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Tropical cyclones represent an important component of intraseasonal atmospheric variability in the southwest Indian Ocean, and their landfall can be devastating to coastal communities. However, little is known about their impact on precipitation in the high-elevation regions of East Africa. Here we combine in situ measurements from the summit of Kilimanjaro and subkilometer atmospheric modeling of the region to investigate the impact of these storms during the 2006-2007 cyclone season, which was characterized by anomalously positive snow accumulation at the summit coinciding with cyclone activity. Observations indicate that two storms are associated with snowfall amounts exceeding 10 cm per day, an amount representing similar to 5% of the observed average annual total. Numerical simulations show that some tropical cyclones transport moisture directly to the region while others induce moisture transport from the continental interior. Our study suggests that these synoptic-scale phenomena have the potential to complicate the extraction of climate signals from glaciers.

Plain Language Summary Tropical cyclones in the southwest Indian Ocean have a devastating impact on the coastal populations of East Africa and Madagascar when they make landfall. However, very little is known about their impact on the high-mountain areas of East Africa and on the small glaciers in those regions. Focusing on Kilimanjaro, we show that these storms coincide with some of the largest measured daily snowfall amounts at the summit, with some transporting moisture to the region through storm winds and others triggering moisture transport from the continental interior. The magnitude of the snowfall that occurs during two tropical cyclones means that these storms, which typically only last for a few days, can be relevant for understanding climate signals recorded by glaciers (e.g., ice cores).