908  
FXCA20 KWBC 081959  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 PM EST FRI DEC 08 2017  
 
TROPICAL DISCUSSION FROM DEC 08/12 UTC: STRONG POLAR TROUGH  
EXITING INTO THE GULF OF MEXICO HAS PRODUCED HISTORIC SNOWFALL IN  
NORTHERN MEXICO. NOW...THE FOCUS FOR THE ACTIVITY IN ASSOCIATION  
WITH THIS TROUGH WILL SWITCH TO AREAS IN THE SOUTHERN GULF OF  
MEXICO AND IN THE NORTHWESTERN CARIBBEAN...INCLUDING CUBA AND THE  
BAHAMAS. AS THE UPPER TROUGH MOVES ACROSS THE WESTERN GULF OF  
MEXICO ON FRIDAY...IT WILL SUSTAIN CYCLOGENESIS. THIS WILL  
CONTINUE DEVELOPING A STRONG COLD FRONT AND NORTES EVENT ACROSS  
THE GULF. BY FRIDAY EVENING...THE FRONT WILL EXTEND ACROSS  
TAMPA...MERIDA IN THE YUCATAN PENINSULA...AND EXTREME NORTHWESTERN  
GUATEMALA. DURING THIS TIME...A PRE-FRONTAL TROUGH IS FORECAST TO  
ORGANIZE ACROSS THE EASTERN YUCATAN PENINSULA INTO NORTH-CENTRAL  
HONDURAS. BY SATURDAY EVENING...THE FRONT WILL CONTINUE ITS RAPID  
PROGRESSION TO EXTEND ACROSS THE CENTRAL BAHAMAS...SOUTH EASTERN  
CUBA...JUST EAST OF THE CAYMAN ISLANDS...EXTREME NORTHEASTERN  
NICARAGUA. BY THIS TIME...A SHEAR LINE WILL ORGANIZE...TO EXTEND  
ACROSS SAN ANDRES/NUEVA PROVIDENCIA IN THE WESTERN CARIBBEAN AND  
INTO BOCAS DEL TORO IN PANAMA. BY SUNDAY EVENING...THE FRONT WILL  
EXTEND ACROSS THE TURKS AND CAICOS...SOUTHEASTERN CUBA...WESTERN  
JAMAICA...CENTRAL NICARAGUA. THE SHEAR LINE WILL EXTEND ACROSS  
HAITI...INTO BOCAS DEL TORO IN PANAMA. BY MONDAY EVENING...THE  
FRONT WILL STALL ACROSS THE TURKS AND CAICOS...ALMOST OVER MONTEGO  
BAY...CENTRAL NICARAGUA. BY THIS PERIOD...THE SHEAR LINE WILL  
START TO LOSE DEFINITION WHILE STILL ENHANCING LOW-LEVEL MOISTURE  
CONVERGENCE...AS IT EXTENDS ACROSS HAITI...JUST TO THE EAST OF  
JAMAICA...INTO BOCAS DEL TORO IN PANAMA.  
 
