Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 020917
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
517 AM AST TUE SEP 2 2014

.SYNOPSIS...AT UPPER LEVELS...THE AXIS OF HIGH PRESSURE WILL CROSS
THROUGH THE LOCAL AREA FROM THE EAST AS LOW PRESSURE OVER THE
BAHAMAS MOVES WEST. ANOTHER LOW PRESSURE NORTH OF THE AREA WILL
SINK SOUTH TO ABOUT 25 NORTH BY SUNDAY. THIS LOW WILL MOVE
NORTHWEST AND THEN BACK TO CUBA DURING THE FOLLOWING WEEK.

AT MID LEVELS...HIGH PRESSURE JUST NORTH OF THE LOCAL AREA WILL
RETREAT TO FLORIDA LEAVING A WEAK RIDGE OVER THE AREA. WEAK LOW
PRESSURE WILL APPEAR OVER THE WEEKEND. HIGH PRESSURE WILL THEN
RIDGE IN WEAKLY FROM THE NORTH AND NORTHEAST NEXT WEEK.

AT LOWER LEVELS...HIGH PRESSURE CONTINUES IN THE WESTERN ATLANTIC
THIS WEEK AND INTO THE NEXT. MOISTURE FROM A TROPICAL WAVE THAT
HAS CROSSED THROUGH THE AREA OVERNIGHT WILL MOVE THROUGH TODAY AND
LINGER INTO WEDNESDAY. A SECOND TROPICAL WAVE WILL MOVE THROUGH ON
FRIDAY WITH MOISTURE ON BOTH SIDES OF ITS AXIS WHILE A THIRD WILL
PULL THROUGH THE AREA ON SATURDAY NIGHT KEEPING THE PERIOD
THURSDAY THROUGH SUNDAY RELATIVELY WET. MOISTURE LINGERS THROUGH
MID WEEK NEXT WEEK.

&&

.DISCUSSION...THE MIMIC PRODUCT SHOWED A STRONG GRADIENT OF
MOISTURE MOVING THROUGH SAINT CROIX...SAINT THOMAS AND SAINT JOHN
EARLIER MONDAY NIGHT AS A BAND OF MOISTURE APPROACHES. THERE WERE SHOWERS
ON THE LEADING EDGE. AT 5 AM AST THESE SHOWERS HAD CROSSED THROUGH
THE WATERS SURROUNDING VIEQUES AND CULEBRA AND WERE ABOUT TO ENTER
PUERTO RICO. THE BAND OF MOISTURE RESPONSIBLE FOR THE SHOWER
ACTIVITY IS ABOUT 180 MILES WIDE AND WILL NOT HAVE COMPLETED ITS
TRANSIT OF PUERTO RICO BY LATE THIS AFTERNOON. HENCE...THE WAVE
WILL ENHANCE SHOWERS AND THUNDERSTORMS DURING THE DAY IN EASTERN
PUERTO RICO AND THIS AFTERNOON IN WESTERN PUERTO RICO. ALTHOUGH
RAINFALL AMOUNTS WILL LIKELY NOT BE EXTREME DUE TO THE GOOD
MOVEMENT OF THE SHOWERS THROUGH THE AREA...SOME AREAS MAY RECEIVE
AMOUNTS HEAVY ENOUGH TO CAUSE LOCAL URBAN AND SMALL STREAM
FLOODING. ALSO THE CULEBRINAS RIVER REACHED FLOOD STAGE OVERNIGHT
MONDAY AND MAY DO SO AGAIN TONIGHT AS WIND FLOW HAS NOT CHANGED
SUBSTANTIALLY SINCE YESTERDAY...BUT MOISTURE HAS INCREASED. IN
GENERAL FLOODING WAS VERY MINOR AND THE PUERTO RICO EMERGENCY
MANAGEMENT AGENCY DID NOT REPORT ANY CLOSED ROADS DURING THE
NIGHT. MOISTURE WILL NOT DIMINISH RAPIDLY TONIGHT ALLOWING SHOWERS
TO CONTINUE FORMING EVEN INTO THE EVENING...MAINLY OVER THE LOCAL
WATERS. SHOWERS AND MOISTURE LINGER INTO WEDNESDAY WITH A SHORT BREAK
LATE WEDNESDAY AND WEDNESDAY NIGHT...BUT MOISTURE AND INSTABILITY
BEGIN TO INCREASE ON THURSDAY WITH THE APPROACH OF THE NEXT WAVE.
THIS APPEARS TO HAVE THE MOST MOISTURE AND ALSO ITS PASSAGE WILL
COINCIDE WITH TEMPERATURES AT THE 500 MB LEVEL REACHING MINUS 8
DEGREES FRIDAY FOR ADDED INSTABILITY... ACCORDING TO THE GFS.
MOISTURE CONTINUES TO STREAM ACROSS PUERTO RICO AND THE U.S.
VIRGIN ISLANDS THURSDAY THROUGH WEDNESDAY...BUT FRIDAY AND SUNDAY
WILL HAVE THE MOST ACTIVE CONVECTION DUE TO THE TROPICAL WAVES
MOVING THROUGH THEN.

&&

.AVIATION...VFR CONDS AT LOCAL TAF SITES WITH VCSH AT TJSJ AND LOCAL
ISLANDS THRU MORNING HOURS. THEN TYPICAL AFTERNOON SHRA POSSIBLE WITH
CHANCE OF TSRA FOR TJMZ AND TJBQ TIL AROUND 02/21Z. WINDS E-SE AT
10-15 KTS FM SFC TO FL200 AFT 02/14Z...WITH SEA BREEZE VARIATIONS.
MTN OBSCURATIONS ARE EXPECTED THROUGHOUT THE PERIOD.

&&

.MARINE...SEAS WILL REACH 5 FEET IN PARTS OF OUR ATLANTIC WATERS
BETWEEN NOW AND THURSDAY NIGHT...BUT CONDITIONS IMPROVE
CONSIDERABLY AFTER THAT.`SEAS IN THE CARIBBEAN WILL REMAIN
GENERALLY 3 TO 5 FEET THROUGH EARLY NEXT WEEK. SMALL CRAFT
ADVISORIES ARE NOT EXPECTED DURING THE NEXT 7 DAYS...BUT
THUNDERSTORMS ARE EXPECTED WITH EACH OF THE WAVE
PASSAGES...ESPECIALLY FRIDAY THROUGH SUNDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  78  89  79 /  60  40  40  50
STT  89  79  89  80 /  50  40  30  50

&&

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

$$

02/12




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