385
FXCA20 KWBC 111246
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
846 AM EDT TUE JUL 11 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
11/12UTC: LINGERING SAHARAN DUST WILL KEEP THINGS RELATIVELY DRY
TODAY...BUT THE SAHARAN DUST IS EXPECTED TO CLEAR TONIGHT WHILE
AN APPROACHING TROPICAL WAVE WILL CAUSE MOISTURE AND SHOWER
ACTIVITY TO INCREASE. THROUGH THE DAY WEDNESDAY...PRECIPITABLE
WATER IS FORECAST TO INCREASE SIGNIFICANTLY...PEAKING NEAR TWO
STANDARD DEVIATIONS ABOVE NORMAL BY WEDNESDAY EVENING. ALTHOUGH
THE DIFFERENT MODEL GUIDANCE IS PROVIDING CONFLICTING
SOLUTIONS...SIGNIFICANT SHOWER ACTIVITY IS EXPECTED ON WEDNESDAY
INTO WEDNESDAY NIGHT...THE HIGHEST AMOUNTS OF RAIN BEING EXPECTED
ACROSS EASTERN PR. SAHARAN DUST WILL RETURN EARLY ON
THURSDAY...CAUSING ANOTHER DRYING TREND FOR THE LATTER PART OF THE
WORKWEEK. THERE WILL BE A WEAK TRADE WIND INVERSION AT AROUND 800
HPA TODAY...THEN A MUCH STRONGER INVERSION IS EXPECTED FROM
THURSDAY AFTERNOON INTO THE WEEKEND. DURING THE 5-DAY
PERIOD...WEDNESDAY IS EXPECTED TO BE THE RAINIEST DAY AND FRIDAY
THE DRIEST.
AN ELONGATED SFC HIGH PRESSURE EXTENDING ACROSS THE TROPICAL
ATLANTIC WILL KEEP E-ESE WINDS DURING THE NEXT 5 DAYS...WITH THE
EXCEPTION OF THE INFLUENCE FROM THE TROPICAL WAVE ON WEDNESDAY.
IT WILL BE BREEZY ACROSS THE LOCAL ISLANDS LATE TONIGHT INTO EARLY
WEDNESDAY...JUST AHEAD OF THE TROPICAL WAVE...WITH WINDS AROUND
20-22 KNOTS ACROSS THE LOCAL WATERS AND COASTAL AREAS. A WEAK MID
LEVEL HIGH PRESSURE IS EXPECTED TO MEANDER ACROSS THE TROPICAL
ATLANTIC THIS WEEK. IN THE UPPER LEVELS...MODEL GUIDANCE INSISTS
IN A NARROW TROUGH EAST OF PR SLOWLY WEAKENING TODAY...THEN A LOW
PRESSURE WILL DEVELOP SSW OF PR BY WEDNESDAY...THEN WILL MOVE WEST
ACROSS THE CARIBBEAN SEA. SOUTHERLY WINDS IN THE UPPER LEVELS ARE
EXPECTED ACROSS THE LOCAL ISLANDS ON WEDNESDAY INTO
THURSDAY...COINCIDING WITH THE APPROACHING TROPICAL WAVE.
THE AVAILABLE MOISTURE WILL BE NEAR NORMAL TODAY THROUGH EARLY
WEDNESDAY...WITH PRECIPITABLE WATER RANGING NEAR 1.6 INCHES. ABOVE
NORMAL PRECIPITABLE WATER IS FORECAST BY WEDNESDAY AFTERNOON...AND
PRECIPITABLE WATER IS EXPECTED TO PEAK NEAR 2.3 INCHES BY
WEDNESDAY EVENING. MOISTURE WILL THEN DECREASE RAPIDLY BY THURSDAY
AFTERNOON INTO FRIDAY...WITH PRECIPITABLE WATER FALLING TO AROUND
1.6 INCHES ON THURSDAY AFTERNOON AND THEN FURTHER DOWN TO NEAR 1.4
INCHES BY FRIDAY AFTERNOON. AN INCREASE IN MOISTURE IS EXPECTED
ON SATURDAY...WITH PRECIPITABLE WATER POSSIBLY REACHING 2 INCHES.
