607  
FXCA20 KWBC 091924  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
224 PM EST TUE JAN 09 2018  
 
TROPICAL DISCUSSION FROM JAN 09/12 UTC: AT 500 HPA...A HIGH OVER  
COLIMA/NAYARIT IN SOUTHWEST MEXICO EXTENDS A RIDGE NORTH ALONG  
100W TO THE WESTERN USA. A SHORT WAVE TROUGH TO THE EAST EXTENDS  
OVER THE EASTERN GULF TO THE YUCATAN PENINSULA...WHILE CENTERING  
ON A CLOSED LOW OVER THE NORTHEAST GULF OF MEXICO. EARLY ON  
WEDNESDAY THE LOW MEANDERS TO THE EAST-SOUTHEAST ACROSS SOUTHERN  
FLORIDA...WHILE SHORT WAVE TROUGH EXTENDS TO THE SOUTHEAST ACROSS  
CUBA TO JAMAICA. THE MID LEVEL TROUGH IS TO THEN REMAIN NEGATIVELY  
TILTED WHILE SLOWLY LIFTING ACROSS THE BAHAMAS ON WEDNESDAY.  
AT 250 HPA A JET MAXIMA IS TO ROUND THE BASE OF THE UPPER LEVEL  
TROUGH...WITH DIVERGENCE ON ITS RIGHT ENTRANCE REGION TO INITIALLY  
VENT DEEP CONVECTION ACROSS THE CAYMAN ISLES-CENTRAL CUBA. AS IT  
ROUNDS THE TROUGH IT IS TO THEN VENT DEEP CONVECTION ACROSS THE  
BAHAMAS. AT LOW LEVELS THIS SUSTAINS A SURFACE LOW OVER THE  
NORTHEAST GULF...WITH ASSOCIATED FRONT TRAILING ACROSS THE GULF TO  
THE CAMPECHE SOUND. LATER TODAY THE FRONT IS TO MOVE TO THE  
YUCATAN...WHILE ON WEDNESDAY MORNING IT ADVANCES ACROSS EASTERN  
CUBA TO THE WESTERN CARIBBEAN/BELIZE. THE FRONT IS TO THEN REMAIN  
NEARLY STATIONARY WHILE GRADUALLY FRONTOLIZING LATER IN THE  
DAY/EARLY ON THURSDAY MORNING. ALSO AT LOW LEVELS...THE FRONTAL  
TROUGH OVER THE EASTERN GULF SUSTAINS AN INDUCED/INVERTED TROUGH  
OVER THE WESTERN CARIBBEAN THAT EXTENDS NORTH ACROSS THE CAYMAN  
ISLES...ACROSS CUBA TO THE NORTHWEST/CENTRAL BAHAMAS. THIS TROUGH  
IS THE FOCUS OF LOW LEVEL MOISTURE CONVERGENCE OVER THE WESTERN  
CARIBBEAN-CUBA-THE BAHAMAS...AND IT IS WHERE WE EXPECT THE MOST  
INTENSE CONVECTION DURING THE NEXT 60 HRS. THE INVERTED TROUGH IS  
TO PERSIST THROUGH WEDNESDAY EVENING...FILLING ON THURSDAY AS THE  
FRONT/TROUGH TO THE NORTH WEAKENS.  
 
OVER SOUTHERN VERACRUZ-CHIAPAS THIS IS TO FAVOR SCATTERED  
CONVECTION THROUGH TUESDAY EVENING WITH RAINFALL AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15MM...WHILE ACROSS THE NORTHERN YUCATAN  
EXPECTING ACCUMULATION OF 00-05MM/DAY AND MAXIMA OF 10MM. ACROSS  
WESTERN-CENTRAL CUBA AND THE CAYMAN ISLES THE PREFRONTAL TROUGH IS  
TO FAVOR RAINFALL AMOUNTS OF 20-30MM/DAY AND MAXIMA OF 40-80MM. ON  
WEDNESDAY...MOST ACTIVE IS EXPECT OVER THE CAYMAN ISLES AND  
CENTRAL CUBA WITH ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF  
20-40MM. OVER THE NORTHWEST BAHAMAS THIS WILL INITIALLY FAVOR  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON  
WEDNESDAY-THURSDAY IT INCREASES TO 15-20MM/DAY AND MAXIMA OF  
35-70MM WHILE BUILDING EAST TO THE CENTRAL BAHAMAS. OVER  
JAMAICA-EASTERN CUBA INITIALLY EXPECTING RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-30MM. ON WEDNESDAY TO THURSDAY IT  
DECREASES TO 05-10MM/DAY AND MAXIMA OF 15-25MM. OVER NORTHERN  
HONDURAS...THE PREFRONTAL NORTHERLIES WILL RESULT IN RAINFALL  
AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 20-40MM. ON WEDNESDAY THIS  
DECREASES TO 00-05MM/DAY AND MAXIMA OF 10MM.  
 
DEEPENING POLAR TROUGH WILL FOLLOW...TO MOVE ACROSS THE WESTERN  
USA LATER ON WEDNESDAY...INTO THE MISSISSIPPI VALLEY ON THURSDAY.  
THIS WILL SUSTAIN A PROGRESSIVE FRONT ACROSS SOUTH TEXAS TO THE  
RIO BRAVO ON THURSDAY EVENING...THAT RACES ACROSS THE FLORIDA  
PENINSULA TO WESTERN CUBA TO THE YUCATAN LATER ON FRIDAY. AS IT  
ENTERS CUBA THIS WILL TRIGGER RAINFALL AMOUNTS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM...WHILE ACROSS THE YUCATAN-BELIZE-GUATEMALA  
EXPECTING ACCUMULATION OF 05-10MM/DAY AND MAXIMA OF 15MM. HIGHER  
AMOUNTS ARE EXPECTED BETWEEN PUERTO BARRIOS GUATEMALA AND TELA/SAN  
PEDRO SULA IN NORTHWEST HONDURAS...WITH ACCUMULATION OF  
15-20MM/DAY AND MAXIMA OF 25-50MM.  
 
