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FXCA20 KWBC 071237
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
837 AM EDT FRI JUL 07 2023
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JUL
07/12UTC: LINGERING SAHARAN DUST WILL BE EXITING THE LOCAL ISLANDS
THIS MORNING...ALLOWING FOR A SLIGHT INCREASE IN MOISTURE
TODAY...BUT STILL REMAINING NEAR NORMAL. AN ELONGATED SURFACE HIGH
PRESSURE FROM THE EAST CENTRAL TO THE CENTRAL ATLANTIC WILL KEEP
AN EAST TO EAST SOUTHEAST WIND FLOW FOR THE NEXT SEVERAL DAYS. A
MID-LEVEL HIGH PRESSURE WILL MEANDER OVER THE SOUTHWESTERN
ATLANTIC...FROM NORTH OF PR INTO THE BAHAMAS THROUGH THE WEEKEND.
THEREAFTER...THE MID LEVEL HIGH PRESSURE WILL MOVE INTO THE
NORTHERN BAHAMAS...AND A MID LEVEL RIDGE WILL MOVE INTO THE
NORTHEASTERN CARIBBEAN. AN UPPER-LEVEL LOW TO THE NORTH OF PUERTO
RICO...IS EXPECTED TO CONTINUE MOVING EAST OVER THE NEXT FEW
DAYS....MEANDERING IN THE ATLANTIC AT AROUND 25N 55W. A TROPICAL
WAVE IS FORECAST TO APPROACH PR/USVI ON LATE SATURDAY INTO
SUNDAY...WHICH WILL CAUSE AN INCREASE IN MOISTURE AND SHOWER
ACTIVITY. BY LATE SUNDAY INTO MONDAY...SAHARAN DUST WILL MOVE
IN...LINGERING INTO MIDWEEK. A TRADE WIND INVERSION WILL COINCIDE
WITH THE ARRIVAL OF THE SAHARAN DUST...AND IS EXPECTED EARLY NEXT
WEEK AT AROUND THE 850 HPA LEVEL.
WITH THE SAHARAN DUST LEAVING THE AREA TODAY...THE OVERALL
AVAILABLE MOISTURE WILL BE RETURNING TO NORMAL...WITH PRECIPITABLE
WATER VALUES INCREASING TO AROUND 1.7 INCHES BY THIS EVENING. THE
PRECIPITABLE WATER VALUES WILL RANGE BETWEEN 1.6 AND 1.8 INCHES
THROUGH MIDDAY SATURDAY...BUT A SHARP INCREASE TO ABOUT 2.2 INCHES
MAY BE POSSIBLE BY SATURDAY NIGHT WITH THE ARRIVAL OF THE TROPICAL
WAVE. THIS TROPICAL WAVE WILL BRING DEEP MOISTURE...AND THE MODELS
ARE SUGGESTING A MAX NEAR 2.4 INCHES OF PRECIPITABLE WATER THIS
WEEKEND. PRECIPITABLE WATER WILL DECREASE AGAIN BY SUNDAY NIGHT
AS THE SAHARAN DUST MOVES IN...BUT SHOULD REMAIN NEAR NORMAL
THROUGH THE EARLY PART OF NEXT WEEK.
FOR TODAY AND SATURDAY...THE OVERALL WEATHER IS EXPECTED TO BE
RELATIVELY TYPICAL. ISOLATED SHOWERS THIS MORNING...BUT AFTERNOON
CONVECTION IS EXPECTED ACROSS WESTERN PR. OVERNIGHT TONIGHT INTO
EARLY SATURDAY...SCATTERED SHOWERS ARE EXPECTED ACROSS THE USVI
AND EASTERN PR...WHILE LOCALLY INDUCED SHOWERS ARE FORECAST ACROSS
WESTERN PR. THE EXPECTED TROPICAL WAVE LATE SATURDAY INTO EARLY
SUNDAY WILL CAUSE AN INCREASE IN SHOWER ACTIVITY...WHICH COULD
CAUSE A WIDER COVERAGE OF SIGNIFICANT RAIN ACROSS THE LOCAL
ISLANDS...ESPECIALLY ACROSS EASTERN PR...WHILE THE USVI WOULD HAVE
PERSISTENT SHOWERS AS THEY MOVE BY. THE LATEST MODEL GUIDANCE IS
MUCH MORE AGGRESSIVE WITH THE AMOUNT OF RAIN FORECAST. FOR THAT
REASON WE INCREASED THE AMOUNTS OF RAINFALL FORECAST FOR THE LATE
SATURDAY INTO SUNDAY PERIOD. THE ARRIVAL OF SAHARAN DUST LATE
SUNDAY INTO MONDAY WOULD DECREASE THE CHANCES OF SIGNIFICANT RAIN
ONCE AGAIN THROUGH THE EARLY PART OF THE WORKWEEK.
THE 5-DAY RAINFALL TOTALS ARE FORECAST TO BE NEAR 2.75 INCHES
ACROSS WESTERN PR...AND BETWEEN 3 AND 3.5 INCHES ACROSS EASTERN
PR. FOR THE USVI...BETWEEN 0.5 AND 1.25 INCHES ARE FORECAST. LATE
SATURDAY INTO SUNDAY IS EXPECTED TO BE THE RAINIEST PERIOD IN THE
NEXT 5 DAYS DUE TO THE ARRIVAL OF THE TROPICAL WAVE.
ALAMO...WPC (USA)
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