170  
FXCA20 KWBC 112006  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
305 PM EST MON DEC 11 2017  
 
TROPICAL DISCUSSION FROM DEC 11/12 UTC: THE SYSTEM OF INTEREST  
CONTINUES TO BE A SHEAR LINE THAT EXTENDS FROM THE WINDWARD  
PASSAGE ACROSS JAMAICA SOUTH INTO WESTERN PANAMA. THIS SHEAR LINE  
HAS BEEN THE FOCUS FOR EXTREME MOISTURE CONVERGENCE DURING THE  
WEEKEND. ALTHOUGH THE STRENGTH OF THE CONVERGENCE WILL GRADUALLY  
DECREASE THROUGH THE CYCLE...SEVERAL DAYS WITH MODERATE RAINS ARE  
STILL EXPECTED IN WESTERN PANAMA AND THE CARIBBEAN BASIN OF COSTA  
RICA.  
 
UPPER TROUGH PATTERN CONTINUES EXTENDING ACROSS MOST OF THE  
EASTERN USA...WHILE A LARGE UPPER RIDGE EXTENDS OVER MOST OF THE  
CARIBBEAN BASIN. THE RIDGE CENTERS ON A HIGH OVER NORTHERN  
COLOMBIA/SOUTHERN CARIBBEAN. FURTHERMORE...A STRONG UPPER TROUGH  
OVER THE ATLANTIC...THAT CENTERS AT 28N 45W...IS EXTENDING AN AXIS  
INTO THE NORTHERN GUIANAS. THE UPPER PATTERN IS FORECAST TO EVOLVE  
VERY LITTLE THROUGH THE CYCLE WITH THE EXCEPTION OF AREAS TO THE  
NORTH OF 30N. IN THIS REGION...ANOTHER UPPER TROUGH WILL EXIT INTO  
THE ATLANTIC ON TUESDAY/EARLY WEDNESDAY. THIS WILL SUSTAIN ANOTHER  
COLD FRONT THAT WILL REINFORCE THE CURRENT FRONT THAT MEANDERS  
ACROSS THE SOUTHEASTERN BAHAMAS/SOUTHEASTERN CUBA INTO NORTHERN  
HONDURAS/NICARAGUA. AT MID-LEVELS...RIDGE IS FORECAST TO GRADUALLY  
BUILD FROM NORTHERN CENTRAL AMERICA NORTHEAST TO OCCUPY MOST OF  
THE NORTHERN CARIBBEAN. THIS WILL REINFORCE CURRENT TRADE WIND CAP  
THAT IS ESTABLISHED ACROSS MOST OF THE NORTHERN ANTILLES...TO  
CONTINUE SUSTAINING GENERALLY FAIR CONDITIONS. THE MID-LEVEL RIDGE  
WILL ALSO CONTINUE LEADING TO A GRADUAL DRYING TREND IN NORTHERN  
CENTRAL AMERICA...WHERE PRECIPITATION WILL BE MOSTLY PRODUCED BY  
COLD AIR CUMULUS IN NORTHERN COASTS AND SLOPES OF SOUTHERN MEXICO  
AND HONDURAS.  
 
REGARDING THE SURFACE FRONTS...BY MONDAY EVENING THE CURRENT FRONT  
WILL EXTEND ACROSS THE TURKS AND CAICOS/SOUTH EASTERN  
BAHAMAS...NORTHWESTERN JAMAICA...NORTHERN HONDURAS-CENTRAL  
GUATEMALA. THE ASSOCIATED SHEAR LINE IS FORECAST TO REMAIN JUST TO  
THE SOUTHEAST OF JAMAICA...INTO BOCAS DEL TORO IN PANAMA. BY  
TUESDAY EVENING...THE FRONT WILL EXTEND ACROSS THE WINDWARD  
PASSAGE...NORTHWESTERN JAMAICA...EXTREME NORTHERN  
NICARAGUA...WHILE THE SHEAR LINE WILL LOSE DEFINITION. ALSO DURING  
TUESDAY EVENING...A NEW FRONT ARRIVING FROM THE SOUTHEASTERN  
UNITED STATES WILL EXTEND ACROSS CENTRAL FLORIDA INTO THE RIO  
BRAVO IN MEXICO. BY WEDNESDAY EVENING...THE SOUTHERNMOST FRONT  
WILL REORGANIZE AGAIN TO EXTEND ACROSS NORTHERN HISPANIOLA AND  
NORTHERN JAMAICA...WHILE TAIL FRONTOLIZES ACROSS THE GULF OF  
HONDURAS. THE SECOND FRONT WILL EXTEND ACROSS THE SOUTHEASTERN  
BAHAMAS TO BECOME STATIONARY ACROSS CENTRAL CUBA. THE SHEAR LINE  
WILL REORGANIZE TO EXTEND INTO EXTREME WESTERN PANAMA.  
 
