161  
FXCA20 KWBC 231105  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
705 AM EDT MON OCT 23 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM OCT 23/06  
UTC: TUTT LOW NEAR 24N 65W EXTENDS A TROUGH TO THE SOUTH ACROSS  
THE EASTERN CARIBBEAN TO NORTHERN VENEZUELA. THE DEEP MID/UPPER  
LEVEL TROUGH PATTERN SUSTAINS AN INVERTED TROUGH IN THE EASTERLY  
WINDS...WITH AXIS NORTH ALONG 57W/58W TO 24N. THE LOW LEVEL  
PERTURBATION IS ENHANCING CONVECTION ALONG THE ITCZ AND TO THE  
EAST OF THE ISLAND CHAIN...WHILE THE TROUGH ALOFT IS ENHANCING  
CONVECTION TO THE NORTH OF THE ISLANDS.  
 
MODELS FORESEE GRADUAL DECOUPLING OF THE MID/UPPER LEVEL TROUGH  
AXIS AS A RIDGE BUILDS FROM THE WEST. THE 250 HPA AXIS IS TO  
SLOWLY RELOCATE ACROSS THE ISLAND CHAIN...WHILE WANING MID LEVEL  
CIRCULATION IS TO MEANDER OVER THE NORTHEAST CARIBBEAN ISLES  
THROUGH WEDNESDAY AFTERNOON. UNDER INFLUENCE OF THE MID/UPPER  
LEVEL FEATURE...BEST CONVECTIVE INSTABILITY IS EXPECTED DURING THE  
NEXT TWO DAYS. AT LOW LEVELS...THE INDUCED TROUGH MOVES ACROSS 60W  
EARLY THIS EVENING...NEARING 64W/65W EARLY ON WEDNESDAY MORNING.  
IT THEN RAPIDLY BECOMES ILL DEFINED AS IT LOSES ITS UPPER LEVEL  
SUPPORT. AHEAD OF THIS PERTURBATION...EASTERLY TRADES ARE TO  
DOMINATE THE ATMOSPHERE BELOW 700 HPA DURING THE NEXT TWO DAYS. ON  
WEDNESDAY THE WINDS ARE TO VEER TO THE SOUTHEAST. THE PREVAILING  
EASTERLY TRADES ARE TO RETURN LATER ON THURSDAY.  
 
OVER THE NEXT TWO DAYS THE DEEP LAYER EASTERLY TRADES AHEAD OF THE  
TUTT INDUCED TROUGH ARE TO ENHANCE CONVERGENCE ACROSS WESTERN  
INTERIOR PORTIONS OF PUERTO RICO. UNDER INFLUENCE OF AN UPPER JET  
MAXIMA REVOLVING AROUND THE UPPER LEVEL TROUGH...THE ENVIRONMENTAL  
CONDITIONS ON TUESDAY BECOME SOMEWHAT MORE FAVORABLE FOR DEEPER  
CONVECTION TO DEVELOP THAN TODAY. SO EXPECTING AN INCREASE ACROSS  
THE GUAJATACA BASIN. ON WEDNESDAY...AS THE STEERING FLOW SHIFTS TO  
THE SOUTHEAST...MOST ACTIVE CONVECTION IS TO CLUSTER ACROSS  
NORTHWEST PUERTO RICO...MAINLY TO THE WEST OF MANATI/BARCELONETA.  
BUT AS THE EASTERLY TRADES RETURN LATER IN THE WEEK... CONVECTION  
IS TO ONCE AGAIN CLUSTER ALONG THE GUAJATACA BASIN/WESTERN  
INTERIOR PORTIONS OF PUERTO RICO.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  

 
 
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