424  
FXCA20 KWBC 252000  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EST THU JAN 25 2018  
 
TROPICAL DISCUSSION FROM JAN 25/12 UTC: A SURFACE COLD FRONT AND  
SHEAR LINE WILL CONTINUE STIMULATING PRECIPITATION IN THE SOUTHERN  
GULF OF MEXICO/NORTHERN CENTRAL AMERICA... CUBA AND THE BAHAMAS.  
BY THURSDAY EVENING THE BOUNDARY WILL MEANDER ACROSS THE NORTHERN  
BAHAMAS...NORTHERN CUBA... WHILE THE TAIL OF THE FRONT CONTINUES  
LOSING DEFINITION OVER THE SOUTHERN GULF OF MEXICO. BY FRIDAY  
EVENING...THE FRONT WILL EXTEND ACROSS THE SOUTH/CENTRAL  
BAHAMAS...NORTHERN CUBA... INTO THE CENTRAL GULF. BY SATURDAY  
EVENING THE FRONT WILL EXTEND ACROSS THE TURKS AND  
CAICOS...BETWEEN CUBA AND THE BAHAMAS...INTO THE FLORIDA  
STRAIGHT...AND INTO THE NORTHEASTERN GULF OF MEXICO. NOTE THAT  
CYCLOGENESIS WILL START DEVELOPING IN THE NORTHERN GULF OF MEXICO  
DURING LATE SATURDAY THROUGH MONDAY. SIMULTANEOUSLY...A  
SHEAR LINE WILL EXTEND ACROSS NORTHERN HISPANIOLA INTO  
NORTHEASTERN NICARAGUA BY THURSDAY EVENING. BY FRIDAY EVENING...IT  
WILL EXTEND ACROSS NORTHERN PUERTO RICO...SOUTHEASTERN  
HISPANIOLA...LOSING DEFINITION ACROSS THE NORTH-CENTRAL CARIBBEAN.  
 
THE BULK OF PRECIPITATION WITH THE FRONT/SHEAR LINE SYSTEM WILL  
OCCUR ALONG THE GULF OF CAMPECHE AND GULF OF HONDURAS.  
UNSEASONABLY HIGH VALUES OF PRECIPITABLE WATER ARE PRESENT IN THIS  
REGION. ESTIMATIONS SUGGEST 100-130% ABOVE AVERAGE OVER THE GULF  
OF HONDURAS...AND 130-160% ABOVE AVERAGE OVER THE GULF OF MEXICO  
EAST INTO CUBA. ALSO...THE CONTINUED PASSAGE OF UPPER TROUGHS WILL  
INTERACT WITH MOIST CONVECTION TO ENHANCE IT. THROUGH EARLY  
FRIDAY...THE LARGEST AMOUNTS ARE EXPECTED IN THE SOUTHERN VERACRUZ  
WHERE EXPECTING 35-70MM/DAY AND ISOLATED MAXIMA OF 100-150MM.  
LOCALLY HEAVY RAIN IS ALSO EXPECTED IN EXTREME NORTHWESTERN  
HONDURAS/SOUTHERN BELIZE WHERE AMOUNTS WILL REACH 20-40MM/DAY AND  
MAXIMA OF 50-100MM. IN THE GULF OF CAMPECHE...ACCUMULATIONS ARE TO  
GRADUALLY DECREASE TO 05-10MM/DAY AND MAXIMA OF 15MM BY  
SATURDAY-SUNDAY. IN SOUTHERN BELIZE...A SIMILAR TREND IS  
EXPECTED...WITH ACCUMULATIONS OF 05-10MM/DAY AND MAXIMA OF 15MM BY  
SATURDAY-SUNDAY AS WELL. CONVECTION IS EXPECTED ON A DAILY BASIS  
IN THE YUCATAN PENINSULA...YET A DECREASING TREND IN COVERAGE IS  
ALSO EXPECTED THROUGH THE CYCLE. NORTHEASTERLY WINDS NORTH OF THE  
SHEAR LINE WILL ALSO STIMULATE TRADE WIND CONVERGENCE IN NORTHERN  
HONDURAS/EXTREME NORTHEASTERN NICARAGUA. IN THESE REGIONS  
EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM THROUGH SUNDAY. A  
TRANSIENT PEAK IN ACCUMULATIONS IS EXPECTED ON  
FRIDAY-SATURDAY...AS DEVELOPING SHOWERS INTERACT WITH PASSING  
UPPER TROUGH.  
 
