674  
FXCA20 KWBC 271928  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
227 PM EST MON NOV 27 2017  
 
TROPICAL DISCUSSION FROM NOV 27/12 UTC: MID/UPPER LEVEL RIDGE  
EXTENDS TO THE NORTH-NORTHEAST FROM A CLOSED HIGH OVER  
MICHOACAN/COLIMA IN SOUTHWEST MEXICO...ACROSS THE NORTHERN STATES  
OF MEXICO TO THE MISSISSIPPI VALLEY IN THE USA. UNDER PRESSURE  
FROM SHORT WAVE TROUGHS STREAMING ACROSS NORTH AMERICA...PORTION  
OF THE RIDGE OVER THE USA IS TO FLATTEN LATER ON TUESDAY. REMNANTS  
OF THIS RIDGE ARE TO THEN CONFINE TO THE NORTHERN STATES OF  
MEXICO. AS IT HOLDS TO THE NORTH...THIS IS TO FAVOR A SUBSIDENCE  
CAP THAT IS TO INHIBIT ORGANIZED DEEP CONVECTION.  
 
A MID LEVEL TROUGH TO THE EAST EXTENDS OVER THE GULF TO THE  
YUCATAN/SOUTHERN STATES OF MEXICO...WHILE ORIGINATING ON A CLOSED  
LOW OVER THE NORTHERN GULF. AT 250 HPA A JET MAXIMA BOUNDS THE  
EASTERN FRINGES OF THIS RIDGE...EXTENDING FROM NORTHERN CENTRAL  
AMERICA/WESTERN CARIBBEAN...ACROSS CUBA TO THE BAHAMAS. THIS  
FAVORS AN UPPER DIVERGENT PATTERN THAT IS VENTING CONVECTION OVER  
THE CENTRAL-WESTERN CARIBBEAN. AS THE RIDGE TO THE WEST  
FLATTENS...THE SHORT WAVE TROUGH IS TO SLOWLY LIFT ACROSS CUBA/THE  
BAHAMAS EARLY ON WEDNESDAY MORNING. THIS IS TO THEN RAPIDLY WEAKEN  
WHILE PRESSING AGAINST A CELL OF THE SUBEQUATORIAL RIDGE TO THE  
EAST. AS THE GRADIENT SLACKENS...THE JET OVER THE WESTERN  
CARIBBEAN IS FORECAST TO WEAKEN. AT LOW LEVELS...THE TROUGH ALOFT  
CONTINUES TO INTERACT WITH A MEANDERING TROUGH OVER THE CENTRAL  
CARIBBEAN. THE TROUGH EXTENDS TO THE NORTH-NORTHWEST FROM  
PANAMA/SOUTHERN CARIBBEAN TO THE CAYMAN ISLES/NORTHWEST CARIBBEAN.  
THIS IS ENHANCING LOW LEVEL MOISTURE CONVERGENCE BETWEEN THE  
CAYMAN ISLES AND EASTERN NICARAGUA/COSTA RICA. AS THE MID/UPPER  
LEVEL TROUGH WEAKENS ON TUESDAY-WEDNESDAY...THE LOW LEVEL INVERTED  
TROUGH IS ALSO FORECAST TO WEAKEN. EARLY IN THE CYCLE THIS IS TO  
FAVOR A MOIST NORTH-NORTHEAST FLOW ACROSS THE WESTERN CARIBBEAN TO  
NORTHERN HONDURAS-SOUTHERN BELIZE/CENTRAL GUATEMALA. BUT AS THE  
TROUGH WEAKENS...PREVAILING EASTERLY TRADES RETURN TO THE WESTERN  
CARIBBEAN ON WEDNESDAY.  
 
OVER COSTA RICA-PANAMA...IN INTERACTION WITH THE ITCZ...EXPECTING  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THIS IS TO  
ALSO ENHANCE CONVECTION ACROSS WESTERN COLOMBIA TO FAVOR RAINFALL  
AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 30-60MM. ON TUESDAY-WEDNESDAY  
THIS DECREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM. BETWEEN  
EASTERN NICARAGUA AND SAN ANDRES ISLAND EXPECTING RAINFALL AMOUNTS  
OF 10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH WEDNESDAY MORNING.  
OVER THE CAYMAN ISLES EXPECTING RAINFALL AMOUNTS OF 15-20MM/DAY  
AND MAXIMA OF 25-50MM. ON TUESDAY IT DECREASES TO 05-10MM/DAY AND  
MAXIMA OF 15-30MM...WHILE ON WEDNESDAY TO THURSDAY THE MAXIMA  
PEAKS AT 15MM. OVER JAMAICA EXPECTING RAINFALL AMOUNT OF  
10-15MM/DAY AND MAXIMA OF 20-40MM DURING THE NEXT TWO  
DAYS...DECREASING TO 05-10MM/DAY AND MAXIMA OF 15MM ON WEDNESDAY.  
ACROSS CUBA THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND  
MAXIMA OF 35-70MM. ON TUESDAY THIS DECREASES TO 10-15MM/DAY AND  
MAXIMA OF 20-35MM...WHILE ON WEDNESDAY THE MAXIMA OVER EASTERN  
PORTIONS OF THE ISLAND IS TO PEAK AT 15-20MM. CONVECTION IS ALSO  
SPREADING ACROSS CUBA TO THE BAHAMAS...WHERE WE EXPECT RAINFALL  
AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 50-100MM. ON TUESDAY THIS  
DECREASES TO 15-20MM/DAY AND MAXIMA OF 35-70MM...WHILE ON  
WEDNESDAY MOST ACTIVE IS EXPECTED ON THE SOUTHEAST BAHAMAS/TURKS  
AND CAICOS WITH ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15-20MM.  
OVER NORTHERN HONDURAS THE NORTHERLIES ARE TO INITIALLY FAVOR  
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. ON WEDNESDAY  
THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-35MM...WITH MOST  
INTENSE ON THE OFFSHORE ISLANDS/ISLAS DE LA BAHIA.  
 
