A detailed examination of the evolution of coastal fronts associated with tropical storm Marco (1990)

Landfalling tropical cyclones (TCs) provide a challenging forecast problem because of their potential to cause heavy rainfall. The precipitation structure associated with a landfalling TC is highly variable, and is much more likely than storm surge or high winds to have maxima far removed from the main circulation. In cases of landfalling TCs, these distant rainfall maxima are found in regions where the flow around the storm interacts with land and terrain features through phenomena such as coastal fronts, orographic enhancement, and cold air damming. The aim of this study is to focus on the temporal and spatial evolution of coastal fronts which are induced or enhanced by the presence of a nearby tropical cyclone.

Atlantic Tropical Storm Marco (1990) was chosen for intensive study because two distinct incidences of coastal frontogenesis, cold air damming, and orographic enhancement significantly alter the final precipitation distribution. Marco was responsible for greater than 500 mm of precipitation in parts of Georgia and South Carolina; much of the heavy rainfall in these regions occurred in or near areas of coastal frontogenesis. A brief overview of the synoptic and mesoscale setup surrounding Marco will highlight the importance of the coastal fronts in the overall precipitation distribution. Then, a thorough examination of the two episodes of coastal frontogenesis will be presented through the use of various kinematic and dynamic fields in both surface and near-surface fields (computed from archived observations and high-resolution reanalyses, respectively).