FVXX21 KWBC 201700 . VOLCANIC ASH ADVISORY STATEMENT ISSUED 1700 UTC 20 MAR 1999 BY THE WASHINGTON VAAC . POPOCATEPETL 99-040 MEXICO 19.02N 98.62W . BACKGROUND: POPOCATEPETL MEXICO (1401-09) SUMMIT HEIGHT 17930 FT (5465 M) . SOURCES OF INFORMATION: GOES-8 VISIBLE AND MULTISPECTRAL IMAGERY 20/1200 UTC MEXICO CITY UPPER AIR SOUNDING. . ERUPTION DETAILS: NEW EXHALATION AT APPROXIMATELY 20/1545 UTC . DETAILS OF ASH CLOUD: A SURFACE OBSERVATION FROM PUEBLA MEXICO INDICATED A COLUMN OF ASH AT 1545 UTC. SATELLITE MULTISPECTRAL IMAGERY CONFIRMED THAT ANOTHER BRIEF ERUPTION HAD OCCURRED. AT 1615 UTC THE ASH CLOUD FROM THIS ERUPTION WAS LOCATED WITHIN 20 KM (11 NMI) OF 19.0N/98.4W. THE ASH CLOUD TOP WAS ESTIMATED AT FL210 BASED ON UPPER AIR DATA FROM MEXICO CITY. THE CLOUD COULD BE SEEN IN VISIBLE IMAGERY INITIALLY BUT BY 1615 UTC HAD BECOME TOO DIFFUSE TO DETECT. THE ASH HAS REMAINED DISCERNIBLE IN MULTISPECTRAL IMAGERY THROUGH 1645 UTC. . TRAJECTORY: TOWARD THE EAST AT 18 KTS. . THIS AND OTHER VOLCANIC ASH ADVISORY STATEMENTS OFTEN ACCOMPANIED BY A MAP DEPICTING ASH LOCATION ARE AVAILABLE AT INTERNET URL ADDRESS www.ssd.noaa.gov/VAAC/messages.html (all lower case except /VAAC/) . OUTLOOK: SEE VAFTAD AND SIGMETS. . THE NEXT MESSAGE WILL BE AT 20/2300 UTC. . PLEASE REFER TO SIGMETS FOR CURRENT WARNINGS. . NNNN