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May - June - July (MJJ) 2008
The following sections describe: (i) the Canonical Correlation Analysis (CCA)-based forecasts for the monthly MEAN and MAXIMUM sea level deviations in the May-June-July (MJJ) 2008 season, and (ii) the monthly sea level deviations observed in the previous season (February-March-April 2008). See Figure 2 at right for location of USAPI tide guage stations.
All units are in inches. 'Deviation’ is defined here as 'the observed or forecast difference between the monthly mean [or maximum] and the climatological monthly mean values (from the period 1975- 1995) computed at each station’. Also, note that the forecasting technique adapted here does not account for sea level deviations created by other atmospheric or geological conditions such as tropical cyclones, storm surges or tsunamis.
(i) Seasonal Sea Level Outlook for May-June-July (MJJ) 2008
Based on the independent SST values observed in the February-March-April 2008 season, the resulting CCA model has been used to forecast the sea-level for the MJJ 2008 season (see Table 1).
Table 1 : Forecasts of MEAN and MAX sea level deviation in inches for MJJ 2008
Tide Gauge Station (*) Data Unavailable.
Deviations between 0~±1 inch are considered to be negligible and are denoted by **.Deviations withing the range of (+/-) 2 inches are unlikely to cause any advers climatic impact. Remarks: The positive sea-level deviations forecast for the MJJ season (above) indicate that sea levels will remain elevated at all USAPI stations for another 1 to 3 months. This trend of elevated sea level is consistent with the on-going La Niña conditions; however, as La Niña conditions weaken, the sea-level is expected to begin receding toward normal levels. Mean sea levels are expected to be 1 to 7 inches above average during the MJJ season. The sea level in the Pacific Islands is sensitive to the ENSO cycle, with falling sea level observed during El Niño years and rising sea level during La Niña years.
As compared to median values (presented in parenthesis in the right column), the MAXIMUM sea level may reach 2 to 4 inches higher than the median value.
*** Sea level data for Chuuk is based on estimates from neighboring tide stations (Yap and Pohnpei) and observations from WSO Chuuk.
(ii) Observed Monthly Sea Level Deviation in Feb-Mar-Apr (FMA) 2008
The monthly time series (February-April 2008) for sea level deviations have been taken from the UH Sea Level Center. Consistent with the on-going La Niña conditions, positive deviations have been observed in most stations since January 2007. The observed values of seasonal mean/max sea level deviations was positive at all stations except for Palau. As compared to March, some stations recorded higher sea levels in April (Yap and Pago Pago); some recorded fall of sea level (Palau); and some stations saw no considerable change (Kwajalein, Guam, and Kapingamarangi). This trend is consistent with the weakening La Niña conditions. As the La Niña continues to weaken, we may expect the sea level to begin falling considerably (from elevated levels back toward average levels) within the next 2 to 3 months.
Table 2 : Observed MEAN and MAX sea level deviation in inches for FMA 2008
* Denotes where data is unavailable. ** Sea level data for Chuuk is based on estimates from neighboring tide stations (Yap and Pohnpei) and observations from WSO Chuuk.
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Pacific ENSO Applications Climate Center