Tropical Storm Iris 1995
Tropical Cyclogenesis Experiment
(950827I Aircraft 43RF)
| Scientific crew |
| Chief Scientist | H. Willoughby |
| Doppler Scientist | F. Marks |
| Dropwindsonde Scientist | J. Franklin |
| Workstation | J. Griffin
P. Leighton |
This document is divided into 3 sections (Each section is written by the Chief Scientist):
Mission Briefing
N43RF's flight on 27AUG95 was part of a two-plane genesis (actually regenesis) mission in tropical storm, formerly hurricane, Iris. The melting level was unusually low so we operated at the 570 mb isobaric level where we still encountered some ice at temp
eratures only a degree or so above 0 C. The planned flight track was a figure four with the legs oriented along the cardinal compass directions and diagonal legs in the southeast and northwest quadrants. Intended ODW drops were at the ends of the radial l
egs and at the center of the southeast diagonal. The forecast center point used in flight planning was 15.5 N and 62.5 W.
Mission Synopsis
We left Barbados at 1603 UT on 27AUG95 and headed northwest toward the forecast center position. In flight we received a revised position for the center 16.1 N 62.1 W and redirected our course toward that point. At 1706 UT, we found the center at 16.8 N,
62.8 W. The strongest winds were about 40 kt 15 nmi east of the center. As we approached that position a depression in the undercast containing a well-marked low-level circulation center as indicated by streaks of stratocumulus. Although we were under an
anvil, only the north quadrant of the depression evidenced convection in the form of a rainshaft and some cloud extending from the undercast to the anvil. The radar showed a disorganized cluster of cells around the center with no indication of an eye. Fr
om the center we continued east of the center along 17.7 N to 56.5 W, beyond the boundary of the convection in the southwesterly flow, where we dispensed a dropsonde and turned onto the southwestward (upwind) diagonal leg that ended at 12.5 N 61.5 W. On t
his leg--which was characterized by abundant, but not notably vigorous convection in southerly flow--we dispensed an ODW at the midpoint, near Barbados, and at the endpoint. From the southernmost point we turned north toward the center, which we reached a
t 2049 UT near 17.3 N, 61.7 W, continued to the north point 21.5 N, 61.5 W, deployed a dropsonde, and turned toward the southwest. The radar showed a narrow band of convection arcing from the north around the east side and extending far south from the cen
ter. Because of clearance problems we were not able to go as far to the west as we had planned. The westernmost point and final dropsonde was at 17.8 N, 64.2 W, not yet in the dry air on the west side of Iris. The final leg of the pattern was eastward to
the center, reached at 2319 UT near 17.5 N, 62.0 W. During the approach to the center, we encountered 45 kt winds 20 nmi out on the east side. As we departed toward SSE, we observed 55 kt winds 40 nmi from the center. The convection had wrapped around the
center to enclose an area of lower reflectivity that suggested an eye. From the center we flew southeastward to landing at Barbados at 0036 on 28 August.
Mission Evaluation and Problems
The aircraft, instrumentation, and dropsondes worked superbly.
This mission was designed for developing tropical waves. The purpose of the flight was to examine Iris' dissipation, but in the event it proved to be a useful baseline for subsequent flights that documented Iris' recovery of hurricane strength. The big
disappointment was the inability to fly far enough to the west to place the westernmost point in dry air outside the circulation.
Return to Iris page.