793  
FXCA20 KWBC 111859  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 PM EST THU JAN 11 2018  
 
TROPICAL DISCUSSION FROM JAN 11/12 UTC: WEST OVER THE DOMAIN...A  
HIGH AMPLITUDE MID/UPPER LEVEL TROUGH IS TO EXTEND ACROSS THE  
MISSISSIPPI VALLEY TO THE WESTERN GULF/SOUTHERN STATES OF MEXICO  
LATER THIS AFTERNOON. ON FRIDAY AFTERNOON THE TROUGH MOVES TO THE  
EASTERN USA-WESTERN CARIBBEAN/NORTHERN CENTRAL AMERICA...WITH  
BROAD POLAR TROUGH PATTERN TO THEN PERSIST ACROSS THE  
CENTRAL/EASTERN USA-THE GULF OF MEXICO/WESTERN CARIBBEAN. AT LOW  
LEVELS THIS SUSTAINS A PROGRESSIVE FRONT THAT MOVES ACROSS THE RIO  
BRAVO TO THE NORTHEAST STATES OF MEXICO LATER TODAY. STRONG  
FRONTAL NORTHERLIES OF 30-35KT WILL THEN DRIVE THIS FRONT SOUTH  
ALONG THE GULF COAST OF MEXICO TO SOUTHERN VERACRUZ EARLY ON  
FRIDAY MORNING. LATER IN THE DAY THE FRONT WILL CONTINUE ACROSS  
FLORIDA TO BELIZE/GUATEMALA. THE STRONG FRONTAL NORTHERLIES ARE TO  
THEN FAVOR A TEHUANTEPECER JET OF 50KT. EARLY ON SATURDAY THE  
FRONT WILL THEN MOVE TO THE NORTHWEST BAHAMAS-WESTERN/CENTRAL CUBA  
INTO THE WESTERN CARIBBEAN/NORTHERN CENTRAL AMERICA...WITH FRONTAL  
NORTHERLIES OF 20-25KT ACROSS THE ISLAS DE LA BAHIA TO NORTHERN  
HONDURAS. LATER ON SATURDAY/EARLY SUNDAY MORNING THE FRONT MOVES  
OVER THE CENTRAL BAHAMAS-CENTRAL CUBA-THE CAYMAN ISLES WHILE  
TRAILING TO NORTHERN CENTRAL AMERICA. FURTHERMORE...AS THE FRONT  
SURGES ACROSS THE GULF OF MEXICO...IT IS TO INDUCE A PREFRONTAL  
SHEAR LINE OVER THE WESTERN CARIBBEAN TO NORTHEAST  
HONDURAS/NICARAGUA ON FRIDAY EVENING. THROUGH SATURDAY THIS MOVES  
TO THE CENTRAL CARIBBEAN-COSTA RICA/WESTERN PANAMA...WITH 850 HPA  
WINDS OVER NICARAGUA-EASTERN PACIFIC FORECAST TO PEAK AROUND  
40-50KT...WHILE THE BOUNDARY LAYER WINDS ARE EXPECTED TO PEAK AT  
30-35KT.  
 
OVER CHIAPAS-TABASCO IN SOUTHERN MEXICO...THE FRONT AND FRONTAL  
NORTHERLIES WILL FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA  
OF 15MM ON THURSDAY AND FRIDAY. SIMILAR AMOUNTS ARE EXPECTED  
ACROSS BELIZE-GUATEMALA ON FRIDAY. HIGHER AMOUNTS ARE EXPECTED  
BETWEEN PUERTO BARRIOS GUATEMALA AND TELA/SAN PEDRO SULA IN  
NORTHWEST HONDURAS-ISLAS DE LA BAHIA...WITH ACCUMULATION OF  
10-15MM/DAY AND MAXIMA OF 20-40MM ON FRIDAY-SATURDAY. ACROSS CUBA  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM  
THROUGH FRIDAY. ON SATURDAY THIS INTENSIFIES AS IT SPREADS ACROSS  
CENTRAL-EASTERN PORTIONS OF THE ISLAND WITH ACCUMULATION OF  
10-15MM/DAY AND MAXIMA OF 20-40MM. ACROSS THE BAHAMAS EXPECTING  
FRONTAL CONVECTION ON FRIDAY TO SUSTAIN RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-40MM. ON SATURDAY EXPECTING SIMILAR  
AMOUNTS ACROSS THE CENTRAL-SOUTHEAST BAHAMAS. SHEAR LINE  
CONFLUENCE OVER THE CAYMAN ISLES ON FRIDAY WILL SUSTAIN RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM. ON SATURDAY...AS THE  
FRONT APPROACHES...THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF  
20-40MM. OVER JAMAICA THE SHEAR LINE AND PREFRONTAL TROUGH WILL  
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM ON  
SATURDAY. MOST INTENSE CONVECTION IS EXPECTED TO THE SOUTH IN  
ASSOCIATION WITH THE SHEAR LINE MOVING TO THE SOUTHERN CARIBBEAN.  
OVER COSTA RICA-WESTERN PANAMA IT IS TO TRIGGER RAINFALL AMOUNTS  
OF 35-70MM/DAY AND MAXIMA OF 125-200MM LATER ON SATURDAY THROUGH  
SUNDAY MORNING AND AGAIN ON SUNDAY TO MONDAY...WITH STORM TOTAL  
AMOUNTS EXPECTED TO PEAK AT 250-400MM.  
 
