371  
FXCA20 KWBC 011924  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
224 PM EST FRI DEC 01 2017  
 
TROPICAL DISCUSSION FROM DEC 01/12 UTC: CONSISTENT WITH PREVIOUS  
ANALYSIS AND FORECAST...A 500 HPA HIGH OVER CENTRAL MEXICO EXTENDS  
A RIDGE ACROSS MEXICO-GULF TO THE SOUTHERN USA. THIS BUILDS ACROSS  
THE WESTERN CARIBBEAN TO CENTRAL AMERICA LATER TODAY/EARLY ON  
SATURDAY MORNING...WHERE IT IS TO THEN HOLD THROUGHOUT THE  
WEEKEND. THE RIDGE...AS IT HOLDS OVER THE GULF...IS TO STEER SHORT  
WAVE TROUGHS ON THE SOUTHERN STREAM FLOW ACROSS THE USA TO THE  
WESTERN ATLANTIC. THESE WILL COMBINE WITH DIGGING TROUGH ON THE  
NORTHERN STREAM TO SUSTAIN A BROAD TROUGH NORTH OF THE GREATER  
ANTILLES. AS THE TROUGH DEEPENS ACROSS THE WESTERN ATLANTIC...IT  
WILL PRESS AGAINST A CELL OF THE SUBEQUATORIAL RIDGE MEANDERING  
OVER THE EASTERN CARIBBEAN. AS A RESULT...THE RIDGE IS TO  
GRADUALLY WEAKEN LATER ON SATURDAY/EARLY SUNDAY MORNING. AS THE  
RIDGE WEAKENS...ASSOCIATED TRADE WINDS CAP WILL GRADUALLY LIFT TO  
550/500 HPA LATER ON SUNDAY/EARLY MONDAY MORNING. THIS WILL ALLOW  
FOR DEEPER MOISTURE TO POOL ACROSS THE NORTHEAST CARIBBEAN ISLES  
DURING THE WEEKEND/EARLY NEXT WEEK...WITH PWAT CONTENT FORECAST TO  
PEAK AT 40-45MM. AT 250 HPA...A SUBTROPICAL JET MAXIMA IS TO BOUND  
THE SOUTHERN FRINGES OF THE DEEPENING POLAR TROUGH. THE JET TENDS  
TO STRENGTHEN EARLY NEXT WEEK...MEANWHILE FAVORING AN UPPER  
DIVERGENT PATTERN THAT IS TO VENT DEEP CONVECTION ACROSS THE  
NORTHEAST CARIBBEAN ISLES ON MONDAY AFTERNOON/ TUESDAY MORNING.  
 
