw-tooth pattern back and forth across the northern eyewall, sampling as much ar ea as possible while at the same time collecting radials that could be used for both pseudo-dual Doppler and true-dual Doppler (with the WSR-88Ds) analysis. From 2000 to 2230 we flew the saw-tooth or zig-zag pattern across the eyewall making center passes at 2012, 2032, 2050, 2122, 2146, 2205, and 2230. The radials through the eyewall were flown some distance inland (30-50 km) and were in close proximity to the VLPS radar. The hub cloud contained a weak (~ 30 m/s) wind maximum but had moderate to high ref lectivity (>40 dBZ) with a few up- and downdrafts of moderate strength (~ 10 m/s) At 2230, the center was on the beach near Pensacola and we headed south to see if the rainbands on the south side were suitable for study. At 2250, it was evident that the c onvection had totally shut down and we headed SE to return to MacDill.
Most of the equipment was in good working order with the following exceptions:
Return to Opal page.