DC-8 Mission Science Report

2 a/c mission in TC Gabrielle, located near 30 N 79 W. (The ER-2 was desired but could not consider operating with the string crosswinds at JAX.) The mission can best be characterized as "extratropical transition", but it should prove to be an excellent data assimilation mission. It does not fit neatly into any category. The storm has just emerged off the Florida coast over the Gulf Stream, and the major issue was whether it would reorganize and intensify.

The principal objective was to map the somewhat unconventional flow fields and thermodynamic fields in a rotated figure-4 pattern, extended as far from the cyclone center as possible. The location on our doorstep permitted legs for the DC8 between 150-250 nm in radius in most quadrants, and mostly accomplished with close coordination with the NOAA P-3 on center crossings.

This storm defied the forecast models. It refused to reintensify as advertised over the Gulf Stream on this flight day. (The next days mission was flown by the P3 and ER-2 only because DC8 had a mechanical problem. That day featured a storm approaching hurricane strength, again not well handled by the models.) The structure was unusual, with a dry southwest flow over and south of the center, and strong convection only to the N and NE of the center. Periodic outbreaks of intense convection persisted in these quadrants (and these quadrants only) for 48 hours, apparently being enough to deepen the storm. The DC8 patterns included several crossings of the dry slot on the SE side of the storm, with extremely low water vapor content measured by LASE and the JPL hygrometer. There were about 9 dropsondes launched, and the first 6 were transmitted to NHC before some unknown failure prevented the remainder from following. The total data coverage from the P3 and its drops, the DC8 and its drops, and the NOAA Gulfstream and its drops, should guarantee one of the most comprehensive data sets on any storm and its environment ever obtained. Modelers take note.

NOAA 49 track west and far NE of storm; many dropsondes