AT LOW LEVELS...A FRONT EXTENDS FROM A DEEPENING LOW TO THE NORTH  
OF PUERTO RICO EARLY THIS MORNING...WITH BOUNDARY TRAILING TO THE  
WEST-SOUTHWEST ACROSS THE SOUTHEAST BAHAMAS-CUBA LATER TODAY.  
SIMULTANEOUSLY...A LOW LEVEL RIDGE IS TO SLOWLY BUILD ACROSS THE  
GULF OF MEXICO-SOUTHEAST USA ON FRIDAY-SATURDAY. AS THE RIDGE  
BUILDS IT IS TO SUSTAIN A BRISK NORTHEASTERLY FLOW ACROSS CUBA-THE  
BAHAMAS TO THE WESTERN CARIBBEAN...WITH BOUNDARY LAYER WINDS OVER  
THE BAHAMAS-CUBA TO PEAK AT 15-20KT. OVER THE WESTERN  
CARIBBEAN/NORTHERN CENTRAL AMERICA THE WINDS ARE TO PEAK AT  
20-25KT. AS THE WINDS INTENSIFY THE FRONT IS TO MOVE SOUTH ACROSS  
THE TURKS AND CAICOS WHILE TRAILING ACROSS CUBA EARLY ON SATURDAY  
MORNING. ON SUNDAY-MONDAY IT IS TO THEN STALL JUST NORTH OF THE  
GREATER ANTILLES WITH AXIS ALONG 20N/21N INTO THE TURKS AND CUBA.  
ALSO OVER THE EASTERN CARIBBEAN...UNDER INFLUENCE OF THE FRONTAL  
LOW NORTH OF THE ISLANDS...AN INDUCED INVERTED TROUGH IS TO EXTEND  
NORTH ALONG 62W/63W. THIS IS ENHANCING MOISTURE TRANSPORT ACROSS  
THE WINDWARD ISLES TO THE EASTERN CARIBBEAN. THE BUILDING POLAR  
RIDGE IS TO ALSO SUSTAIN A PREFRONTAL SHEAR LINE THAT MOVES ACROSS  
PUERTO RICO TO THE VIRGIN ISLES EARLY ON SATURDAY...MOVING ACROSS  
THE LEEWARD ISLES LATER ON SATURDAY. THIS BRIEFLY BECOMES ILL  
DEFINED ON SUNDAY...BUT ON MONDAY AS THE TRADES INTENSIFY ACROSS  
THE NORTHEAST CARIBBEAN THE SHEAR LINE IS TO FORM ONCE AGAIN  
ACROSS SAINT MARTIN-VIRGIN ISLES-PUERTO RICO. THE BRISK  
NORTHEASTERLY TRADES WILL SUSTAIN A COOL ADVECTIVE PATTERN ON  
TUESDAY ACROSS THE WARM WATERS NORTH OF THE ISLANDS.  
THIS...IN-TURN...WILL RESULT IN CONVECTIVE INSTABILITY AND  
GENERATION OF TRADE WIND SHOWERS.  
 
ACROSS THE BAHAMAS-CUBA THE FRONT AND COLD POST FRONTAL  
NORTHERLIES ARE TO FAVOR SCATTERED SHALLOW CONVECTION...TO TRIGGER  
RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM/DAY. THROUGH  
SUNDAY THE FOCUS OF THE CONVECTION SHIFTS TO THE SOUTHEAST  
BAHAMAS...TURKS AND CAICOS TO EASTERN CUBA...WITH RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15MM. ACROSS NORTHERN HISPANIOLA  
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM  
THROUGH SATURDAY...WHILE ON SUNDAY-MONDAY EXPECTING ACCUMULATION  
OF 05-10MM/DAY AND MAXIMA OF 15MM. OVER PUERTO RICO-VIRGIN ISLES  
THE PREFRONTAL SHEAR LINE IS TO TRIGGER RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM LATER ON FRIDAY THROUGH SATURDAY  
MORNING. ON SATURDAY-SUNDAY THIS INCREASES TO 05-10MM/DAY AND  
MAXIMA OF 15-20MM. ON MONDAY TO TUESDAY HIGHER AMOUNTS ARE HIGHLY  
PROBABLE AS ENHANCED BY UPPER LEVEL JET MAXIMA AND LOW LEVEL SHEAR  
LINE CONFLUENCE...WITH MAXIMA LIKELY TO EXCEED 25MM/DAY. OVER THE  
LEEWARD ISLES THE PREFRONTAL SHEAR LINE IS TO THEN FAVOR RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM EARLY ON SUNDAY  
MORNING...WHILE ON SUNDAY-MONDAY IT DECREASES TO 00-05MM/DAY AND  
MAXIMA OF 10MM.  
 
OVER THE EASTERN CARIBBEAN...THE INDUCED PREFRONTAL TROUGH IS TO  
SUSTAIN A MOIST SOUTHEASTERLY FLOW ACROSS THE WINDWARD ISLANDS.  
OVER TRINIDAD AND TOBAGO AND THE SOUTHERN WINDWARD ISLANDS THIS IS  
TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM.  
HIGHER AMOUNTS ARE EXPECTED OVER THE NORTHERN WINDWARD  
ISLANDS/FRENCH ISLES...WITH RAINFALL AMOUNTS OF 10-15MM/DAY AND  
MAXIMA OF 20-30MM. ON SATURDAY THIS DECREASES TO 05-10MM/DAY AND  
MAXIMA OF 15-20MM.  
 