IN TERMS OF PRECIPITATION...FRONTAL AND SHEAR LINE CONVERGENCE  
WILL CONTINUE STIMULATING THUNDERSTORM DEVELOPMENT ACROSS JAMAICA  
AND SOUTH EASTERN CUBA...WHERE EXPECTING 15-20MM/DAY AND MAXIMA OF  
25-50MM. SHEAR LINE CONVECTION IN INTERACTION WITH THE COAST IN  
COSTA RICA AND WESTERN PANAMA WILL PRODUCE 50-75MM/DAY AND MAXIMA  
OF 100-150MM. IN THE SOUTHEASTERN BAHAMAS/TURKS AND  
CAICOS...EXPECTING 10-15MM/DAY AND MAXIMA OF 20-40MM. COLD AIR  
CUMULUS CONVECTION IN NORTHERN HONDURAS WILL PRODUCE 10-15MM/DAY  
AND MAXIMA OF 20-40MM...WHILE IN THE GULF OF CAMPECHE EXPECTING  
MAXIMA OF 20-30MM. BY TUESDAY-WEDNESDAY...ENHANCED MOISTURE  
CONVERGENCE IN COSTA RICA WILL LEAD TO 15-20MM/DAY AND MAXIMA OF  
30-60MM. ACROSS JAMAICA EXPECTING 10-15MM/DAY AND MAXIMA OF  
20-45MM. IN NORTHERN HAITI/SOUTHEASTERN BAHAMAS/TURKS AND  
CAICOS/SOUTHEASTERN CUBA EXPECTING 10-15MM/DAY AND MAXIMA OF  
20-35MM. COLD AIR CUMULUS CONVECTION WILL LEAD TO MAXIMA OF  
20-35MM CROSS NORTHERN HONDURAS...AND LESSER AMOUNTS IN THE  
SOUTHERN GULF OF CAMPECHE. BY WEDNESDAY-THURSDAY...EXPECTING AN  
INCREASE IN ACCUMULATIONS IN NORTHERN HISPANIOLA...WHERE NORTH  
EASTERLIES WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 30-60MM.  
MOISTURE CONVERGENCE IN COSTA RICA AND WESTERN PANAMA WILL  
CONTINUE PRODUCING 10-15MM/DAY AND MAXIMA OF 30-60MM. OVER  
JAMAICA...EXPECTING A SIGNIFICANT DECREASE IN ACCUMULATIONS TO  
10-15MM/DAY AND MAXIMA OF 20-30MM.  
 
IN NORTHERN SOUTH AMERICA AND THE WINDWARD ISLANDS...A  
TUTT-INDUCED WAVE WILL PROPAGATE AS AN EASTERLY WAVE TO ENHANCE  
ACCUMULATIONS LATER IN THE CYCLE (SEE BELOW). IN  
COLOMBIA...ACTIVITY WILL GENERALLY PEAK ALONG THE WEST COAST AND  
VALLE DEL CAUCA/EJE CAFETERO...WHERE EXPECTING 10-15MM/DAY AND  
MAXIMA OF 20-30MM ON MONDAY...DECREASING AFTER. NOTE THAT A  
SIGNIFICANT DRYING TREND IS EXPECTED IN COLOMBIA BY  
WEDNESDAY-THURSDAY...WHERE ACTIVITY WILL BE VERY ISOLATED AND  
MAXIMA BELOW 10MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
52W 55W 58W 61W 64W 67W 70W 73W TUTT INDCD 20N  
 
A TUTT-INDUCED WAVE IN THE WESTERN ATLANTIC IS STARTING TO  
PROPAGATE AS AN EASTERLY WAVE. THIS WAVE WILL SLOWLY REGAIN  
DEFINITION AS IT PROPAGATES ACROSS THE SOUTHERN CARIBBEAN. IT WILL  
STIMULATE PRECIPITATION IN TRINIDAD AND TOBAGO/NORTHERN GUYANA ON  
TUESDAY...WHERE IT WILL PRODUCE 05-10MM/DAY AND MAXIMA OF 15-20MM.  
ON WEDNESDAY...EXPECTING SIMILAR AMOUNTS EXPANDING INTO  
NORTH-CENTRAL AND NORTH EASTERN VENEZUELA.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
GALVEZ...WPC (USA)  
 

 
 
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