497
FXCA20 KWBC 191255
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
855 AM EDT WED APR 19 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM APR
19/12UTC: THE AVAILABLE MOISTURE WILL BE CLOSE TO NORMAL OVER THE
NEXT 5 DAYS WITH THE EXCEPTION OF TODAY AS MOISTURE DECREASES TO
BELOW NORMAL BY THIS EVENING...BUT WILL GRADUALLY INCREASE AGAIN
OVERNIGHT INTO THURSDAY MORNING. THIS IS SUGGESTED BY THE LATEST
GUIDANCE...HAVING PRECIPITABLE WATER OF 1.5 INCHES THIS
MORNING...WHICH IS NORMAL...THEN DECREASING TO BELOW NORMAL AT 1.2
INCHES BY THIS EVENING. THE PRECIPITABLE WATER WILL THEN GRADUALLY
INCREASE TO NEAR NORMAL ON THURSDAY TO AROUND 1.4 INCHES...STAYING
BETWEEN 1.4 AND 1.6 INCHES THROUGH THE WEEKEND. AN UPPER LEVEL
RIDGE WILL BE OVER PR/USVI TODAY...WHILE MOVING EAST...WITH AN
UPPER LEVEL TROUGH APPROACHING THE AREA FROM THE WEST...WITH ITS
AXIS MOVING ACROSS PR/USVI BY SATURDAY AFTERNOON. THIS WILL CAUSE
STRONGER WINDS ALOFT...POSSIBLY OVER 70KT...AND CAUSING
DIVERGENCE. A MID LEVEL RIDGE IS ALSO PRESENT AND IS MOVING
EAST...WHILE A MID LEVEL TROUGH ALSO APPROACHES THE NORTHEAST
CARIBBEAN LATE FRIDAY AND SATURDAY. WEAK SURFACE HIGH PRESSURES
ACROSS THE CENTRAL AND WESTERN ATLANTIC WILL MAINTAIN AN EASTERLY
TO SOUTHEASTERLY WIND FLOW TODAY THROUGH FRIDAY...BUT A WEAK
SURFACE LOW WILL DEVELOP JUST EAST OF THE SOUTHERN BAHAMAS BY
SATURDAY...RELAXING THE LOCAL PRESSURE GRADIENT AND CAUSING LIGHT
WINDS INTO EARLY NEXT WEEK.
IN TERMS OF EXPECTED RAINFALL...LOCALLY INDUCED...AND TRADE WIND
SHOWERS ARE EXPECTED THROUGH THE REST OF THE WORKWEEK. GIVEN THE
DECREASE IN MOISTURE EXPECTED TODAY...THE RAINFALL AMOUNTS ARE
EXPECTED TO BE MODEST...WITH A MAX OF JUST OVER A HALF AN INCH OF
RAIN ACROSS NORTHWESTERN PR THIS AFTERNOON...AND UNDER A QUARTER
OF AN INCH ACROSS EASTERN PR AND PERHAPS A FEW HUNDREDTHS OF AN
INCH ACROSS THE USVI. A SIMILAR PATTERN AND RAINFALL ACCUMULATION
IS FORECAST FOR THURSDAY...AS THE MOISTURE...ALTHOUGH SLOWLY
INCREASING...IT IS STILL EXPECTED TO BE LIMITED. FRIDAY WILL START
TO CHANGE A LITTLE AS THE MOISTURE IS HIGHER BUT THE MID TO UPPER
LEVEL DYNAMICS MAY NOT BE QUITE THERE YET FOR SIGNIFICANT RAINFALL
DEVELOPMENT. HOWEVER...IF THE MODEL TIMING IS OFF...AND THE COLDER
500MB TEMPS AND THE INCREASE IN MID LEVEL RELATIVE HUMIDITY
REACHES THE ISLANDS DURING TIME OF PEAK HEATING...ISOLATED
THUNDERSTORMS COULD OCCUR ON FRIDAY. THAT SAID...THE WINDS ARE
GOING TO GRADUALLY DECREASE ON FRIDAY...AND THE LATEST MODEL
GUIDANCE IS SUGGESTING THAT THE AFTERNOON CONVECTION OVER PR WILL
BE ACROSS NORTH CENTRAL TO SLIGHTLY NORTHWESTERN PR...SO AREAS
FROM THE MUNICIPALITIES OF CIALES TO BARCELONETA...WEST TO LARES
AND CAMUY WOULD HAVE THE BEST CHANCE OF THUNDERSTORMS....BUT THERE
IS STILL SOME UNCERTAINTY SINCE TIMING WILL PLAY A SIGNIFICANT
ROLE. AS THE UPPER TROUGH CONTINUES TO APPROACH PR/USVI...THE EAST
SIDE OF THE TROUGH AXIS WILL PROVIDE THE BEST AREA FOR
CONVECTION...MEANING THAT CENTRAL TO EASTERN PR WOULD HAVE THE
HIGHEST RAINFALL ACCUMULATION ON SATURDAY AND SUNDAY.
ALAMO/ACOSTA...WPC (USA)
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page