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000
FXCA62 TJSJ 191442
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1042 AM AST SUN MAY 19 2013

.UPDATE...ESSENTIALLY NOTHING TO ADJUST IN TODAYS FORECAST GRIDS.

&&

.DISCUSSION...TYPICAL TRADE WIND PATTERN TO PROBABLY PERSIST ALL
WEEK. BUT PRECIPITABLE WATER WILL INCREASE TUE/WED AS MID-LEVEL
FLOW BECOMES MORE PERSISTANTLY FROM SOUTHEAST.

PRECIPITABLE WATER TO BE SLIGHTLY LESS THAN IT WAS SAT AS WE HAVE
NO AREA OF HIGHER VALUES UPSTREAM TO PASS OVER LOCAL ISLANDS
VERSUS THE SMALL AREA THAT DEVELOPED JUST SOUTH OF USVI AND SPREAD
NORTHWEST YESTERDAY. SO IS HARD TO ARGUE FOR MORE THAN SCATTERED
AFTERNOON SHOWERS/ISOLATED THUNDER AT BEST.

OTHERWISE...TYPICAL AFTERNOON IN STORE WITH STREAMERS MOVING WEST
OF THE LARGER ISLANDS.

&&

.AVIATION...SEA BREEZES AND TRADES HAVE GRADUALLY BECOME DOMINANT
WINDS LATE THIS MORNING AND EXPECT THEY WILL CONTINUE THROUGH
AFTERNOON. STREAMERS MIGHT BE A FACTOR FOR SOME OF THE ISLANDS BUT
MAINLY DOWNWIND OF TIST/TISX/TNCM/TKPK. LESS THAN VFR CONDITIONS
APPEAR UNLIKELY FOR ANY OF THE TAF SITES THROUGH AFTERNOON.

&&

.MARINE...SEAS TO CHANGE LITTLE NEXT COUPLE OF DAYS. WINDS NOT
ENOUGH TO INCREASE WAVES VERY MUCH THOUGH SMALL CRAFT SHOULD BE
CAUTIOUS.

&&

.PREV DISCUSSION... /ISSUED 429 AM AST SUN MAY 19 2013/

SYNOPSIS...SURFACE HIGH PRESSURE EXTENDING SOUTHWARDS FROM THE
NORTHEASTERN ATLANTIC...WILL BE RE ENFORCED BY A SECONDARY AREA OF
HIGH PRESSURE...WHICH WILL ENTER THE NORTHWESTERN ATLANTIC LATER
TODAY...THEN SPREAD SOUTHWARDS INTO THE SOUTHWEST ATLANTIC.
SLIGHTLY AMPLIFIED MID TO UPPER LEVEL TROUGH JUST WEST OF THE AREA
AND HIGH PRESSURE RIDGE EXTENDING ACROSS THE LESSER ANTILLES INTO
THE EASTERN CARIBBEAN...WILL MAINTAIN A DOMINANT WEST TO SOUTHWEST
WIND FLOW ALONG WITH A FAIRLY DRY AND CONVERGENT UPPER LEVEL
PATTERN ACROSS THE REGION THROUGH AT LEAST MONDAY. UPPER TROUGH IS
TO THEN SHIFT EASTWARD ACROSS THE REGION BY THURSDAY AND DURING
THE LATTER PART OF THE WORK WEEK.

DISCUSSION...THE OVERALL PATTERN CONTINUES TO BE INFLUENCED BY
HIGH PRESSURE NORTH OF THE AREA. EXPECT THE LOCAL PRESSURE GRADIENT
TO TIGHTEN ACROSS THE REGION...AS THE SURFACE HIGH BUILDS NORTH
OF THE AREA BY MID WEEK. THIS WILL CREATE MODERATE TO STRONG TRADE
WINDS. WEAK PERTURBATIONS MOVING WESTWARD IN THE PREVAILING WIND
FLOW WILL HELP TRANSPORT SHALLOW PATCHES OF LOW LEVEL TRADE WIND
MOISTURE ACROSS THE REGION FROM TIME TO TIME. EXPECT ONLY A FEW
PASSING SHOWERS TO AFFECT THE LOCAL WATERS DURING THE MORNING
HOURS...FOLLOWED BY SOME BRIEF SHOWERS AND POSSIBLY AN ISOLATED
THUNDERSTORM DURING THE AFTERNOON MAINLY OVER THE INTERIOR SECTIONS
OF PUERTO RICO. LIMITED OR NO SHOWER ACTIVITY IS EXPECTED OVER THE
VIRGIN ISLANDS TODAY.

LATEST GPS DERIVED IPW AND LAYERED PRECIPITABLE WATER PRODUCTS
SHOWED A GRADUAL DECLINE IN PRECIPITABLE WATER DURING THE PAST 24
HOURS. EXPECT THIS DECREASING TREND TO CONTINUE AT LEAST THROUGH
TUESDAY. EXPECT TROPICAL MOISTURE TO INCREASE ONCE AGAIN BY MID
WEEK AND INTO THE UPCOMING WEEKEND AS A LOW LEVEL CONVERGENCE ZONE
IS FORECAST TO DEVELOP ACROSS THE EASTERN CARIBBEAN...THEN LIFT
NORTHWARD ACROSS THE AREA. THIS ALONG WITH THE PROXIMITY OF THE
UPPER LEVEL TROUGH WILL RESULT IN BETTER CHANCE FOR ENHANCED EARLY
MORNING AND AFTERNOON CONVECTION. IN ADDITION BY LATE FRIDAY INTO
SATURDAY MODEL GUIDANCE ALSO SUGGESTS THAT AN EASTERLY WAVE WILL
ENTER THE EASTERN CARIBBEAN AND MOVE SOUTH OF THE AREA. THIS MAY
ALSO INCREASE THE CHANCES FOR MORE SHOWER ACTIVITY ACROSS THE
REGION. WILL HOWEVER CONTINUE TO MONITOR AND SEE HOW THIS UNFOLDS.

AVIATION...MOSTLY VFR CONDITIONS EXPECTED AT ALL TAF SITES UNTIL
19/16Z. MVFR AND POSSIBLE BRIEF IFR CONDITIONS WILL REMAIN LIKELY
BETWEEN 19/17Z-18/21Z ALONG THE CORDILLERA CENTRAL AND ACROSS TJMZ
AND TJBQ IN AREAS OF +SHRA/TSRA. MOUNTAINS TOPS MAY BE OBSCURED OVER
WRN INTERIOR OF PR. FOR TAF SITES ACROSS THE NORTHERN LEEWARD
ISLANDS...MAINLY VFR CONDITIONS ARE EXPECTED. TJSJ 19/00Z SOUNDING
INDICATES AND EASTERLY WIND FLOW AT 20 KNOTS OR LESS UP TO 15
KFT...BECOMING WESTERLY AND STRONGER ABOVE 15KFT.

MARINE...SMALL CRAFT SHOULD EXERCISE CAUTION DUE TO WINDS OF UP TO
19 KNOTS. SEAS ARE EXPECTED TO REMAIN AT 5 FEET OR LESS. THIS GENERAL
PATTERN IN MARINE CONDITIONS IS EXPECTED FOR THE NEXT FEW DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  77  86  76 /  20  20  20  20
STT  87  77  87  78 /  20  20  20  30

&&

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

$$

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