CENAPRED reported that activity at Popocatépetl intensified during 16-23 May after recent activity characterized by the formation of small to medium lava domes on the summit crater floor and their subsequent destruction. There were 154-168 daily steam, gas, and ash emissions and minor-to-moderate explosions during 16-19 May. Periods of high-frequency tremor lasted more than 12 hours during 16-17 May and more than 10 hours during 17-18 May. Minor ashfall was reported on 18 May in the municipalities of Atlixco (25 km SE) and Cholula (35 km E), Puebla. Six volcano-tectonic earthquakes with magnitudes as high as 1.8 were recorded along with over 2 hours of high-frequency tremor on 19 May. Residents of Tétela del Volcán (18 km SW), Morelos, noted minor ashfall. According to the Washington VAAC ash plumes rose 6.7-7 km (22,000-23,000 ft) a.s.l., or 1.3-1.6 km above the summit, during 16-19 May.
A period of high-frequency tremor that began at around 1800 on 19 May and lasted about 10 hours until about 0400 on 20 May was accompanied by steam, gas, and ash plumes that drifted NNW and continuous ejection of incandescent tephra onto the flanks as far as 1.5 km from the crater. On 20 May the Benito Juárez International Airport closed during about 0430-1000 and the Felipe Ángeles International Airport closed during 0600-1100 in order to clear ash from runways. Ash fell in multiple areas downwind including in the municipalities of Venustiano Carranza (66 km NW), Gustavo A. Madero (73 km NW), Azcapotzalco (78 km NW), Tlalpan (62 km NW), Iztapalapa (58 km NW), Amecameca (18 km NW), Ayapango (21 km NW), Ozumba (18 km W), Ecatzingo (15 km SW), Atlautla (16 km W), Valle de Chalco (44 km NW), La Paz (50 km NW), Chalco (38 km NW), Nezahualcóyotl (56 km NW), Temamatla (32 km NW), Tenango del Aire (29 km NW), Tlalmanalco (27 km NW), Juchitepec (28 km NW), Cocotitlán (34 km NW), and Tepetlixpa (21 km W). Ashfall in Puebla municipalities included Huejotzingo (28 km NE), Nealtican (21 km E), Chignahuapan (108 km NE), Puebla Capital (44 km E), San Martín Texmelucan (35 km NE), and San Felipe Teotlalcingo (26 km NE).
Additional explosions were recorded at 1047, 1247, 1454, 2136, 2238, and 2253 on 20 May. Almost 19 hours of high-frequency tremor recorded during 20-21 May was accompanied by continuous emissions of steam, gas, and ash and occasional ejections of incandescent material short distances onto the flanks. The Washington VAAC reported that activity intensified at 1453 on 20 May as a large, dense ash plume was visible in webcam images. By 1551 the ash plume was visible in satellite images rising to 8.2 km (27,000 ft) a.s.l., or 2.8 km above the summit. By 2041 the dense ash plume had risen to 9.1 km (30,000 ft) a.s.l., or 3.7 km above the summit, and drifted ENE far over the Gulf of Mexico. The plume rose as high as 9.7 km (32,000 ft) a.s.l., or 4.3 km above the summit by 2136 and remained at that altitude at least through 0341 on 21 May as it fanned out to the NE and ENE. By 0951 on 21 May ash plumes were rising to 9.1 km and at 1436 plumes were reaching 8.5 km (28,000 ft) a.s.l., or 3.1 km above the summit. Satellite images showed a large dense ash plume drifting 388 km NE over the Bay of Campeche, but emissions were most dense within 65 km of the summit. Webcam images showed that continuing dense ash emissions.
According to CENAPRED the Scientific Advisory Committee of the Popocatépetl Volcano announced on 21 May that the Alert Level was raised from Yellow, Phase 2, to Yellow, Phase 3, the highest of the three sub-phases based on the intensifying activity over the previous few days. The National Coordination of Civil Protection (CNPC) announced actions to be implemented by the state civil protection units including preparing evacuation routes and evacuation teams and shelters. Ashfall was reported in Puebla state, in the municipalities of San Andrés Cholula (36 km E), San Pedro Cholula (34 km E), Cuautlancingo (38 km E), Amozoc (61 km E), Puebla Capital (44 km E), Zacatlán (121 km NE), Tetela de Ocampo (121 km NE), and Chignahuapan (108 km NE). The Hermanos Serdán International Airport, in Puebla (30 km NE), closed at 2300 on 21 May until 0700 on 22 May according to Gobierno de Puebla.
High-frequency tremor was almost constant for over 23 hours during 21-22 May. Steam, gas, and ash emissions were continuous with occasional ejections of incandescent material short distances onto the flanks. Explosions occurred at 1355 on 21 May and 0533 on 22 May. According to the Washington VAAC satellite images acquired at 0236, 0821, 1421, and 1936 revealed continuing ash emissions to 3.7 km above the summit, drifting E and ENE. An accompanying very large sulfur dioxide plume drifted as far as Cancun, 1,295 km E. Ashfall occurred in the municipalities of San Andrés Cholula (36 km E), San Pedro Cholula (34 km E), Cuautlancingo (38 km E), Amozoc (61 km E), Zacatlán (121 km NE), Tetela de Ocampo (121 km NE), San Nicolás de los Ranchos (15 km NE), Palmar de Bravo (115 km SE), Tepeaca (76 km E), in Izúcar de Matamoros (51 km S), Epatlán (51 km SE), Teopantlán (52 km SE), Tlapacoya (144 km NE), Huatlatlauca Chignahuapan (72 km SE), and in the Puebla capital, in the state of Puebla. Ash also fell in Juchitepec (28 km W), State of Mexico, Hueyapan (17 km SW), Locality of Xochitepec (municipality of Jolalpan) (68 km SW), in Morelos, and in the capital of the state of Tlaxcala (50 km NE). At 1651 on 22 May the Hermanos Serdán International Airport suspended operations due to ash on the runway.
Tremor remained nearly continuous (more than 20 hours) during 22-23 May. Ongoing steam, gas, and ash emissions drifted NE, and occasional ejections of incandescent material short distances onto the flanks. Ash fell in the municipalities of Nealtican, Tianguismanalco, Atlixco, San Diego la Mesa, Huaquechula, and Atzizihuacán, State of Puebla. Ash plumes rose as high as 3.7 km above the summit and drifted E according to the Washington VAAC.
Sources: Centro Nacional de Prevencion de Desastres (CENAPRED), Washington Volcanic Ash Advisory Center (VAAC), Simple Flying, Gobierno de Puebla, Cuenta Oficial de la Coordinación General de Protección Civil del Estado de Puebla