BROAD CELL OF THE SUBEQUATORIAL RIDGE TO THE EAST DOMINATES THE  
FLOW ACROSS THE CENTRAL/EASTERN CARIBBEAN-NORTHERN SOUTH AMERICA  
INTO THE WESTERN ATLANTIC...WITH MID LEVEL RIDGE ANCHORING ON A  
CLOSED HIGH TO THE EAST-NORTHEAST OF ANTIGUA. AS THE  
AFOREMENTIONED MID LEVEL TROUGH LIFTS ACROSS CUBA-THE BAHAMAS ON  
WEDNESDAY IT IS TO PRESS AGAINST THIS RIDGE. THIS IS TO THEN  
INDUCE THE RAPID EROSION OF MID LEVEL RIDGE PATTERN TO THE NORTH  
OF 20N ON WEDNESDAY. SHORT WAVE RIDGE IS TO THEN CONFINE TO THE  
CARIBBEAN BASIN. OVER THE GUIANAS-VENEZUELA-EASTERN CARIBBEAN  
ISLANDS THIS IS TO INITIALLY FAVOR AN UPPER CONVERGENT PATTERN  
THAT IS TO INHIBIT ORGANIZED DEEP CONVECTION. EARLY ON WEDNESDAY  
MORNING...AS THE RIDGE FLATTENS...THE SUBSIDENCE CAP RELAXES ITS  
FOOTHOLD...LIFTING ABOVE 600/500 HPA. ACROSS NORTHERN  
GUYANA-NORTHEAST VENEZUELA EXPECTING IN RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-25MM IN SHALLOW CONVECTION. THIS  
INCREASES ON TUESDAY-WEDNESDAY TO 10-15MM/DAY AND MAXIMA OF  
20-30MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
SOF  
44W 47W 50W 53W 56W 59W 61W 64W TUTT-INDCD  
12N  
61W 63W 66W 69W 71W 72W 74W 76W TUTT-INDCD  
23N  
 
A TUTT INDUCED EASTERLY WAVE IS INITIALIZED ALONG 44W AND TO THE  
SOUTH OF 12N. AS IT NEARS NORTHERN FRENCH GUIANA ON TUESDAY  
MORNING THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-30MM. THIS SPREADS ACROSS SURINAME TO GUYANA LATER IN  
THE DAY. ON WEDNESDAY...AS THE WAVE MEANDERS AWAY...THIS DECREASES  
TO 05-10MM/DAY AND MAXIMA OF 15MM. ON WEDNESDAY...OVER NORTHERN  
GUYANA-NORTHEAST VENEZUELA-TRINIDAD/TOBAGO THE ENVIRONMENTAL  
CONDITIONS WILL BE MORE FAVORABLE AND CONDUCIVE TO CONVECTION TO  
DEVELOP. AS A RESULT EXPECTING RAINFALL AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-45MM. ACROSS THE SOUTHERN WINDWARD ISLANDS EXPECTING  
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM.  
 
ANOTHER TUTT INDUCED WAVE ALONG 61W LIES TO THE NORTH OF 16N. THIS  
MOVES TO THE LEEWARD/VIRGIN ISLES LATER THIS EVENING...BUT UNABLE  
TO OVERCOME NEGATIVE INFLUENCE OF MID LEVEL RIDGE IT IS TO ONLY TO  
SUSTAIN LIGHT RAINFALL AMOUNTS IN ISOLATED CONVECTION. PLUME OF  
MOISTURE TRAILING THIS WAVE THEN MOVES TO THE NORTHERN  
LEEWARD/VIRGIN ISLES ON TUESDAY EVENING...TO FAVOR RAINFALL  
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. THIS SPREADS ACROSS  
PUERTO RICO TO EASTERN HISPANIOLA ON WEDNESDAY TO ALSO FAVOR  
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM. HIGHER AMOUNTS  
ARE EXPECTED OVER THE TURKS AND CAICOS/SOUTHEAST BAHAMAS ON  
WEDNESDAY EVENING/THURSDAY MORNING...WITH ACCUMULATION OF  
05-10MM/DAY AND MAXIMA OF 15-20MM.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  
 

 
 
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