Thermodynamic and dynamic processes in the updraft region of GALE IOP9

Abstract

A detailed diagnostic examination of the warm frontal region ahead of the surface cyclone in Intensive Observation Period (IOP) 9 of the Genesis of Atlantic Lows Experiment (GALE) is conducted. Data for this study consists of normal synoptic observations and special GALE observations, analyzed by the Navy Operational Regional Analysis and Predictions System (NORAPS), which uses optimal interpolation. These analyses are enhanced by hand-drawn fronts and cloud outlines from Geostationary Operational Environmental Satellite (GOES) imagery. Symmetric stability is evaluated on cross-sectional analyses of pseudo-absolute momentum and equivalent potential temperature, and reveal conditions of moist symmetric neutrality in the warm frontal region. The planetary boundary layer theta budget is examined to determine what processes heated and moistened the region. Surface heat and moisture fluxes were found to contribute to significant theta increases only in the early stages of development. Upper-level divergence and surface frontogenesis are studied to determine their contributions to forcing the warm frontal updraft. Results indicate that during the period of explosive development, upper-level forcing was unfavorable for development. Low-level frontogenetical forcing in the presence of symmetric neutrality was found to be strong enough to oppose this negative upper-level forcing to force rapid development. Meteorology, Explosive cyclogenesis, Theses