969  
FXCA20 KWBC 311910  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
210 PM EST WED JAN 31 2018  
 
TROPICAL DISCUSSION FROM JAN 31/12 UTC: A 500 HPA HIGH OFF THE  
COAST OF BELIZE ANCHORS A RIDGE THAT EXTENDS EAST ACROSS THE  
NORTHERN CARIBBEAN TO THE LEEWARD ISLANDS. THROUGH THURSDAY  
EVENING THE CLOSED HIGH RELOCATES ACROSS BELIZE/THE YUCATAN TO THE  
CAMPECHE SOUND...WHILE ASSOCIATED RIDGE PATTERN OVER THE CARIBBEAN  
HOLDS. THE RIDGE SUSTAINS A STRONG TRADE WINDS CAP ACROSS THE  
NORTHERN CARIBBEAN ISLANDS...THAT IS FAVORING THE RAPID EROSION OF  
AVAILABLE MOISTURE ACROSS THE NORTHEAST CARIBBEAN ISLES. OVER THE  
NEXT COUPLE OF DAYS THIS IS TO FAVOR FAIR WEATHER CONDITIONS  
ACROSS THE NORTHEAST CARIBBEAN. SHALLOW PLUME OF MOISTURE ENTERING  
THE NORTHEAST CARIBBEAN ON FRIDAY IS TO THEN FAVOR SCATTERED  
RAINFALL SHOWERS WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF  
15-20MM...WITH MOST ACTIVE OVER PUERTO RICO AND THE VIRGIN ISLANDS.  
 
A MID/UPPER LEVEL SHORT WAVE TROUGH TO THE WEST OF THIS RIDGE  
MEANDERS OVER THE EASTERN PACIFIC OFF THE COAST OF MEXICO. UNDER  
THE INFLUENCE OF THE MID LEVEL RIDGE THE SHORT WAVE TROUGH IS TO  
SLOWLY LIFT ACROSS THE BAJA PENINSULA TO THE NORTHWEST STATES OF  
MEXICO LATER ON THURSDAY/EARLY FRIDAY MORNING. THIS WILL BE  
ACCOMPANIED BY A PLUME OF DEEP TROPICAL MOISTURE. ACROSS SOUTHERN  
BAJA PENINSULA THIS IS TO FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY  
AND MAXIMA OF 10MM ON THURSDAY. HIGHER AMOUNTS ARE EXPECTED  
BETWEEN SONORA AND COLIMA/NAYARIT. ON WEDNESDAY TO THURSDAY  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.  
ON THURSDAY TO FRIDAY THIS DECREASES TO 00-05MM/DAY AND MAXIMA OF  
10MM.  
 
A BROAD POLAR TROUGH LIES TO THE NORTH...EXTENDING OVER THE  
WESTERN NORTH ATLANTIC WHILE BOTTOMING OUT TO THE NORTH OF 25N.  
THE TROUGH IS FORECAST TO WEAKEN AS IT MEANDERS EAST INTO THE  
CENTRAL ATLANTIC ON THURSDAY-FRIDAY. AT LOW LEVELS...A POLAR RIDGE  
IS ROLLING ACROSS THE EASTERN USA. THIS FAVORS A BRISK  
NORTH-NORTHWESTERLY FLOW ACROSS THE WESTERN ATLANTIC. THIS IS  
DRIVING A SURFACE FRONT ACROSS THE CENTRAL ATLANTIC WHILE TRAILING  
ACROSS THE CENTRAL BAHAMAS TO WESTERN CUBA. IT ALSO FAVORS A  
PREFRONTAL SHEAR LINE THAT EXTENDS ACROSS HISPANIOLA TO NORTHEAST  
NICARAGUA. THE FRONT IS TO CONTINUE TO THE EAST-SOUTHEAST OVER THE  
NEXT DAY OR SO...BOTTOMING OUT TO THE NORTH OF 23N/24N LATER THIS  
EVENING/EARLY THURSDAY MORNING. AS IT LOSES ITS UPPER LEVEL  
SUPPORT THE FRONT IS TO FRONTOLIZE ON THURSDAY TO FRIDAY...AND THE  
PREFRONTAL SHEAR LINE WILL QUICKLY BECOME ILL DEFINED. OVER THE  
NORTHWEST BAHAMAS...POST FRONTAL CONVECTION IS TO SUSTAIN RAINFALL  
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ON THE TURKS AND  
SOUTHEAST BAHAMAS FRONTAL/PREFRONTAL CONVECTION WILL SUSTAIN  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER EASTERN  
CUBA THE MAXIMA PEAKS AT 15-25MM. OVER HISPANIOLA AND JAMAICA THE  
SHEAR LINE IS TO MEANWHILE FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY  
AND MAXIMA OF 10MM. OVER NORTHEAST NICARAGUA/HONDURAS EXPECTING  
ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. OTHER CONVECTION  
IS TO CLUSTER OVER ISLAS DE LA BAHIA/NORTH COAST OF  
HONDURAS...WITH ACCUMULATION OF 15-20MM/DAY AND MAXIMA OF 30-60MM.  
BUT AS THE FRONT AND SHEAR LINE WEAKEN...AND EASTERLY TRADES  
RETURN TO THE WESTERN CARIBBEAN...THE FOCUS OF THE MOISTURE  
CONVERGENCE SHIFTS TO BELIZE LATER ON THURSDAY...TO FAVOR RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM IN SCATTERED  
CONVECTION. THROUGH FRIDAY THIS DECREASES TO 00-05MM/DAY AND  
MAXIMA OF 10MM WHILE BUILDING WEST ACROSS THE YUCATAN PENINSULA.  
 
