Volcanic Ash in Puerto Rico, March 10, 2004

PUERTO RICO AND U.S. VIRGIN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1100 AM AST WED MAR 10 2004

INCREASING LLVL MOISTURE ACROSS THE LOCAL AREA THIS MORNING IN THE
SE FLOW IS ADVECTING CLOUDINESS AND INSTABILITY AND WILL RESULT IN
SCATTERED SHOWERS THROUGHOUT THE AFTERNOON. WIDELY SCATTERED
ACTIVITY HAS ALREADY AFFECTED EASTERN INTERIOR SECTIONS OF P.R. AND
S AND SW PORTIONS OF THE SAN JUAN METRO AREA. DIURNAL PROCESSES
SHOULD FOCUS RAINFALL ACROSS THE NORTH CENTRAL AND NORTHWESTERN
SECTIONS DURING THE AFTERNOON...AND ISOLATED ALONG THE SOUTH COAST.
VOLCANIC ASH DISPERSING FROM PLUME EXITING TRPM AND LEADING EDGE NOW
OVER ST CROIX. STILL WAITING FOR VISIBLE CONFIRMATION OF THIS ASH.
NW SWELL NOW BEGINNING TO SHOW AND SHOULD BUILD TO AROUND 4 FEET BY
MID AFTERNOON. SEA YOU IN THE WATER.

.4AM DISCUSSION...LOW PRESSURE AT THE SURFACE EXITED THE
GEORGIA/SOUTH CAROLINA COAST LAST NIGHT ON A NORTHEAST TRAJECTORY.
HIGH PRESSURE IS ARCHING OVER THE TOP OF THAT LOW AND WILL REJOIN
THE HIGH NOW IN THE CENTRAL ATLANTIC ABOUT 2000 MILES EAST-NORTHEAST
OF PUERTO RICO. BETWEEN THE TWO SYSTEMS...THE HIGH AND THE
LOW...SURFACE FLOW OVER THE AREA IS NOW SOUTHEAST AND LOOKS TO
REMAIN SO UNTIL AROUND THURSDAY NIGHT.

MODELS SHOW SOME MOISTURE PEAKING AROUND THIS AFTERNOON AND THEN
GRADUALLY SUBSIDING AT 850 MB. SO THURSDAY SHOULD BE RELATIVELY DRY.
ON FRIDAY RELATIVE HUMIDITY RETURNS TO THE AREA ACCORDING TO THE
GFS. SATELLITE PICTURES SUGGEST THAT MOISTURE PUSHING TOWARD THE
WINDWARD ISLANDS WILL CONTINUE TO WEAKEN AS THE AIRMASS APPROACHES
PUERTO RICO AND THE U.S. VIRGIN ISLANDS BUT THAT SOME MOISTURE WILL
REMAIN TO YIELD SCATTERED SHOWERS IN THE USUAL DIURNAL PATTERN. THUS
THE EXACT LOCATION OF PATCHES OF MOISTURE AND BREAKS IN THE HUMIDITY
MAY NOT BE RESOLVABLE BEYOND 24 HOURS AND SO CANNOT RELY ON THE
EXACT POSITION OF THESE PATCHES OF RAIN DEPICTED IN THE MODELS.

THE NEXT FRONT...THE ONE CURRENTLY OVER CENTRAL CUBA...WILL MAKE IT
AS FAR AS THE DOMINICAN REPUBLIC...BUT WILL THEN BE REPULSED TOWARD
THE NORTHWEST THURSDAY AS THE AIR FROM THE EAST PUSHES IT BACK. FOR
PUERTO RICO IT WILL NOT REALLY BECOME A PLAYER EXCEPT TO ENHANCE THE
SOUTHEAST FLOW ALREADY IN PROGRESS.

THICKNESS ANALYSES SUGGEST THAT LITTLE CHANGE WILL OCCUR IN THIS
PATTERN OF EASTERLY FLOW AND SCATTERED SHOWERS THROUGH WEDNESDAY OF
NEXT WEEK.

&&

.AVIATION...SEVERAL POTENTIAL PROBLEMS EXIST FOR AVIATION. FIRST...
WITH SOUTHEAST WINDS...FLOW OFF OF MONTSERRAT WILL BE DIRECTLY OVER
THE AREA AND RISK OF ASH IN THE LOCAL AREA IS CONSIDERABLE. ALTHOUGH
REDUCTIONS TO VISIBILITY ARE POSSIBLE WITH LARGE ERUPTIONS...THEY
ARE NOT LIKELY. THE MAIN HAZARD WOULD BE DUE TO A LOW CONCENTRATION
OF PARTICULATES. THIS ASH SHOULD BEGIN TO TAKE A MORE SOUTHERLY
TRACK FRIDAY.

