888  
FXCA20 KWBC 081813  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
113 PM EST MON JAN 08 2018  
 
TROPICAL DISCUSSION FROM JAN 08/12 UTC: A MID/UPPER LEVEL HIGH TO  
THE SOUTH OF THE BAJA PENINSULA EXTENDS A RIDGE NORTH ACROSS  
MEXICO TO THE WESTERN USA. UNDER INFLUENCE OF THIS RIDGE A TROUGH  
DEEPENED ACROSS THE MISSISSIPPI VALLEY TO THE GULF OF MEXICO.  
EARLY IN THE CYCLE THE TROUGH IS TO SPLIT IN TWO...WITH NORTHERN  
HALF TO QUICKLY LIFT ACROSS THE NORTHEAST USA WHILE THE SOUTHERN  
HALF MEANDERS OVER THE GULF. LATER THIS EVENING/EARLY ON TUESDAY  
MORNING THE SOUTHERN SEGMENT IS TO EVOLVE INTO A CLOSED LOW OVER  
THE EASTERN GULF...WITH SHORT WAVE TROUGH ACROSS WESTERN CUBA TO  
THE WESTERN CARIBBEAN/NORTHERN CENTRAL AMERICA. THE LOW IS TO  
MEANDER ACROSS WESTERN CUBA TO THE NORTHWEST BAHAMAS LATER ON  
WEDNESDAY/EARLY THURSDAY MORNING...WHILE SHORT WAVE TROUGH TRAILS  
TO THE WESTERN CARIBBEAN. AT LOW LEVELS THE TROUGH ALOFT IS TO  
INTERACT WITH SURFACE FRONT MEANDERING ACROSS THE BAHAMAS-STRAITS  
OF FLORIDA-THE GULF OF MEXICO...TRIGGERING CYCLOGENESIS OVER THE  
NORTHEASTERN GULF LATER THIS EVENING. THIS LOW WILL THEN DRIVE THE  
FRONT ACROSS THE YUCATAN PENINSULA ON TUESDAY AFTERNOON...INTO THE  
WESTERN CARIBBEAN ON WEDNESDAY EVENING WHERE IT IS FORECAST TO  
FRONTOLIZE. EARLY ON THURSDAY THE LOW FILLS AND THE FRONT IS TO  
DISSIPATE. FURTHERMORE...AS THE MID/UPPER LEVEL TROUGH MEANDERS  
OVER THE NORTHWEST CARIBBEAN A JET MAXIMA IS TO ROUND THE BASE OF  
THE TROUGH ON WEDNESDAY-THURSDAY. DIVERGENCE ON ITS RIGHT ENTRANCE  
REGION IS TO INITIALLY VENT DEEP CONVECTION ACROSS THE CAYMAN  
ISLES...TO SPREAD ACROSS JAMAICA ON WEDNESDAY MORNING.  
 
OVER SOUTHERN VERACRUZ-CHIAPAS THIS IS TO FAVOR SCATTERED  
CONVECTION THROUGH TUESDAY WITH RAINFALL AMOUNTS OF 00-05MM/DAY  
AND MAXIMA OF 10MM. ACROSS WESTERN CUBA THIS IS TO THEN FAVOR  
RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM ON  
TUESDAY...WHILE OVER EASTERN CUBA EXPECTING RAINFALL AMOUNTS OF  
20-30MM/DAY AND MAXIMA OF 40-80MM. OVER THE CENTRAL-NORTHWEST  
BAHAMAS THIS WILL SUSTAIN RAINFALL AMOUNTS OF 15-20MM/DAY AND  
MAXIMA OF 25-50MM. THROUGH WEDNESDAY THIS INCREASES TO 15-20MM/DAY  
AND MAXIMA OF 35-70MM. FURTHERMORE...AS THE MID/UPPER LEVEL TROUGH  
MEANDERS OVER THE NORTHWEST CARIBBEAN A JET MAXIMA IS TO ROUND THE  
BASE OF THE TROUGH ON WEDNESDAY-THURSDAY. DIVERGENCE ON ITS RIGHT  
ENTRANCE REGION IS TO THEN VENT CONVECTION ACROSS JAMAICA. ACROSS  
THE CAYMAN ISLANDS THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF  
20-30MM/DAY AND MAXIMA OF 40-80MM...WITH SIMILAR AMOUNTS INTO  
WESTERN JAMAICA EARLY ON WEDNESDAY MORNING. OVER EASTERN SIDE OF  
THE ISLAND...MEANWHILE...EXPECTING ACCUMULATION OF 05-10MM/DAY AND  
MAXIMA OF 15-25MM. OVER NORTHERN HONDURAS...FRONTAL NORTHERLIES ON  
TUESDAY WILL RESULT IN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA  
OF 15-25MM.  
 
