MATYAS – Tropical cyclones in the northern Mozambique Channel: composite intra-seasonal forcing and 2019 event
Mark R. Jury & Corene J. Matyas
Article first published online: 12 July 2022
DOI: https://doi.org/10.1007/s00703-022-00911-8
ABSTRACT: Tropical cyclone (TC) activity in the northern Mozambique Channel (nMC) during the satellite era is studied, culminating with the anomalous 2019 season. We identify 21 westward-moving TCs since 1979 and analyze regional to local conditions as they move over the nMC. As easterly flow is needed to steer these TC into the channel and over land, we look for scenarios under which this flow is established along with thermodynamic conditions necessary to support TCs. At seasonal scales there is a dichotomy between westward steering flow and reduced thermodynamic energy during Pacific La Niña and cool-phase Indian Ocean Dipole (–IOD). Equatorial convective systems (Madden Julian Oscillation, MJO) entering the west Indian Ocean can trigger TC formation and subtropical ridging, more effectively at the end of austral summer. Conditions in early 2019 favoured westward flow over Madagascar. The onset of warm phase + IOD was evident in the Walker circulation and downwelling ocean Rossby wave that warmed SST to 31 °C north of Madagascar. High-amplitude MJO triggered the genesis of TCs Idai (March) and Kenneth (April) and both TCs transited the Mozambique Channel causing unprecedented floods. TC Kenneth intensified rapidly, and satellite rainfall and upper level ozone indicated the presence of a southern spiral cloud band that shielded the TC from the sub-tropical jet over Madagascar. Numerical model forecasts of track and intensity are evaluated.
Read the full publication in Meteorology and Atmospheric Physics.