Physical drivers for multi-seasonal persistence of droughts over Hawaii and USAPI

The phase and intensity of El Nino-Southern Oscillation (ENSO) exert detectable imprints on the onset, severity and maintenance of droughts over Hawaii and the U.S. affiliated Pacific Islands (USAPI). However, observations show drought occurrences of unprecedented persistence beyond ENSO timescales implying factors other than ENSO are also involved. There is a need in the Insular Pacific to identify precursors to monitor and predict the severity and persistence of droughts, and to develop a Drought Early Warning System (DEWS). In this research, with a particular focus on multi-seasonal persistence, process-oriented diagnostics are applied to a multitude of observations and reanalysis products to identify leading processes and feedbacks associated with the life-cycle (onset, amplification, spatial-extent, duration and termination) of droughts of varying categories. Furthermore, the ability of CFSv2, the NOAA operational seasonal prediction system in representing these processes and feedbacks is critically evaluated, and the skill, together with uncertainties, in predicting onset, amplification, spatial-extent, duration and termination of droughts at various lead times are assessed. Results will be placed in the context of recent multi-seasonal persistence of observed droughts leading to the development of a DEWS for Hawaii and USAPI.