626  
FXCA20 KWBC 271217  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
717 AM EST SAT JAN 27 2018  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM JAN 27/06  
UTC: POLAR RIDGE OVER THE WESTERN ATLANTIC/EASTERN USA WILL  
CONTINUE DRIVING A POLAR FRONT TO THE NORTH OF THE ISLANDS. THIS  
HAS TRIGGERED A PRE-FRONTAL SHEAR LINE THAT IS ILL-DEFINED WHILE  
EXTENDING INTO THE NORTHERN VIRGIN ISLANDS. FROM NOW AND THROUGH  
LATE MONDAY...THE MOST SIGNIFICANT PROCESS IS THE ACCELERATION OF  
THE TRADE WINDS. THESE HAVE REACHED SPEEDS OVER 30KT. THIS IS  
LEADING TO LARGE VALUES OF MOISTURE CONVERGENCE...ESPECIALLY ALONG  
NORTHEASTERN PORTIONS OF PUERTO RICO AND HISPANIOLA. AN ELEVATED  
TRADE WIND CAP SITS AT 650 HPA. THIS IS ALLOWING FOR SOME VERTICAL  
DEVELOPMENT OF TRADE WIND SHOWER CONVECTION. YET...THE ENHANCED  
LOW-LEVEL SHEAR AND FAST PROPAGATION OF THE SHOWERS IS LIMITING  
ACCUMULATIONS.  
 
THE SURFACE FRONT WILL MEANDER SOUTHWARD JUST NORTH OF THE  
FORECAST AREA THROUGH SUNDAY MORNING. AS IT GRADUALLY  
FRONTOLIZES...REMNANT SHOWERS ALONG THE REMNANTS OF THE FRONT WILL  
CROSS PUERTO RICO AND THE USVI FROM EAST TO WEST DURING LATE  
SUNDAY THROUGH EARLY TUESDAY. THIS WILL CONTINUE FAVORING ENHANCED  
PRECIPITATION IN EASTERN PARTS OF PUERTO RICO...ACCOMPANIED BY A  
DECREASING TREND IN RAINFALL AMOUNTS. THE TRADE WIND SPEEDS ARE  
FORECAST TO DECREASE FROM 25-35KT ON SATURDAY AND SUNDAY...TO  
20-25KT BY MONDAY...AND TO 15-20KT ON TUESDAY. THIS WILL SUSTAIN A  
GRADUAL DECREASE IN MOISTURE CONVERGENCE AND ASSOCIATED RAINFALL  
ACCUMULATIONS. YET...ENHANCED TRADE WIND SHOWERS AND WINDY  
CONDITIONS WILL CONTINUE INTO EARLY NEXT WEEK...ESPECIALLY ON  
SATURDAY THROUGH EARLY SUNDAY...WITH LARGEST AFFECTATIONS IN PARTS  
OF NORTHEASTERN PUERTO RICO.  
 
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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