An analysis of mesoscale convective systems observed during the 1992 tropical cyclone motion field experiment.

Abstract

An analysis of two tropical Mesoscale Convective Systems (MCS) observed during the Tropical Cyclone Motion - 92 (TCM-92) mini-field experiment is accomplished. A discussion of TCM-92, its primary and secondary missions, and the resulting data sets is provided. Primary data sets for the two cases include high-density (one minute) WC-130 aircraft data, 44 omega dropwindsondes and visual and infrared (IR) geostationary satellite imagery. The observed characteristics exhibited by the tropical MCSs of the two cases are related to the hypothesized characteristics of midlatitude MCSs as suggested by Frank and Chen (1991), Raymond and Jiang (1990), Hertenstein and Schubert (1991), Menard and Fritsch (1989) and others. Thus, the goal of the analyses is to document, for the first time, the horizontal and vertical scales in terms of the expected structure and evolution of the tropical MCS. The MCSs of the two cases were in the mature and decaying stages of the convective life cycle. Mid-level (500 mb) vortices that are apparently created in the stratiform rain regions of the MCSs are clearly discernable in the wind fields. In both cases, these vortices are seen to build upward to 300 mb or originate higher than the 500 mb surface. Downward translation of the vortex to 700 mb is evident in both aircraft and satellite data in one case. Convective signatures in the temperature and dewpoint fields are not as significant as the wind fields. Because signatures are observed in the synoptic scale, such as anticyclonic outflow in the MCS regions, these systems apparently were significant mesoscale features of sufficient intensity and duration to alter the large-scale regime for over 24 h.