Thursday, 26 January 2012
Development of Conceptual Models of the Impacts of ENSO and Arctic Oscillation Interactions on Temperature Extremes During the Florida Dry Season
Hall E (New Orleans Convention Center )
Poster PDF (2.5 MB)
The El Niño – Southern Oscillation (ENSO) is the most important teleconnection influencing storminess, rainfall, and temperature during the Florida dry season (November – April). Typically, strong El Niños and La Niñas have profound and predictable effects on short-term climate variability and Florida's dry season weather extremes with a lead time on the order of months. Reliable forecasts of significant El Niño's and La Niña's are now available and their occurrence and impacts are widely anticipated. The general mechanism by which they influence Florida weather by modifying the mean position of the subtropical jet stream and storm track is well-known and simple conceptual models exist to aid in decision-making and outreach with the media and public to communicate the forecasts. Typically, Florida is colder, wetter and stormier than normal, with an increased risk of severe weather during El Niño winters. During La Niña winters Florida is drier and warmer than normal, with an increased likelihood of drought and wildfires. Other teleconnections, especially the AO, can at times have a significant impact on intraseasonal temperature variability during the dry season, especially the occurrence of freezes during the critical December to February (DJF) period. The AO is a leading indicator of Florida winter temperature on the scale of a few weeks with positive AO conditions generally associated with warm weather and negative AO conditions with cold weather. However, on the seasonal scale, the extreme influence of the AO has rarely occurred during a strong El Niño or La Niña. Indeed, the greatest influence of the AO in Florida has traditionally been thought to occur during ENSO- neutral conditions. During the back-to-back strong El Niño winter of 2009-10 and strong La Niña winter of 2010-11 record cold occurred during record low values of the AO index. The resulting hundreds of millions of dollars in economic losses and societal impact from the record cold spell of January to March 2010, and the all-time record cold December of 2010 were the major weather stories of the past two Florida dry seasons. The immediate question from the media and public to meteorologists and climatologists in the weather enterprise was: are these extreme temperature events attributable to ongoing strong El Niño or La Niña events? The AO is not well-known. It is often difficult to satisfactorily explain the complex influence of ENSO on weather and climate in Florida, to include the interaction of extreme phases of the AO into the equation further complicates the process of crafting a coherent message for decision-makers, media, and the public. Large scale conceptual models of the AO exist, but they lack detail, and cannot be used alone during strong phases of ENSO. To facilitate outreach, and understanding of uncertainty and usage of long-range and seasonal forecasts simple conceptual models of how the interactions of the ENSO and the AO can significantly impact Florida dry season weather are being completed. Illustrations of the meaning of the AO index and case studies of the past two dry seasons and the 1988-89 extreme La Niña and positive AO event will also be presented.
Supplementary URL: http://www.srh.noaa.gov/media/mlb/pdfs/Florida_Dry_Season_Forecast.pdf