Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 240153
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
953 PM AST THU OCT 23 2014

.UPDATE...FEW SHOWERS AND THUNDERSTORMS PERSISTED OVER THE
NORTHWEST QUADRANT OF PUERTO RICO DURING THE LATE EVENING HOURS.
ISOLATED SHOWERS WERE ALSO DETECTED OVER EASTERN SECTIONS OF PUERTO
AND ACROSS THE WATERS BETWEEN PUERTO RICO AND THE U.S. VIRGIN
ISLANDS SO FAR THIS EVENING. ELSEWHERE ACROSS THE FORECAST
AREA...CLEAR TO PARTLY CLOUDY SKIES WERE OBSERVED. FOR THE OVERNIGHT
AND EARLY MORNING HOURS...ISOLATED TO SCATTERED SHOWERS ARE EXPECTED
AS MOISTURE INCREASES IN ASSOCIATION WITH A TROPICAL ACROSS THE
SOUTHEASTERN CARIBBEAN THIS EVENING. HOWEVER...THE BULK OF MOISTURE
ASSOCIATED WITH THE TROPICAL WAVE IS EXPECTED TO PASS WELL SOUTH OF
THE LOCAL ISLANDS TOMORROW AND SATURDAY. THEREFORE FOR THE NEXT FEW
DAYS WE CAN STILL EXPECT THE REGULAR PATTERN OF SHOWERS AND
THUNDERSTORMS OVER THE AREAS OF SEA BREEZE CONVERGENCE IN THE
WESTERN AND NORTHWESTERN SECTIONS OF PR DURING THE AFTERNOONS. FOR
WEDNESDAY AND THURSDAY...THE GFS MODEL GUIDANCE SHOWS AN INCREASE
IN MOISTURE WITH PRECIPITABLE WATER VALUES OVER 2 INCHES ACROSS THE
LOCAL AREA.

&&

.AVIATION...AS A WEAK TROPICAL WAVE MOVES ACROSS THE EASTERN CARIBBEAN...
SOME PASSING SHOWERS WILL REMAIN POSSIBLE OVERNIGHT AND FRIDAY MORNING
IN AND AROUND KPK/ISX/IST AND JSJ. AFT 23/16Z SHOWER AND THUNDERSTORM
DEVELOPMENT EXPECTED OVER AND NORTH OF THE CORDILLERA CENTRAL. THIS MAY
CAUSE BRIEF MVFR CONDITIONS AND MOUNTAIN OBSCURATIONS AT JMZ AND JBQ
THROUGH AT LEAST 23/22Z. ESE LOW LEVEL WINDS AT 5 TO 15 KNOTS EXPECTED.

&&

.MARINE...NO CHANGE TO PREVIOUS REASONING.

&&

.PREV DISCUSSION... /ISSUED 256 PM AST THU OCT 23 2014/

SYNOPSIS...MID LEVEL HIGH PRESSURE IS STILL EXPECTED TO REMAIN
OVER THE LOCAL AREA THROUGH THE END OF THE WEEK. ALSO...THE
POSITIONING OF THE TUTT ALONG WITH THE MID LEVEL RIDGE IS WORKING
TO INDUCE SUBSIDENCE OVER THE LOCAL ISLANDS. THIS SUBSIDENT
PATTERN IS EXPECTED TO CONTINUE THROUGH THE END OF THE WEEK AS
WELL. TROPICAL WAVE EAST OF THE LESSER ANTILLES WILL SLOWLY MOVE
WEST AND PASS SOUTH OF THE LOCAL ISLANDS...MOISTURE WILL INCREASE
SLIGHTLY...POSSIBLY CAUSING SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS OVER THE NEXT FEW DAYS.

DISCUSSION...FAIRLY QUIET IN THE MORNING HOURS...BECOMING MOSTLY
SUNNY BY MID MORNING. THEN ONE STREAMER DEVELOPED OFF SAINT CROIX
WHILE CLOUDINESS INCREASED A BIT OVER WESTERN AND NORTHWESTERN
PUERTO RICO IN THE AFTERNOON...BUT SO FAR NO SIGNIFICANT SHOWERS
HAVE DEVELOPED...HAVING SAID THAT...WE STILL EXPECT SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS PORTIONS OF WESTERN AND NORTHWESTERN
PR WITH THE REST OF THE AREA REMAINING PARTLY CLOUDY WITH ONLY A
SLIGHT CHANCE OF SHOWERS. ISOLATED TO SCATTERED SHOWERS ARE
EXPECTED OVERNIGHT AS MOISTURE INCREASES...ALTHOUGH THE INCREASE
IN MOISTURE IS NOT EXPECTED TO BE TOO SIGNIFICANT UNTIL FRIDAY
AFTERNOON WHEN PRECIPITABLE WATER VALUES INCREASE TO 1.7
INCHES...UP FROM 1.5 INCHES EXPECTED LATE THIS AFTERNOON INTO THE EVENING.

FOR THE NEXT FEW DAYS WE CAN STILL EXPECT THE REGULAR PATTERN OF
SHOWERS AND THUNDERSTORMS OVER THE AREAS OF SEA BREEZE CONVERGENCE
IN THE WESTERN AND NORTHWESTERN SECTIONS OF PR. EVEN WITH THE
TROPICAL WAVE MOVING IN THIS WEEKEND...THE SUBSIDENCE PATTERN BY
THE MID AND UPPER LEVEL HIGH PRESSURES SHOULD KEEP CONVECTION
SUPPRESSED. SUNDAY LOOKS TO BE THE DAY WITH THE HIGHEST AVAILABLE
MOISTURE...WITH SOME LINGERING MOISTURE ON MONDAY AND TUESDAY.

IN THE LONG RANGE...FOR WEDNESDAY AND THURSDAY...GFS MODEL SHOWS A
PRETTY SIGNIFICANT INCREASE IN MOISTURE WITH PRECIPITABLE WATER
VALUES SURPASSING 2 INCHES ACROSS THE LOCAL AREA. ALTHOUGH IT IS A
BIT FAR OUT TO HAVE MUCH CONFIDENCE...THE LOCAL AREA MAY RECEIVE
SOME GOOD RAIN THOSE DAYS IF THE MODELS VERIFY.

AVIATION...VFR CONDS WILL PREVAIL ACROSS THE LOCAL FLYING AREA THRU
THE FCST PERIOD. HOWEVER SOME CLOUDINESS ACROSS W-NW PR WITH
VCSH/VCTS STILL PSBL OVR WRN PR NR TJMZ AND TJBQ TIL 23/22. CU LINES
MAY DEVELOP OVR WRN PORTIONS OF THE ADJACENT ISLANDS AND STREAM
FURTHER W OVER THE COASTAL WATERS...WITH FEW TCU EN ROUTE BTW LOCAL
ISLANDS. EARLIER TJSJ 23/12Z UPPER AIR SOUNDING SHOWED WND 10-15 KTS
BLO FL150...BECOMING FM NNE AND INCR W/HT ABV FL200.

MARINE...SEAS 2-4 FEET AND WINDS 15 KNOTS OR LESS CAN BE EXPECTED
ACROSS THE REGIONAL WATERS OVER THE NEXT FEW DAYS. PULSES OF A SMALL
NORTHEASTERLY SWELL WILL CONTINUE TO REACH THE LOCAL ATLANTIC WATERS
AND PASSAGES THROUGH EARLY NEXT WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  77  89  76  90 /  40  40   0  20
STT  78  88  79  88 /  40  40  30  30

&&

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

$$

23/72





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