235  
FXCA20 KWBC 291055  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
655 AM EDT SUN OCT 29 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM OCT 29/06  
UTC: UNDER THE INFLUENCE OF A TUTT LOW TO THE SOUTHWEST AND A  
POLAR TROUGH TO THE NORTH...A PLUME OF DEEP TROPICAL MOISTURE  
CONTINUES TO ENVELOP THE ENTIRE FORECAST AREA... WITH THE  
SATELLITE DERIVED PWAT ESTIMATES SHOWING TWO INCHES OF AVAILABLE  
WATER BETWEEN THE LEEWARD ISLES AND PUERTO RICO/USVI. ALSO UNDER  
THE INFLUENCE OF THE DEEP TUTT...A DEEP LAYER SOUTH-SOUTHEAST  
STEERING FLOW ENVELOPS THE NORTHEAST CARIBBEAN ISLES. THIS IS  
FORECAST TO PERSIST THROUGH THIS EVENING...WITH WINDS BRIEFLY  
SHIFTING TO THE SOUTHWEST EARLY MONDAY MORNING. MEANWHILE...THE  
SOUTHERLY WINDS ARE TO FAVOR ADIABATIC COMPRESSION ACROSS NORTHERN  
PORTIONS OF PUERTO RICO. THIS WILL COMBINE WITH HIGH MOISTURE  
CONTENT TO SUSTAIN HOT AND MUGGY CONDITIONS ACROSS THE NORTHERN  
HALF OF THE ISLAND. IT IS TO ALSO DELAY ONSET DIURNAL CONVECTION  
OVER NORTHERN PUERTO RICO TO THE MIDAFTERNOON HOURS...WHILE OVER  
THE VIRGIN ISLES EXPECTING AN EARLIER ONSET. ACROSS THE VIRGIN  
ISLES THIS WILL FAVOR LIGHT TO MODERATE RAINFALL AMOUNTS...WITH  
SLIGHTLY HIGHER AMOUNTS ACROSS SAINT CROIX THAN OVER THE NORTHERN  
VI. ACROSS PUERTO RICO THIS WILL COMBINE WITH SEA BREEZE  
CONVERGENCE TO SUSTAIN MODERATE CONVECTION ALONG THE NORTH COAST.  
PER THE GFS AND ECMWF GDI GUIDANCE IT LOOKS LIKE THE BEST  
INSTABILITY IS TO REMAIN JUST NORTH OF PUERTO RICO.  
 
SIMULTANEOUSLY...A POLAR TROUGH LIFTING ACROSS THE EASTERN USA IS  
TO INDUCE THE RAPID INTENSIFICATION OF A MID/UPPER LEVEL RIDGE  
OVER THE WESTERN ATLANTIC/NORTH OF THE ISLANDS...WITH MID LEVEL  
AXIS TO CENTER ON A CLOSED HIGH NORTH OF PUERTO RICO EARLY IN THE  
CYCLE. THE BUILDING RIDGE WILL GRADUALLY STRENGTHEN THE TRADE  
WINDS CAP...WITH MODELS SHOWING THE GRADUAL EROSION OF AVAILABLE  
MOISTURE DURING THE DAY ON TUESDAY. A DRYER AIR MASS IS TO THEN  
ENVELOP THE ENTIRE FORECAST AREA BY THE END OF THE WEEK. ALSO  
UNDER THE INFLUENCE OF THIS RIDGE...TRADE WIND EASTERLIES RETURN  
TO THE FORECAST AREA LATE ON MONDAY-TUESDAY. THIS...HOWEVER...WILL  
BE SHORT LASTING...WITH THE WINDS BACKING TO THE NORTHEAST ON  
WEDNESDAY. ON WEDNESDAY TO THURSDAY THIS IS TO SUSTAIN A COOL  
ADVECTIVE PATTERN ACROSS THE ENTIRE FORECAST AREA. THE DRYER AIR  
MASS AND COOL NORTHEASTERLY TRADES WILL THEN BRING A MUCH NEEDED  
RESPITE FROM HOT AND MUGGY CONDITIONS AS OF LATE...WHILE THE  
STRENGTHENING TRADE WINDS CAP IS TO INHIBIT ORGANIZED DEEP  
CONVECTION.  
 
ON MONDAY-TUESDAY THE LIGHT EASTERLY TRADES WILL COMBINE WITH LAND  
BREEZE CONVERGENCE OVER EASTERN PUERTO RICO TO FAVOR EARLY MORNING  
COASTAL CONVECTION. BUT THESE ARE TO ONLY TRIGGER LIGHT RAINFALL  
AMOUNTS IN ISOLATED TO SCATTERED SHOWERS. MEASURABLE AMOUNTS WILL  
LIMIT TO WESTERN INTERIOR PORTIONS OF PUERTO RICO IN AFTERNOON  
CONVECTION. ON WEDNESDAY-THURSDAY THE COOL NORTHEASTERLY TRADES  
WILL TRIGGER EARLY MORNING SHOWERS ACROSS THE VIRGIN ISLES AND  
ALONG THE NORTH-NORTHEAST COAST OF PUERTO RICO. MEASURABLE AMOUNTS  
WILL THEN CONFINE TO SOUTHWEST PORTIONS OF PUERTO RICO IN  
AFTERNOON CONVECTION.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page