AS THE POLAR TROUGH DEEPENS ACROSS THE GULF OF MEXICO IT IS TO  
PRESS AGAINST A WANING MID/UPPER LEVEL RIDGE THAT EXTENDS FROM  
CENTRAL/SOUTHERN MEXICO ACROSS THE GULF OF MEXICO TO THE EASTERN  
USA/WESTERN ATLANTIC. UNDER PRESSURE...THE RIDGE COLLAPSES LATER  
ON THURSDAY/EARLY FRIDAY MORNING. A SHORT WAVE TROUGH TO THE EAST  
OF THIS RIDGE EXTENDS OVER THE BAHAMAS-CUBA-WESTERN CARIBBEAN. AS  
IT REMAINS CUT OFF FROM THE FLOW THE TROUGH IS FORECAST TO  
GRADUALLY WEAKEN. ON FRIDAY THE REMNANTS WILL LIFT TO THE  
NORTH-NORTHEAST AHEAD OF THE DEEPENING POLAR TROUGH TO THE WEST.  
OVER THE DAY TODAY THIS WILL ENHANCE CONVECTION ACROSS THE  
CENTRAL-NORTHWEST BAHAMAS TO FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-45MM. ACROSS CUBA/JAMAICA THIS WILL FAVOR  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.  
 
DOWNSTREAM OVER THE CARIBBEAN...A 250 HPA HIGH OVER ISLA DE  
MARGARITA ANCHORS A CELL OF THE SUBEQUATORIAL RIDGE THAT EXTENDS  
OVER THE CARIBBEAN TO THE WESTERN ATLANTIC. AT 500 HPA...A HIGH TO  
THE NORTH OF THE LEEWARD/VIRGIN ISLES EXTENDS A RIDGE TO THE  
SOUTH-SOUTHEAST INTO THE EASTERN CARIBBEAN...WHERE IT FAVORS AN  
ELEVATED CAP INVERSION. AT LOW LEVELS...BROAD CELL OF THE BERMUDA  
RIDGE DOMINATES THE FLOW OVER THE ATLANTIC...SUSTAINING A TIGHT  
GRADIENT ACROSS THE CARIBBEAN BASIN AND A BRISK EAST-SOUTHEAST  
FLOW ACROSS THE ISLAND CHAIN INTO THE CARIBBEAN BASIN. THE BRISK  
EASTERLY FLOW FAVORS GENERATION OF STREAMERS ACROSS THE VIRGIN  
ISLES-EASTERN PUERTO RICO...TRIGGERING PASSING SHOWERS/LIGHT  
RAINFALL AMOUNTS. THIS IS ALSO ADVECTING A PLUME OF DEEPER  
TROPICAL MOISTURE ACROSS THE NORTHEAST CARIBBEAN ISLES. THIS WILL  
FEED CONVECTIVE DEVELOPMENT ACROSS PUERTO RICO DURING THE DAY  
TODAY...AND ACROSS HISPANIOLA TODAY AND ON FRIDAY. IN THIS AREA  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
OVER THE LESSER ANTILLES EXPECTING ACCUMULATION OF 00-05MM/DAY AND  
MAXIMA OF 10MM.  
 
