Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 190227
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1027 PM AST THU SEP 18 2014

.UPDATE...WHILE SHOWERS ARE TAPERING OFF IN NORTHERN PUERTO RICO
HEAVY SHOWERS CONTINUE IN EAST CENTRAL PUERTO RICO. HEAVY SHOWERS
ARE ALSO CONTINUING OVER THE ATLANTIC AND CARIBBEAN WATERS WITH
SOME LIGHTING OBSERVED. EMERGENCY MANAGERS DID REPORT SOME DAMAGE
DUE TO STRONG THUNDERSTORMS IN QUEBRADILLAS...MOCA... AND SAN
SEBASTIAN. TREES AND POWER LINES WERE KNOCKED DOWN. MOSTLY URBAN
AND SMALL STREAM FLOODING WAS REPORTED ELSEWHERE DURING THE
EVENING.

&&

.DISCUSSION...THE AXIS OF THE UPPER LEVEL TROUGH WAS OVER AND JUST
EAST OF THE U.S. VIRGIN ISLANDS THIS EVENING AND MUCH OF THE
STRONG CONVECTION WAS JUST EAST AND WEST OF THE AXIS. NEVERTHELESS
THE STRONGEST THUNDERSTORM ACTIVITY WAS NORTH OF THE LEEWARD
ISLANDS...THE VIRGIN ISLANDS AND LASTLY PUERTO RICO. THE MIMIC
PRODUCT SHOWS A CONSIDERABLE AMOUNT OF MOISTURE YET TO PASS...BUT
MOST OF THE DEEPEST MOISTURE WILL HAVE ALREADY CROSSED THE U.S.
VIRGIN ISLANDS BY 19/18Z. THIS WILL LEAVE CONSIDERABLE MOISTURE
OVER WESTERN PUERTO RICO THROUGH SUNSET FRIDAY. WITH A SLIGHT
SOUTHERLY COMPONENT IN THE EASTERLY WIND TONIGHT AND TOMORROW...WILL
EXPECT STRONG CONVECTION TO AGAIN RE-VISIT THE NORTHWEST PORTION
OF PUERTO RICO AND NOT SPARE THE CENTRAL PORTIONS EITHER. MORE
HEAVY RAIN EPISODES ARE EXPECTED FRIDAY IN THE AREA WITH MAINLY
MINOR RIVER RISES EXPECTED AND SCATTERED AREAS OF URBAN AND SMALL
STREAM FLOODING. THE NAM5 MODEL CONTINUES TO SHOW WET CONDITIONS
FOR FRIDAY NIGHT AS MOISTURE LEAVES THE AREA AND GOOD EPISODES OF
AFTERNOON CONVECTION FOR WESTERN PUERTO RICO BOTH SATURDAY AND
SUNDAY AFTERNOONS. CURRENT MODELS FRAGMENT THE WAVE ACTIVITY
THROUGH THE NEXT FIVE DAYS BUT LEAVE MOST OF THE MOISTURE IN PLACE
AND THIS SHOULD KEEP GOOD CHANCES FOR RAIN IN THE TYPICAL AREAS
THROUGHOUT THE PERIOD.

&&

.AVIATION...WX CONDS WILL CONTINUE TO DETERIORATE AS A TROPICAL WAVE
MOVES OVER THE FLYING AREA ON FRI. SHRA/ISOLD TSRA ASSOCIATED WITH
THE WAVE WILL MOVE IN AND AROUND TJSJ AND TIST AND TISX BTWN
19/03-08Z. NEW SHWR/TSRA ACTIVITY IS EXPECTED THRU FRIDAY AFTERNOON.
THEREFORE...MVFR/IFR CONDS AND MOUNTAIN OBSCURATIONS CAN BE
EXPECTED IN SHRA/TSRA AT MOST OF PR TERMINALS FROM TIME TO TIME. E TO
SE WINDS OF 10-15 KT WILL PREVAIL BELOW FL150... WITH HIGHER GUSTS
AROUND 30 KT NEAR TSRA.


