The Sumatra squall formed in the afternoon due to strong westerly wind shear (about 50 km/h from surface to 700mb-level) and intense surface evaporation over Strait of Malacca on 17 Sept 2024. It swept over Singapore around nightfall as shown in the picture above. The gust front would be located just ahead (east) of the line of heavy rainfall. The strongest gust recorded for this storm is 83.2 km/h in East Coast Park at 7.33 pm according to Meteorological Service Singapore (MSS).
To know more, read The Straits Times article here.