These are the Antarctic Meteorological Research Center’s (AMRC) Synoptic chart that contains the Global Forecast System’s (GFS) Mean Sea Level Pressure (MSLP), Synoptic, Ship, and Buoy observation station plots, and the infrared AMRC Satellite Composite. Combined they make up a weather depiction map. They are produced on an hourly basis.

The file naming scheme is ANTSYNCHART_yyyymmdd_hhZ.JPG where yyyy is the year, m or mm is the month, d or dd is the day, hh is the hour in UTC. e.g. ANTSYNCHART_200991_00Z.JPG.