Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 040147
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
947 PM AST THU SEP 3 2015

.UPDATE...LAST SHOWERS HAD DISSIPATED AROUND 7 PM AST...BUT ONE
PERSISTENT SHOWER GREW JUST AFTER THAT AND DID NOT DISSIPATE
UNTIL AROUND 9:10 PM AST.

&&

.DISCUSSION...LATEST SOUNDING AT 04/00Z SHOWED LITTLE CHANGE
DURING LAST 24 HOURS...BUT LIFTED INDEX AND PRECIPITABLE WATER
WERE BOTH POINTING TO SLIGHTLY BETTER STABILITY. MODELS SHOW
INCREASING 500 MB TEMPERATURES AND HENCE A LESS EXPLOSIVE
ATMOSPHERE FOR TOMORROWS NEXT ROUND OF SHOWERS. HOWEVER...MOISTURE
WILL HAVE DIMINISHED VERY LITTLE BY THEN FROM TODAY AND WOULD
EXPECT SHOWERS TO BE VERY HEAVY WHERE THEY DEVELOP. MIMIC PRODUCT
ALSO SHOWS MOISTURE CIRCLING AROUND TO THE NORTHEAST OF THE AREA
AND ENTERING SOME NORTHEAST FLOW AT 700 MB THAT WILL ALSO ENHANCE
THE MOISTURE OVER THE AREA AT MAX HEATING FRIDAY. SINCE SURFACE
WINDS WILL BE A LITTLE STRONGER FROM THE EAST TOMORROW THAN THEY
WERE TODAY...SHOWERS MAY MOVE A LITTLE FARTHER WEST. ALTHOUGH
STABILITY WILL HAVE INCREASED...THE CENTER OF THE UPPER LEVEL LOW
IS STILL VERY CLOSE AND ONLY A LITTLE FILLING HAS OCCURRED...
THEREFORE HAVE UPPED POPS IN THE INTERIOR OF PUERTO RICO AND
INCREASED THE LIKELIHOOD OF THUNDERSTORMS THERE. MOST COASTAL
AREAS WILL STILL HAVE ONLY A SLIGHT CHANCE OF SHOWERS OR
THUNDERSTORMS.

&&

.AVIATION...VFR CONDS EXPECTED THROUGH 04/16Z ACROSS THE  LOCAL
TERMINALS. LIGHT AND VRB WINDS THROUGH 04/13Z...BECOMING EASTERLY
WITH SEA BREEZE VARIATIONS THEREAFTER. +TSRA EXPECTED ACROSS
PORTIONS OF PUERTO RICO...ESPECIALLY THE INTERIOR...AFTER 04/16Z
WHICH WILL CAUSE MTN OBSCURATIONS AND LIKELY AFFECT THE VICINITY OF
TJBQ/TJMZ/TJPS/TJSJ AND POSSIBLY THE STATIONS THEMSELVES. WX CONDS
IMPROVING AFTER 04/23Z...LEAVING VFR CONDS AND LIGHT WINDS ONCE
AGAIN.

&&

.MARINE...GENTLE TO MODERATE WINDS WITH SEAS OF 3 FEET OR LESS
WILL CONTINUE INTO EARLY NEXT WEEK. NO CAUTIONS OR ADVISORIES
FORESEEN NEXT 7 DAYS.

&&

.PREV DISCUSSION... /ISSUED 406 PM AST THU SEP 3 2015/

SYNOPSIS...TUTT WILL CONTINUE TO MEANDER OVER AND NORTH OF
THE LOCAL ISLANDS THROUGH SUNDAY WITH MID LEVEL HIGH PRESSURE
BUILDING IN FROM THE EAST. WEAK SURFACE HIGH NORTH OF THE AREA
WILL MAINTAIN A LIGHT TO GENTLE EAST SOUTHEAST WIND FLOW THROUGH
SATURDAY...BECOMING MODERATE EARLY NEXT WEEK.

DISCUSSION...STRONG THUNDERSTORMS DEVELOPED ACROSS THE CENTRAL
INTERIOR WITH HAIL AND STRONG GUSTY WINDS REPORTED. THESE SHOWERS
AND THUNDERSTORMS WILL CONTINUE OVER THE NEXT FEW HOURS BUT
DIMINISHING NEAR SUNSET. TUTT WILL CONTINUE TO MEANDER OVER AND
NORTH OF THE LOCAL ISLANDS THROUGH SUNDAY WHILE WEAKENING. AS
THIS FEATURE WEAKENS...MID TO UPPER LEVEL RIDGE WILL SLOWLY BUILD
ACROSS THE AREA. MID TO UPPER LEVEL RIDGE WILL THEN HOLD THROUGH
AT LEAST MIDWEEK NEXT WEEK. WEAK SURFACE HIGH NORTH OF THE AREA
WILL MAINTAIN A LIGHT TO GENTLE EAST SOUTHEAST WIND FLOW THROUGH
SATURDAY... BECOMING MODERATE EARLY NEXT WEEK. UNDER THE PROXIMITY
OF TUTT AND SEA BREEZE REGIME...EXPECT GOOD AFTERNOON CONVECTION
EACH AFTERNOON OVER THE CORDILLERA CENTRAL THOUGHT AT LEAST
SUNDAY. TROPICAL WAVE NEAR 46W WILL REACH THE FORECAST AREA LATE
SUNDAY/EARLY MONDAY. BUT LACKING UPPER LEVEL SUPPORT THIS IS TO
ONLY FAVOR LIGHT TO MODERATE RAINFALL AMOUNTS. LATEST GUIDANCE
SUGGESTED A VIGOROUS TROPICAL WAVE MOVING ACROSS THE AREA BY THE
END OF NEXT WEEK.

AVIATION...MAINLY VFR CONDS ACROSS ALL TAF SITE. MOUNTAIN OBSC
WITH TSRA ARE POSSIBLE OVER THE CORDILLERA CENTRAL...SOME OF OF
THIS SHRA/TSRA ARE POSSIBLE OVER TJBQ/TJMZ/TJSJ AFT 03/18Z. AFT
0323Z...LIGHT PASSING SHOWERS MAY BE POSSIBLE OVER
TIST/TISX/TJSJ/TNCM/TKPK FROM TIME TO TIME. WINDS FROM THE EAST-
SOUTHEAST AT 10 TO 15 MPH WITH SEA BREEZE VARIATIONS...AND LOCALLY
HIGHER IN/NEAR TSRA/SHRA. FOLLOWED BY CALM TO LIGHT AND VARIABLE
WINDS AND LAND BREEZE VARIATIONS ALONG THE COASTAL SECTIONS AFT
0323Z.

MARINE...TRANQUIL MARINE CONDITIONS EXPECTED OVER THE NEXT FEW
DAYS WITH SEAS 4 FEET OR LESS AND WINDS UP TO 10 KNOTS THROUGH
SATURDAY. WINDS EXPECTED TOO BECOME MODERATE EARLY NEXT WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  92  78  92  78 /  20   0  20  30
STT  88  78  89  79 /  20  10  20  30

&&

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

$$

25/12


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