This section of the report will provide a rolling three month update on a monthly basis of the state of the climatic and ecological indicators used in monitoring areas at risk to RVF activity. These indicators include, global SST anomalies patterns, Equatorial Western Indian Ocean (WIO) and Eastern Pacific Ocean (EPO: NINO 3.4) SST anomalies, Southern Oscillation Index (SOI) and Outgoing Longwave Radiation (OLR) anomalies, Rainfall and anomalies, Normalized Difference Vegetation index anomalies and RVF risk map for Africa and the Arabian Peninsula.
1. SOI and SST Indices
The SOI index remained consistently negative with a value of -0.9 in September as was in August. However, convective cloudiness remained generally near average over most of the region, except for below average cloudiness observed across the central and western Pacific. These conditions generally reflect the prevalence of ENSO-neutral conditions. September monthly SST anomalies in the NINO3.4 SST have remained near normal at +0.30°C in September and so are the WIO SST (0.2°C) anomalies indicating the prevalence of normal conditions over these ocean basins. Even though above-average sea surface temperatures (SST) (below) in the NINO 1& 2 regions of the far eastern equatorial Pacific continued during September 2014, they remained near average in the central equatorial Pacific and in particular most of the Niño indices remained unchanged. The absence of a clear atmospheric response to the positive SSTs indicates ENSO-neutral conditions. As a result, nearly all model forecasts have further delayed the onset to the October - December 2014 period and to peak at weak strength during the winter (3-month values of the Niño 3.4 index between 0.5°C and 0.9°C) and last into the Northern Hemisphere spring 2015.
Cumulative NDVI anomalies for Africa for July 2014 to September 2014 show positive anomalies concentrated over parts of central Sudan, north-western Ethiopia, Botswana and Namibia following the above normal rainfall in these areas in the last several months. The RVF risk map below was derived from thresholding NDVI anomaly data to detect areas persistent of above normal NDVI. Periods of widespread and prolonged heavy rainfall lead to flooding of dambos and anomalous green up in vegetation, creating ideal ecological conditions for the emergence RVF vectors. For the period July 2014 to September 2014, the RVF persistence model identifies isolated areas in Sudan and South Sudan where ecological conditions would support the emergence of RVF vectors. Enhanced surveillance is advised in these areas. These locations have reported cases Cholera over the last few months due to flooding and poor sanitary conditions.