Tropical Storm Iris
Extended Cyclone Dynamics Experiment (XCDX)
(950828H Aircraft 42RF)

Scientific crew
Chief Scientist H. Willoughby
Doppler Scientist M. Black
C-SCAT Scientist P. Black
Observer R. Smith (Univ. of Munich)

This document is divided into 3 sections (Each section is written by the Chief Scientist):

Mission Briefing

N42RF's flight on 28AUG95 was a single-plane Extended Cyclone Dynamics (XCDX) experiment in Iris as it regained hurricane intensity. Because the melting level had been so low on the previous day we operated at the 600 mb to avoid icing and charging of th e aircraft. The planned flight track was six sided figure traverses of the center directed along 030, 150, and 270. The forecast center point used in flight planning was 20.2 N and 62.5 W.

Mission Synopsis

We left Barbados at 1717 UT on 28AUG95 and headed northwest toward the initial point of the pattern, 17.0 N, 64.5 W, nominally 250 nmi SSW of the forecast center position. From there we tracked 30 toward the center, which we reached at 1944 UT, 20.8 N, 62.5 W. The radar showed a tight half circle of >35 dB(Z) reflectivity with a long trailing band of convective cells extending from the east side of the center toward the SSE. From the center we continued NNE to 24.2 N to 60.25 W, where turned westward to fly along the northern boundary of the CDO until we reached 24.2 N, 64.7 W. We then tracked 150 deg. back toward the center, reaching it at 21.1 N, 62.4 W. The tight arc of convection present on the previous visit had dissipated by this time, but the lon g curving band to the southeast and south had become better organized. A dropsonde deployed in the center measured hydrostatic and splash pressures within < 1 hPa of 982 hPa. We continued along 150 to 17.5 N, 60.2 W and turned NNE to a point east of th e center, 21.1 N, 58.0 W. As on the 27th, the southeast quadrant was characterized by southerly flow and abundant, but not notably vigorous, convection. The final traverse of the circulation toward 270 deg reached the center at 0109 UT, 21.4 N, 62.4 W and continued on to 24.4 W. At that point fuel expenditure dictated that we break off the pattern and head for St. Croix, where we landed at 0230 UT.

Mission Evaluation and Problems

The aircraft, instrumentation, and dropsondes worked superbly.

This mission was designed to augment Air Force reconnaissance with radar and flight-level data at another altitude over a larger domain. The data document Iris' recovery of hurricane strength and provide time continuity between the previous day's missions and the VME mission flown on the next day. It was somewhat disappointing that we again were unable to fly far enough to the west observe dry air outside the circulation.

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