084  
FXCA20 KWBC 051916  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
215 PM EST FRI JAN 05 2018  
 
TROPICAL DISCUSSION FROM JAN 05/12 UTC: BROAD POLAR TROUGH EXTENDS  
OVER THE EASTERN USA-WESTERN ATLANTIC TO THE GULF OF  
MEXICO/NORTHWEST CARIBBEAN. THE MID/UPPER LEVEL TROUGH IS PRESSING  
AGAINST A RIDGE TO THE EAST. THE LATTER EXTENDS TO THE NORTHEAST  
FROM A 250 HPA HIGH OVER NORTHERN VENEZUELA/ABC ISLES...PUERTO  
RICO/LEEWARD ISLANDS INTO THE CENTRAL ATLANTIC. THE MID/UPPER  
LEVEL TROUGH IS TO REMAIN ACROSS THE EASTERN USA-WESTERN ATLANTIC  
THROUGH SUNDAY MORNING. LATER IN THE DAY IT IS TO THEN PULL TO THE  
NORTHEAST AS THE SUBEQUATORIAL RIDGE TO THE SOUTH GRADUALLY BUILDS  
ACROSS THE CARIBBEAN BASIN/GREATER ANTILLES. AT 500 HPA THIS WILL  
ALLOW FOR THE MID LEVEL RIDGE PATTERN TO ALSO STRENGTHEN. EARLY IN  
THE CYCLE IT IS TO EXTEND FROM A CLOSED HIGH NEAR 30N 40W. EARLY  
NEXT WEEK A SECONDARY HIGH IS TO CLOSE JUST NORTH OF PUERTO RICO.  
EARLY IN THE CYCLE THE MID LEVEL RIDGE PATTERN IS TO FAVOR AN  
ELEVATED CAP INVERSION ACROSS THE NORTHEAST CARIBBEAN...WHICH  
IN-TURN IS TO ALLOW PLUMES OF SHALLOW MOISTURE TO ADVECT ACROSS  
THE EASTERN CARIBBEAN ISLES. BUT AS THE MID LEVEL RIDGE  
BUILDS...AND TRADE WINDS CAP STRENGTHENS...EXPECTING A DRYING  
TREND ACROSS THE EASTERN CARIBBEAN EARLY NEXT WEEK.  
 
AT LOW LEVELS...THE TROUGH ALOFT SUSTAINS A POLAR FRONT ACROSS  
HAITI-JAMAICA TO NORTHERN HONDURAS-GUATEMALA. BOUNDARY IS TO  
REMAIN NEARLY STATIONARY THROUGH MID AFTERNOON ON SATURDAY. LATER  
IN THE DAY IT STARTS TO RETROGRESS TO THE TURKS/SOUTHEAST  
BAHAMAS-EASTERN CUBA TO THE NORTHWEST CARIBBEAN. ON MONDAY IT IS  
TO MEANDER OVER THE BAHAMAS-CUBA WHERE IT IS FORECAST TO  
FRONTOLIZE. THE FRONT SUSTAINS A PREFRONTAL SHEAR LINE ACROSS THE  
DOMINICAN REPUBLIC-CENTRAL CARIBBEAN TO BOCAS DEL TORO IN WESTERN  
PANAMA. THE TRAILING END OF THIS SHEAR LINE RETROGRESSES TO COSTA  
RICA ON SATURDAY AFTERNOON...MOVING TO JAMAICA-NORTHEAST NICARAGUA  
ON SUNDAY. THIS IS TO GRADUALLY WEAKEN EARLY NEXT WEEK. MOST  
ACTIVE CONVECTION IS DEVELOPING IN ASSOCIATION WITH THE SHEAR  
LINE. AS IT MEANDERS OVER NORTHERN HISPANIOLA EARLY IN THE CYCLE  
THIS IS TO SUSTAIN RAINFALL AMOUNTS OF 35-70MM/DAY AND MAXIMA OF  
100-150MM THROUGH SATURDAY. OVER JAMAICA INITIALLY EXPECTING  
RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF 25-50MM. ON  
SATURDAY...AS THE SHEAR LINE MOVES OVER THE ISLAND...EXPECTING  
RAINFALL AMOUNTS OF 15-30MM/DAY AND MAXIMA OF 40-80MM. OVER THE  
SOUTHEAST BAHAMAS/TURKS AND CAICOS-EASTERN CUBA THE FRONT/SHEAR  
LINE WILL THEN FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA OF  
25-50MM. OVER WESTERN PANAMA INITIALLY EXPECTING RAINFALL AMOUNTS  
OF 50-75MM/DAY AND MAXIMA OF 150-250MM. ON SATURDAY...AS IT TRAILS  
INTO COSTA RICA...EXPECTING RAINFALL AMOUNTS OF 35-70MM/DAY AND  
MAXIMA OF 100-150MM. ON SUNDAY...OVER NORTHEAST NICARAGUA-HONDURAS  
EXPECTING THIS TO TRIGGER RAINFALL AMOUNTS OF 15-30MM/DAY AND  
MAXIMA OF 40-80M.  
 
