
000
FXCA62 TJSJ 190916
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
516 AM AST FRI SEP 19 2008
.SYNOPSIS...
AN AREA OF DISTURBED WEATHER ASSOCIATED WITH A TROPICAL WAVE
NOW CROSSING THE LESSER ANTILLES AND ENTERING THE EASTERN
CARIBBEAN...WILL CONTINUE TO MOVE SLOWLY WEST NORTHWEST TODAY
THROUGH THE WEEKEND. THIS FEATURE AND ASSOCIATED MOISTURE WILL
MOVE ACROSS OR JUST SOUTH OF THE LOCAL AREA LATE SATURDAY THROUGH
SUNDAY.AN UPPER LOW AND ASSOCIATED TUTT CONTINUES TO SLOWLY LIFT
NORTH NORTHWEST OF THE LOCAL AREA WHILE FILLING.
&&
.DISCUSSION...
THE DISTURBED WEATHER/TROPICAL WAVE CONTINUES TO PRODUCE A BROAD
AREA OF SHOWERS AND THUNDERSTORMS OVER THE LESSER ANTILLES AS IT
MOVES SLOWLY WEST NORTHWEST. THIS FEATURE WILL UNDERGO LESSER UPPER
LEVEL SHEAR AS THE TUTT LOW LIFTS FURTHER NORTHWARDS...AND EXPECT
A GRADUAL DEVELOPMENT WITH INCREASING ASSOCIATED CONVECTION OVER
THE WEEKEND. ITS EXTENSIVE AREA OF DEEP MOISTURE WILL COMBINE WITH
LOCAL AND DIURNAL EFFECTS AS WELL AS FAVORABLE UPPER LEVEL CONDITIONS
THROUGH THE WEEKEND...TO PRODUCE SHOWERS AND THUNDERSTORMS WITH LOCALLY GUSTY WINDS AND INCREASING SEAS ACROSS THE REGION. THEREFORE...A
FAIRLY MOIST AND UNSTABLE ATMOSPHERE WILL CONTINUE OVER THE NEXT
FEW DAYS...THEREBY INCREASING CHANCES OF SHOWERS AND THUNDERSTORM
ACTIVITY WITH LOCALLY HEAVY RAINFALL SATURDAY INTO SUNDAY.
LATEST GFS MODEL GUIDANCE SUGGESTS THAT THE MOISTURE FIELD ASSOCIATED
WITH THE TROPICAL WAVE WILL TRACK JUST SOUTH OF THE LOCAL AREA
WHILE MOVING TOWARDS THE WEST NORTHWEST. UNSETTLED WEATHER CONDITIONS...WITH SIGNIFICANT AMOUNTS OF CLOUDINESS...SHOWERS AND THUNDERSTORMSCAN BE EXPECTED TO CONTINUE TO DEVELOP ACROSS THE AREA TODAY ANDINTO THE EARLY PART OF THE UPCOMING WEEK AS TROPICAL WAVES WILL APPROACHES THE REGION EVERY COUPLE DAYS OR SO. ALSO...HOW THIS
PRESENT FEATURE EVOLVES OVER THE NEXT DAY OR SO..WOULD DETERMINE
THE EXTENT OF THE RAINFALL ACROSS THE LOCAL ISLANDS AND SURROUNDING
WATERS. REGARDLESS...EXPECT CONSIDERABLE AMOUNTS OF TROPICAL MOISTURE
AND UNSTABLE CONDITIONS TO PREVAIL ACROSS THE REGION AS UPPER LEVEL
CONDITIONS BECOME MORE FAVORABLE FOR INCREASED ACTIVITY. THEREFORE
BASED ON LATEST GUIDANCE AND PRESENT CONDITIONS...EXPECT INCREASED
POTENTIAL FOR AREAS OF LOCALLY HEAVY RAINFALL ACROSS THE LOCAL...
ISLANDS WHICH IN TURN COULD LEAD TO URBAN AND FLASH AND OR RIVER
FLOODING. ALL LOCAL RESIDENTS AND VISITORS SHOULD MONITOR HOW THIS
SYSTEM UNFOLDS DURING THE NEXT COUPLE OF DAYS.
&&
.AVIATION...
CLOUDINESS AND SHOWERS AHEAD OF AN AREA OF DISTURBED WEATHER
ASSOCIATED WITH A TROPICAL WAVE ACROSS THE LEEWARD ISLANDS THIS
MORNING...WILL AFFECT TKPK AND TNCM UNTIL EARLY THIS AFTERNOON...
PRODUCING BRIEF MVFR OR EVEN IFR CONDITIONS UNTIL AT LEAST 18Z.
TEMPORARY MVFR CONDITIONS WILL SPREAD ACROSS TIST AND TISX
GENERALLY AFTER 17Z. LOW LEVEL MOISTURE AND GOOD HEATING WITH
NORTHEASTERLY WIND FLOW WILL BRING CONVECTION TO THE SOUTHWEST TWO
THIRDS OF PUERTO RICO AFTER 17Z...LASTING UNTIL AT LEAST 23Z...WITH
MOUNTAIN OBSCURATIONS...LOWER CEILINGS AND VISIBILITIES IN LOCALLY
HEAVY RAIN ACROSS TJPS AND TJMZ. PERIODS OF MVFR ARE ALSO EXPECTED
THIS AFTERNOON ACROSS TJSJ AND TJBQ IN SHRA UNTIL AT LEAST 22Z.
LATEST TJSJ 00Z SOUNDING INDICATED AN EAST NORTHEAST WIND FLOW UP
TO 20 KNOTS FROM THE SURFACE TO AROUND 20K FEET.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 87 77 / 40 40 50 50
STT 86 78 86 78 / 40 60 60 50
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
&&
$$
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