MVO reported that during 19-26 December activity from Soufrière Hills lava dome was characterized by increased lava extrusion, rockfalls, and pyroclastic flows. Lava extrusion on the N, W, and SW sides of the dome continued and incandescence on the dome was visible at night when weather was favorable. Rockfall events increased by 80 percent compared to the previous week. Pyroclastic flows began to enter Tyers Ghaut (NW) on 20 December and likely reached the bottom of the ghaut (ravine) on 21, 23, and 25 December. On 22 December, the Hazard Level was increased to 4 due to the repeated occurrences of pyroclastic flows in the lower part of Tyers Ghaut. On 24 December, a large pyroclastic flow that reached Plymouth (about 5 km W), and possibly the sea, generated an ash plume to an altitude of 3 km (10,000 ft) a.s.l. Large incandescent blocks, deposited by rockfalls and pyroclastic flows, were visible on multiple occasions at night in the upper and middle parts of Tyers Ghaut.
Based on analysis of satellite imagery, the Washington VAAC reported that during 26-30 December ash plumes drifted W, WSW, SW, and S. Intermittent thermal anomalies were detected on satellite imagery on 27 December. Plumes rose to altitudes of 2.1-4.9 km (7,000-16,000 ft) a.s.l. on 28 and 30 December.