Extreme Precipitation in Weakly Forced Environments Along the Northwest Gulf (147)
Robert Megnia, National Weather Service WFO Lake Charles, LA, Lake Charles, LA
Jared Rackley, National Weather Service WFO Lake Charles, LA
Timothy Humphrey, National Weather Service WFO Lake Charles, LA
Seth Warthen, National Weather Service WFO Lake Charles, LA
Andrew Patrick, National Weather Service WFO Lake Charles, LA
Previous research has suggested that extreme precipitation events (EPEs) are fairly well forecasted in strongly forced synoptic environments with high values of integrated water vapor transport (IVT). However, EPEs in weakly forced environments with lower values of IVT have presented challenges. A weakly forced can be characterized by a lack of any obvious forcing mechanisms (highly amplified flow, frontal boundaries, vorticity advection, large IVT ect.) Extreme precipitation events that occur in weakly forced environments are common occurrences in the National Weather Service Lake Charles (LCH) county warning area. The precipitation that occurs in these events is at times under-forecast. Thus, there is a need to identify the forcing mechanisms behind EPEs in weakly forced environments. For this study, the 99th percentile of precipitation days (excluding days with tropical cyclone related precipitation) are gathered from the five LCH climate sites. Days with tropical precipitation are excluded so composites of the strongly forced events (made up mostly of mid-latitude events) can be compared to weakly forced events. IVT data from the North American Regional Reanalysis (NARR) data set from the 99th percentile days are examined to identify which days had weakly forced environments. Various forcing parameters are then examined on these days to identify any mechanism(s) that contribute to extreme precipitation. Although this study is primarily focused on a local region, the results may be applicable to other regions that experience EPEs in weakly forced environments as well.