BY FRIDAY-SATURDAY...EXPECTING AN INCREASE IN ACTIVITY IN SOUTHERN  
BELIZE/NORTHWESTERN HONDURAS AND EASTERN GUATEMALA...WHERE  
ENHANCED OROGRAPHIC UPLIFT AS THE NORTHERLIES ARRIVE...WILL LEAD  
TO 15-20MM/DAY AND MAXIMA OF 25-50MM. OROGRAPHIC ENHANCEMENT IN  
THE SOUTHERN GULF LF MEXICO WILL LEAD TO MAXIMA OF 20-35MM.  
PRE-FRONTAL CONFLUENCE WILL ALSO ENHANCE ACCUMULATIONS IN WESTERN  
CUBA...WHERE EXPECTING 15-30MM/DAY AND MAXIMA OF 40-80MM.  
ELSEWHERE ACROSS THE YUCATAN PENINSULA/BELIZE EXPECTING MAXIMA OF  
15MM. BY SATURDAY-SUNDAY...ENHANCED OROGRAPHIC UPLIFT ALONG THE  
NORTHERN COAST OF HONDURAS WILL LEAD TO 75-100MM/DAY AND ISOLATED  
MAXIMA OF 150-250MM. ALSO...FRONTAL AND SHEAR LINE CONVERGENCE  
WILL INTERACT WITH MOISTURE POOL IN THE WESTERN CARIBBEAN...TO  
SUSTAIN HEAVY RAIN FROM SAN ANDRES/NUEVA PROVIDENCIA NORTH INTO  
THE CAYMAN ISLANDS/WESTERN JAMAICA AND CENTRAL CUBA. IN THESE  
REGIONS...EXPECTING 15-20MM/DAY AND MAXIMA OF 35-70MM. ENHANCED  
OROGRAPHIC UPLIFT IN EASTERN COSTA RICA/WESTERN PANAMA...AS SHEAR  
LINE DEVELOPS AND LOW-LEVEL JET FROM THE NORTH ESTABLISHES...WILL  
LEAD TO 75-100MM/DAY AND MAXIMA OF 150-250MM. BY  
SUNDAY-MONDAY...LARGEST AMOUNTS ARE EXPECTED WITH THE LOW-LEVEL  
JET FROM THE NORTH AND THE SHEAR LINE IN COSTA RICA...WHERE  
ACCUMULATIONS WILL REACH 75-100MM/DAY AND ISOLATED MAXIMA OF  
200-300MM. ENHANCED CONVECTION ALONG THE SHEAR LINE AND FRONT WILL  
LEAD TO 15-20MM/DAY AND MAXIMA OF 25-50MM IN EASTERN CUBA AND  
JAMAICA. AND 10-15MM/DAY AND MAXIMA OF 20-40MM ACROSS SAN ANDRES  
AND NUEVA PROVIDENCIA...AND 10-15MM/DAY AND MAXIMA OF 20-35MM IN  
THE TURKS AND CAICOS...AND SOUTHEASTERN BAHAMAS. BY  
MONDAY-TUESDAY...LOCALLY HEAVY RAINFALL WILL CONTINUE ACROSS COSTA  
RICA AND WESTERN PANAMA...YET A DECREASING TREND WILL BE IN PLACE.  
 
OTHER SYSTEM OF INTEREST...IS WEAKENING A COLD FRONT MEANDERING  
SOUTHWARD ACROSS THE EASTERN CARIBBEAN. BY FRIDAY EVENING...THE  
REMNANTS OF THE FRONT WILL CROSS THE CENTRAL  
ANTILLES/BARBADOS...TO PRODUCE RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-25MM. BY SATURDAY SUNDAY...THE REMNANTS WILL REACH  
NORTHERN SOUTH AMERICA...TO PRODUCE SCATTERED ACCUMULATIONS OF  
05-10MM/DAY AND MAXIMA OF 15MM ACROSS NORTHERN VENEZUELA INTO  
TRINIDAD AND TOBAGO. SIMILAR AMOUNTS ARE EXPECTED ON  
SUNDAY-MONDAY...TO DECREASE ON MONDAY.  
 
ELSEWHERE IN NORTHERN SOUTH AMERICA...MOST ACTIVE WILL CLUSTER IN  
THE AMAZON BASIN...WHERE EXPECTING GENERALLY 10-15MM/DAY AND  
MAXIMA OF 20-35MM. SIMILAR AMOUNTS ARE EXPECTED IN THE GUIANAS  
EARLY IN THE CYCLE...YET A SLIGHT DECREASING TREND IS TO FOLLOW.  
IN COLOMBIA...MOST ACTIVE WILL CLUSTER TO THE WEST OF THE  
ANDES...WHERE EXPECTING 15-20MM/DAY AND ISOLATED MAXIMA OF  
25-50MM. AS THE LLANOS DRY OUT UNDER THE INFLUENCE OF THE  
LOW-LEVEL JET...EXPECTING A SEASONAL DECREASE IN ACCUMULATIONS IN  
THE ANDES OF CENTRAL AND NORTHERN COLOMBIA...WHERE MAXIMA WILL BE  
GENERALLY UNDER 15MM/DAY AND ISOLATED.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
37W 39W 41W 43W 46W 49W 52W 55W TUTT INDCD 19N  
 
A WAVE IS INITIALIZED AT 37W AND TO THE SOUTH OF 19N. THIS WAVE IS  
BEING INDUCED BY A STRONG POLAR TROUGH IN THE MIDDLE OF THE NORTH  
ATLANTIC. AS THE POLAR TROUGH PULLS...THE WAVE IS FORECAST TO  
SLOWLY PROPAGATE WESTWARD AS AN EASTERLY WAVE. THIS SYSTEM WILL  
REACH THE FORECAST AREA ONLY MONDAY...WHERE IT IS FORECAST TO  
PRODUCE SLIGHT ENHANCEMENT IN CONVECTION OVER THE GUIANAS.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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