824  
FXCA20 KWBC 131146  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
646 AM EST MON NOV 13 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM NOV 13/06  
UTC: MID/UPPER LEVEL RIDGE OVER MEXICO/THE GULF IS TO STEER SHORT  
WAVE PERTURBATIONS ACROSS THE SOUTHEAST USA TO THE WESTERN  
ATLANTIC. INFLOW OF SUCCESSIVE VORTICES WILL HELP CARVE A TROUGH  
ACROSS THE BAHAMAS-NORTHERN CARIBBEAN ISLES BY THE MIDDLE OF THE  
WEEK. AS THE TROUGH DEEPENS IT WILL PRESS AGAINST MEANDERING CELL  
OF THE SUBEQUATORIAL RIDGE OVER THE EASTERN CARIBBEAN. THE RIDGE  
EXTENDS NORTH FROM VENEZUELA TO PUERTO RICO-VIRGIN ISLES/LESSER  
ANTILLES...WHERE IT FAVORS A TRADE WINDS CAP. UNDER PRESSURE FROM  
THE DEEPENING TROUGH THE RIDGE RELAXES ITS FOOTHOLD ACROSS THE  
FORECAST AREA ON WEDNESDAY MORNING. SHORT WAVE VORTICES ARE TO  
THEN STREAM BETWEEN THE TROUGH AND THE RIDGE TO THE EAST...LIFTING  
ACROSS EASTERN PORTIONS OF THE DOMINICAN REPUBLIC/MONA PASSAGE AND  
AFFECTING PUERTO RICO FROM TIME TO TIME.  
 
AT LOW LEVELS...A RIDGE OVER THE CENTRAL ATLANTIC FAVORS A BRISK  
EASTERLY FLOW ACROSS THE FORECAST AREA. POLAR FRONT EXITING THE  
EASTERN USA WILL PUSH AGAINST THIS RIDGE...DISPLACING IT EAST. AS  
THE RIDGE RELOCATES THE LOW LEVEL WINDS ARE TO VEER TO THE  
SOUTH-SOUTHEAST LATER ON TUESDAY. ALTHOUGH THE SURFACE FRONT IS  
NOW EXPECTED TO STALL FAR TO THE NORTH...IT IS TO SUSTAIN A BROAD  
SURFACE TROUGH. THIS WILL COMBINE WITH MID/UPPER LEVEL TROUGH AXIS  
TO SUSTAIN AN INDUCED TROUGH/ILL ORGANIZED CYCLONIC CIRCULATION  
OVER THE CENTRAL CARIBBEAN. UNDER INFLUENCE OF THIS FEATURE THE  
LOW LEVEL WINDS ON WEDNESDAY VEER TO THE SOUTH-SOUTHWEST. THIS IS  
TO THEN FAVOR A LONG FETCH MOIST ADVECTIVE PATTERN ACROSS THE  
CENTRAL CARIBBEAN. AS MOISTURE CONVERGES ACROSS THE FORECAST AREA  
ON WEDNESDAY THE PWAT CONTENT WILL INCREASE TO AROUND TWO INCHES  
BY MIDMORNING. HIGH MOISTURE CONTENT IS FORECAST TO LAST THROUGH  
THE END OF THE WEEK. IN A DEEP LAYER SOUTHWESTERLY FLOW...FOCUS OF  
THE DIURNAL CONVECTION WILL SHIFT FROM NORTHWESTERN PUERTO RICO TO  
NORTH CENTRAL/NORTHEAST PUERTO RICO ON WEDNESDAY AFTERNOON...WITH  
MODERATE RAINFALL AMOUNTS LIKELY ACROSS THE SAN JUAN METRO AREA ON  
WEDNESDAY-FRIDAY. MOST INTENSE... HOWEVER...IS EXPECTED TO THE  
WEST TO AFFECT SOUTHERN PORTIONS OF HISPANIOLA.  
 
DAVISON...WPC (USA)  
 

 
 
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