631  
FXCA20 KWBC 211248  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
848 AM EDT FRI APR 21 2023  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR  
21/12UTC: THE AVAILABLE MOISTURE WILL BE BELOW NORMAL THIS  
MORNING...BUT WILL GRADUALLY START INCREASING LATER IN THE  
AFTERNOON. PRECIPITABLE WATER WILL BE NEAR 1.7 INCHES...WHICH IS  
NEAR THE 75TH PERCENTILE...BY SATURDAY MORNING. THE LATEST MODEL  
GUIDANCE KEEPS THE PRECIPITABLE WATER AT AROUND 1.6 INCHES THROUGH  
SUNDAY MORNING...THEN DROPPING TO NEARLY 2 STANDARD DEVIATIONS  
BELOW NORMAL ON SUNDAY NIGHT INTO MONDAY MORNING. AN UPPER LEVEL  
TROUGH IS APPROACHING THE AREA FROM THE WEST..WHICH WILL CAUSE  
INSTABILITY PARTICULARLY ON SATURDAY. THE APPROACHING TROUGH WILL  
CAUSE RELATIVELY STRONG WINDS ALOFT...OVER 70KT...CAUSING UPPER  
LEVEL DIVERGENCE. A MID LEVEL TROUGH ALSO APPROACHES THE NORTHEAST  
CARIBBEAN LATE FRIDAY NIGHT INTO SATURDAY. A SURFACE HIGH PRESSURE  
ACROSS THE WESTERN ATLANTIC WILL MAINTAIN AN EASTERLY TO  
SOUTHEASTERLY WIND FLOW THROUGH THIS AFTERNOON...BUT A SURFACE LOW  
WILL DEVELOP JUST EAST OF THE SOUTHERN BAHAMAS TONIGHT INTO  
SATURDAY...RELAXING THE LOCAL PRESSURE GRADIENT AND CAUSING LIGHT  
WINDS OVER PR/USVI STARTING STARTING THIS AFTERNOON...WITH LIGHT  
WINDS PREVAILING INTO MONDAY...WHEN THE SURFACE LOW WEAKENS AND  
DISSIPATES JUST NORTH OF PR. EASTERLY MODERATE WINDS ARE EXPECTED  
TO RETURN TO PR/USVI ON TUESDAY.  
 
LOCALLY INDUCED AND TRADE WIND SHOWERS ARE EXPECTED TODAY...WITH  
THE NORTHWESTERN QUADRANT OF PR HAVING THE BEST CHANCE OF  
OBSERVING AFTERNOON SHOWERS. THE RAINFALL TOTALS THIS AFTERNOON  
ARE EXPECTED TO RANGE GENERALLY BETWEEN 0.75 AND 1 INCH ACROSS  
AREAS NEAR AND BETWEEN CIALES WEST TO SAN SEBASTIAN. UNDER A  
QUARTER OF AN INCH EXPECTED ACROSS NORTHEASTERN PR AND PERHAPS A  
FEW HUNDREDTHS OF AN INCH ACROSS THE USVI. SATURDAY LOOKS LIKE A  
DAY WITH THE POTENTIAL OF MODERATE TO HEAVY RAIN AND A FEW  
THUNDERSTORMS AS THE UPPER TROUGH CONTINUES TO APPROACH PR/USVI  
AND THE AVAILABLE MOISTURE INCREASES TO ABOVE NORMAL LEVELS.  
CENTRAL TO EASTERN PR IS EXPECTED TO HAVE THE HIGHEST AMOUNTS OF  
RAIN ON SATURDAY AND SUNDAY AS THE MID AND UPPER TROUGH CONTINUES  
TO MOVE EAST. AT THIS TIME...THE FORECAST SUGGESTS A WIDE AREA  
FROM CENTRAL TO EASTERN PR RECEIVING OVER AN INCH OF RAIN ON  
SATURDAY...WITH SOME SECTIONS APPROACHING 2 INCHES OF RAIN. IF THE  
MODEL GUIDANCE VERIFIES...
SOME THUNDERSTORMS COULD PRODUCE  
ISOLATED HIGHER AMOUNTS. EARLY IN THE UPCOMING WORKWEEK...THE  
EASTERN SECTIONS OF PR ARE FORECAST TO RECEIVE THE HIGHEST AMOUNTS  
OF RAIN ON MONDAY AS LIGHT WINDS CONTINUE AND BECOME VARIABLE  
BEFORE TRANSITIONING TO EASTERLY WINDS ON TUESDAY.  
 
ALAMO...WPC (USA)  

 
 
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