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During 1999–2014, Tanzania experienced below average precipitation in two important seasons: December to February (DJF) in the south and during March to June (MAMJ) in the northeast. We explore DJF and MAMJ precipitation in the areas with drying trends and examine their relationships with anomalous sea surface temperatures (SSTs) in the Indo‐Pacific and corresponding circulation patterns. At seasonal time scales, precipitation in DJF and MAMJ trend areas appears inversely related to diabatic forcing in the equatorial Pacific. Dominant influence for droughts in DJF is eastern Pacific SST while for droughts in MAMJ it is West Pacific SST. A bivariate regression model with West Pacific and Niño3.4 region SST as predictors is found to recreate multidecadal DJF variability after the 1950s and the extreme drying in MAMJ during the 2000s. The regression model coefficients also indicate differential eastern versus western Pacific forcing for DJF versus MAMJ. Thus, we suggest that recent La Niña‐like conditions, characterized by an enhanced Pacific SST gradient due to cooling in the eastern Pacific and warming in the western Pacific, played a substantial role in Tanzania's recent multi‐season drying trends. SST change scenarios (difference between 2023–2037 and 2000–2014 means) based on CMIP5 projections and observed trends illustrate the uncertainty of future precipitation outcomes, as well as the potential implications of contrasting linkages to eastern versus western Pacific SSTs. These scenarios are mainly optimistic for the DJF southern Tanzania trend area, because it appears dominated by Niño3.4 cooling at both seasonal and decadal time scales. Conversely, our scenarios are quite pessimistic for the MAMJ northeastern Tanzania trend area, because we find a dominant negative influence of warming West Pacific SST. [ABSTRACT FROM AUTHOR]

Southern Africa (SA) and eastern Africa (EA) experienced a sequence of severe droughts in December–February (SA DJF) 2015–2016, October–December (EA OND) 2016 and March–April–May 2017 (EA MAM). This sequence contributed to severe food insecurity. While climate variability in these regions is very complex, the goal of this study is to analyse the role played by unusually warm Indo–Pacific SSTs, where unusual is defined as a 1‐in‐6 year event. We use observed sea‐surface temperatures (SST) and satellite–gauge rainfall observations, a 20‐member ensemble of Community Atmospheric Model version 5.1 simulations (CAM5), and a 40‐member ensemble of climate change simulations from the Community Earth Systems Model version 1 (CESM1) Large Ensemble Community Project (LENS) to explore climate conditions associated with warm events identified based on eastern and western Pacific SSTs. Our analysis suggests that strong El Niño's may be followed by warm western Pacific SST conditions, which can lead to conditions conducive to successive and potentially predictable droughts in SA DJF, EA OND and EA MAM. We show that different regions of warm SST are related to recent droughts—SA DJF: Niño 3.4; EA OND: western equatorial Pacific (WEP); and EA MAM: western North Pacific (WNP). For DJF and MAM, respectively, the CAM5 model driven with observed SST and the same model driven within a climate change experiment indicate that warmer El Niño's and WNP events produce more intense atmospheric responses, potentially associated with more severe droughts. OND climate seems to be strongly influenced by the Indian Ocean Dipole, which corresponds with some WEP events. Given global warming, we suggest that the extreme Niño 3.4 and west Pacific SST events responsible for 2015–2017 droughts are likely to reoccur, thus humanitarian agencies should prepare to predict and respond to multi‐year drought and substantial food insecurity in SA and EA. Southern and eastern Africa experienced a sequence of severe droughts and food insecurity in 2015–2017. This study analyses how unusually warm eastern Pacific (Niño 3.4) and western Pacific (Western V) sea‐surface temperatures contributed to large‐scale modulations of the Walker Circulation, increases in diabatic forcing, and potential opportunities for prediction. El Niño events and South African droughts tend to be followed by western Pacific warming and East African drought. Climate change may be increasing the frequency of these warm events. [ABSTRACT FROM AUTHOR]

Southwest Asia, defined as the region containing the countries of Afghanistan, Iran, Iraq, and Pakistan, is water scarce and receives nearly 75% of its annual rainfall during the boreal cold season of November-April. The forcing of southwest Asia precipitation has been previously examined for the entire boreal cold season from the perspective of climate variability originating over the Atlantic and tropical Indo-Pacific Oceans. This study examines the intermonthly differences in precipitation variability over southwest Asia and the atmospheric conditions directly responsible in forcing monthly November-April precipitation. Seasonally averaged November-April precipitation over southwest Asia is significantly correlated with sea surface temperature (SST) patterns consistent with Pacific decadal variability (PDV), El Niño-Southern Oscillation (ENSO), and the long-term change of global SST (LT). In contrast, the precipitation variability during the individual months of November-April is unrelated and is correlated with SST signatures that include PDV, ENSO, and LT in different combinations. Despite strong intermonthly differences in precipitation variability during November-April over southwest Asia, similar atmospheric circulations, highlighted by a stationary equivalent barotropic Rossby wave centered over Iraq, force the monthly spatial distributions of precipitation. Tropospheric flow on the eastern side of the equivalent barotropic Rossby wave modifies the flux of moisture and advects the mean meridional temperature gradient, resulting in temperature advection that is balanced by vertical motions over southwest Asia. The forcing of monthly southwest Asia precipitation by equivalent barotropic Rossby waves is different from the forcing by baroclinic Rossby waves associated with tropically forced-only modes of climate variability. [ABSTRACT FROM AUTHOR]

The article discusses whether sea surface temperatures (SST) caused poor rainfall in eastern Kenya and southern Somalia from March to May 2012 and the frequency of dry events from 2003 to 2012. It mentions the use of two Global Forecast System version 2 modeling ensembles to estimate fractions of attributable risk. Possible contributions to dry weather in East Africa include warming in the western Pacific and stronger western-to-central Pacific SST gradients.

Summertime (June-September) precipitation in the Ethiopian highlands, serving as the main source for the Blue Nile River, exhibits a characteristically high level of inter-annual variability. Precipitation received during this season has explicit effects on rain-fed and irrigated agriculture in addition to hydropower infrastructure, not the least of which is the massive, soon-to-be online Grand Ethiopian Renaissance Dam. Season-ahead precipitation and streamflow predictions have accordingly been developed over the past decades in an attempt to inform sectoral decision-making, including both empirical and dynamical modeling approaches. Variables describing ENSO, the Tropical Easterly Jet, Indian Ocean sea-surface temperatures, pressure systems, etc. have previously been identified as significantly correlated with summertime precipitation, and thus commonly included as predictors in empirical models. Preliminary evaluation of these models and individual teleconnections, however, illustrate very different relationships, as pre-2000 predictors correlate with summertime precipitation on the order of 0.6 on average, whereas for post-2000 this drops to 0.2. Although seasonal precipitation amounts have remained relatively stable across both periods according to many observational and reanalysis data products, nearly all predictors identified in literature show a significant decline in relationship. This change is not immediately evident in an assessment of dynamical model relationships. Further analysis reveals that this phenomenon appears to not be isolated strictly to the Ethiopian highlands, and may be connected to global circulation changes including the AMO and western Pacific warm pool circulation anomalies. This begs the question of whether this may be attributable to a regime shift, global warming, or simply within the scope of long-term, low frequency climate variability. This apparent shift in the relationship of previously identified teleconnections with Ethiopian highland precipitation warrants further investigation, as the current set of prediction models may be over-representing expected prediction skill, resulting in direct implications to societal welfare. [ABSTRACT FROM AUTHOR]