211
FXCA20 KWBC 191414
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
913 AM EST THU DEC 19 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI DEC 19/14UTC:
THE AVAILABLE MOISTURE WILL REMAIN ABOVE NORMAL FOR THE NEXT
WEEK...WITH PRECIPITABLE WATER VALUES NEAR 1.8 TO 2.0 INCHES. THE
ABOVE NORMAL MOISTURE WILL REACH THE MID LEVELS...WITH GUIDANCE
ALSO SUGGESTING ABOVE NORMAL RELATIVE HUMIDITY IN THE 850-700MB
AND 700-500MB LAYERS FOR THE NEXT SEVERAL DAYS. THE LOW LEVEL
WINDS WILL BE MAINLY EASTERLY TODAY...BUT WILL BE MORE ESE ON
FRIDAY...THEN LIGHTER AND MORE SOUTHEASTERLY THIS WEEKEND...AS A
FRONTAL BOUNDARY MOVES EAST FROM THE WESTERN ATLANTIC LATE THIS
WEEK INTO THE CENTRAL ATLANTIC BY MONDAY. THE LOCAL WINDS WILL
BECOME EAST NORTHEASTERLY FROM MONDAY ONWARD...AFTER THE FRONT
PASSES TO THE NORTH OF PR/USVI.
THERE IS A MID LEVEL HIGH PRESSURE ACROSS THE CARIBBEAN...WHICH
WILL SLOWLY MOVE EAST AND OVER THE LOCAL ISLANDS LATE THIS WEEK.
HOWEVER...A BROAD MID LEVEL TROUGH WILL MOVE INTO THE WESTERN
ATLANTIC...TO THE NORTH OF PR/USVI AND CAUSING LOCALLY STRONGER
WINDS IN THE MID LEVELS BUT NORTH OF THE LOCAL ISLANDS. THE
STRONGER WINDS TO THE NORTH MAY CAUSE A BRIEF MID LEVEL SHORTWAVE
TROUGH OVER PR/USVI ON SUNDAY...WHICH MAY CAUSE A BRIEF INCREASE
IN MID LEVEL DIVERGENCE SUNDAY INTO MONDAY. THAT BEING SAID...A
RIDGE PATTERN WILL RETURN ON MONDAY EVENING AND WILL PERSIST OVER
THE NEXT WORKWEEK. THE UPPER LEVELS WILL HAVE A SIMILAR
PATTERN...THOUGH THE LATEST GUIDANCE SHOWS A MORE GENERALIZED
RIDGE PATTERN OVER PR/USVI. THERE IS ALSO THE POSSIBILITY OF
RELATIVELY STRONG UPPER LEVEL WINDS TO THE NORTH OF PR/USVI...BUT
THE UPPER LEVEL WINDS OVER THE LOCAL ISLANDS MAY REMAIN AT AROUND
55 KNOTS OR LESS.
CONSIDERING THE HIGHER THAN NORMAL MOISTURE IN THE LOW TO MID
LEVELS AND THE VERY MARGINAL INSTABILITY...THE RAINFALL PATTERN
OVER PR IS EXPECTED TO BE THAT OF SCATTERED TO LOCALLY NUMEROUS
SHOWERS AFFECTING THE WINDWARD SIDE OF PR AND ACROSS THE
USVI...WITH THE POSSIBILITY OF ISOLATED THUNDERSTORMS AND SOME
SHOWERS BEING MODERATE TO LOCALLY HEAVY. AN INCREASE IN
INSTABILITY IS POSSIBLE ON SUNDAY AS A FRONTAL BOUNDARY MOVES
NORTH OF PR/USVI AND A SHORTWAVE MID LEVEL TROUGH DEVELOPS OVER
THE AREA...COMBINING WITH THE ABOVE NORMAL MOISTURE. ON
MONDAY...THE WINDS WILL SHIFT TO AN ENE DIRECTION...BUT THE EGDI
ALGORITHM STILL SUGGESTS THE POSSIBILITY OF ISOLATED
THUNDERSTORMS...WHICH THEN WOULD SUGGEST POSSIBLE CONVECTION ON
MONDAY AFTERNOON ACROSS THE SOUTHWEST QUADRANT OF PR. FROM LATE
MONDAY ONWARD...THE EGDI ALGORITHM SUGGESTS MAINLY SHALLOW
CONVECTION...WHICH WOULD FAVOR SOME RAINFALL ONCE AGAIN ON THE
WINDWARD SIDE OF PR AND OVER THE USVI.
ALAMO...WPC (USA)
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