189  
FXCA20 KWBC 021917  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
216 PM EST FRI FEB 02 2018  
 
TROPICAL DISCUSSION FROM FEB 02/12 UTC: SEASONALLY DRY CONDITIONS  
ARE ESTABLISHING ACROSS MOST OF THE CARIBBEAN AND CENTRAL AMERICA  
AS THE MID-LEVEL RIDGE PERSIST THROUGH THE CYCLE. THE RIDGE IS  
FORECAST TO ANCHOR ON A HIGH OVER THE SOUTHERN YUCATAN PENINSULA  
THROUGH MONDAY...WHILE EXTENDING AN AXIS ZONALLY ACROSS THE ENTIRE  
CARIBBEAN. THERMODYNAMIC ANALYSIS SHOWS THAT THE RIDGE IS  
SUSTAINING A STRONG CAP ACROSS THE NORTHERN CARIBBEAN...WHICH IS  
LIMITING THE VERTICAL DEVELOPMENT OF CONVECTION. ACROSS THE  
SOUTHERN CARIBBEAN...THE CAP IS WEAKER YET THE AIR MASS OVER THE  
REGION IS VERY DRY...REACHING DEW POINT TEMPERATURES UNDER -40C IN  
SOME LOCATIONS. BOTH PROCESSES WILL LIMIT PRECIPITATION ACROSS THE  
ENTIRE CARIBBEAN THROUGH THE CYCLE. A TUTT-INDUCED WAVE ENTERS THE  
LESSER ANTILLES AS AN EASTERLY WAVE DURING SUNDAY. A SHALLOW  
MOISTURE PLUME TRAILING BEHIND THIS WAVE WILL LEAD TO A MINOR  
ENHANCEMENT OF TRADE WIND SHOWERS ACROSS THE FRENCH ANTILLES. THIS  
WILL SUSTAIN RAINFALL MAXIMA UNDER 15MM ON SUNDAY-MONDAY.  
OTHERWISE EXPECTING ISOLATED TRADE WIND SHOWERS TO PRODUCE MAXIMA  
UNDER 10MM ON A DAILY BASIS.  
 
IN THE PACIFIC...A DEEP UPPER TROUGH THAT CENTERS ON AN UPPER LOW  
CONTINUES MEANDERING NORTHWARD JUST OFF THE COASTS OF THE BAJA  
CALIFORNIA PENINSULA. ALTHOUGH THE MID-LEVELS ARE DRY...THE  
DYNAMIC FORCING COMBINED WITH THE LITTLE MOISTURE AVAILABLE ARE  
SUFFICIENT TO SUSTAIN SCATTERED SHOWERS IN NORTHERN MEXICO.  
EXPECTING SCATTERED LIGHT ACCUMULATIONS THROUGH EARLY SATURDAY TO  
REACH 00-05MM/DAY AND ISOLATED MAXIMA OF 10MM. ACTIVITY WILL  
DECREASE IN COVERAGE AND INTENSITY AFTERWARDS.  
 
A SURFACE FRONT IS ENTERING THE BASIN ON FRIDAY...BUT GIVEN THE  
LACK OF A STRONG POLAR HIGH...NORTHERLY WINDS ARE WEAK AND WILL  
THUS ALLOW THE FRONT TO BECOME STATIONARY ACROSS THE GULF OF  
MEXICO DURING FRIDAY. BY FRIDAY EVENING THE FRONT WILL EXTEND  
ACROSS SOUTH-CENTRAL FLORIDA INTO NORTHERN TAMAULIPAS. BY SATURDAY  
EVENING...THE FRONT WILL HAVE ADVANCED INTO THE NORTHERN  
BAHAMAS...WHERE IT WILL BECOME STATIONARY AND START LOSING  
DEFINITION...WHILE THE WESTERN PART OF THE BOUNDARY STARTS  
RETREATING AS A WARM FRONT ACROSS THE GULF OF MEXICO. DURING  
SUNDAY...THE FRONT WILL START RAPIDLY LOSING DEFINITION WHILE  
RETREATING NORTHWARD. GIVEN THE LIMITED DYNAMIC FORCING AND  
MOISTURE AVAILABLE WITH THIS SYSTEM...RAINFALL ACCUMULATIONS WILL  
GENERALLY LIMIT TO 05-10MM AND ISOLATED MAXIMA OF 15MM IN THE  
NORTHWESTERN BAHAMAS ON SATURDAY-SUNDAY. OTHERWISE...EXPECTING  
GENERALLY FAIR CONDITIONS. DURING MONDAY...THE REMNANTS OF THIS  
FRONT ARE FORECAST TO MERGE WITH A STRONGER FRONT ARRIVING FROM  
THE UNITED STATES. YET...MODELS AGREE ON LIGHT RAINFALL  
ACCUMULATIONS ACROSS THE NORTHERN BAHAMAS ON MONDAY-TUESDAY...AS  
THE SYSTEM MOVES RAPIDLY ACROSS THE REGION. WE FORECAST TOTALS  
UNDER 10MM/DAY ACCUMULATING GENERALLY DURING THE DAY ON MONDAY.  
 
