Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 231909
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
309 PM AST WED APR 23 2014

.SYNOPSIS...AT UPPER LEVELS...A WEAK RIDGE WITH NEARLY ZONAL FLOW
WILL PERSIST OVER THE EAST CENTRAL CARIBBEAN TODAY AND TOMORROW.
THEN A WEAK SHORT WAVE WILL PASS THROUGH PULLING THE SUB TROPICAL
JET SOUTH AND INTO THE A FORECAST AREA ON MONDAY. HIGH PRESSURE
WILL BUILD OVER THE AREA LATER NEXT WEEK.

AT MID LEVELS...HIGH PRESSURE OVER THE CARIBBEAN WILL GIVE WAY TO
A BROAD TROUGH FROM A LONG WAVE TROUGH THAT WILL DROP INTO THE
WESTERN ATLANTIC SUNDAY. HIGH PRESSURE WILL RE-BUILD FROM THE
WESTERN CARIBBEAN OVER THE AREA AFTER WEDNESDAY OF NEXT WEEK.

AT LOWER LEVELS...HIGH PRESSURE IN THE EASTERN ATLANTIC IS
RETREATING TOWARD THE NORTHEAST WHILE A STRONG LOW PRESSURE MOVING
EAST SOUTHEAST OUT OF MAINE WILL ROTATE AROUND ANOTHER ALREADY
NORTH OF THE AREA AND MOVE NORTHEAST. THIS WILL ALLOW WEAK HIGH
PRESSURE TO DROP SOUTHEAST OUT OF THE UNITED STATES INTO THE
ATLANTIC JUST NORTHWEST OF THE AREA AND CLOSE THE SADDLE IN THE
RIDGE FROM THE HIGH PRESSURE IN THE EASTERN ATLANTIC. ANOTHER HIGH
WILL MOVE INTO THE ATLANTIC A LITTLE MORE NORTH OF THE AREA AND
REPEAT THE CYCLE. THIS WILL KEEP LOW LEVEL WINDS EAST SOUTHEAST TO
SOUTHEAST THROUGH NEXT WEEK. AFTER FRIDAY...MOISTURE WILL BE
LIMITED.


&&

.DISCUSSION...SMALL SHALLOW SHOWERS DEVELOPED AFTER NOON ACROSS
PUERTO RICO FROM ANASCO TO COROZAL. A STREAMER ALSO DEVELOPED WELL
DOWN STREAM FROM SAINT CROIX TO THE WESTERN END OF SAINT THOMAS IN
SOUTH SOUTHEAST FLOW. SHOWERS WILL ABATE EARLY AS GFS MODEL SHOWS
A MOISTURE MINIMUM OVERNIGHT...FOLLOWED BY THE BEST MOISTURE OF
THE NEXT 7 DAYS LATE AFTERNOON ON THURSDAY. MOISTURE REMAINS
RELATIVELY LIMITED DURING THE REST OF THE WEEK AS WEAK UPPER AND
LOWER FEATURES PLAY OUT OVER THE AREA...INCLUDING THE
FOREMENTIONED JET STREAM AND THE SERIES OF SURFACE HIGHS THAT
KEEP GENTLE TO MODERATE TRADE WINDS OVER THE AREA. DURING THIS
TIME NO WIDESPREAD PRECIPITATION IS EXPECTED NOR ORGANIZED LOCAL
CONVECTION AS HIGH PRESSURE DOMINATES THE AREA. MOISTURE DOES
EXHIBIT ONE POP AS A WEAK UPPER LEVEL TROUGH MOVES THROUGH THE
AREA AND WOULD EXPECT A SLIGHTLY BETTER CHANCE OF A SHOWER THEN
SUNDAY NIGHT AND MONDAY.

&&

.AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS THE LOCAL
FLYING AREA THROUGH THE FORECAST PERIOD. EXPCT BRIEF PERIODS OF MVFR
CONDITIONS IN -SHRA AND LOCAL MOUNTAIN OBSCURATIONS...AFFECTING TJMZ
AND TJBQ THROUGH ABOUT 23/21Z. LOW LEVEL WINDS WILL BE MAINLY
SOUTHEAST AT 10 TO 15 KTS...WITH SEA BREEZE VARIATIONS.

&&

.MARINE...SEAS WILL CONTINUE TO DIMINISH SLIGHTLY UNTIL
FRIDAY...BUT SEAS ARE NOT EXPECTED TO EXCEED 6 FEET AT ANY TIME
DURING THE NEXT 7 DAYS. MARINE WINDS WILL CONTINUE TO HAVE A
SOUTHERLY COMPONENT. WIND SPEED WILL INCREASE THROUGH THE END OF
NEXT WEEK BUT WINDS WILL REMAIN LOWER THAN USUAL WITH GENERALLY
LESS THAN 15 KNOTS.


&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  76  92  75  92 /  10  30  10  20
STT  77  85  78  85 /  20  20  10  10

&&

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

$$

15/12




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