The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 13-18 November with a larger eruption on 19 November. White-and-gray or gray ash plumes rose 400-800 m above the summit and drifted N, NE, and E during 13-14 and 16-17 November. Eruptive events were sometimes recorded during 14-17 November, but weather conditions prevented visual confirmation.
At 1413 on 19 November activity intensified and a series of pyroclastic density currents (PDCs) traveled down the flanks. Although foggy conditions obscured views, incandescent avalanches of material were visible descending the Besuk Kobokan drainage on the S flank. PDCs continued descending the flanks through 1558. At 1600 the Alert level was raised to 3 (the second highest level on a scale of 1-4) and the public was warned to stay at least 5 km away from the summit in all directions, 17 km from the summit to the SE, and 500 m from the banks of the Kobokan drainage as far as 17 km from the summit. Seismicity activity indicated that the eruption continued at a high level with increasing numbers of signals indicating avalanches. At 1700 the Alert level was raised to 4 (the highest level) and the exclusion zone was expanded 8 km from the summit in all directions, 20 km from the summit to the SE, and 500 m from the banks of the Kobokan drainage.