AS THE MID LEVEL RIDGE HOLDS TO THE NORTH OF THE ISLANDS...IT IS  
TO STEER A TUTT TO THE SOUTH-SOUTHWEST. THE BASE OF THE 250 HPA  
TROUGH IS TO EXTEND OVER THE NORTHEAST CARIBBEAN EARLY ON SATURDAY  
MORNING. A JET MAXIMA ROUNDING THE BASE OF THE TROUGH IS TO  
BRIEFLY FAVOR AN UPPER DIVERGENT PATTERN ACROSS PUERTO RICO-VIRGIN  
ISLES ON SATURDAY MORNING/EARLY AFTERNOON. BUT AS THE JET MAXIMA  
PULLS AWAY AND THE TROUGH SETTLES TO THE EAST...AN UPPER  
CONVERGENT PATTERN QUICKLY RETURNS LATER ON SATURDAY EVENING.  
MODELS THEN AGREE ON RAPID EROSION OF AVAILABLE MOISTURE AS THE  
TRADE WINDS CAP STRENGTHENS ITS FOOTHOLD ACROSS THE NORTHEAST  
CARIBBEAN ISLES. AT LOW LEVELS...BROAD RIDGE ENVELOPING THE  
ATLANTIC IS TO PERSIST THROUGH SUNDAY MORNING... TO CONTINUE  
FAVORING AN EASTERLY FLOW ACROSS THE TROPICAL ATLANTIC-EASTERN  
CARIBBEAN ISLES. EMBEDDED IN THIS FLOW...MODELS AGREE ON A  
SECONDARY PLUME OF DEEPER TROPICAL MOISTURE TO ONCE AGAIN MOVE  
ACROSS THE ISLAND CHAIN TO THE NORTHEAST CARIBBEAN LATER ON FRIDAY  
EVENING...WITH PWAT CONTENT OF 40-45MM EXPECTED THROUGH SATURDAY  
EVENING. THIS IS TO FEED ANOTHER ROUND OF CONVECTION ACROSS THE  
LEEWARD ISLES EARLY ON SATURDAY WHERE WE EXPECT RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER PUERTO RICO AND  
HISPANIOLA THIS WILL COINCIDE WITH MAX HEATING TO SUSTAIN RAINFALL  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. THE MOST INTENSE IS  
EXPECTED ACROSS THE WESTERN INTERIOR PORTIONS OF PUERTO RICO AND  
CENTRAL HISPANIOLA.  
 
OVER THE SOUTHERN CARIBBEAN AN ILL ORGANIZED CELL OF THE  
PANAMANIAN LOW/TROUGH EXTENDS FROM THE GULF OF URABA TO WESTERN  
COLOMBIA. THIS IS TO REMAIN NEARLY UNCHANGED OVER THE NEXT DAY OR  
SO...WITH DEEPENING POLAR TROUGH TO THE NORTH TO THEN INDUCED AN  
INVERTED/PREFRONTAL TROUGH OVER THE CENTRAL CARIBBEAN ON SATURDAY.  
THIS WILL THEN MERGE WITH PANAMANIAN TROUGH PATTERN TO THE SOUTH  
TO ENHANCE MOISTURE TRANSPORT ACROSS THE CENTRAL CARIBBEAN.  
MEANWHILE...BEST MOISTURE CONVERGENCE IS EXPECTED ALONG THE WEST  
COAST OF COLOMBIA. OVER SOUTHWEST COLOMBIA INITIALLY EXPECTING  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. THROUGH  
SATURDAY THIS INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-30MM. OVER  
THE EJE CAFETERO AND ANDEAN REGION EXPECTING RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15MM...WITH MAXIMA OF 15-25MM/DAY ON  
FRIDAY-SATURDAY.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
70W 73W 76W 78W DISSIPATES EW 19N  
 
AN EASTERLY WAVE ALONG 70W AND SOUTH OF 19N IS TO DISSIPATE EARLY  
ON SATURDAY. MOST ACTIVE CONVECTION WITH THIS FEATURE IS EXPECTED  
TO THE SOUTH ACROSS SOUTHERN VENEZUELA TO EASTERN COLOMBIA...WHERE  
IT IS TO TRIGGER RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-40MM. OVER HAITI EXPECTING ACCUMULATION OF 05-10MM/DAY AND  
MAXIMA OF 15-25MM. AS IT MOVES ACROSS NORTHERN COLOMBIA ON FRIDAY  
THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-25MM. OVER JAMAICA THIS IS TO THEN SUSTAIN ACCUMULATION OF  
10-15MM/DAY AND MAXIMA OF 20-40MM.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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