FVXX21 KWBC 091700 . VOLCANIC ASH ADVISORY STATEMENT ISSUED 1700 UTC 09 DEC 1999 BY THE WASHINGTON VAAC . TUNGURAHUA 99-225 ECUADOR 1.47S 78.44W . BACKGROUND: TUNGURAHUA ECUADOR (1502-08) SUMMIT HEIGHT 16480 FT (5023 M) . SOURCES OF INFORMATION: GOES-8 MULTISPECTRAL AND VISIBLE IMAGERY...UPPER AIR DATA AND REPORTS FROM THE GEOPHYSICAL INSTITUTE... . ERUPTION DETAILS: CONTINUOUS EMISSION OF ASH AND STEAM....SHOWING SIGNS OF WEAKENING AND GRADUALLY BECOMING INTERMITTENT... . DETAILS OF ASH: VISIBLE AND MULTISPECTRAL SATELLITE IMAGERY THROUGH 09/1615 UTC DOES NOT SHOW ANY ASH BECAUSE OF EXTENSIVE METEOROLOGICAL CLOUDS OVER THE AREA. OVER THE LAST TWO WEEKS THERE HAS BEEN A NOTICEABLE DECREASE IN THE AMOUNT OF ASH RELEASED BY THE VOLCANO. THE GEOPHYSICAL INSTITUTE CONFIRMS AN OVERALL DECREASE IN THE NUMBER OF EXPLOSIONS. HOWEVER THE VOLCANO REMAINS VERY UNSTABLE AND THERE STILL IS VENTING OF ASH AND STEAM FROM THE SUMMIT. ASH AND STEAM ARE ESTIMATED TO BE NEAR-SUMMIT AND REACHING AS HIGH AS FL180. . TRAJECTORY: ANY REMAINING ASH AND STEAM AT FL180 IS FORECASTED TO MOVE TOWARD THE SOUTHWEST AT ABOUT 10 KNOTS. . REAL TIME SATELLITE IMAGERY ALONG WITH THIS AND OTHER VOLCANIC ASH ADVISORY STATEMENTS OFTEN ACCOMPANIED BY A MAP DEPICTING ASH LOCATION ARE AVAILABLE AT INTERNET URL ADDRESS http://www.ssd.noaa.gov/VAAC/washington.html (all lower case except /VAAC/) . OUTLOOK: SEE SIGMETS . EFFECTIVE JANUARY 3 2000 AT 0000 UTC... ALL REFERENCES TO LATITUDE AND LONGITUDE IN VOLCANIC ASH ADVISORY STATEMENTS WILL BE IN DEGREES AND MINUTES OF A DEGREE. EXAMPLE: 16.70N 62.20W WILL BE 1642N6212W . THE NEXT STATEMENT WILL BE ISSUED BY 09/2300 UTC. . PLEASE REFER TO SIGMETS FOR CURRENT WARNINGS. . NNNN