FOR TODAY...THE OVERALL WEATHER IS EXPECTED TO BE RELATIVELY DRY
AND A BIT HAZY. ISOLATED SHOWERS AND BRIEF AND ISOLATED AFTERNOON
CONVECTION ACROSS WESTERN PR IS FORECAST...BUT RAINFALL
ACCUMULATIONS ARE EXPECTED TO BE UNDER A QUARTER OF AN INCH...WITH
POSSIBLY HIGHER AMOUNTS ACROSS VERY ISOLATED AREAS OF WESTERN PR.
WEDNESDAY...WITH THE AFOREMENTIONED TROPICAL WAVE...SIGNIFICANT
RAINFALL IS EXPECTED. MODEL GUIDANCE SOLUTIONS ARE DIFFERING TO A
DECENT EXTENT FROM EACH OTHER. EVEN THOUGH THEY SEEM TO AGREE THAT
EASTERN PR WILL SEE SIGNIFICANT RAIN...THE RAIN AMOUNTS AND ALSO
THE MAX RAIN LOCATION VARIES. THE GFS MODEL FAVORS THE HIGHEST
RAINFALL ACROSS EASTERN AND NORTHWESTERN PR. THE ECMWF FAVORS
EASTERN AND SOUTHERN PR...AS WELL AS THE USVI. THE ECMWF SOLUTION
IS MORE CONSISTENT WITH THE IMPACT THESE TROPICAL WAVES HAVE HAD
IN THE PAST SEVERAL WEEKS. THAT BEING SAID...THE REASON WHY THE
GFS FAVORS CONVECTION ACROSS NW-PR IS THAT IT HAS LESS CLOUD COVER
EARLY IN THE DAY...BEFORE THE DEEP MOISTURE AND ESE WINDS COME IN
LATER ON WEDNESDAY. HOWEVER...ACCORDING TO THE LATEST SATELLITE
IMAGERY...THE TROPICAL WAVE HAS SIGNIFICANT CLOUD COVER AND
THUNDERSTORM ACTIVITY. THE OTHER MODEL SOLUTIONS AND BLENDS ALL
HAVE THEIR OWN VERSION OF WHERE THE HIGHEST AMOUNTS OF RAIN WILL
BE. THEREFORE...CONSIDERING THE MODEL GUIDANCE AND RECENT HISTORY
WITH TROPICAL WAVES...OUR FORECAST FAVORS OVER 2 INCHES OF RAIN
ACROSS A GOOD PORTION OF EASTERN PR...WITH ONE INCH OR MORE ACROSS
CENTRAL TO W-SW PR. WE ALSO INCREASED THE AMOUNTS ACROSS NORTH
CENTRAL TO NORTHWESTERN PR...WITH AROUND 0.50 INCHES IN THE
FORECAST. THE NORTHERN USVI ALSO SAW AN INCREASE IN THE RAINFALL
FORECAST...0.50 TO 0.75 INCHES...WHILE SAINT CROIX IS FORECAST
UNDER A HALF AN INCH OF RAIN. GIVEN THE MODEL
DISCREPANCY...CONFIDENCE IS A BIT LOWER THAN TYPICAL...BUT THERE
IS HIGH CONFIDENCE THAT THERE WILL BE SIGNIFICANT RAINFALL ACROSS
EASTERN PR.
THE 5-DAY RAINFALL TOTALS ARE FORECAST TO BE 3 TO 3.25 INCHES
ACROSS EASTERN PR...AND 1.75 TO 2 INCHES ACROSS WESTERN PR. FOR
THE USVI...BETWEEN 0.5 AND 1 INCH IS FORECAST.
ALAMO/GALVEZ...WPC (USA)
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page