Sea Level Forecasts and Early Warning Application in the Pacific

Because of the need for information related to the variability and predictability of sea level on season-to-longer time scales, the Pacific ENSO Applications Climate (PEAC) Center runs the El Niño-Southern Oscillation (ENSO)-based canonical correlation analysis (CCA) statistical model to generate sea level forecasts for the U.S.-affiliated Pacific Islands (USAPI) (Fig. 1) with lead times of 3-6 months in advance. The ENSO climate cycle and sea-surface temperatures (SST) in the tropical Pacific Ocean are taken as the primary factors in modulating these forecasts. Over the years, the 3-6 month forecasts have served our clients well. However, the demand for longer lead-time (e.g., 6-12 months) forecasts has increased considerably in order to better support planning and management in climate-sensitive sectors. Therefore, in order to expand the scope of our operational sea level forecasts, in addition to SST, we added trade-winds (U) for modulating sea level variability on longer time scales. For 6-12-months lead-time, the combined SST and U-based forecasts are found to be more skillful than the SST-based forecasts alone. This improvement has enabled our clients to develop a more efficient long-term response plan for hazard management. In a recent ‘Regional Integrated Water Level Service' meeting (held in Honolulu on January 10-11, 2012), discussions among representatives of the US National Oceanic and Atmospheric Administration (NOAA), New Zealand (NZ) National Institute for Water and Atmospheric Research (NIWA) and Met Service, Australia's Bureau of Meteorology (BOM), and Commonwealth Scientific and Industrial Research Organisation (CSIRO) revealed that the development and distribution of ‘seasonal sea level outlooks' in the Pacific basin region is an area of mutual interest. We are therefore motivated to establish an experimental framework for the development of sea level-related seasonal and annual outlooks tailored towards coastal flooding/erosion risk warning and water resources management for the non-USAPI region (Fig. 1). We added nine non-USAPI south Pacific stations (i.e., Nauru, Honiara, Funafuti, Penrhyn, Kanton, Christmas, Rarotonga, Papeete, and Rikitea) to our current season-to-annual sea level forecasting scheme. The overall forecast skills for the non-USAPI stations have been found to be skillful; however, it is slightly weaker than the northwest USAPI region. The PEAC forecasts are regularly updated and disseminated through the appropriate channels to enhance the governance capacity in the USAPI region. The southwest non-USAPI region may also use these products to enhance their ability to address disasters. In this paper, we synthesize the current operational forecasting, warning, and response activities of the PEAC Center and discuss the manner in which our experience can contribute to the development of operational strategies for longer time-scale sea level variability for the non-USAPI region.