9B.3
Using Three Global Climate Indices to Forecast Hurricane Activity in the Pacific and Atlantic Oceans

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Wednesday, 7 January 2015: 12:00 AM
122BC (Phoenix Convention Center - West and North Buildings)
Jason P. Giovannettone, HydroMet, Alexandria, VA

Quantitative relationships between global climate indices and hurricane activity in both the Pacific and Atlantic Oceans have not been widely explored. Some studies up to the present have explored qualitative relationships between hurricane activity and such climate indices as the North Atlantic Oscillation and sea-surface temperatures, among others. The current study presents the most comprehensive analysis of the potential relationships between 39 different global climate indices and hurricane activity using regression and frequency analysis. Attempts are made to develop statistical relationships between any one of these indices and hurricane number/intensity in the eastern and western Pacific Ocean as well as in the Atlantic Ocean. There were three climate indices, one per region, that showed significantly greater correlation than the others in each region. These were the ENSO Precipitation Index (EPI) in the western Pacific, the Atlantic Multi-decadal Oscillation (AMO) in the eastern Pacific, and the Atlantic Meridional Mode (AMM) in the Atlantic. The linear relationships between each climate index and hurricane numbers resulted in Pearson-R values of near 0.65 or greater. In addition, the Madden-Julian Oscillation showed some correlation with hurricane activity in all three regions, and therefore was included in the analysis. Several important results were found during these analyses. For instance, the relationship between the AMM index and hurricane numbers in the Atlantic Ocean revealed that the average July October AMM index was greater than -0.5 within a range of -5.0 to 5.0 for all years in the last 70 years when the number of hurricanes during that same period was greater than 7. It is also shown that the number of hurricanes that can be expected to be exceeded or not exceeded at frequencies of 50- to 100-years, for example, varies substantially depending on the range of AMM index values being analyzed. Similar results are shown for the eastern and western Pacific Ocean as well. Such relationships provide forecasters with a simple tool using only one variable that can be used to develop a rough estimate of the number of hurricanes that will occur during the upcoming hurricane season.