Synoptic Patterns associated with Non-Tropical Cyclone Heavy Rainfall Events in the Corpus Christi Area

This study focused on identifying synoptic patterns that can enhance the formation of heavy rainfall events in the Corpus Christi Area. In this study, heavy rainfall will be defined as three or more inches of rain occurring in a 24-hour period.  Heavy rainfall events associated with tropical cyclones have been excluded from this study.  The period considered exactly matched with the Climate Forecast System Reanalysis (CFSR) dataset which extends from January 1, 1979 through March 31, 2011.  Nine CFSR variables that enhance heavy rainfall development were chosen and include the following: mean sea level pressure, surface dew point, precipitable water, 850 mb and 300 mb U and V wind components, 500 mb geopotential heights, and 500 mb absolute vorticity.  A total of 92 dates were identified in the Corpus Christi area as having received heavy rainfall during the period of interest. Corresponding CFSR data on these same dates were viewed and analyzed.  The resulting composite maps convey a synoptic pattern
associated with heavy rainfall events in the Corpus Christi area, not associated with tropical cyclones.

Several synoptic patterns were identified.  The presence of a surface low pressure system over the western Gulf of Mexico along with a surface trough axis extending into South Texas produced a long fetch of east and southeast surface winds.  A likely surface boundary either in South Texas or close to South Texas further aided these east to southeast winds across the area.  The presence of east to southeast surface winds, southerly winds at 850 mb, and west to southwest winds at 300 mb correlated well with the abnormally high precipitable water values observed due to Gulf and Pacific moisture advection into the area.  A mid to upper level trough axis west of the area suggests a key lifting mechanism likely necessary for many of these heavy rainfall events.