856  
FXCA20 KWBC 261935  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
234 PM EST TUE DEC 26 2017  
 
TROPICAL DISCUSSION FROM DEC 26/12 UTC: AT 500 HPA...A MID LEVEL  
RIDGE EXTENDS WEST-TO-EAST FROM CENTRAL MEXICO...ACROSS THE  
GREATER ANTILLES/NORTHERN CARIBBEAN TO THE CENTRAL ATLANTIC. AXIS  
ANCHORS ON CLOSED HIGHS...WITH ONE MEANDERING OVER CUBA AND THE  
OTHER NORTH OF HISPANIOLA. THROUGH THURSDAY THESE COMBINE INTO A  
SINGLE HIGH NORTH OF HISPANIOLA. BROAD POLAR TROUGH LIES TO THE  
NORTH...ENVELOPING THE CONTINENTAL USA-WESTERN ATLANTIC WHILE  
BOTTOMING OUT TO THE NORTH OF 30N. AS THE TROUGH MEANDERS TO THE  
NORTH...IT WILL SUSTAIN AN ELONGATED SURFACE FRONT ACROSS THE  
FLORIDA PENINSULA-NORTHERN GULF OF MEXICO TO THE RIO BRAVO. THIS  
FRONT IS TO REMAIN NEARLY STATIONARY DURING THE NEXT FEW  
DAYS...FROM TIME-TO-TIME MEANDERING SOUTH INTO THE NORTHWEST  
BAHAMAS-SOUTH FLORIDA. BUT THESE INCURSIONS WILL BE SHORT  
LIVED...WITH THE FRONT QUICKLY BOUNCING BACK INTO CENTRAL PORTIONS  
OF FLORIDA. THE FRONT IS TO ALSO FAVOR GENERATION OF A PREFRONTAL  
SHEAR LINE ACROSS THE CENTRAL BAHAMAS-CENTRAL CUBA TO NORTHWEST  
HONDURAS ON WEDNESDAY-THURSDAY. ACROSS THE BAHAMAS-CUBA THE SHEAR  
LINE IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-20MM...WHILE OVER THE CAYMAN ISLANDS EXPECTING RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER SOUTHERN BELIZE-NORTHEAST  
GUATEMALA-NORTHWESTERN HONDURAS AND THE ISLAS DE LA BAHIA  
INITIALLY EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-20MM. ON WEDNESDAY THIS IS TO INCREASE TO 10-15MM/DAY AND  
MAXIMA OF 20-35MM. ON THURSDAY MOST INTENSE IS TO FOCUS BETWEEN  
SOUTHERN BELIZE AND NORTHWEST HONDURAS WITH RAINFALL AMOUNTS OF  
15-20MM/DAY AND MAXIMA OF 35-70MM.  
 
A TUTT LOW OVER THE CENTRAL ATLANTIC EXTENDS A TROUGH WEST ACROSS  
THE FRENCH/WINDWARD ISLES TO THE EASTERN CARIBBEAN. UNDER  
INFLUENCE OF THE MID LEVEL RIDGE TO THE NORTH THE TROUGH IS  
FORECAST TO SLOWLY SPREAD ACROSS THE EASTERN TO THE CENTRAL  
CARIBBEAN LATER ON WEDNESDAY/EARLY THURSDAY MORNING...WHERE IT IS  
TO THEN PERSIST THROUGH THE END OF THE WEEK. AT IT PRESSES AGAINST  
THE RIDGE TO THE NORTH...THIS IS TO WEAKEN THE CAP INVERSION OVER  
THE CARIBBEAN. THIS...IN-TURN...WILL ALLOW FOR PLUME OF DEEPER  
TROPICAL MOISTURE TO SPREAD ACROSS THE ISLAND CHAIN INTO THE  
EASTERN-CENTRAL CARIBBEAN. AT LOW LEVELS...BRISK EASTERLY TRADES  
DOMINATE THE NORTHERN CARIBBEAN...WITH BOUNDARY LAYER WINDS  
PEAKING AT 15-20KT. STRONGER WINDS TO THE SOUTH OF 17N WILL  
ENVELOP MOST OF THE BASIN-CENTRAL AMERICA...TO PEAK BETWEEN  
20-30KT DURING THE NEXT FEW DAYS. NOTE THAT MUCH STRONGER WINDS  
ARE EXPECTED AT 850 HPA ACROSS CENTRAL AMERICA TO THE EASTERN  
TROPICAL PACIFIC. THE STRONG WINDS ACROSS THE BASIN WILL ENHANCE  
MOISTURE TRANSPORT. OVER THE ISLAND CHAIN THIS IS TO FAVOR LIGHT  
RAINFALL AMOUNTS WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF  
10MM IN PASSING SHOWERS. HIGHER AMOUNTS ARE EXPECTED OVER PUERTO  
RICO AND THE DOMINICAN REPUBLIC...WITH ACCUMULATION OF 05-10MM/DAY  
AND MAXIMA OF 15-20MM. ACROSS CENTRAL AMERICA MOST ACTIVE  
CONVECTION WITH THE TRADES IS EXPECTED OVER EASTERN NICARAGUA AND  
CARIBBEAN COASTAL PLAINS OF COSTA RICA...WITH RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-25MM.  
 
