531  
FXCA20 KWBC 161937  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
237 PM EST TUE JAN 16 2018  
 
TROPICAL DISCUSSION FROM JAN 16/12 UTC: UPPER RIDGE EXTENDS FROM  
NORTHEASTERN SOUTH AMERICA ACROSS VENEZUELA INTO  
JAMAICA-HISPANIOLA AND PUERTO RICO. THIS PATTERN IS FORECAST TO  
HOLD THROUGH THE CYCLE. AT MID-LEVELS...A RIDGE IS FORECAST TO  
MEANDER ALONG THE NORTHERN CARIBBEAN ISLES INTO THE GULF OF  
HONDURAS THROUGH THE CYCLE. AS THIS RIDGE CONFIGURATION HOLDS...IT  
WILL FORCE UPPER TROUGHS TO MEANDER EAST-NORTHEASTWARD ALONG THE  
GULF OF MEXICO/UNITED STATES...WITHOUT DIGGING INTO THE NORTHERN  
CARIBBEAN. AS A RESULT...ASSOCIATED SURFACE FRONTS AND SHEAR LINES  
WILL LIMIT TO CENTRAL AMERICA AND THE EXTREME NORTHWESTERN  
CARIBBEAN/CUBA/BAHAMAS.  
 
INITIALLY...A LINGERING SURFACE FRONT WILL CONTINUE MEANDERING  
NORTHWESTWARD ACROSS THE NORTHWESTERN ANTILLES-NORTHERN HONDURAS.  
BY TUESDAY EVENING IT WILL EXTEND ACROSS ANDROS ISLAND IN THE  
NORTH-CENTRAL BAHAMAS...NORTH-CENTRAL CUBA...INTO THE NORTHERN  
YUCATAN PENINSULA. THIS WILL BE ACCOMPANIED BY AN ILL-DEFINED  
SHEAR-LINE THAT WILL EXTEND ACROSS CENTRAL CUBA...CAYMAN  
ISLANDS...NORTHEASTERN HONDURAS. AS A POLAR HIGH BUILDS OVER THE  
CENTRAL USA...NORTHERLY WINDS ARE TO INCREASE DURING LATE TUESDAY  
INTO WEDNESDAY ACROSS THE NORTHWESTERN CARIBBEAN. THIS WILL PUSH  
THE FRONT ONCE AGAIN TO THE SOUTHEAST WHILE IT WEAKENS. BY  
WEDNESDAY EVENING THE ILL-DEFINED FRONT WILL EXTEND ACROSS  
CENTRAL-EASTERN CUBA...NORTHWEST OF THE CAYMAN ISLANDS...INTO  
QUINTANA ROO...TO LOSE DEFINITION AFTER. BY THIS TIME...THE SHEAR  
LINE WILL EXTEND ACROSS EASTERN CUBA...BETWEEN THE JAMAICA...AND  
INTO SAN ANDRES ISLAND AND COSTA RICA.  
 
A SECOND FRONT WILL ENTER THE BASIN ON TUESDAY. BY TUESDAY EVENING  
IT WILL EXTEND ACROSS THE NORTHWESTERN GULF INTO A LOW AT 24N  
95W...TO CENTRAL VERACRUZ. BY WEDNESDAY EVENING THE FRONT WILL  
EXTEND ACROSS THE NORTHERN BAHAMAS...NORTHERN CUBA...NORTHERN  
YUCATAN INTO SOUTHERN VERACRUZ. BY THURSDAY EVENING THE FRONT WILL  
BECOME STATIONARY ACROSS THE SOUTHEASTERN BAHAMAS...SOUTHEASTERN  
CUBA...JUST TO THE SOUTH OF THE CAYMAN ISLANDS...INTO NORTHERN  
HONDURAS/SOUTHERN BELIZE. THIS NEW FRONT WILL INTERACT WITH THE  
SHEAR LINE...WHICH IS FORECAST TO EXTEND ACROSS NORTHERN  
HAITI...INTO SOUTHERN NICARAGUA.  
 
