Temperature and rainfall anomalies over a typical 90-day season can be disproportionately influenced by a few high-impact weather events that occur during the season. High-impact weather events such as heat waves (HWs), the landfall of a tropical cyclone (TCs), or the passage of severe organized mesoscale convective systems (MCSs) can contribute to significant temperature and rainfall variability on intraseasonal time scales. The purpose of this presentation is to explore the linkage between seasonal climate regimes, as measured by typical time-mean temperature and rainfall anomalies, and the prevailing weather patterns associated with these climate regimes, as defined by the occurrence of high-impact weather events such as HWs, TCs and MCSs.

Examples of high-impact weather and climate linkages will be drawn from recent seasons and will include the TCs and heavy rains over the eastern United States (US) from August to October 2005 (e.g., TCs Katrina and Wilma), the extensive eastern US flooding of June 2006 (e.g., rainfall that rivaled what fell in June 1972 in conjunction with TC Agnes), the serious HW of June and July 2006 over much of the western and central US (e.g., temperatures in South Dakota in July that equaled standards set during the Dust Bowl of the 1930s) and the associated severe MCSs that created major urban dislocation problems (e.g., the widespread power outages in the St. Louis area during mid-July).