266  
FXCA20 KWBC 241142  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
641 AM EST FRI NOV 24 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO FROM NOV 24/06 UTC:  
FORECAST AREA REMAINS ON THE CONVERGENT SIDE OF A MID LEVEL CELL  
OF THE SUBEQUATORIAL RIDGE EXTENDING OVER THE EASTERN CARIBBEAN TO  
THE WESTERN ATLANTIC. AT 500 HPA THE RIDGE ANCHORS ON A CLOSED  
HIGH TO THE NORTH-NORTHEAST OF PUERTO RICO. AT LOW  
LEVELS...REMNANTS OF A TUTT INDUCED PERTURBATION IN THE EASTERLY  
TRADES IS PULLING ACROSS THE MONA PASSAGE EARLY THIS MORNING.  
PLUME OF TROPICAL MOISTURE TRAILS THIS PERTURBATION...AS IT  
EXTENDS OVER PUERTO RICO-USVI TO THE NORTHERN LEEWARD ISLANDS.  
ALTHOUGH THIS FAVORS HIGH MOISTURE...WITH PWAT CONTENT OF 1.75-2.0  
INCHES...THE ENVIRONMENTAL CONDITIONS REMAIN HOSTILE TO ORGANIZED  
DEEP CONVECTION. AS A RESULT...ONLY EXPECTING LIGHT-MODERATE  
CONVECTION TO AFFECT PUERTO RICO DURING THE DAY TODAY...WITH MOST  
ACTIVE ALONG THE CORDILLERA AND POSSIBLY WESTERN INTERIOR PORTIONS  
OF THE ISLAND IN MIDAFTERNOON CONVECTION.  
 
THE MID LEVEL RIDGE PATTERN IS TO GENERALLY HOLD OVER THE NEXT FEW  
DAYS. LATER ON SUNDAY...HOWEVER...RIDGE STARTS TO FLATTEN AS A  
LONG WAVE TROUGH TO THE WEST STARTS TO LIFT OVER THIS AXIS.  
EROSION OF THE RIDGE OVER THE WESTERN ATLANTIC CONTINUES ON  
TUESDAY/WEDNESDAY...WHEN THE RIDGE IS TO THEN CONFINE TO THE  
CENTRAL/WESTERN CARIBBEAN AND TO THE SOUTH OF 20N. ALTHOUGH THE  
RIDGE TENDS TO WEAKEN...THE ENVIRONMENTAL CONDITIONS ARE TO REMAIN  
HOSTILE TO ORGANIZED CONVECTION. AS THE PATTERN HOLDS...PLUME OF  
TROPICAL MOISTURE SEEPING UNDER THE RIDGE IS TO RAPIDLY MOVE AWAY  
ON SATURDAY. IN A DEEP LAYER EASTERLY FLOW...A DRYER AIR MASS THEN  
ENTRAINS FROM THE EAST EARLY ON SATURDAY MORNING. THIS IS TO  
PERSIST THROUGHOUT THE WEEKEND...TO GENERALLY FAVOR FAIR WEATHER  
CONDITIONS ACROSS THE ENTIRE FORECAST AREA. DURING THE  
WEEKEND...IN A COOL ADVECTIVE PATTERN...EARLY MORNING TRADE WIND  
SHOWERS ARE TO PESTER THE VIRGIN ISLES/EASTERN PUERTO RICO FROM  
TIME-TO-TIME. BUT THESE ARE TO GENERALLY FAVOR TRACE RAINFALL  
AMOUNTS IN BRIEF RAIN SHOWERS. OTHER CONVECTION IS EXPECTED ACROSS  
WESTERN PUERTO RICO DURING THE AFTERNOON HOURS...TO CLUSTER  
BETWEEN RINCON-AGUADILLA/ISABELA...WHERE IT IS TO SUSTAIN LIGHT  
RAINFALL AMOUNTS. A SLIGHT INCREASE IS POSSIBLE ON MONDAY AS A  
SECONDARY MOIST PLUME ADVECTS ACROSS THE NORTHEAST CARIBBEAN. BUT  
THIS WILL BE SHORT LASTING...AS A DRYER AIR MASS IT TO QUICKLY  
TAKE ITS PLACE ON TUESDAY-WEDNESDAY.  
 
DAVISON...WPC (USA)  
 

 
 
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