UNDER A PERSISTENT UPPER TROUGH PATTERN TO THE WEST...MODELS  
CONTINUE SHOWING FAVORABLE VENTILATION FOR ANY CELL THAT IS FORCED  
TO BREAK THE SUBSIDENCE CAP IN EASTERN CENTRAL AMERICA.  
ALSO...PRECIPITABLE WATER VALUES REMAIN HIGH ALONG THE EASTERN  
COAST OF CENTRAL AMERICA...WITH VALUES EXCEEDING 50MM OFF THE  
COASTS OF NICARAGUA AND HONDURAS. THIS WILL SUSTAIN ENHANCED  
PRECIPITATION THROUGH THE CYCLE IN THE CARIBBEAN COASTS OF CENTRAL  
AMERICA BETWEEN WESTERN PANAMA AND SOUTHERN BELIZE DURING  
DIFFERENT PERIODS OF THE CYCLE. THROUGH EARLY WEDNESDAY...LARGEST  
ACCUMULATIONS ARE EXPECTED IN NORTHERN AND NORTHEASTERN  
HONDURAS...WHERE ENHANCED MOISTURE CONVERGENCE IN THE TAIL OF THE  
SHEAR LINE WILL LEAD TO 15-30MM/DAY AND MAXIMA OF 40-80MM. IN  
NORTHERN COSTA RICA/SOUTHERN NICARAGUA EXPECTING 15-20MM/DAY AND  
MAXIMA OF 25-50MM. WITH THE SURFACE FRONT...EXPECTING  
ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-30MM IN THE  
NORTH-CENTRAL BAHAMAS. IN THE CENTRAL BAHAMAS AND CENTRAL CUBA  
EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM. SIMILAR AMOUNTS ARE  
EXPECTED IN THE CAYMAN ISLANDS UNDER INTERACTION WITH THE SHEAR  
LINE...WHEREAS IN JAMAICA...EXPECTING SIMILAR ACCUMULATIONS DUE TO  
THE PRE-FRONTAL TROUGH AND INTERACTIONS BETWEEN THE TRADES AND THE  
WINDWARD PASSAGE/HISPANIOLA IN REGIONS UPSTREAM. BY WEDNESDAY INTO  
EARLY THURSDAY...AS THE NORTHERLY COMPONENT OF THE TRADES  
INCREASES IN THE GULF OF HONDURAS...EXPECTING AN INCREASE IN  
ACCUMULATIONS TO 15-30MM/DAY AND MAXIMA OF 50-100MM. IN EASTERN  
COSTA RICA EXPECTING 15-20MM/DAY AND MAXIMA OF 25-50MM WITH THE  
SHEAR LINE. REGARDING THE FRONT...LARGEST ACCUMULATIONS ARE  
EXPECTED IN THE NORTHERN BAHAMAS WHERE LOW-LEVEL MOISTURE  
CONVERGENCE AND ENHANCED UPPER DIVERGENCE IN THE RIGHT ENTRANCE OF  
AN UPPER JET WILL FAVOR RAINFALL AMOUNTS OF 15-20MM/DAY AND MAXIMA  
OF 25-50MM. IN CENTRAL CUBA...CAYMAN ISLANDS AND SOUTHERN BELIZE  
EXPECTING 05-10MM/DAY AND MAXIMA OF 15-25MM. IN JAMAICA...UNDER  
THE INFLUENCE OF THE SHEAR LINE...EXPECTING ISOLATED AMOUNTS OF  
05-10MM/DAY AND MAXIMA OF 15-20MM. BY THURSDAY-EARLY FRIDAY  
EXPECTING LARGEST AMOUNTS IN NORTHERN HONDURAS AND EXTREME  
SOUTHERN BELIZE/EASTERN GUATEMALA WHERE ENHANCED MOISTURE  
CONVERGENCE WILL LEAD TO 25-50MM/DAY AND MAXIMA OF 75-125MM.  
ENHANCED MOISTURE CONVERGENCE IN WESTERN PANAMA/EASTERN COSTA RICA  
WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 40-80MM. FRONTAL AND  
SHEAR-LINE CONVECTION IN SOUTHEASTERN CUBA/NORTHEASTERN HISPANIOLA  
AND THE TURKS AND CAICOS WILL LEAD TO 05-10MM/DAY AND MAXIMA OF  
15-25MM.  
 
IN THE NORTHEASTERN CARIBBEAN...ALTHOUGH MID-LEVEL RIDGE PATTERN  
IS TO PERSIST...TRADE WINDS WILL BE SUFFICIENTLY LIGHT TO FAVOR  
CIRCULATIONS TRIGGERED BY DIURNAL HEATING. FURTHERMORE...SST  
ANOMALIES ARE ABOVE AVERAGE ACROSS MOST OF THE REGION. THIS IS  
SUFFICIENT TO ALLOW FOR AFTERNOON SHOWERS AND ISOLATED  
THUNDERSTORMS IN WESTERN PUERTO RICO AND PARTS OF  
HISPANIOLA...THAT ARE CAPABLE OF PRODUCING 15-20MM/DAY AND MAXIMA  
OF 25-50MM. THIS IS TO CONTINUE THROUGH THURSDAY  
MORNING...FOLLOWED BY A DECREASE ON THURSDAY TO 05-10MM/DAY AND  
MAXIMA OF 15-25MM.  
 
IN NORTHERN SOUTH AMERICA...LARGEST ACCUMULATIONS ARE TO CLUSTER  
IN THE AMAZON BASIN INCLUDING SOUTHEASTERN COLOMBIA. EXPECTING  
15-30MM/DAY AND MAXIMA OF 40-80MM THROUGH EARLY  
WEDNESDAY...DECREASING TO 15-20MM/DAY AND MAXIMA OF 25-50MM AFTER.  
ELSEWHERE...MODERATE RAINFALL AMOUNTS ARE EXPECTED WHERE THE  
ATLANTIC ITCZ CONVERGES WITH THE COAST. THIS WILL LEAD TO TOTALS  
OF 10-15MM/DAY AND MAXIMA OF 20-35MM IN THE GUIANAS ON  
TUESDAY-EARLY WEDNESDAY...CONSTRAINING TO FRENCH GUIANA AND AMAPA  
IN BRAZIL AFTER. IN COLOMBIA...DIURNAL CONVECTION WILL LEAD TO  
05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM...WHILE IN SOUTHWESTERN  
COLOMBIA/CAUCA VALLEY AND NORTHWESTERN ECUADOR EXPECTING  
10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH THURSDAY MORNING.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
NONE  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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