Record-breaking rainfall in Sri Lanka in 2014 enhanced by the MJO

Kajakokulan, P. and Hunt, K. M.R. ORCID: https://orcid.org/0000-0003-1480-3755 (2026) Record-breaking rainfall in Sri Lanka in 2014 enhanced by the MJO. Natural Hazards, 122. 130. ISSN 1573-0840 doi: 10.1007/s11069-025-07932-7

Abstract/Summary

Sri Lanka has experienced a number of severe floods over the past decades, illustrating the importance of understanding the events leading to extreme rainfall. The Madden–Julian Oscillation (MJO), an intraseasonal phenomenon over the tropical ocean, strongly influences interannual precipitation variability in Sri Lanka. However, the impact of the MJO on rainfall over Sri Lanka during the October–November–December (OND) period is less well understood. In this study, we use reanalysis data to explore the impact of the MJO on Sri Lankan rainfall during this season. We show that OND seasons with heavier-than-usual rainfall typically have more days where an active MJO is in phases 2 and 3 and that this is also true for 2014, where both November and December experienced about a week of strong phase 3 MJO. This led to a persistent synoptic-scale circulation anomaly over Sri Lanka, which increased moisture convergence over the island, leading to widespread and long-lived deep convection. We also argue that the persistent 2014 MJO events adjusted the Walker circulation, leading to anomalous ascent over Sri Lanka, which further amplified the seasonal rainfall. This study shows that a better understanding of the link between the MJO and local thermodynamics is needed to improve extreme precipitation forecasts over Sri Lanka.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/128526
Identification Number/DOI	10.1007/s11069-025-07932-7
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > NCAS Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Springer
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