The combination of Potential Evapo-transpiration (PET) and rainfall is fundamental in the water balance of the environment and therefore very useful for agricultural planning of farm operations (Kumar, 1987; Jagtap et al, 1989; Idowu et al, 2002). However, rainfall is the most variable of all climatic elements and is evident from the recent increasing trend in the severity of tropical cyclones, floods and droughts that climatic variables such as rainfall are very difficult and complex to predict using Numerical Weather Prediction (NWP) models. A more complete understanding of the regional scaling of carbon, water, and energy exchange between human-modified landscapes as controlled by climatic and biophysical processes is therefore essential to evaluating our ability to use regional climate models to predict climatic changes.

The United Kingdom Meteorological Office (UKMO) have developed a 20km resolution Limited Area Model over Africa (Africa LAM) available for use by the National Meteorological and Hydrological Services (NMHS's) in Africa for operational weather forecasting and research.

This paper examines the weaknesses and strengths of the Africa LAM products in forecasting rainfall and temperature over the humid tropical area of Nigeria, especially during the onset and cessation of the raining seasons of 2005 and 2006. In order to summarize the performance of the Africa LAM forecast products, Model Output Statistical (MOS) analysis will be done using the Climate Predictability Tool (CPT) developed by the International Research Institute for climate and Society, USA. Forecast NWP products from Africa LAM with some station data and the revised Penman equation (FAO, 1992) would thereafter be used to calculate PET. Results will be presented and a schedule of agricultural activities would be suggested for the humid tropical area of Nigeria.