Understanding Ocean Surges And Possible Signals Over The Nigerian Coast Using a Multi-Model Ensemble of the Sub-Seasonal to Seasonal Forecasts

Occurrence of ocean surge events over the beach of the Victoria Island in Nigeria has been a consistence yearly phenomena. The yearly devastating consequences resulting from flooding, erosion and lost of lives is massive .

The state-of-the-art S2S forecasts from ECMWF, BoM NCEP and CMA are used to investigate the ocean-atmospheric dynamics, especially before during and after every surge events from 1994 – 2012.

It revealed that all ocean surges apart from the surge of March 1996 were experienced in summer months but frequent in August.The occurrence of the ocean surge might not be unconnected with the convective cloud cluster located over Atlantic ocean.

The storm cell creates pressure gradient of about 10mb between the ocean and the coast especially 2 days before the occurrence of any surge event. The resulting effect generate winds (between 15 - 18kts in strength on the average) over the fetch (Lat. 10°S – 20°S and Long. 0°E – 10°E). These winds were observed to be generally strongest three to two days before the event. They can generate wave height of about 1.8m and with favorable cross equatorial flow, the swell may reach the coast in about 2 – 4 days and when they coincide with high tide they can inundate the beach.

Finally the work shows that the s2s has a good skill in forecasting the ocean-atmospheric dynamics that could be responsible for the initiation of ocean surge over the Nigerian coast and could be use as an early-warning tool in prevention of life and properties along the coast.