551  
FXCA20 KWBC 131819  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
218 PM EDT FRI OCT 13 2017  
 
TROPICAL DISCUSSION FROM OCT 13/12 UTC: UNDER THE INFLUENCE OF THE  
UPPER CONVERGENT PHASE OF THE MADDEN-JULIAN  
OSCILLATION...EXPECTING GENERALLY FAIR CONDITIONS ACROSS THE  
FORECAST AREA. THE REGIONS WITH STRONG CONVECTION AND HEAVY  
RAINFALL WILL BE GENERALLY ISOLATED THROUGH THE FORECAST CYCLE.  
 
A WEAKENING NORTHERLY SURGE IN THE GULF OF MEXICO IS ENHANCING  
MOISTURE CONVERGENCE ALONG SOUTHERN VERACRUZ/TABASCO IN MEXICO.  
THROUGH SATURDAY...THIS WILL CONTINUE STIMULATING PRECIPITATION TO  
PRODUCE 10-15MM/DAY AND MAXIMA OF 20-35MM. AMOUNTS WILL DECREASE  
RAPIDLY AFTER. A NEW FRONT WILL ARRIVE ON SUNDAY. BY SUNDAY  
EVENING IT WILL EXTEND INTO NORTHERN NUEVO LEON-COAHUILA. BY  
MONDAY MORNING THE FRONT WILL EXTEND INTO NORTHERN TAMAULIPAS...BY  
MONDAY EVENING IT WILL EXTEND INTO SOUTHERN TAMAULIPAS. A  
NORTHERLY SURGE IS ALSO EXPECTED. THE NORTHERLY SURGE WILL DEVELOP  
GRADUALLY DURING SUNDAY...AND BY MONDAY MORNING IT WILL REACH 35KT  
OFF THE COASTS OF VERACRUZ AND THE TEHUANTEPECER JET 35-45KT. BY  
MONDAY EVENING THE SURGE WILL REACH 35-40KT OFF THE COASTS OF  
VERACRUZ AND THE TEHUANTEPECER 45-50KT. MODELS ARE FORECASTING THE  
TEHUANTEPECER REMAINING UNTIL MID-WEDNESDAY. ALSO...THE SYSTEM  
WILL DEVELOP A SHEAR LINE WHICH WILL EXTEND INTO EXTREME NORTHER  
VERACRUZ...AND BY MONDAY EVENING...AN ILL-DEFINED SHEAR LINE WILL  
EXTEND ACROSS EXTREME WESTERN CUBA INTO THE CENTRAL YUCATAN  
PENINSULA. THIS WILL ENHANCE LOW-LEVEL MOISTURE CONVERGENCE...TO  
SUSTAIN MODERATE RAINFALL AMOUNTS. ON SUNDAY-MONDAY...WITH THE  
FRONT...EXPECTING 05-10MM/DAY AND MAXIMA OF 15MM IN COAHUILA/NUEVO  
LEON. WITH THE SHEAR LINE...EXPECTING 05-10MM/DAY AND MAXIMA OF  
15-20MM IN NORTHERN VERACRUZ/NORTHERN PUEBLA. WITH THE NORTHERLY  
SURGE...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-25MM IN SOUTHERN  
VERACRUZ/TABASCO. LARGER AMOUNTS ARE EXPECTED ON MONDAY.  
 
ALSO IN MEXICO...DIURNAL CONVECTION ALONG THE SIERRA MADRE  
OCCIDENTAL AND SIERRA MADRE DEL SUR IS BECOMING ISOLATED.  
EXPECTING LIGHT RAINFALL ACCUMULATIONS THROUGH THE CYCLE.  
 
UPPER TROUGH CONTINUES MEANDERING OVER WESTERN CUBA AND THE  
NORTHWESTERN BAHAMAS. NORTHERLY FLOW ALOFT ALONG THE EAST COAST OF  
THE USA ON FRIDAY WILL DEEPEN THE TROUGH...WHICH WILL EVOLVE INTO  
A CLOSED UPPER LOW BY SUNDAY...WHILE MEANDERING OVER THE NORTHERN  
BAHAMAS. THE TROUGH HAS A STRONG REFLECTION AT 500 HPA...THUS IT  
IS ENHANCING CONVECTIVE INSTABILITY AND MOIST CONVECTION IN THE  
BAHAMAS...WESTERN CUBA AND FLORIDA. THROUGH EARLY  
SATURDAY...LARGEST ACCUMULATIONS ARE EXPECTED IN THE NORTHERN  
BAHAMAS AND CENTRAL/SOUTHEASTERN CUBA...TO REACH 05-10MM/DAY AND  
MAXIMA OF 15-25MM. BY SUNDAY-MONDAY...EXPECTING A DECREASE TO  
MAXIMA OF 15MM.  
 
