Climate Forecasts

West Africa

Average to above-average rainfall forecast through October

Late-August to late-September rainfall levels were overall above-average throughout much of the region (Figure 1-left). This further contributed to the average to above-average rainfall totals seen since June over the Sahelian and Sudanian-Guinean zones (Figure 1-middle). While this produced generally favourable conditions for cropping and pastoral practices, above-average rainfall resulted in localized flooding, particularly in Chad, Nigeria, Niger, Senegal, Burkina Faso, and Ghana. Conversely, the bimodal zone—which consists of the southern coastal portions of Liberia, Côte d’Ivoire, Ghana, Togo, Benin, and Nigeria—was affected by a prolonged spell from July to August. These dry conditions continued through September for much of the bimodal zone with rainfall less than 80% of average in Ghana, Togo, Benin, and Nigeria. In contrast, September rains were above-average in Liberia and Côte d’Ivoire.

The 30-day forecast indicates rainfall is expected to be average in the north, and above-average in the south (Figure 1-right). The above-average rainfall predicted in the bimodal zone indicates a late but likely favourable start to the minor season.

Figure 1. Estimated percent-of-average anomaly for August 26^th to September 25^th, estimated percent-of-average anomaly since June 1^st, and a 30-day rainfall anomaly forecast from September 24^th. The left and middle panels are UCSB Climate Hazards Center Early Estimates. They compare 2020 rainfall amounts to the 1981-2019 CHIRPS average. The right panel is a 30-day forecast from September 24^th. The image shows the average of five Subseasonal Experiment (SubX) model forecasts from that day. The anomaly is based on the 1999 to 2016 model average. Skill assessments of SubX can be accessed here.

Based on recent forecast products, the start of the 2020-2021 rainfall season in Southern Africa is likely to be normal with near-average rainfall likely throughout the region in October. Seasonal forecasts, based on September conditions, indicate near-normal cumulative rainfall for most areas during October to December and increased chances for above-normal December-to-February rainfall—the critical rainfall period for cereal crops in much of Southern Africa (Figure 1). La Niña conditions are currently present and likely to remain through the start of 2021. Historically, La Niña conditions typically result in above-normal precipitation between October and April in Southern Africa, although regional factors such as the phase of the Subtropical Indian Ocean Dipole (SIOD) can moderate the influence of La Niña in the region. As such, it would be prudent to continue to monitor seasonal progress for this region.

Figure 1. 3-month NMME probabilistic forecast for December to February, based on September conditions. The forecast probability is calculated as the percentage of all 79 NMME ensemble members that fall in a given tercile (above/below/near normal). White color indicates there is no dominant category across the model forecasts. NMME image from NOAA CPC.

Southeast Asia

Likelihood of above-average rainfall through the October to December rainfall period

Rainfall from late-August to late-September was average to slightly below-average across much of the northern parts of the region with rainfall totals ranging from 40-80% of average in western Myanmar, north-central Thailand, central Laos, Vietnam, and the Philippines. In contrast, rainfall was average to above-average in the southern half of the region, including rainfall totals exceeding 200% of average in southern Thailand, Malaysia, and Indonesia (Figure 1-left). This spatial pattern of slightly below-average rainfall in the north and above-average rainfall in the south is consistent with the seasonal rainfall anomaly since April 1^st (Figure 1-middle). However, given the sufficient rainfall experienced in this region over the course of a growing season, these slight deficits in the north are unlikely to have adverse effects on production in the area which is about halfway through its primary rice season.

The 3-month forecast indicates an increased likelihood of above-normal rainfall in Thailand, Laos, Vietnam, the Philippines, and Indonesia, providing favourable growing conditions throughout the region (Figure 1-right).

Figure 1. Estimated percent-of-average anomaly for August 26^th to September 25^th, estimated percent-of-average anomaly since April 1^st, and a 3-month probability forecast. The left and middle panels are UCSB Climate Hazards Center Early Estimates. They compare 2020 rainfall amounts to the 1981-2019 CHIRPS average. On the right is the 3-month NMME experimental probabilistic forecast for October to December, 2020, based on September conditions. The forecast probability is calculated as the percentage of all 79 NMME ensemble members that fall in a given tercile (above/below/near normal).

Central America & Caribbean

Above-average rainfall expected to continue across the region through October to December

Seasonal rainfall totals since the start of August have been near-average (Figure 1-middle), despite sporadic rainfall from late-August to late-September, with rainfall totals less than 80% of average in Belize, eastern El Salvador, eastern Honduras, eastern Nicaragua, Cuba, and Haiti (Figure 1-left).

The 3-month forecast indicates an increased likelihood of above-normal precipitation throughout Central America and Haiti and is inconclusive for Cuba. The prevailing La Niña ENSO conditions suggest a likelihood of an above-normal hurricane season in the Caribbean.  Hurricane Delta formed in the Caribbean Sea on October 5th and passed by the west coast of Cuba, bringing heavy rains and winds before moving towards the Gulf Coast of the United States.

Figure 1. Estimated percent-of-average anomaly for August 26th to September 25th, estimated percent-of-average anomaly since August 1st, and a 3-month probability forecast. The left and middle panels are UCSB Climate Hazards Center Early Estimates. They compare 2020 rainfall amounts to the 1981-2019 CHIRPS average. On the right is the 3-month NMME experimental probabilistic forecast for October to December, 2020, based on September conditions. The forecast probability is calculated as the percentage of all 79 NMME ensemble members that fall in a given tercile (above/below/near normal).