969  
FXCA20 KWBC 291931  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
230 PM EST MON JAN 29 2018  
 
TROPICAL DISCUSSION FROM JAN 29/12 UTC: A LARGE POLAR TROUGH IS  
MOVING ACROSS THE EASTERN UNITED STATES WHILE SUSTAINING A SURFACE  
COLD FRONT ACROSS THE FLORIDA PENINSULA AND INTO THE GULF OF  
MEXICO. BY MONDAY EVENING THE FRONT WILL EXTEND ACROSS THE  
NORTHERN BAHAMAS...NORTHERN CUBA...THE CENTRAL YUCATAN PENINSULA  
INTO CHIAPAS. BY WEDNESDAY EVENING...IT WILL EXTEND ACROSS THE  
CENTRAL BAHAMAS...SOUTHEASTERN CUBA...THE CAYMAN ISLANDS...INTO  
EXTREME NORTHWESTERN HONDURAS AND CENTRAL GUATEMALA. BY THURSDAY  
EVENING...THE FRONT WILL EXTEND ACROSS SOUTHEASTERN  
BAHAMAS...SOUTHEASTERN CUBA...CAYMAN ISLANDS...CENTRAL BELIZE.  
NOTE THAT THE BOUNDARY WILL START TO LOSE DEFINITION OVER THE GULF  
OF HONDURAS BY THIS PERIOD. A SHEAR LINE IS ALSO ORGANIZING...AND  
BY LATE MONDAY IT WILL EXTEND ACROSS THE CAYMAN ISLANDS INTO  
NORTHEASTERN HONDURAS. BY TUESDAY EVENING IT WILL EXTEND ACROSS  
THE WINDWARD PASSAGE...JUST TO THE SOUTH OF JAMAICA...INTO  
NORTHEASTERN NICARAGUA. THE SHEAR LINE WILL RAPIDLY LOSE  
DEFINITION AFTER.  
 
LARGEST ACCUMULATIONS WITH THE FRONT/SHEAR LINE SYSTEM WILL  
CLUSTER ALONG NORTHERN AND EASTERN SLOPES OF SOUTHERN MEXICO AND  
NORTHERN CENTRAL AMERICA...ESPECIALLY BETWEEN CHIAPAS/TABASCO AND  
NORTHWESTERN HONDURAS. PRECIPITABLE WATER REMAINS WELL ABOVE  
AVERAGE IN THESE REGIONS. AS THE NORTHERLIES INTERACT WITH  
OROGRAPHY...EXPECTING ENHANCED MOISTURE CONVERGENCE TO SUSTAIN  
LOCALLY HEAVY RAINFALL. THROUGH EARLY TUESDAY...EXPECTING  
30-60MM/DAY AND MAXIMA OF 100-150MM BETWEEN SOUTHEASTERN  
VERACRUZ-CHIAPAS-TABASCO INTO CENTRAL GUATEMALA. IN EXTREME  
SOUTHERN BELIZE AND NORTHERN HONDURAS EXPECTING 15-20MM/DAY AND  
MAXIMA OF 30-60MM. IN CENTRAL AND NORTHERN VERACRUZ EXPECTING  
10-15MM/DAY AND MAXIMA OF 20-40MM. PREFRONTAL CONVECTION ACROSS  
THE CENTRAL/EASTERN YUCATAN PENINSULA AND BELIZE WILL LEAD TO  
10-15MM/DAY AND MAXIMA OF 20-30MM. BY TUESDAY-WEDNESDAY...LARGEST  
ACCUMULATIONS WILL CLUSTER NEAR THE BELIZE-HONDURAS-EASTERN  
GUATEMALA REGION...WHERE EXPECTING 30-60MM/DAY AND MAXIMA OF  
100-150MM. ELSEWHERE BETWEEN NORTHERN HONDURAS...CENTRAL  
BELIZE...NORTHERN GUATEMALA INTO SOUTHERN VERACRUZ EXPECTING  
15-20MM/DAY AND MAXIMA OF 25-50MM.IN NORTHEASTERN BELIZE/COASTAL  
QUINTANA ROO EXPECTING 10-15MM/DAY AND MAXIMA OF 20-30MM. BY  
WEDNESDAY-THURSDAY...ACTIVE CONVECTION WILL PERSIST IN NORTHERN  
HONDURAS/EXTREME EASTERN GUATEMALA/SOUTHEASTERN BELIZE...WHERE  
ENHANCED MOISTURE CONVERGENCE WILL SUSTAIN 15-20MM/DAY AND MAXIMA  
OF 30-60MM. BY THURSDAY-FRIDAY...MOISTURE IS FORECAST TO RETURN  
WESTWARD TO SUSTAIN SCATTERED SHOWERS AND THUNDERSTORMS IN BELIZE.  
 
