Synoptic-Scale Precursors to High-Impact Weather Events in the Georgia and South Carolina Coastal Region

To better anticipate and predict high-impact weather events in the SE United States Atlantic coastal region, an examination of the precursor synoptic-scale weather patterns to these events was undertaken. High-impact weather events were defined as extreme cold, extreme heat, strong tornadoes, very large hail, and hurricanes because these events have the potential to cause significant loss of life and property or a major disruption to commerce. Some signals were found in weather patterns days in advance of these events that will improve forecasting of them, which in turn will aid geologists, biologists, policy managers, and others in assessing threats to their interests. Surface high pressure, building south into the northern Gulf of Mexico coast, often preceded extreme cold events, as did the existence of a cold air mass several days before. Low-level, positive temperature anomalies in the lower troposphere often transited from the lower Great Lakes into the Mid-Atlantic before an extreme heat event. Significant tornadic events were generally preceded by a strong jet-stream disturbance near California several days in advance, transitioning into a dual jet-stream structure at 300 hPa. Significant, southerly wind and temperature positive anomalies in the lower levels over the Gulf of Mexico were also a strong indicator of tornadic events. Tropical cyclones were often preceded by a blocking ridge over the western Atlantic and a weak, low-pressure system over Florida, causing these tropical systems to move NW instead of making their usual turn to the north out to sea in the eastern Atlantic Ocean.