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FXCA20 KWBC 081420
PMDCA
TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1019 AM EDT THU AUG 08 2024
WEEKLY DISCUSSION FOR PUERTO RICO AND THE USVI AUG 08/12UTC: AS OF
THIS WRITING...THE NATIONAL HURRICANE CENTER (NHC)IS MONITORING A
TROPICAL WAVE THAT IS JUST COMING OFF THE WEST COAST OF
AFRICA...AND HAS A NEAR ZERO CHANCE OF TROPICAL CYCLONE FORMATION
THROUGH 48 HOURS...AND A 30% CHANCE OF TROPICAL CYCLONE FORMATION
THROUGH 7 DAYS. THIS TROPICAL WAVE COULD APPROACH PR/USVI IN ABOUT
A WEEK AND THEREFORE SHALL BE MONITORED. THERE IS CURRENTLY TOO
MUCH UNCERTAINTY ON THE POTENTIAL DEVELOPMENT OF THIS SYSTEM...AS
THE GLOBAL MODELS DIFFER ON THEIR SOLUTIONS EVEN THOUGH THEY ARE
CURRENTLY SUGGESTING SOME DEVELOPMENT OF THIS SYSTEM. THERE WILL
ALSO BE SOME SAHARAN DUST PRESENT ACROSS THE ATLANTIC THIS
WEEK...WHICH ADDS TO THE OVERALL UNCERTAINTY.
CONTINUING WITH THE SAHARAN DUST...ANOTHER PLUME OF DUST IS
EXPECTED TO APPROACH PR/USVI BY THIS AFTERNOON...AND THE
CONCENTRATION WILL BE SIGNIFICANT OVER PR BY FRIDAY MORNING.
ALTHOUGH THE CONCENTRATION OVER THE ISLANDS WILL VARY OVER THE
NEXT SEVERAL DAYS...THE LATEST MODEL GUIDANCE SUGGESTS THAT AT
LEAST SOME SAHARAN DUST WILL BE PRESENT OVER PR/USVI EVERY DAY
THROUGH TUESDAY.
AT THE SFC...THERE IS A BROAD HIGH PRESSURE OVER THE NORTH
ATLANTIC...WHICH WILL PERSIST OVER THE NEXT WEEK...KEEPING
EASTERLY TO SOUTHEASTERLY WINDS OVER THE LOCAL ISLANDS. THERE IS A
MID LEVEL HIGH PRESSURE STACKED ON TOP OF THE SFC HIGH OVER THE
NORTH CENTRAL ATLANTIC...WHILE THERE IS A WEAKNESS IN THE MID
LEVEL RIDGE OVER THE CENTRAL TROPICAL ATLANTIC. THIS WEAKNESS IN
THE MID LEVEL RIDGE IS ASSOCIATED WITH AN UPPER TROUGH THAT IS
RETROGRADING AND IS FORECAST TO MOVE JUST NORTHEAST OF THE
NORTHEAST CARIBBEAN. NORMALLY A TUTT TO THE NORTHEAST WOULD
SUGGEST SUBSIDENCE OVER THE LOCAL ISLANDS...BUT A RETROGRADING
TUTT TENDS TO PROMOTE RISING MOTION TO THE SOUTHWEST OF ITS
CENTER...WHICH IS CONSISTENT WITH THE REASON WHY THERE IS A
WEAKNESS IN THE MID LEVEL RIDGE TO BEGIN WITH. AS THE TUTT MOVES
TO THE NORTHEAST OF THE NE CARIBBEAN...A TROPICAL WAVE IS FORECAST
TO MOVE INTO THE CARIBBEAN AND PASS THROUGH PR/USVI SATURDAY
NIGHT.
THE AVAILABLE MOISTURE WILL ALSO REFLECT THE INCOMING TROPICAL
WAVE THIS WEEKEND. PRECIPITABLE WATER WILL BE BELOW NORMAL BY THIS
AFTERNOON INTO THIS EVENING...BUT THEN WILL INCREASE AND WILL BE
ABOVE NORMAL ON SATURDAY. PRECIPITABLE WATER WILL BE FROM NEAR TO
ABOVE NORMAL INTO EARLY NEXT WEEK. THE LOW LEVEL AND MID LEVEL
RELATIVE HUMIDITY WILL ALSO INCREASE THIS WEEKEND WITH THE
TROPICAL WAVE AND THE MID LEVEL TROUGH AND TUTT. THAT BEING
SAID...THE OVERALL RAINFALL PATTERN OVER PR/USVI IS EXPECTED TO BE
FAIRLY TYPICAL OVER THE NEXT 5 DAYS...BUT UNCERTAIN THEREAFTER AS
IT DEPENDS ON THE EVENTUAL DEVELOPMENT AND TRACK OF THE
AFOREMENTIONED TROPICAL WAVE. THEREFORE...BRIEF SHOWERS ACROSS
EASTERN PR AND THE USVI ARE EXPECTED EACH DAY...MOSTLY IN THE
NIGHTTIME AND MORNING HOURS...THEN AFTERNOON CONVECTION ACROSS
CENTRAL TO WESTERN PR...DEPENDING ON THE GENERAL WIND FLOW AND SEA
BREEZE CONVERGENCE. THE EGDI ALGORITHM SUGGESTS SOME POTENTIAL FOR
ISOLATED THUNDERSTORMS FROM FRIDAY ONWARD...WITH A BETTER CHANCE
OF THUNDERSTORMS AS THE TUTT APPROACHES.
ALAMO...WPC (USA)
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