ALSO WITH THE FRONT...EXPECTING PRECIPITATION ACROSS CUBA AND THE  
BAHAMAS. IN CUBA...MAXIMA WILL PEAK MONDAY EVENING-EARLY TUESDAY  
TO REACH 15MM IN WESTERN PARTS OF THE ISLAND. A DECREASING TREND  
FOLLOWS. OVER THE BAHAMAS...LARGER ACCUMULATIONS ARE EXPECTED ON  
MONDAY...AS A FRONTAL WAVE INTERACTS WITH THE UPPER TROUGH. THIS  
WILL LEAD TO 15-20MM/DAY AND MAXIMA OF 25-50MM FROM ANDROS  
ISLAND/NASSAU TO THE NORTH. BY TUESDAY-WEDNESDAY EXPECTING  
05-10MM/DAY AND MAXIMA OF 15-25MM IN THE SOUTHEASTERN BAHAMAS  
WHILE A SHARP DRYING TREND ESTABLISHES TO THE NORTHWEST OF THE  
FRONT. SIMILAR ACCUMULATIONS ARE EXPECTED ACROSS CENTRAL/EASTERN  
CUBA INTO THE TURKS AND CAICOS ON WEDNESDAY-THURSDAY.  
 
PRECIPITATION IS ALSO EXPECTED WITH THE SHEAR LINE. THROUGH EARLY  
TUESDAY EXPECTING 15-20MM/DAY AND MAXIMA OF 30-60MM/DAY IN  
NORTHERN HONDURAS. BY TUESDAY-WEDNESDAY...LARGEST ACCUMULATIONS  
WILL REACH 10-15MM/DAY AND ISOLATED MAXIMA OF 20-30MM ACROSS  
EASTERN NICARAGUA.  
 
A DRYING TREND IS EXPECTED ACROSS THE EASTERN CARIBBEAN...AS THE  
MID-LEVEL RIDGE MEANDERS FROM THE NORTH OF PUERTO RICO ON  
MONDAY...TO EXTEND ZONALLY ALONG 15N-18N ACROSS THE CARIBBEAN.  
TRADE WINDS ARE FORECAST TO DECREASE IN SPEED ON TUESDAY. THIS  
WILL DECREASE THE OCCURRENCE OF STREAMERS AND LOCALIZED OROGRAPHIC  
RAINFALL MAXIMA ASSOCIATED WITH ENHANCED TRADE WIND CONVERGENCE.  
THESE FACTORS WILL LEAD A DECREASE IN ACCUMULATIONS. THROUGH EARLY  
TUESDAY...LARGEST AMOUNTS ARE EXPECTED WITH A WEAKENING SHEAR LINE  
IN THE WINDWARD ISLANDS. HERE...EXPECTING 05-10MM/DAY AND MAXIMA  
OF 15-25MM. IN THE VIRGIN ISLANDS AND PUERTO RICO...AND  
NORTHEASTERN HISPANIOLA...EXPECTING 05-10MM/DAY AND MAXIMA OF  
15-20MM. THIS WILL DECREASE TO MAXIMA UNDER 10MM FROM TUESDAY AND  
THEREAFTER.  
 
IN NORTHERN SOUTH AMERICA...THE UPPER WESTERLY JET FROM THE  
PACIFIC CONTINUES EXTENDING INTO COLOMBIA. THIS IS AIDING WITH THE  
TRANSPORT OF A DRY AIR MASS FROM THE WEST...AND SUSTAINING THE  
CURRENT DRY PATTERN. AT LOW-LEVELS...THE JET IN THE LLANOS IS  
GAINING STRENGTH...WHICH IS ALSO LEADING TO DRIER CONDITIONS...AS  
IT TRANSPORTS A DRY AIR MASS FROM THE CARIBBEAN INTO THE WESTERN  
AMAZON. THIS WILL CONTINUE LEADING TO THE CURRENT SEASONALLY DRY  
PATTERN IN NORTHERN SOUTH AMERICA. CONVECTION WILL CLUSTER MOSTLY  
TO THE PACIFIC BASINS OF COLOMBIA AND ECUADOR...WHERE EXPECTING  
05-10MM/DAY AND ISOLATED MAXIMA OF 15MM THROUGH THE CYCLE. IN  
ANDEAN COLOMBIA AND ANDEAN VENEZUELA...ISOLATED DIURNAL SHOWERS  
WILL FAVOR MAXIMA UNDER 10MM ON A DAILY BASIS. DRY PATTERN IS ALSO  
EXPECTED IN THE GUIANAS AS THE ATLANTIC ITCZ HAS SHIFTED SOUTHWARD  
INTO BRAZIL. IN THE GUIANAS...EXPECTING TRACE ACCUMULATIONS ON  
DAILY TRADE WIND SHOWERS.  
 
PECK...MS (JAMAICA)  
GORDON...NMS (BELIZE)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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