AS THE TROUGH DEEPENS ACROSS THE GULF OF MEXICO IT IS TO PRESS  
AGAINST A CELL OF THE SUBEQUATORIAL RIDGE TO THE EAST. AT 250 HPA  
THE RIDGE ANCHORS ON A CLOSED HIGH OFF THE COAST OF  
VENEZUELA...WITH AXIS ENVELOPING THE CENTRAL-EASTERN CARIBBEAN. AS  
THE TROUGH DEEPENS TO THE WEST THE UPPER LEVEL RIDGE IS TO BUILD  
NORTH BETWEEN 60W-70W TO 30N LATER ON TUESDAY. AT 500 HPA THE MID  
LEVEL RIDGE ANCHORS ON A CLOSED HIGH THAT MEANDERS JUST NORTH OF  
THE LEEWARD ISLES...WHILE EXTENDING A SHORT WAVE RIDGE TO THE  
NORTHEAST CARIBBEAN. OVER PUERTO RICO-VIRGIN ISLES AND THE ISLAND  
CHAIN THIS FAVORS A MID LEVEL CONVERGENT PATTERN THAT IS  
INHIBITING ORGANIZED DEEP CONVECTION. ENVIRONMENTAL CONDITIONS  
ACROSS HISPANIOLA...HOWEVER... ARE TO REMAIN MORE FAVORABLE FOR  
CONVECTION TO DEVELOP. ACROSS HAITI EXPECTING RAINFALL AMOUNTS OF  
15-20MM/DAY AND MAXIMA OF 35-70MM THROUGH TUESDAY  
MORNING...DECREASING TO 05-10MM/DAY AND MAXIMA OF 15-25MM ON  
TUESDAY-WEDNESDAY. OVER THE DOMINICAN REPUBLIC EXPECTING RAINFALL  
AMOUNTS OF 00-05MM/DAY AND MAXIMA OF 10MM IN ISOLATED CONVECTION.  
 
A TUTT LOW NEAR 16N 48W EXTENDS A SHORT WAVE TROUGH OVER THE  
TROPICAL ATLANTIC TO JUST NORTH OF THE GUIANAS. UNDER INFLUENCE OF  
THE MID LEVEL RIDGE THE SHORT WAVE TROUGH STRETCHES OVER THE  
SOUTHERN WINDWARD ISLES/GRENADINES EARLY ON WEDNESDAY MORNING. AS  
IT PRESSES AGAINST THE RIDGE TO THE WEST...TRADE WINDS CAP  
ENVELOPING THE NORTHEAST CARIBBEAN WEAKENS ENOUGH TO ALLOW FOR A  
DEEPER PLUME OF MOISTURE TO ENTER THE FORECAST AREA. AT LOW  
LEVELS...A HIGH ROLLS ACROSS THE MID ATLANTIC REGION IN THE USA TO  
THE WESTERN ATLANTIC LATER ON TUESDAY...TO BUILD A BROAD RIDGE  
ACROSS THE WESTERN ATLANTIC ON WEDNESDAY-THURSDAY. THE BUILDING  
RIDGE WILL THEN SUSTAIN BRISK EASTERLY TRADES ACROSS THE NORTHEAST  
CARIBBEAN ISLES...WITH THE 925-950 HPA WINDS FORECAST TO PEAK AT  
25-30KT ON WEDNESDAY-FRIDAY. THIS WILL THEN TRANSPORT A PLUME OF  
MOISTURE ACROSS THE LEEWARD ISLES EARLY ON WEDNESDAY...TO PUERTO  
RICO/EASTERN HISPANIOLA LATER IN THE DAY. PWAT CONTENT DURING THAT  
PERIOD IS EXPECTED TO PEAK AT 40-45MM. THIS WILL FEED CONVECTIVE  
DEVELOPMENT OVER THE LEEWARD ISLES TO FAVOR RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-25MM ON TUESDAY TO WEDNESDAY. ACROSS  
THE VIRGIN ISLES TO EASTERN PUERTO RICO AND EASTERN HISPANIOLA  
THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA  
OF 15-20MM ON WEDNESDAY-THURSDAY. AS THE MID LEVEL TROUGH MEANDERS  
NORTH OF THE GUIANAS IT IS TO THEN ENHANCE CONVECTION. EARLY IN  
THE CYCLE EXPECTING CONVECTION ACROSS FRENCH GUIANA TO TRIGGER  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. AS IT  
SPREADS ACROSS SURINAME TO GUYANA ON TUESDAY THIS IS TO THEN  
SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
AN ILL ORGANIZED CELL OF THE PANAMANIAN LOW DOMINATES THE FLOW  
OVER THE SOUTHERN CARIBBEAN/WESTERN COLOMBIA. THE MEANDERING  
TROUGH WILL ENHANCE MOISTURE CONVERGENCE ACROSS THE CAUCA/CAUCA  
VALLEY TO THE SOUTHWEST...TO RESULT IN RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-30MM. THROUGH TUESDAY EVENING THIS  
INCREASES TO 10-15MM/DAY AND MAXIMA OF 20-40MM. OVER NORTHWEST  
COLOMBIA/ANDEAN REGION...MEANWHILE... EXPECTING RAINFALL AMOUNTS  
OF 05-10MM/DAY AND MAXIMA OF 15MM. THROUGH WEDNESDAY THE DAILY  
MAXIMA INCREASES TO 15-25MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
48W 51W 53W 55W 57W 59W 61W 63W TUTT INDCD 15N  
 
THE TUTT OVER THE TROPICAL ATLANTIC INDUCED A PERTURBATION IN THE  
EASTERLY TRADES...WITH AXIS NORTH ALONG 48W TO 15N. THIS MOVES TO  
FRENCH GUIANA EARLY ON TUESDAY MORNING...TO SUSTAIN RAINFALL  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-30MM. DURING THE DAY THIS  
IS TO THEN ENHANCE SEA BREEZE CONVERGENCE ACROSS SURINAME TO FAVOR  
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THE WAVE  
ENTERS GUYANA-WINDWARD ISLES ON WEDNESDAY...TO SUSTAIN RAINFALL  
AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15-25MM.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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