FVXX20 KWBC 201930
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VOLCANIC ASH ADVISORY STATEMENT
ISSUED 1930 UTC 20 JULY 1999 BY THE WASHINGTON VAAC 
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SOUFRIERE HILLS 99-181    WEST INDIES 16.7N 62.2W
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BACKGROUND:    SOUFRIERE HILLS MONTSERRAT (1600-05)
               SUMMIT HEIGHT 3000 FT (915M)
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SOURCES OF INFORMATION: GOES-8 INFRARED AND MULTISPECTRAL IMAGERY
THROUGH 20/1845 UTC.  MONTSERRAT VOLCANO OBSERVATORY.  12 UTC
GUADELOUPE RADIOSONDE. GOES SATELLITE DERIVED WINDS.

ERUPTION DETAILS:  ERUPTION OCCURRED AT ABOUT 20/0910 UTC.
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DETAILS OF ASH CLOUD: THE 1845 UTC SATELLITE IMAGE SHOWS LOW LEVEL ASH 
EXTENDING ALONG A LINE FROM THE SUMMIT (16.7N 62.2W) WESTWARD TO 17.0N
64.9W.  THE LOW LEVEL ASH PLUME IS APPROXIMATELY 290 KM (157 NMI) LONG
AND 100 KM (54 NMI) WIDE.  UPPER LEVEL ASH PLUME EXTENDS ALONG A LINE
FROM WEST OF THE SUMMIT (17.0N 62.8W) TO 20.3N 59.3W.  THE UPPER LEVEL
PLUME IS OVER 544 KM (294 NMI) LONG AND UP TO 220 KM (119 NMI) WIDE. 
ASH EXTENDS FROM THE SURFACE TO APPROXIMATELY FL400.
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TRAJECTORY: ASH IS GENERALLY MOVING IN TWO DIRECTIONS... WITH LOW
LEVEL ASH SPREADING WEST WHILE UPPER LEVEL ASH IS SPREADING GENERALLY
TOWARDS THE NORTH. DETAILS OF MOVEMENT... ASH BETWEEN THE SUMMIT AND
FL120 IS MOVING TOWARDS THE WEST AT 20 KNOTS.  ASH BETWEEN FL120 AND
FL200 IS MOVING TOWARDS THE WEST AT 5-10 KNOTS.  ASH BETWEEN FL200 AND
FL230 IS NEARLY STATIONARY DUE TO LIGHT AND VARIABLE WINDS.  ASH ABOVE
FL230 TOP APPROX FL400 IS SPREADING TOWARDS THE NORTHEAST AT 20-25
KNOTS WHILE THE ENTIRE UPPER LEVEL PLUME IS SLOWLY BEGIN ADVECTED
NORTH AND NORTHWESTWARD.
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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
www.ssd.noaa.gov/VAAC/washington.html
(all lower case except /VAAC/)
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OUTLOOK:  SEE LATEST SIGMETS AND VAFTAD.
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THE NEXT MESSAGE WILL BE ISSUED BY 21/0130 UTC.
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PLEASE REFER TO SIGMETS FOR CURRENT WARNINGS.
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"Attached Graphic Map Depicting Ash" 

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