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 negative with a value of -1.0 in November indicating persistence of below normal conditions as has been the case since July 2014. Monthly SST anomalies in all NINO monitoring regions have increased, with NINO3.4 SST anomalies at ~ +0.85°C in November. The western Indian Ocean also continued recent warming pattern, with the WIO SST index at +0.45°C indicating the prevalence of warmer than normal conditions over these ocean basins. Even though above-average sea surface temperatures (SST) (below) and in all the NINO regions of the equatorial eastern equatorial Pacific continued during November and 2014 exhibited are features characteristic of El Niño conditions, the overall atmospheric circulation has yet to show a clear coupling to the anomalously warm waters as such the combined atmospheric and oceanic state remains in ENSO-neutral state. As in the last three months, nearly all model forecasts predict El Niño conditions during the November-January 2014-15 period. If El Niño fully emerges, the prediction consensus favors a weak event, with an 65% chance of El Niño conditions during the Northern Hemisphere winter, which are expected to last into the Northern Hemisphere spring 2015.
Cumulative NDVI anomalies for Africa for September to November 2014 2014 show positive anomalies concentrated over parts of central to eastern Sudan, Eritrea, eastern Ethiopia, northern Somalia, northern Kenya, 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 September to November 2014, the RVF persistence model identifies isolated areas in Sudan and where ecological conditions would support the emergence of RVF vectors. Enhanced surveillance is advised in these areas. These locations have reported Cholera cases over the last few months due to flooding and poor sanitary conditions and recently reported cases of undiagnosed hemorrhagic fever.