Sunday, November 10, 2019

Regional October precipitation

The upper photo provides another perspective on Kilimanjaro snow, complementing those of the previous post on this blog. It was sent recently by Simon of SENE, taken from Moshi in the first few days of November. On the satellite image above from 5 November, snowcover is reduced within the large summit caldera relative to that of 26 October, yet the snowline on the southwest flank appears even lower. Today's Sentinel-2 image (10 November, not shown) reveals a fresh dusting over the entire mountain, with higher amounts just west of Reusch Crater.

Simon wrote of anomalous October rainfall in the area, with a frequency more like that of the long-rain season. This appears to have also been the case for a larger region of East Africa, especially Kenya, southern Somalia and southern Ethiopia - and has led to flooding to the north and east of Kilimanjaro. The situation is shown clearly on a European Commission map for 5 November, from the Emergency Response Coordination Centre (ERCC). [Kilimanjaro can be seen, in shaded relief, where the northern border of Tanzania jogs a bit; it is southwest of the flooded area in Kenya (red dots).]

Why has the region been so wet during October? One good possibility is related to sea surface temperatures in the western Indian Ocean: anomalously warm water! Warmer than normal SSTs in the west, with cool SSTs in the east, sets up a positive Indian Ocean Dipole (IOD) event, associated with increased convection and precipitation over East Africa. During September the IOD strengthened markedly, becoming one of the most-positive events in many decades. Further information can be found here. Once precipitation data from the mountain are available, we will have a better understanding on how the 2019 IOD event is impacting the Kilimanjaro region.

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