Synergistic Analysis of Moisture Flux and Convective Asymmetry in Tropical Cyclone Senyar

Information from the abstract

Tropical Cyclone Senyar was a rare near-equatorial tropical cyclone that triggered hydrometeorological disasters in Aceh and North Sumatera. This study aims to quantify the role of moisture flux convergence (MFC), intensity of shear convective asymmetry, and rainfall intensity and distribution of Senyar Tropical Cyclone during 23 – 28 November 2025. A quantitative descriptive approach used ERA5 reanalysis (streamline, moisture transport, Moisture Flux Convergence (MFC), and Vertical Wind Shear (VWS)), Himawari-9 convective index (CI), and GSMaP rainfall, partitioned into four shear-relative quadrants to calculate an Asymmetry Index (AI). Upper-air sounding data from Kualanamu Meteorological Station provided in situ validation of these remote sensing and reanalysis results through convective available potential energy (CAPE) and convective inhibition (CIN). A closed 850 hPa circulation with winds exceeding 45 knots developed together with strengthening MFC over northern Sumatra and the Malacca Strait, and the sounding showed CAPE of 2,041 J/kg on 25 November. Under weak to moderate VWS (12–19 knots), convection and rainfall concentrated in the downshear-left quadrant on 25 and 27 November (AI of rainfall = 0.97 and 2.64), but AI did not scale with VWS, and decay on 28 November followed landfall. Moisture supply governed the magnitude and persistence of rainfall, while shear organized its distribution.

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Related topics: Tropical and Extratropical Cyclones Research · Meteorological Phenomena and Simulations · Climate variability and models