000  
FXCA20 KWBC 091139  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
639 AM EST THU NOV 09 2017  
 
PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI FROM NOV 09/06  
UTC: TUTT LOW NEAR JAMAICA ANCHORS A SHORT WAVE TROUGH ACROSS THE  
CENTRAL CARIBBEAN. AT LOW LEVELS THIS REFLECTS AS AN INVERTED  
TROUGH THAT EXTENDS NORTH BETWEEN COLOMBIA AND HAITI...WITH AXIS  
ANCHORING ON A LOW NORTH-NORTHWEST OF BARRANQUILLA IN NORTHERN  
COLOMBIA. THE LOW LEVEL TROUGH IS ENHANCING MOISTURE CONVERGENCE  
ACROSS THE NORTHERN CARIBBEAN...WITH PWAT CONTENT OF NEARLY THREE  
INCHES JUST SOUTH OF THE DOMINICAN REPUBLIC. AS CONVECTION BUILDS  
SOUTH OF THE REPUBLIC...A CELL OF THE SUBEQUATORIAL RIDGE TO THE  
EAST IS STEERING THE ACTIVITY TO THE EAST-NORTHEAST ACROSS THE  
CARIBBEAN WATERS OF PUERTO RICO/SOUTHERN PORTIONS OF THE ISLAND.  
 
CONSISTENT WITH PREVIOUS FORECASTS...UPPER FLOW PATTERN IS TO  
RAPIDLY CHANGE DURING THE NEXT 24-30 HRS. UNDER PRESSURE FROM  
DIGGING TROUGH OVER THE GULF...THE TUTT ALOFT OVER THE CARIBBEAN  
IS TO RAPIDLY WEAKEN WHILE SHEARING SHORT WAVE ENERGY OVER  
BUILDING CELL OF THE SUBEQUATORIAL RIDGE TO THE EAST. BY MIDDAY ON  
FRIDAY THE TROUGH ALOFT IS TO DISSIPATE WITH SUBEQUATORIAL RIDGE  
ALOFT TO REMAIN AS THE DOMINANT UPPER FEATURE. AS THE RIDGE ALOFT  
HOLDS...AN UPPER DIVERGENT PATTERN IS TO PERSIST THROUGHOUT THE  
WEEKEND/EARLY NEXT WEEK. AT MID LEVELS...THE TUTT APPEARS SOMEWHAT  
MORE RESILIENT THAN AT 250 HPA... WITH A WEAK CUTOFF LOW TO  
MEANDER OVER THE CENTRAL CARIBBEAN THROUGHOUT THE FORECAST PERIOD.  
AS A RESULT...THE INDUCED LOW LEVEL TROUGH AND ASSOCIATED  
CIRCULATION ARE TO ALSO PERSIST DURING THE NEXT FEW DAYS. THIS IS  
TO SUSTAIN A DEEP LAYER SOUTHEASTERLY FLOW ACROSS THE EASTERN  
CARIBBEAN...WITH HIGH MOISTURE CONTENT TO PERSIST ACROSS THE  
FORECAST AREA. THE PWAT CONTENT IS EXPECTED TO PEAK AROUND TWO  
INCHES THROUGH AT LEAST SUNDAY EVENING.  
 
AS THE UPPER TUTT WEAKENS EARLY IN THE CYCLE...DYNAMICAL SUPPORT  
FOR MCS DEVELOPMENT OVER THE CENTRAL CARIBBEAN WILL WANE ON  
FRIDAY. DIURNAL/SEA BREEZE RELATED CONVECTION WILL THEN BECOME THE  
PRIMARY DRIVER FOR CONVECTIVE DEVELOPMENT ACROSS THE ENTIRE  
FORECAST AREA. THIS PATTERN IS EXPECTED TO HOLD THROUGH AT LEAST  
SUNDAY EVENING. MODELS THEN DIVERGE ON HOW LONG MOIST PLUME  
ENVELOPING FORECAST AREA IS GOING TO LAST...WITH ECMWF SHOWING  
EROSION OF AVAILABLE MOISTURE FROM THE EAST WHILE THE GFS FORESEES  
A LONGER LASTING MOIST TONGUE ACROSS THE FORECAST AREA. MOST  
ACTIVE CONVECTION IS TO CLUSTER ACROSS NORTHWEST PUERTO RICO IN  
AFTERNOON CONVECTION...WITH LESSER AMOUNTS TO AFFECT EASTERN  
PORTIONS OF THE ISLAND.  
 
DURING THE MEDIUM RANGE PERIOD...POLAR FRONT EXITING THE EASTERN  
USA ON SUNDAY EVENING/MONDAY MORNING IS TO QUICKLY MOVE ACROSS THE  
WESTERN ATLANTIC. ALTHOUGH THE FRONT IS TO REMAIN FAR TO THE NORTH  
AND WEST...IT IS TO SUSTAIN AN INDUCED/PREFRONTAL TROUGH NORTH OF  
THE ISLANDS. THIS TROUGH WILL THEN BECOME FOCUS OF MOISTURE  
CONVERGENCE BY THE MIDDLE OF THE WEEK.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  
 

 
 
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