Santa María Volcanic Ash — Aviation Impact, November 2026: Advisories Every Day Since 23 October, Ash SFC/FL140 Drifting West, a Three-Day Eastward Swing That Stayed 77 km From Guatemala City (GUA), No Airport Inside an Observed Ash Area

A November page for an advisory run that did not stop. The October page closed on 14 October on the signals it had opened on: the north-east pulse toward Quetzaltenango was over and VAAC Washington had scheduled no further advisory. The volcano did not wait long — advisories resumed 30 hours later and, after one more silence of 115 hours, have come every day since 23 October. This page therefore opens on the first advisory of November, not on a new eruption: the 04:52 UTC bulletin describes the kind of emission Santa María has produced all year — a thin plume seen on satellite, the webcam showing activity at the summit, ash from the surface to FL140 drifting west at 10 kt. What makes the late-October run worth a page of its own is its persistence — 34 bulletins on ten consecutive days, 16 ash-bearing advisories in a row since 28 October — and, for three and a half days, its direction.

For three and a half days the ash drifted east — toward the capital's side of the volcano, not to the capital. Of the 13 ash areas VAAC Washington drew between 20:04 UTC on 23 October and 23:34 UTC on 26 October, 11 moved east, north-east or south-east (one south, one south-west). That heading is rare for this volcano: 18 of the 321 observed areas in our record before 15 October had an eastward component. The ash moved slowly, at 5 kt, and stayed within about 40 km of the summit; its nearest edge to La Aurora was about 77 km, on the 13:57 UTC advisory of 24 October — an area estimated from the webcam and model winds because weather cloud hid the plume from satellite, and itself a correction issued three minutes after the original to change the forecast drift from west to east and north-east. Quetzaltenango's airfield (AAZ), 13 km north-north-east of the vent, sat inside the forecast area of the 19:53 UTC advisory that evening; the nearest observed edge was about 8 km. The same days carried the run's highest tops — FL150 on six advisories, from 14:10 UTC on 23 October to 19:53 UTC on 24 October, the first FL150 since 21 August (the record high in our data is FL160, in May). From 18:55 UTC on 28 October every drawn area has moved south-west or west again; the widest, at 17:10 UTC on 31 October, reached about 68 km west of the vent and about 23 km from Tapachula (TAP) on the Mexican side. None of this is a forecast we make: it is the published geometry, and wind at ash level can turn.

FL140 is a low-level hazard — the airfields that matter are the near ones. Santa María's summit stands at 12,287 ft, and every advisory since 15 October has reported ash from the surface to between FL125 and FL150 — a pressure altitude of roughly 12,500 to 15,000 ft, at most a few thousand feet above the crater. Traffic crossing Central America at cruise passes far above that band, which is how a volcano can generate 419 advisories in our record without touching the long-haul network. The band matters where aircraft are low, in the approach and departure paths of fields near the summit. Retalhuleu (RER), on the coastal plain 30 km south-south-west, has been closest to the ash in this run: the satellite-observed area of 18:55 UTC on 28 October, drifting south-west at 5 kt, passed about 2 km from the field, and the forecast areas of that advisory and of 12:25 UTC on 17 October contained it. Quetzaltenango (AAZ) came within about 3 km on 16 October and sat inside two forecast areas. No airport has been inside an observed area since advisories resumed on 15 October; across our full record Retalhuleu has been inside two, Quetzaltenango three and Tapachula three, the latest on 3 October. La Aurora, at 4,952 ft and 112 km east, works arrivals and departures through the same altitude band but has been inside none of the 359 observed or 764 forecast areas since 12 May. That is why dispatchers read the reported level and the drift line in each advisory, not the distance from the summit alone.

One FIR, two volcanoes — read FIR-level signals as FIR-level. Santa María and Fuego both sit in the Central American FIR, and the Tegucigalpa watch office issues the volcanic-ash SIGMETs for both — under the ident MHTG for the airspace designated MHCC, one FIR with two codes in the published record. It has issued 38 Santa María SIGMETs since 15 October (a correction re-issued for the same period counted once): tops of 15,000 ft on the six of 23–24 October, 12,500–14,000 ft on the rest, and 16 in a row since 13:50 UTC on 28 October, each picking up within minutes of the last. The current one, SIGMET A1, runs 05:00–11:00 UTC on 1 November, surface to FL140, moving west at 10 kt. Across the whole FIR, observed en-route traffic ran between 0.89× and 1.30× expected in the daily readings for 23–31 October, and the 24-hour reading behind our ash map stood at −8% at 06:25 UTC on 1 November — a FIR-wide figure spanning several countries, which we do not attribute to either volcano. Our detection layer has logged one low-confidence tracking entry for this airspace since the October page closed, on 21 October, and none since. The FIR's NOTAM set, refreshed at 05:02 UTC on 1 November, carries no ash notice and no airport closure; its one airspace restriction is a route closure in Guatemalan airspace (ATS route R644, AUR–TIDER, surface to FL170) in force since 2 September, whose text gives no cause. The set holds current notices, so it cannot show one that has already lapsed.

What we watch for escalation. Three signals would change this page. Cadence: the run has held four advisories a day since 29 October; a sustained 10-plus a day would mark a different volcano — the busiest day in our record is six, on 5 July. Height: reported tops above FL160, the record high in our data, set in May. Reach: an observed ash area over one of the exposed fields — Retalhuleu while the drift holds south-west, Quetzaltenango if it swings north-east, La Aurora if an eastward drift returns and carries further than the 77 km of 24 October. The 04:52 UTC advisory expects the winds at ash level to back toward east-north-east over the next 18 hours, which would carry the plume west-south-west. Automated multi-signal analysis checks all three every three hours, alongside observed airport movements and FIR-level traffic, and this page, the GUA brief and the live ash map update from the same cycle. The operating decision on any given day stays where it belongs — with the airport, the airline and the Guatemalan and Mexican authorities.