513  
FXCA20 KWBC 081158  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
658 AM EST WED NOV 08 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM NOV 08/06  
UTC: CONSISTENT WITH PREVIOUS FORECASTS A TUTT EXTENDS TO THE  
SOUTH-SOUTHWEST ACROSS EASTERN CUBA-CENTRAL CARIBBEAN...WHILE A  
CELL OF THE SUBEQUATORIAL RIDGE DOMINATES THE EASTERN CARIBBEAN.  
THIS FAVORS AN UPPER DIVERGENT PATTERN ACROSS HISPANIOLA-PUERTO  
RICO/ VIRGIN ISLES. AT LOW LEVELS...THE TROUGH ALOFT FAVORS THE  
NORTHWARD AMPLIFICATION OF A TROUGH ACROSS THE CENTRAL CARIBBEAN.  
THE ENSUING SOUTHEASTERLY FLOW SUSTAINS THE ADVECTION AND  
CONVERGENCE OF DEEP TROPICAL MOISTURE ACROSS THE FORECAST  
AREA...WHERE PWAT CONTENT PEAKS AROUND TWO INCHES. IN THIS PATTERN  
ORGANIZED DEEP CONVECTION IS CLUSTERING TO THE WEST-SOUTHWEST OF  
PUERTO RICO AND TO THE NORTH OF THE ISLANDS.  
 
DIGGING POLAR TROUGH OVER THE GULF OF MEXICO IS TO FAVOR NORTHWARD  
AMPLIFICATION OF THE SUBEQUATORIAL RIDGE ACROSS THE EASTERN  
CARIBBEAN. AS THE GRADIENT TIGHTENS THE TUTT IS TO GRADUALLY SHEAR  
TO THE NORTHEAST...WITH UPPER LEVEL AXIS DISSIPATING EARLY ON  
FRIDAY MORNING. AT 500 HPA...MODELS FORESEE A SLOWER  
EVOLUTION...WITH A MID LEVEL LOW FORMING OVER THE CENTRAL  
CARIBBEAN EARLY IN THE CYCLE. THIS IS TO PERSIST DURING THE NEXT  
FOUR-FIVE DAYS. AT LOW LEVELS THIS WILL THEN SUSTAIN DEVELOPMENT  
OF A CLOSED CIRCULATION TO THE SOUTH-SOUTHEAST OF JAMAICA. UNDER  
INFLUENCE OF THIS FEATURE DEEP PLUME OF TROPICAL MOISTURE IS TO  
CONTINUE ENVELOPING THE FORECAST AREA. THIS IS EXPECTED TO PERSIST  
THROUGHOUT THE WEEKEND/EARLY NEXT WEEK.  
 
EARLY IN THE PERIOD...THE TUTT WILL PROVIDE THE DYNAMICAL SUPPORT  
TO CONVECTIVE DEVELOPMENT OVER WATER. ACROSS PUERTO RICO AND THE  
VIRGIN ISLES DENSE CIRRUS BLOWING OFF FROM THE DEEP CONVECTION TO  
THE WEST/SOUTHWEST WILL DELAY ONSET OF DIURNAL CONVECTION. AS A  
RESULT...MOST ACTIVE OVER PUERTO RICO DURING THE DAY TODAY IS  
EXPECTED IN THE LATE AFTERNOON HOURS. BUT AS THE TUTT  
WEAKENS...AND UPPER CLOUD COVER THINS OUT...DIURNAL PATTERN IS TO  
ONCE AGAIN PREVAIL WITH BREEZES TO BECOME MAIN DRIVER FOR  
CONVECTIVE DEVELOPMENT. AS A SOUTH-SOUTHEASTERLY FLOW  
PERSISTS...THIS IS TO CONTINUE FAVORING MOST ACTIVE ACROSS  
NORTHWEST PORTIONS OF PUERTO RICO AND SAINT CROIX. ALSO...WITH LOW  
LEVEL WINDS PEAKING AT 15-20KT...STREAMERS ARE LIKELY TO FORM  
DOWNSTREAM FROM SAINT CROIX TO AFFECT SOUTHEAST PORTIONS OF PUERTO  
RICO FROM TIME-TO-TIME.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  
 

 
 
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