&&

.MARINE...MARINE CONDITIONS WILL CONTINUE MAINLY 3 TO 5 FEET IN
EXPOSED WATERS WITH WINDS GENERALLY BELOW 18 KNOTS FOR THE NEXT 5
TO 7 DAYS. EVEN BETTER CONDITIONS ARE EXPECTED IN THE CARIBBEAN
WATERS WHICH WILL REMAIN SOMEWHAT SHELTERED.


&&

.PREV DISCUSSION... /ISSUED 216 PM AST THU SEP 18 2014/

SYNOPSIS...LEADING EDGE OF TROPICAL WAVE WILL MOVE ACROSS PUERTO
RICO AND THE U.S. VIRGIN ISLANDS TONIGHT. TROPICAL WAVE WILL MOVE
ACROSS THE LOCAL AREA TOMORROW AND WILL EXIT THE REGION FRIDAY
NIGHT. STRONG HIGH PRESSURE WILL EXIT THE EASTERN U.S. AND WILL
MOVE ACROSS THE WESTERN NORTH ATLANTIC DURING THE WEEKEND. ANOTHER
TROPICAL WAVE WILL MOVE ACROSS THE REGION MONDAY.

DISCUSSION...ISOLATED SHOWERS WITH THUNDERSTORMS DEVELOPED THIS
AFTERNOON OVER COAMO AND VILLALBA. REST OF PUERTO RICO AND THE
U.S. VIRGIN ISLANDS WERE UNDER PARTLY CLOUDY TO SUNNY SKIES.
LEADING EDGE OF TROPICAL WAVE WILL MOVE ACROSS PUERTO RICO AND THE
U.S. VIRGIN ISLANDS TONIGHT. THEREFORE...AN INCREASE IN SHOWERS
AND THUNDERSTORMS IS EXPECTED FROM EAST TO WEST. BETTER CHANCES
FOR SHOWERS TONIGHT WILL BE OVER THE U.S. VIRGIN ISLANDS AND
EASTERN PUERTO RICO. FOR TOMORROW...THE TROPICAL WAVE WILL MOVE
ACROSS THE LOCAL ISLANDS. THE COMBINATION OF THE TROPICAL
WAVE...WITH DAYTIME HEATING AND LOCAL EFFECTS PROMISE TO BRING A
GOOD DEAL OF SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE
REGION...MAINLY IN THE AFTERNOON HOURS. PRECIPITABLE WATER VALUES
ARE EXPECTED TO BE ABOVE 2.0 INCHES MOST OF THE DAY
TOMORROW...WITH MOISTURE LINGERING THROUGH FRIDAY NIGHT.

WEATHER CONDITIONS WILL IMPROVE QUICKLY...AS A DRIER AIR MASS MOVES
ACROSS THE REGION BEHIND THE WAVE. SUNDAY LOOKS THE DRIEST
DAY...WITH ANOTHER TROPICAL WAVE EXPECTED TO AFFECT THE REGION BY
MONDAY AND TUESDAY NEXT WEEK. AS STRONG HIGH PRESSURE BUILDS NORTH
OF THE AREA DURING THE WEEKEND...PRESSURE GRADIENT WILL
TIGHTEN...WHICH WILL ALLOW TO AN INCREASE IN WINDS ACROSS THE
AREA.

AVIATION...VFR CONDS EXPECTED TO CONTINUE WITH VCSH/VCTS FOR
ALMOST ALL TAF SITES THIS AFTERNOON AND TONIGHT AS TROPICAL WAVE
APPROACHES FROM THE EAST. AS THE NIGHT PROGRESSES...MVFR CONDS ARE
POSSIBLE FOR ISLANDS TAF SITES...TJSJ AND TJPS. WIND BLO FL150
FROM E TO SE 6-14 KTS BECOMING NW ABV FL300 AT GREATER THAN 25
KTS.

MARINE...SEAS UP TO 4 FEET AND WINDS UP TO 16 KNOTS ARE EXPECTED
ACROSS THE COASTAL WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  87  79  88 /  70  70  10  20
STT  78  88  80  90 /  60  70  10  20

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

11/12





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