IN CENTRAL AMERICA...FAIR CONDITIONS WILL PREVAIL THROUGH THE  
CYCLE UNDER THE INFLUENCE OF THE AFOREMENTIONED MID-LEVEL RIDGE.  
LARGEST ACCUMULATIONS WILL ASSOCIATE WITH TRADE WIND CONVERGENCE  
ALONG CARIBBEAN COASTS AND NORTHEASTERN SLOPES...TO PRODUCE MAXIMA  
GENERALLY UNDER 10MM/DAY. A TRANSIENT ENHANCEMENT IN ACCUMULATIONS  
IS EXPECTED ALONG THE NORTHEASTERN SLOPES OF  
CHIAPAS...GUATEMALA...NORTHERN HONDURAS...AND PARTS OF EXTREME  
SOUTHERN BELIZE ON FRIDAY-SATURDAY. THIS WILL DEVELOP IN  
ASSOCIATION WITH AN INCREASE MOISTURE CONVERGENCE AS A NORTHERLY  
COMPONENT IN THE TRADES DEVELOPS. THIS WILL LEAD TO AMOUNTS OF  
05-10MM/DAY AND ISOLATED MAXIMA OF 15-20MM ON FRIDAY-SATURDAY. AS  
THE WINDS RELAX AND MOISTURE CONVERGENCE DECREASES DURING  
SATURDAY...LARGEST ACCUMULATIONS ON SATURDAY-SUNDAY WILL CLUSTER  
IN CENTRAL GUATEMALA/SOUTHERN BELIZE...WHERE MAXIMA WILL BE UNDER  
15MM. A SHARP DECREASE FOLLOWS.  
 
IN NORTHERN SOUTH AMERICA...THE SUBEQUATORIAL UPPER JET IS  
WEAKENING OVER COLOMBIA. THE WEAKENING OF THE WINDS IS MORE  
SIGNIFICANT AT MID-LEVELS. THIS WILL LEAD TO A DECREASE IN WIND  
SHEAR THAT WILL BE SUFFICIENT TO ALLOW THE DEVELOPMENT OF A  
FEW THUNDERSTORMS IN ANDEAN COLOMBIA ON BOTH FRIDAY AND SATURDAY.  
ALTHOUGH THE MID-LEVELS ARE GENERALLY DRY...ENHANCED CONVECTION  
OFF THE COAST OF SOUTHERN COLOMBIA AND ECUADOR IS BUILDING A LOCAL  
MOISTURE POOL IN CENTRAL AND SOUTHERN COLOMBIA. THIS WILL BE  
SUFFICIENT TO SUSTAIN RAINFALL ACCUMULATIONS OF 10-15MM/DAY AND  
MAXIMA OF 20-35MM THROUGH SATURDAY. BY SATURDAY-SUNDAY THIS WILL  
DECREASE TO 05-10MM/DAY AND MAXIMA OF 15-20MM. A MORE SIGNIFICANT  
DECREASE IS EXPECTED AFTER...TO SUSTAIN MAXIMA UNDER 15MM  
CLUSTERING IN SOUTHWESTERN COLOMBIA ON SUNDAY-MONDAY. TO THE  
EAST...ACCUMULATIONS ARE DECREASING IN SURINAME AND FRENCH GUIANA  
AS LOW-LEVEL SHEAR INCREASES AND AVAILABLE MOISTURE DECREASES.  
YET...AN INCREASE IN TRADE WIND CONVERGENCE IN GUYANA WILL SUSTAIN  
A SLIGHT INCREASE IN ACCUMULATIONS TO REACH 05-10MM/DAY AND MAXIMA  
OF 15MM BY SATURDAY THROUGH MONDAY.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
53W 54W 55W 57W 60W 64W 68W 71W TUTT INDCD 33N  
 
A WEAKENING UPPER TROUGH IN THE ATLANTIC IS INDUCING AN ELONGATED  
TROUGH IN THE TRADES. THIS TUTT-INDUCED TROUGH IS INITIALIZED AT  
53W AND TO THE SOUTH OF 33N. THE WAVE WILL MOVE VERY LITTLE  
THROUGH EARLY SATURDAY...WHILE ITS INFLUENCED BY THE UPPER TROUGH.  
YET...AS THE UPPER TROUGH WEAKENS...THE WAVE WILL PROPAGATE  
WESTWARD AS AN EASTERLY WAVE...TO ENTER THE ARC OF THE LESSER  
ANTILLES DURING SUNDAY. MOISTURE IS LIMITED WITH THIS WAVE...YET A  
SHALLOW TRAILING MOIST PLUME WILL LEAD TO AN INCREASE IN RAINFALL  
ACCUMULATIONS ACROSS THE ARC OF THE CENTRAL LESSER ANTILLES ON  
SUNDAY-MONDAY...TO SUSTAIN 05-10MM/DAY AND ISOLATED MAXIMA OF 15MM.  
 
GORDON...NMS (BELIZE)  
NIXON...BDM (THE BAHAMAS)  
DAVISON/GALVEZ...WPC (USA)  
 

 
 
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