ACROSS THE CARIBBEAN...LARGEST ACCUMULATIONS ARE EXPECTED TO  
DEVELOP ON SATURDAY IN ASSOCIATION WITH A ROBUST TROPICAL WAVE.  
THIS WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 25-50MM ACROSS THE  
WINDWARD ISLANDS AND THE EASTERN LEEWARD/FRENCH ISLANDS. THIS WILL  
EXTEND TO THE SOUTHERN LEEWARDS ON SUNDAY-MONDAY. MOISTURE PLUME  
TRAILING BEHIND THE WAVE WILL ENHANCE ACCUMULATIONS IN THE VIRGIN  
ISLANDS AND PUERTO RICO ON SUNDAY-MONDAY...TO PRODUCE 10-15MM/DAY  
AND MAXIMA OF 20-35MM.  
 
IN NORTHERN SOUTH AMERICA...ACTIVITY IS BEING MODULATED WITH THE  
AFOREMENTIONED TROPICAL WAVE. INITIALLY...THIS WILL LEAD TO  
05-10MM/DAY AND MAXIMA OF 15MM FOR TRINIDAD AND  
TOBAGO/NORTHEASTERN VENEZUELA...AND 10-15MM/DAY AND MAXIMA OF  
20-30MM TO THE SOUTH. ON SATURDAY-SUNDAY EXPECTING MAXIMA OF  
20-30MM/DAY ACROSS CENTRAL VENEZUELA...AND ON SUNDAY-MONDAY  
EXPECTING MAXIMA OF15-20MM/DAY IN NORTHERN AND EASTERN  
COLOMBIA/WESTERN VENEZUELA...AND MAXIMA OF 20-35MM/DAY ALONG  
WESTERN COLOMBIA. ALSO...A SOUTHEASTERLY SURGE ACROSS THE AMAZON  
BASIN WILL ENHANCE CONVECTION IN EASTERN ECUADOR/SOUTHERN COLOMBIA  
ON SUNDAY-MONDAY TO PRODUCE MAXIMA OF 25-50MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
35W 40W 44W 49W 52W 56W 60W 63W TW 12N  
57W 59W 62W 64W 67W 70W 73W 75W TW 22N  
80W 82W 84W 86W 88W DISSIPATES TW 19N  
 
A TROPICAL WAVE IS INITIALIZED AT 35W. THIS WAVE WILL APPROACH THE  
GUIANAS ON SUNDAY...YET THE ITCZ WILL BE TOO FAR NORTH FOR THE  
WAVE TO HAVE A SIGNIFICANT IMPACT. THE IMPACT WILL BE LARGER ON  
MONDAY IN THE LESSER ANTILLES...AS MODELS ARE CONFIDENT ABOUT A  
ROBUST MOISTURE PLUME ESTABLISHING IN THE ISLANDS BETWEEN  
BARBADOS/ST. VINCENT NORTH INTO THE FRENCH ANTILLES.  
 
A TROPICAL WAVE INITIALIZED AT 57W WILL STIMULATE CONVECTION  
MOSTLY IN NORTHERN SOUTH AMERICA AND THE LESSER ANTILLES AS IT  
PROPAGATES. LARGEST AMOUNTS ARE EXPECTED ON THE LESSER ANTILLES ON  
SATURDAY-MONDAY...AS THE MOISTURE PLUME LINGERS. EXPECTING AMOUNTS  
OF 15-20MM/DAY AND MAXIMA OF 25-50MM/DAY.  
 
A TROPICAL WAVE...INITIALIZED AT 80W CONTINUES TO BE ILL-DEFINED.  
YET...IT WILL STIMULATE CONVECTION AND PRECIPITATION IN CENTRAL  
AMERICA MARGINALLY...TO SUSTAIN AMOUNTS OF 05-10MM/DAY AND MAXIMA  
OF 15-20MM ON SATURDAY-SUNDAY. TRAILING MOISTURE PLUME WILL LEAD  
TO 10-15MM/DAY AND MAXIMA OF 20-35MM ON SUNDAY-MONDAY ACROSS  
EASTERN NICARAGUA/EASTERN HONDURAS.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
GALVEZ...WPC (USA)  

 
 
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