OVER THE WESTERN CARIBBEAN...THE BRISK NORTHEASTERLY WINDS ARE TO  
ENHANCE MOISTURE CONVERGENCE ACROSS NORTHERN HONDURAS-SOUTHERN  
BELIZE. EARLY IN THE CYCLE MOST ACTIVE IS TO CLUSTER ACROSS  
NORTHWEST HONDURAS-SOUTHERN BELIZE...WITH RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-40MM...WHILE OVER NORTHEAST HONDURAS/  
NICARAGUA EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF  
10MM. ON SUNDAY-MONDAY CONVECTION ACROSS NORTHERN HONDURAS  
INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-30MM. ACROSS  
JAMAICA...THE BRISK NORTHEASTERLY WINDS ARE TO RESULT IN LIGHT  
RAINFALL AMOUNTS WITH ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF  
10MM.  
 
AS THE TRADES OVER THE WESTERN CARIBBEAN/CENTRAL AMERICA  
INTENSIFY...THIS IS TO SLOWLY DRIVE THE EASTERN PACIFIC ITCZ  
SOUTH. ACROSS SOUTHERN NICARAGUA-COSTA RICA TO PANAMA EXPECTING  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-20MM. OVER EJE  
CAFETERO IN NORTHWEST COLOMBIA...INITIALLY EXPECTING RAINFALL  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. BUT AS THE ITCZ  
MEANDERS SOUTH THIS GRADUALLY DECREASES TO 05-10MM/DAY AND MAXIMA  
OF 15-20MM ON SATURDAY-SUNDAY. LIKEWISE...OVER THE CAUCA VALLEY TO  
THE SOUTHWEST...INITIALLY EXPECTING RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM. ON SATURDAY-SUNDAY THIS  
INCREASES TO 15-20MM/DAY AND MAXIMA OF 25-50MM. ON THE ANDEAN  
REGION OF COLOMBIA-SOUTHERN VENEZUELA EXPECTING RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15-20MM/DAY...WHILE OVER AMAZONIA TO  
THE SOUTH THE MAXIMA IS TO PEAK AT 20-45MM ON SATURDAY-MONDAY  
MORNING.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
SOF  
44W 51W 55W 59W 63W 66W 69W 72W TWS  
11N  
66W 68W 70W 72W 74W 76W 78W 80W EW  
16N  
 
A TRADE WIND SURGE IS INITIALIZED ALONG 44W AND SOUTH OF  
11N...WITH A DRY SAHARAN AIR LAYER TRAILING THIS PERTURBATION.  
THIS REACHES FRENCH GUIANA LATER THIS EVENING...FASTER THAN  
ORIGINALLY ANTICIPATED...WHERE IT IS TO TRIGGER RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15-20MM. THIS SPREADS ACROSS SURINAME  
LATER IN THE DAY/EARLY SATURDAY MORNING...AND NORTHERN  
GUYANA/NORTHEAST VENEZUELA LATER ON SATURDAY. ON MONDAY MAXIMA  
ACROSS TRINIDAD-NORTHEAST VENEZUELA INCREASES TO 20-30MM. ACROSS  
SOUTHERN VENEZUELA EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM....WHILE OVER THE ABC ISLANDS EXPECTING  
ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM ON SUNDAY-MONDAY.  
 
AN EASTERLY WAVE ALONG 66W AND TO THE SOUTH OF 16N IS INTERACTING  
WITH THE INDUCED PREFRONTAL TROUGH OVER THE EASTERN  
CARIBBEAN...SUSTAINING A PLUME OF DEEP TROPICAL MOISTURE ACROSS  
THE WINDWARD ISLANDS. AS IT STREAMS ACROSS VENEZUELA TO COLOMBIA  
THIS IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-20MM. OVER THE ABC ISLANDS IT IS TO ALSO TRIGGER SIMILAR  
RAINFALL AMOUNTS. OVER NORTHWEST COLOMBIA TO EASTERN PANAMA THIS  
WILL TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM  
ON MONDAY...WHILE OVER THE CAUCA VALLEY TO THE SOUTHWEST EXPECTING  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM.  
 
PECK...MS (JAMAICA)  
RIVAS...SENAMHI (PERU)  
DAVISON...WPC (USA)  
 

 
 
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