AS THE FRONT MEANDERS OVER THE WESTERN ATLANTIC-HAITI...IT IS TO  
SUSTAIN AN INDUCED PREFRONTAL TROUGH ACROSS THE MONA  
PASSAGE/EASTERN HISPANIOLA. THIS...IN-TURN...WILL FAVOR A MOIST  
SOUTHEASTERLY FLOW ACROSS THE LEEWARD ISLES TO PUERTO RICO/VIRGIN  
ISLES. ACROSS THE LEEWARD/VIRGIN ISLES THE INFLOW OF LOW LEVEL  
MOISTURE IS TO FAVOR RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-20MM. ACROSS PUERTO RICO MOST ACTIVE IS TO CLUSTER OVER  
NORTHWEST PORTIONS OF THE ISLAND...WITH ACCUMULATION OF  
10-15MM/DAY AND MAXIMA OF 20-30MM. ON SATURDAY THIS DECREASES TO  
05-10MM/DAY AND MAXIMA OF 15-20MM. ON SUNDAY...AS THE MID LEVEL  
RIDGE STRENGTHENS ITS FOOTHOLD ACROSS THE EASTERN CARIBBEAN...ONLY  
EXPECTING RAINFALL AMOUNTS OF 00-05MM/DAY IN ISOLATED TRADE WIND  
SHOWERS.  
 
EAST OF THE SUBEQUATORIAL RIDGE...A TUTT LOW AT 18N 33W EXTENDS A  
TROUGH TO FRENCH GUIANA/AMAPA IN BRASIL. AS THE RIDGE TO THE WEST  
BUILDS THE TUTT LOW IS TO RETROGRESS ACROSS THE TROPICAL ATLANTIC.  
OVER FRENCH GUIANA THIS IS TO INITIALLY FAVOR RAINFALL AMOUNTS OF  
00-05MM/DAY AND MAXIMA OF 10MM. ON SATURDAY-SUNDAY THIS INCREASES  
TO 05-10MM/DAY AND MAXIMA OF 15-20MM. ACROSS COLOMBIA...MOST  
ACTIVE CONVECTION IS EXPECTED ALONG THE WEST COAST AND ANDEAN  
REGION...WHERE DIURNAL CONVECTION IS TO SUSTAIN RAINFALL AMOUNTS  
OF 10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
NONE  
 
REMNANTS OF A TUTT INDUCED PERTURBATION IS INITIALIZED ALONG 62W  
TO 24N. OVER THE FRENCH-LEEWARD AND VIRGIN ISLES THIS IS TO  
SUSTAIN RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF 15MM. AS IT  
MOVES ACROSS PUERTO RICO ONLY EXPECTING LIGHT CONVECTION WITH  
ACCUMULATION OF 00-05MM/DAY IN WIDELY ISOLATED RAIN SHOWERS.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON...WPC (USA)  
 

 
 
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