THE BRISK EASTERLIES ACROSS CENTRAL AMERICA ALSO FAVOR A FAIRLY  
STRONG CELL OF THE PANAMANIAN LOW OVER THE EASTERN PACIFIC THAT IS  
TO MEANDER OFF THE CENTRAL COAST OF COLOMBIA. THIS TROUGH WILL  
ENHANCE COASTAL CONVERGENCE BETWEEN THE CAUCA VALLEY TO THE  
SOUTHWEST AND THE EJE CAFETERO TO THE NORTHWEST...TO RESULT IN  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. ON THE  
ANDEAN REGION OF COLOMBIA... MEANWHILE...EXPECTING RAINFALL  
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.  
 
EAST OF THE ISLANDS...THE AFOREMENTIONED TUTT IS TO MEANDER OVER  
THE CENTRAL ATLANTIC WHILE ANCHORING ON A CLOSED LOW NEAR 22N 42W.  
THIS IS TO REMAIN OVER THE CENTRAL ATLANTIC DURING THE NEXT FEW  
DAYS...MEANWHILE FAVORING AN UPPER DIVERGENT PATTERN THAT IS TO  
VENT TRADE WIND RELATED CONVECTION ACROSS THE NORTHERN  
GUIANAS-NORTHEAST VENEZUELA. ACROSS THE GUIANAS THIS IS TO FAVOR  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH  
THURSDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM.  
HIGHER AMOUNTS ARE EXPECTED OVER NORTHERN GUYANA AND TRINIDAD ON  
WEDNESDAY WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 25-50MM.  
ON THURSDAY...THE MAXIMA ACROSS NORTHERN GUYANA IS TO PEAK AT  
30-60MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
SOF  
51W 54W 57W 60W 64W 67W 71W 74W TUTT INDCD  
26N  
59W 62W 65W 67W 69W 72W 75W 78W TUTT INDCD  
27N  
66W 70W 73W 76W 79W 82W 85W 88W TUTT INDCD  
25N  
 
MEANDERING TUTT OVER THE TROPICAL ATLANTIC FAVORS GENERATION OF  
INDUCED PERTURBATIONS IN THE LOW/MID LEVEL EASTERLY TRADES.  
 
ONE ALONG 51W AND SOUTH OF 26N IS TO ENTER THE ISLAND CHAIN LATER  
ON WEDNESDAY...TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA  
OF 10MM. ON THURSDAY IT MOVES ACROSS THE VIRGIN ISLES TO PUERTO  
RICO...WHERE IT IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15MM. EARLY ON FRIDAY MORNING IT WILL MOVE TO THE  
DOMINICAN REPUBLIC TO ALSO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY  
AND MAXIMA OF 15MM. OVER THE ABC-NORTHERN VENEZUELA EXPECTING  
HIGHER RAINFALL AMOUNTS...WITH ACCUMULATION OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM.  
 
A TUTT INDUCED PERTURBATION ALONG 59W MOVES ACROSS THE ISLAND  
CHAIN EARLY IN THE CYCLE TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY  
AND MAXIMA OF 10MM. ACROSS PUERTO RICO THIS INCREASES TO  
05-10MM/DAY AND MAXIMA OF 15MM ON WEDNESDAY...WHILE OVER THE ABC  
ISLANDS/NORTHERN VENEZUELA IT IS TO TRIGGER RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM. ACROSS HISPANIOLA THIS IS TO THEN  
TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM LATER  
ON WEDNESDAY-THURSDAY.  
 
A TUTT INDUCED PERTURBATION ALONG 66W AND SOUTH OF 25N IS TO  
TRIGGER SCATTERED CONVECTION ACROSS WESTERN PUERTO RICO-THE  
DOMINICAN REPUBLIC THIS AFTERNOON...WITH RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM. OVER HAITI THIS IS TO SUSTAIN  
RAINFALL AMOUNTS OF 00-05MM/DAY...WHILE OVER JAMAICA EXPECT  
ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. THIS REACHES  
NICARAGUA-COSTA RICA LATER ON THURSDAY TO SUSTAIN RAINFALL AMOUNTS  
OF 10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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