SECOND...DUST CONTINUES TO STREAM OFF OF THE AFRICAN CONTINENT FROM
THE SAHARA DESERT AND THE AREA OF DUST HAS PUSHED MORE THAN HALFWAY
TOWARD PUERTO RICO. THE CURRENT WESTERN LIMIT OF THE DUST CLOUD IS
23 NORTH 30 WEST...10 NORTH 52 WEST...7.5 NORTH 52 WEST. THE EDGE OF
THE DUST IS MOVING WEST AT 12 KNOTS AND THIS WOULD BRING IT OVER
PUERTO RICO BY SATURDAY. THIS APPEARS TO BE A SIGNIFICANT EVENT WITH
RESTRICTIONS TO VISIBILITIES POSSIBLE OVER A WIDE AREA. AFRICAN DUST
IS CONTINUING TO POUR OFF OF THE CONTINENT AND THE WIND PATTERN WILL
REMAIN MUCH THE SAME FOR THE FORESEEABLE FUTURE...THEREFORE HAVE
ADDED HAZE TO THE FORECAST FROM SATURDAY THROUGH DAY 7. THE TIMING
ON THIS EVENT IS SOMEWHAT UNCERTAIN AS 1000-850 MB AND 850-700 MB
MEAN FLOW FORECASTS ARE GENERALLY STRONGER THAN 12 KNOTS...AND
LOCALLY AS MUCH AS 25 KNOTS...SO FIRST SIGNS OF THE DUST COULD
ARRIVE BEFORE SUNSET FRIDAY. WHEN THE DUST ACTUALLY ARRIVES BETTER
ESTIMATES OF ITS DURATION AND IMPACT WILL BE POSSIBLE. SNELL

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JUAN PR
630 AM AST WED MAR 10 2004

PRZ001>013-AMZ710>750-101000-
630 AM AST WED MAR 10 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO.

.TODAY AND TONIGHT...A SLIGHT INCREASE LOW LEVEL MOISTURE ACROSS THE
AREA WILL COMBINE WITH LOCAL EFFECTS TO PRODUCE AREAS OF MODERATE TO
HEAVY SHOWERS IN ISOLATED AREAS. THIS MAY LEAD TO MINOR FLOODING OF
MAINLY STREETS AND POOR DRAINAGE AREAS.

.SPOTTER CALL TO ACTION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY.

.THURSDAY THROUGH TUESDAY... ON THURSDAY...SCATTERED SHOWERS EXPECTED
IN THE EAST SECTIONS OF THE ISLAND DURING THE EARLY MORNING HOURS
...AND IN THE WEST AND NORTHWEST SECTIONS DURING THE AFTERNOON. THIS
MAY LEAD TO MINOR FLOODING OF STREETS AND POOR DRAINAGE AREAS MAINLY
DURING THE AFTERNOON. NO SIGNIFICANT HAZARDS ARE EXPECTED
THEREAFTER. A SURGE IN THE WINDS IS EXPECTED STARTING ON SATURDAY
AND THIS MAY PRODUCE GUSTS OF UP TO 30 MPH.

VIZ001-002-AMZ710>730-101000-
630 AM AST WED MAR 10 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS.

.TODAY AND TONIGHT...ISOLATED AREAS OF OCCASIONAL MODERATE TO HEAVY
SHOWERS MAY DEVELOP ACROSS THESE ISLANDS DURING THE AFTERNOON. THIS
MAY CAUSE SOME MINOR FLOODING OF ROADS...GUTS AND POOR DRAINAGE
AREAS.

.SPOTTER CALL TO ACTION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY.

.THURSDAY THROUGH TUESDAY... NO HAZARDOUS WEATHER CONDITIONS ARE
EXPECTED. HOWEVER A WIND SURGE IS EXPECTED STARTING ON SATURDAY
WHICH MAY BRING GUSTS OF UP TO 30 MPH.

FOR ADDITIONAL INFORMATION...VISIT THE NATIONAL WEATHER SERVICE WEB
SITE FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS AT (ALL LOWERCASE
LETTERS): HTTP://WWW.SRH.NOAA.GOV/SJU.