A BUILDING CELL OF THE SUBEQUATORIAL RIDGE LIES TO THE SOUTHEAST  
OF THIS TROUGH...WITH 250 HPA RIDGE DOMINATING THE CARIBBEAN  
BASIN/NORTHERN SOUTH AMERICA-WESTERN ATLANTIC WHILE CENTERING ON A  
CLOSED HIGH OVER NORTHERN VENEZUELA. THE UPPER LEVEL RIDGE IS TO  
HOLD NEARLY UNCHANGED THROUGH THURSDAY MORNING. AT 500 HPA...A  
HIGH TO THE NORTH-NORTHEAST OF PUERTO RICO ANCHORS A SHORT WAVE  
RIDGE OVER THE EASTERN CARIBBEAN. THIS FAVORS A FAIRLY STRONG  
TRADE WINDS CAP ACROSS THE ISLAND CHAIN-PUERTO RICO. ACROSS  
HISPANIOLA IT FAVORS A WEAK CONVERGENT PATTERN...STRONG ENOUGH TO  
DELAY ONSET OF DIURNAL CONVECTION BUT NOT STRONG ENOUGH TO  
SUPPRESS IT. TO THE EAST OF THIS RIDGE A TUTT LOW OVER THE  
TROPICAL ATLANTIC EXTENDS A SHORT WAVE TROUGH NORTH OF THE GUIANAS  
TO JUST EAST OF THE LESSER ANTILLES. UNDER THE INFLUENCE OF THE  
MID LEVEL RIDGE TO THE NORTH...THE TROUGH IS TO AMPLIFY ACROSS THE  
WINDWARD/FRENCH ISLES EARLY ON WEDNESDAY MORNING. THIS IS TO THEN  
SHEAR A SHORT WAVE VORTEX THAT SLOWLY MIGRATES JUST SOUTH OF  
PUERTO RICO ON THURSDAY...WEAKENING AS IT MEANDERS FARTHER WEST  
ACROSS THE BASIN. MEANWHILE...AS THE MID LEVEL PERTURBATION  
PRESSES AGAINST THE RIDGE TO THE NORTH...THE TRADE WINDS CAP WILL  
WEAKEN ENOUGH TO ALLOW A PLUME OF DEEPER MOISTURE TO ADVECT ACROSS  
THE NORTHEAST CARIBBEAN ISLES ON WEDNESDAY-FRIDAY MORNING.  
 
AT LOW LEVELS...A HIGH ROLLS ACROSS THE MID ATLANTIC REGION IN THE  
USA TO THE WESTERN ATLANTIC LATER ON TUESDAY/EARLY ON WEDNESDAY  
MORNING...TO THEN BUILD A BROAD RIDGE ACROSS THE WESTERN ATLANTIC  
ON WEDNESDAY-THURSDAY. THE BUILDING RIDGE WILL THEN SUSTAIN BRISK  
EASTERLY TRADES ACROSS THE EASTERN-CENTRAL CARIBBEAN...WITH THE  
925-950 HPA WINDS FORECAST TO PEAK AT 25-30KT ON WEDNESDAY-FRIDAY.  
THIS WILL ALSO ADVECT 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 15MM  
ON TUESDAY TO WEDNESDAY....DECREASING TO 00-05MM/DAY AND MAXIMA OF  
10MM ON THURSDAY. ACROSS THE VIRGIN ISLES-PUERTO RICO AND  
HISPANIOLA THIS IS TO THEN FAVOR RAINFALL AMOUNTS OF 10-15MM/DAY  
AND MAXIMA OF 20-30MM ON WEDNESDAY-THURSDAY. AS THE MID LEVEL  
TROUGH MEANDERS NORTH OF THE GUIANAS IT IS TO THEN ENHANCE DIURNAL  
CONVECTION. OVER FRENCH GUIANA EXPECTING RAINFALL AMOUNTS OF  
10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH THURSDAY MORNING. OVER  
SURINAME-GUYANA MOST ACTIVE IS ON TUESDAY-WEDNESDAY...WITH  
ACCUMULATION OF 10-15MM/DAY AND MAXIMA OF 20-35MM. THROUGH  
THURSDAY AFTERNOON THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF  
15-20MM.  
 
AN ILL ORGANIZED CELL OF THE PANAMANIAN LOW CONTINUES TO DOMINATE  
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 20-40MM ALONG THE COAST.  
THROUGH THURSDAY THIS DECREASES TO 05-10MM/DAY AND MAXIMA OF  
15-25MM. OVER NORTHWEST COLOMBIA/ANDEAN REGION...MEANWHILE...  
EXPECTING RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
54W 57W 60W 63W 66W 69W 72W 75W EW 15N  
 
AN EASTERLY WAVE ALONG 54W AND SOUTH OF 15N...FORMERLY A TUTT  
INDUCED PERTURBATION...MOVES ACROSS SURINAME TO GUYANA LATER TO  
DAY...TO SUSTAIN RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF  
20-35MM. EARLY ON WEDNESDAY THIS MOVES OVER THE WINDWARD/FRENCH  
ISLES TO SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-25MM. OVER VENEZUELA/ABC ISLES THIS IS TO ONLY FAVOR WIDELY  
ISOLATED CONVECTION WITH LIGHT RAINFALL AMOUNTS.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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