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This loop of GOES-8 visible imagery shows the spread of the ash plume following the eruption of the Popocatepetl volcano just southeast of Mexico City (MMMX) at 19:02 UTC on 04 December 1998. Most of the ash plume was moving to the north and northwest, although some ash can be seen moving southward.
Surface observations are plotted on the imagery, with restrictions to visibility (H = haze; K = smoke) in red. The reports of smoke and haze were not due to the high-altitude volcanic ash, but low-level smog that is often trapped in the valleys during periods of weak surface winds. In fact, Mexico City was under a smog alert during this period.