ALSO WITH THE FRONT/SHEAR LINE SYSTEM...EXPECTING PRECIPITATION IN  
CUBA...BAHAMAS...HISPANIOLA AND PUERTO RICO. IN THE  
BAHAMAS...EXPECTING 05-10MM/DAY AND MAXIMA OF 15MM THROUGH  
SATURDAY...MEANDERING FROM THE CENTRAL-NORTHERN ISLANDS ON  
THURSDAY-FRIDAY TO THE SOUTHERN ISLANDS BY FRIDAY-SATURDAY. A  
SHARP DECREASE IS EXPECTED AFTER WHILE THE ISLANDS REMAIN  
POST-FRONTAL. IN CUBA EXPECTING SIMILAR AMOUNTS MOSTLY ALONG  
NORTHEASTERN COASTS. A TRANSIENT PEAK IS EXPECTED IN NORTH-CENTRAL  
CUBA ON FRIDAY-SATURDAY...WHEN ENHANCED MOISTURE CONVERGENCE WILL  
LEAD TO MAXIMA OF 15-25MM. IN HISPANIOLA...SHEAR LINE CONVECTION  
WILL LEAD TO 10-15MM/DAY AND MAXIMA OF 20-35MM ON THURSDAY.  
SIMILAR AMOUNTS WILL LINGER ON FRIDAY-SATURDAY. MODELS ARE  
SUGGESTING A SIGNIFICANT SPEED UP OF THE TRADES FROM FRIDAY AND  
ON. AS OROGRAPHICALLY-FORCED CONVERGENCE PEAKS ON  
SATURDAY...EXPECTING A PEAK IN ACCUMULATIONS TO REACH MAXIMA OF  
25-50MM. IN PUERTO RICO...SHEAR LINE CONVERGENCE WILL COINCIDE  
WITH THE SPEEDING OF THE TRADES AND THE PASSAGE OF AN EASTERLY  
WAVE. THIS WILL LEAD TO A PEAK OF 15-20MM/DAY AND MAXIMA OF  
25-50MM IN NORTHEASTERN PARTS OF THE ISLAND ON FRIDAY-SATURDAY. A  
SLIGHT DECREASE IS EXPECTED ON SATURDAY. NOTE THAT THE SUBSIDENCE  
CAP WILL PERSIST ACROSS THE GREATER ANTILLES UNDER THE INFLUENCE  
OF THE MID-LEVEL RIDGE. YET...THE STRONG TRADES WILL LEAD TO  
PERSISTENT TRADE WIND SHOWERS AND EXACERBATED LOW-LEVEL MOISTURE  
CONVERGENCE ALONG NORTHEASTERN SLOPES.  
 
ALSO IN NORTHERN PARTS OF THE FORECAST DOMAIN...UNSEASONABLY  
ACTIVE CONVECTION IS DEVELOPING IN MEXICO. THIS IS DUE TO THE  
COMBINATION OF ABOVE-AVERAGE MOISTURE CONTENT...AND BY THE  
PERSISTENCE OF PASSING UPPER TROUGHS AND ASSOCIATED JETS OVER THE  
REGION. LARGEST AMOUNTS ARE EXPECTED THROUGH FRIDAY TO REACH  
05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM IN THE THUNDERSTORMS  
THAT DEVELOP. THIS IS TO DECREASE TO MAXIMA OF 15MM ON  
FRIDAY-SATURDAY. BY SATURDAY-SUNDAY...THE FOCUS OF ACTIVITY WILL  
CONCENTRATE IN NORTHEASTERN MEXICO. REGARDING THE AFOREMENTIONED  
CYCLOGENESIS...MODELS AGREE ON STRONG NORTHERLIES DEVELOPING INTO  
EARLY NEXT WEEK. AS THE WINDS REACH SPEEDS OF 30-40KT IN THE  
SOUTHERN GULF AND MOISTURE CONTENT REMAINS HIGH...MODELS ARE  
AGREEING ON HEAVY RAINFALL DEVELOPING FROM LATE SUNDAY THROUGH  
TUESDAY/WEDNESDAY. ALTHOUGH THE EXACT EVOLUTION IS STILL  
UNCLEAR...EXPECTING LARGEST ACCUMULATIONS STRETCHING FROM NORTHERN  
VERACRUZ TO NORTHERN HONDURAS AGAIN. THIS TIME...EXPECTING THE  
POTENTIAL FOR SEVERAL AREAS RECEIVING TOTALS OVER 100MM/DAY.  
 
A CONTINUED DECREASING TREND IN ACCUMULATIONS IS EXPECTED IN  
SOUTHERN CENTRAL AMERICA. ALSO...THE PACIFIC ITCZ IS FORECAST TO  
CONTINUE MEANDERING BACK INTO SOUTHERN COLOMBIA...AS THE NORTHERLY  
TRADES INCREASE ACROSS THE PANAMA ISTHMUS. ALSO...UNDER PERSISTENT  
WESTERLIES IN THE MID-UPPER TROPOSPHERE...THE MID-UPPER LEVELS  
CONTINUE TO BE DRY. THIS WILL LIMIT THE COVERAGE OF CONVECTION AND  
ASSOCIATED RAINFALL AMOUNTS. IN WESTERN COLOMBIA...ISOLATED  
CONVECTION THROUGH THE CYCLE WILL LEAD TO 05-10MM/DAY AND MAXIMA  
OF 15-20MM THROUGH EARLY SATURDAY. THIS IS DECREASING TO 15MM BY  
SATURDAY-SUNDAY. IN COSTA RICA...TRADE WIND CONVERGENCE WILL  
CONTINUE LEADING TO ISOLATED ACCUMULATIONS OF 05-10MM/DAY AND  
MAXIMA OF 15-20MM THROUGH SATURDAY...DECREASING RAPIDLY AFTER.  
 
ELSEWHERE IN SOUTH AMERICA AND IN THE LESSER ANTILLES...ACTIVITY  
WILL REMAIN LIGHT AND GENERALLY ISOLATED.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE  
SOF  
60W 62W 64W 67W 70W 74W 77W 80W TUTT INDCD  
24N  
 
A TUTT-INDUCED WAVE IS INITIALIZED AT 60W. THIS WAVE WILL  
INITIALLY INTERACT WITH A PRE-FRONTAL TROUGH IN THE REGION...BUT  
WILL THEN PROPAGATE AS AN EASTERLY WAVE ACROSS THE NORTHERN  
ANTILLES. THE WAVE WILL INTERACT WITH THE REORGANIZING SHEAR LINE  
IN PUERTO RICO ON FRIDAY-SATURDAY TO FAVOR ISOLATED MAXIMA OF  
25-50MM. IT WILL THEN BECOME ILL-DEFINED AS IT PROPAGATES ALONG  
THE NORTHERN CARIBBEAN THROUGH THE WEEKEND.  
 
GORDON...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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