An Examination of Three Challenging to Predict Mesoscale Convective Events during May 2016

Three challenging to predict mesoscale convective system (MCS) events associated with a rich variety of sensible weather elements occurred during 17–20 May 2016 across southern Texas, over portions of the northern Gulf of Mexico and adjacent coastal regions, and in central Florida. This poster will show the results of an analysis of these three MCS events in which particular attention is paid to the mesoscale aspects of development and maintenance. All three events occurred in an environment that was unusually baroclinic in conjunction with an anomalously strong subtropical jet (STJ) across the northern Gulf of Mexico.

The first event began the morning of 18 May and involved the formation and organization of convection over the elevated terrain of northern Mexico. This convection crossed into Texas, became surface-based, and morphed into a radar-indicated severe weather-producing MCS south of Laredo, Texas. This MCS propagated eastward before rapidly weakening prior to reaching the Gulf coast. The second event was associated with a large MCS that formed over the central Gulf of Mexico beneath the STJ on the morning of 17 May. This MCS moved east-northeastward and was associated with extensive heavy rainfall over Florida. Noteworthy was Vero Beach, Florida, on 17 May more than doubed their previous May daily precipitation record. The third event was an MCS that developed along the Texas-Mexico border by 1200 UTC 19 May. This MCS straddled the Gulf coast as it propagated eastward into the morning hours of 20 May. This MCS unexpectedly transitioned into a bowing configuration with a well-developed 3-5 hPa cold pool that resembled a low-end derecho. Extensive wind damage from gusts that reached 50 kt occurred from southern Louisiana eastward to the Florida panhandle. Each of these three events produced unexpected results and all occurred within synoptic environments favorable to convective development and could be traced back to isolated antecedent convection.

Three separate mesoanalyses were performed to better understand the physical processes underlying each of these MCS events. High resolution numerical model data (e.g., the HRRR and the NCAR real-time mesoscale ensemble) and high density surface observation will be used to construct representative analyses and meteograms for each MCS event.. Since the MCSs in two of the aforementioned events formed and transitioned over the Gulf of Mexico, radar observations of convective initiation is limited. To rectify this data gap, a network of buoy observations from the National Data Buoy Center were employed to track variables such as temperature, wind, and pressure prior, during, and after MCS traversal over select stations. The ability to better understand the interaction of important mesoscale features associated with evolving MCSs through a localized analysis may lead to the identification of key features and patterns governing MCS life cycles that could possibly be used to improve the forecasting of similar MCS events in the future.