
000
FXCA62 TJSJ 060943
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
543 AM AST TUE APR 6 2010
.SYNOPSIS...AT UPPER LEVELS...THE CORE OF THE SUB TROPICAL JET WITH 90
KNOTS OF WIND LIES OVER THE U.S. VIRGIN ISLANDS. SEVERAL SHORT
WAVES WILL MOVE THROUGH. THE FIRST HAS JUST PASSED. THE SECOND
SHOULD PASS MID-MORNING ON WEDNESDAY AND THE THIRD LATE WEDNESDAY
NIGHT. A BREAK IN THE JET WILL SIGNAL RIDGING OVER THE AREA...BUT
THE JET WILL RE-FORM JUST NORTH OF THE AREA ON SATURDAY AND THE
JET CORE WILL APPROACH THE LOCAL AREA AGAIN BY THE FOLLOWING
THURSDAY AS A SHORT WAVE TROUGH MOVES INTO THE BAHAMAS.
AT MID LEVELS...A TROUGH FROM A RECEDING LOW PRESSURE TO THE
NORTHEAST WILL REMAIN OVER PUERTO RICO AND THE U.S. VIRGIN ISLANDS
THROUGH FRIDAY...THOUGH LITTLE MOISTURE IS PRESENT AT MID LEVELS
UNTIL THEN. THERE IS A MOISTURE BREAK ON SUNDAY AND THEN MID-
LEVELS MOISTEN UP CONSIDERABLY. A SHORT WAVE TROUGH FORMS MONDAY
BUT DOES NOT REACH THE LOCAL AREA BY THE FOLLOWING FRIDAY.
AT LOWER LEVELS...NORTHEASTERLY FLOW OVER THE AREA IS KEEPING
TEMPERATURES COOL. BANDS OF MOISTURE ARE SENDING SHOWERS OVER THE
LOCAL AREA NORTH OF THE CORDILLERA CENTRAL WITH AMOUNTS GENERALLY
LESS THAN ONE TENTH INCH. HIGH PRESSURE WILL REMAIN OVER THE
WESTERN ATLANTIC UNTIL WEDNESDAY AND THEN MOVE FROM THERE TO THE
CENTRAL ATLANTIC WEDNESDAY THROUGH FRIDAY. THE LOW PRESSURE THEN
MOVES QUICKLY NORTHEAST AND ANOTHER HIGH OVER MISSISSIPPI MOVES
INTO THE WESTERN ATLANTIC BY MONDAY. A WEAK INVERTED TROUGH CAN BE
SEEN OVER HAITI OVER NEXT WEEKEND AND PUERTO RICO BY THE FOLLOWING
WEDNESDAY.
&&
.DISCUSSION...NORTHEASTERLY FLOW IS BRINGING BANDS OF MOISTURE
THROUGH THE AREA AND SCATTERED TO NUMEROUS SHOWERS HAVE BEEN
PUSHING ONSHORE OVER PUERTO RICO'S NORTHERN COAST. SOME SHOWERS
HAVE ALSO BEEN NOTED OVER SAINT THOMAS AND SAINT CROIX. UP TO 5 AM
AMOUNTS HAD BEEN LESS THAN 5 HUNDREDTHS OF AN INCH ANYWHERE...BUT HEAVIER
SHOWERS HAVE COME ON SHORE SINCE. THE NAM HAS HAD A HEALTHY HANDLE
ON THIS DEVELOPMENT AND IS SHOWING MUCH DRIER AIR ENTERING THE
ISLAND DURING THE AFTERNOON. THE NEXT BAND OF MOISTURE HEADS
TOWARD THE MONA CHANNEL ON WEDNESDAY AND THE FOLLOWING BAND MOVES
THROUGH THE U.S. VIRGIN ISLANDS AND THEN PUERTO RICO ON THURSDAY.
SHORT WAVES TRAVELING THROUGH THE UPPER LEVEL JET WILL HELP THE
DYNAMICS SOME...BUT SHOWERS ARE SHALLOW AND MOISTURE IS GENERALLY
LACKING IN THE MID LEVELS...EXCEPT BRIEFLY ON FRIDAY AND THEN NEXT
WEEK. THE SHORT WAVE TODAY MAY ENHANCE THE AFTERNOON
CONVECTION...YIELDING ISOLATED THUNDERSTORMS.
&&
.AVIATION...
VCSH OR PASSING SHRA EXPECTED ACROSS TJSJ..TJBQ...TIST
AND TNCM THROUGH 06/14Z...RESULTING IN BRIEF PERIODS OF MVFR...BUT
OVERALL...PREVAILING VFR CONDITIONS EXPECTED ACROSS ALL TAF SITES
FOR NEXT 24 HOURS...EXCEPT IN WESTERN PUERTO RICO WHERE MVFR CIGS
AND MOUNTAIN OBSCURATIONS WILL BE FOUND FROM AROUND 06/17Z TO
06/23Z.
&&
.MARINE...SEAS WILL INCREASE BY WEDNESDAY AND SMALL CRAFT
ADVISORIES WILL GO UP THEN AND SPREAD SOUTHWARD THROUGH THE
PASSAGES BEGINNING THURSDAY. THE WAVE WATCH SHOWS PERIOD AROUND 6
SECONDS SO WAVES COULD BE QUITE STEEP AND ROUGH.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 84 72 86 74 / 40 20 30 30
STT 85 74 86 76 / 30 20 20 20
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
&&
$$
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