958
FXCA20 KWBC 261240
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
840 AM EDT MON JUN 26 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUN
26/12UTC: AN UPPER TROUGH EXTENDS FROM 26N 64W INTO HISPANIOLA.
THE TROUGH IS DISCONNECTED FROM THE LOW-LEVELS...AS A MID-LEVEL
RIDGE AXIS EXTENDS FROM THE WESTERN CARIBBEAN ACROSS SOUTHERN
HISPANIOLA INTO PUERTO RICO. THIS IS ASSOCIATED WITH A TRADE WIND
CAP SITTING NEAR 800 HPA...AS EVIDENCED BY THE 00UTC SAN JUAN
SOUNDING. IN THE LOW-LEVELS...THE TRADES ARE FROM THE EAST WITH
SPEEDS OF 05-10KT. PRECIPITABLE WATER IS INCREASING BUT NEAR
AVERAGE...WITH VALUES IN THE ORDER OF 45MM. SATELLITE IMAGERY
SHOWS VERY LITTLE CLOUDINESS THIS MORNING. VERY ISOLATED LIGHT
RAIN SHOWERS ARE OCCURRING MOSTLY OFF THE COASTS OF SOUTHERN AND
NORTHERN PUERTO RICO. A ROBUST TROPICAL WAVE IS PROPAGATING NEAR
55W AND TO THE SOUTH OF 16N. POSITIVE INTERACTION BETWEEN THE WAVE
AND A DEVELOPING UPPER TROUGH WILL POTENTIALLY FAVOR MODERATE TO
HEAVY PRECIPITATION IN THE MID TO LATTER PART OF THE WORKWEEK.
THIS APPROACHING TROPICAL WAVE WILL CAUSE A SIGNIFICANT INCREASE
IN MOISTURE. REGARDING TROPICAL CYCLONE ACTIVITY...THE LAST NHC
ADVISORY FOR THE REMNANTS OF CINDY WAS ISSUED AT 03UTC
TODAY...INDICATING DISSIPATION NEAR 22.8N 60.0W.
SIGNIFICANT SHOWER ACTIVITY IS EXPECTED EACH DAY THIS WEEK. THE
AVAILABLE MOISTURE WILL INCREASE TODAY AND WILL REMAIN GENERALLY
ABOVE NORMAL THROUGH THE WEEK. PRECIPITABLE WATER VALUES ARE
CURRENTLY AT AROUND 1.7 INCHES...WHICH IS NEAR NORMAL...BUT WILL
INCREASE TO NEAR 2 INCHES BY THIS EVENING...DIP DOWN BRIEFLY ON
TUESDAY TO NEAR 1.8 INCHES BUT THEN INCREASE AGAIN TO 2 INCHES AND
HIGHER FROM TUESDAY EVENING ONWARD. THE PRECIPITABLE WATER COULD
MAX OUT NEAR 2.3 INCHES ON WEDNESDAY AND THURSDAY...WHICH IS NEAR
2 STANDARD DEVIATIONS ABOVE NORMAL. THIS INCREASE IN MOISTURE WILL
BE REFLECTED IN THE MID LEVELS AS WELL...WITH A GRADUAL INCREASE
IN RELATIVE HUMIDITY IN THE MID LEVELS...ALSO PEAKING AT OR BEYOND
2 STANDARD DEVIATIONS HIGHER THAN NORMAL IN THE MID TO LATTER PART
OF THE WEEK. THERE IS A THREAT OF THUNDERSTORMS...BUT THE 500MB
TEMPERATURES ARE EXPECTED TO BE ON THE HIGHER END OF NORMAL...SO
THEY MIGHT BE A BIT TOO WARM TO PROMOTE SEVERE THUNDERSTORMS. THE
EGDI AND THE GR02T ALGORITHMS ARE IN AGREEMENT WITH THIS
ASSESSMENT...THE EGDI SHOWING THE POTENTIAL FOR SCATTERED
THUNDERSTORMS WITH HEAVY RAIN...BUT THE GR02T ALGORITHM INDICATING
ONLY A MARGINAL TO SLIGHT RISK OF SEVERE STORMS.
TODAY AND TUESDAY...SHOWERS AND THUNDERSTORMS ARE FORECAST IN THE
AFTERNOON HOURS ACROSS THE NORTHWESTERN QUADRANT OF PR...POSSIBLY
CAUSING SIGNIFICANT AMOUNTS OF RAIN WITH DECENT COVERAGE OF RAIN
OF OVER AN INCH OF RAIN...WITH ISOLATED AMOUNTS OF OVER 2 INCHES.
EASTERN PR AND THE USVI WILL HAVE A MORE ADVECTIVE PATTERN WITH
SCATTERED SHOWERS CAUSING BRIEF SHOWERS OVER THE AREA. ON
WEDNESDAY AND THURSDAY...THE TROPICAL WAVE IS EXPECTED TO MOVE IN
AND CAUSE A GENERALIZED RISK FOR SIGNIFICANT SHOWERS AND
THUNDERSTORMS. THERE IS SOME DISCREPANCY AMONG THE MODEL GUIDANCE
IN SHOWING THE AREAS WITH THE HIGHEST AMOUNTS OF RAIN.
HOWEVER...RAINFALL ACROSS MOST OF THE LOCAL ISLANDS CAN BE
EXPECTED. WEDNESDAY MAY HAVE MORE AFTERNOON CONVECTION ACROSS THE
NORTHWESTERN QUADRANT OF PR BUT EASTERN PR AND THE USVI ARE
EXPECTED TO HAVE THE MAX RAINFALL ON THURSDAY. MOISTURE AND SHOWER
ACTIVITY WILL DECREASE ON FRIDAY...AS SAHARAN DUST MOVES IN. THE
5-DAY TOTAL RAINFALL FORECAST IS SIGNIFICANT...WITH PORTIONS OF
THE NORTHWESTERN QUADRANT OF PR HAVING OVER 7 INCHES OF
RAIN...EASTERN PR OVER 5 INCHES...AND THE USVI BETWEEN 1 AND 2
INCHES.
ALAMO/GALVEZ/ACOSTA...WPC (USA)
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