THE NEXT POLAR TROUGH MOVES ACROSS THE EASTERN USA TO THE WESTERN  
ATLANTIC LATER ON FRIDAY...WITH ASSOCIATED FRONT RACING ACROSS  
CENTRAL FLORIDA TO NORTHEAST MEXICO. ON SATURDAY IT IS TO MEANDER  
INTO THE NORTHWEST BAHAMAS-STRAITS OF FLORIDA WHILE TRAILING END  
RETROGRESSES TO TEXAS. THIS IS TO FAVOR A PREFRONTAL SHEAR LINE  
ACROSS THE SOUTHEAST BAHAMAS-EASTERN CUBA-NORTHEAST NICARAGUA ON  
FRIDAY....THAT QUICKLY MOVE ACROSS HISPANIOLA TO PUERTO RICO ON  
SATURDAY. AS THE FRONT ENTERS NORTHEAST MEXICO ON FRIDAY IT IS TO  
FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. FRONTAL  
NORTHERLIES ACROSS SOUTHERN VERACRUZ TO NORTHERN CHIAPAS-CENTRAL  
GUATEMALA ARE TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM. ACROSS THE NORTHWEST BAHAMAS THE FRONT IS TO  
THEN SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM ON  
SATURDAY TO SUNDAY. SHEAR LINE CONVERGENCE OVER THE SOUTHEAST  
BAHAMAS-TURKS AND EASTERN CUBA ON FRIDAY IS TO TRIGGER RAINFALL  
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. OVER NORTHERN HONDURAS  
EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF  
15-20MM...WHILE OVER NORTHEAST NICARAGUA THIS WILL FAVOR RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER HISPANIOLA THIS  
WILL THEN SUSTAIN RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF  
10MM...WHILE OVER PUERTO RICO EXPECTING ACCUMULATION OF  
05-10MM/DAY AND MAXIMA OF 15MM.  
 
A 500 HPA TROUGH BOUNDS THE EASTERN FRINGES OF THE CARIBBEAN  
RIDGE...WITH AXIS OVER THE TROPICAL ATLANTIC TO THE NORTHERN  
GUIANAS/NORTHEAST VENEZUELA. AN AMPLIFYING TROUGH OVER THE CENTRAL  
ATLANTIC ON THURSDAY-FRIDAY IS TO THEN PHASE WITH THIS  
PERTURBATION...TO HELP SUSTAIN A BROAD TROUGH THROUGH THE END OF  
THE WEEK. AT LOW LEVELS THE ITCZ EXTENDS ACROSS THE TROPICAL  
ATLANTIC TO AMAPA IN NORTHERN BRASIL-SOUTHERN FRENCH GUIANA. MOST  
ACTIVE CONVECTION WITH THIS FEATURE IS ALONG THE NORTH COAST OF  
BRASIL-AMAZON RIVER DELTA REGION. ACROSS FRENCH GUIANA EXPECTING  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH  
FRIDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF 15MM. OVER  
SURINAME MOST ACTIVE IS EXPECTED ON THURSDAY AND FRIDAY...WITH  
ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OTHER  
CONVECTION IS EXPECTED ACROSS TRINIDAD-TOBAGO-THE GRENADINES AND  
NORTHEAST VENEZUELA. IN THIS AREA A MEANDERING SUBEQUATORIAL JET  
MAXIMA IS ENHANCING CONVECTIVE DEVELOPMENT. IN THIS AREA INITIALLY  
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.  
THROUGH FRIDAY THIS INCREASES TO 05-10MM/DAY AND MAXIMA OF  
15-20MM.  
 
OVER THE EASTERN PACIFIC...THE ITCZ MEANDERS EAST INTO CENTRAL  
COAST OF COLOMBIA. UNDER THE INFLUENCE OF THE PANAMANIAN TROUGH  
THE ITCZ IS TO REMAIN NEARLY STATIONARY DURING THE NEXT FEW  
DAYS...ENHANCING MOISTURE CONVERGENCE ALONG THE WEST COAST AND  
ANDEAN REGION. ON THE CAUCA/CAUCA VALLEY TO THE SOUTHWEST  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
THROUGH FRIDAY THE MAXIMA DECREASES TO 15MM/DAY. OVER THE EJE  
CAFETERO TO THE NORTHWEST EXPECTING RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM.  
 
PECK...MS (JAMAICA)  
GORDON...NMS (BELIZE)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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