The African Monsoon Recent Evolution and Current Status

The African Monsoon Recent Evolution and Current Status Update prepared by Climate Prediction Center / NCEP 04 August 2008 For more information, visit: http: //www. cpc. ncep. noaa. gov/products/Global_Monsoons/African_Monsoons/precip_monitoring. shtml

Outline • Highlights • Recent Evolution and Current Conditions • NCEP GEFS Forecasts • Experimental Week-1 and Week-2 Outlooks • Summary

Highlights: Last 7 Days • For the week ending 02 August 2008, much of the Gulf of Guinea region and parts of Sahel including Senegal had beneficial rains. However, some parts of Sahel had received slightly below normal rain for the week. • Below normal rainfall conditions persisted over some parts of Eritrea, adjoining northern parts of Ethiopia and central Sudan.

Rainfall Patterns: Last 180 Days Over the past 180 days, rainfall was above average over most areas in the Sahel, the Gulf of Guinea region, central Africa. Rainfall was below average in portions of central Ethiopia, central and western Kenya, Zimbabwe and parts of Mozambique.

Rainfall Patterns: Last 90 Days Over the past 90 days, rainfall was above average over much of the Sahel, the Gulf of Guinea and parts of central Africa with the exception of southeastern Nigeria and the bordering Cameroon where the rainfall was below normal over the same period. In the eastern Africa, dryness persisted over the parts of central Sudan, Eritrea, southern Ethiopia, Kenya. Southern African remained seasonably dry with the exception of South Africa, where some parts had above normal rainfall

Rainfall Patterns: Last 30 Days Over the last 30 days, rainfall was above average over most of the Gulf of Guinea region and the Sahel, except over the southeastern Nigeria and the adjoining mountainous region of Cameroon which experienced below normal rainfall. Below normal rainfall conditions persisted over parts of Eritrea and central Sudan.

Rainfall Patterns: Last 7 Days During the past 7 days, rainfall was above average over parts of the Sahel and portions of the Gulf of Guinea region. However, parts of southeastern Nigeria and pockets along the Gulf of Guinea coast received below average rainfall. Rainfall was also below average over part of south-central Sudan, western Ethiopia and Eretria.

Recent Rainfall Evolution For the past 30 days, despite some recent beneficial rains, below normal rainfall conditions continued over southeastern Nigeria and parts of Eritrea and central Sudan.

SST: Last 7 Days 27 July - 02 August 2008 Mean Anomalies The mean SST map (left panel) features a warming northern Atlantic ocean. SST off the coast of tropical west Africa north of the equator are slightly warmer than the average temperatures. Below normal SST conditions prevailed in the western part of the Indian Ocean breaking the earlier warming trend.

Atmospheric Circulation: Last 7 Days Over the past 7 days, the 850 h. Pa wind anomaly (left panel) featured a weakenening of the westerly wind anomalies in the eastern Atlantic just north of the equator. Stronger westerly anomalies were evident in the southern Atlantic while weaker westerly wind anomalies prevailed over the central equatorial IO. The 200 h. Pa wind anomaly (right panel) featured northwesterly wind anomalies over northwest Africa while southwesterly anomalies are evident in the southwestern Indian Ocean.

NCEP GEFS Model Forecasts Non-Bias Corrected Probability of precipitation exceedance Week-1: Valid 05 – 11 August, 2008 Week-2: Valid 12 - 18 August, 2008 NCEP global ensemble forecast system (GEFS) suggests for week-1 and week-2 a high tilt in the odds (90% or above) for precipitation to exceed 50 mm over parts of the Sahel region, CAR and western Ethiopia.

Experimental Week-1 Precipitation Outlook Valid 05 - 11 August, 2008 1. An increased chance for above average rainfall over the Western Gulf of Guinea coast countries. Favorable westerly wind from the Atlantic ocean is expected to increase precipitation over the area. Confidence: Moderate

Experimental Week-2 Precipitation Outlook Valid 12– 18 August, 2008 • Skill is Low to issue a forecast.

Summary • Over the past 7 days, beneficial rains continued to fall across the western Sahel and Gulf of Guinea improving the conditions in the parts of southeastern Nigeria. Rainfall was near-normal or above normal over most parts of the Gulf of Guinea region. Seasonably dry weather prevailed in most areas in central and southern Africa. • Much of West Africa had above normal rainfall over the past 30 and 90 days with some exceptions over parts of Nigeria and Cameroon. Over the 180 -day period, parts of Kenya, central Ethiopia, much of Zimbabwe and Mozambique had experienced rainfall deficits. • For the week 1 ending 11 August, 2008), there is an increased chance for above average rainfall over the parts of the Sahel region and parts of western Ethiopia. For the week 2 ending 18 the August there is an increased chance for above average rainfall over parts of Sahel and Central African Republic and western Ethiopia.