321  
FXCA20 KWBC 271804  
PMDCA  
 
TROPICAL DISCUSSION - INTERNATIONAL DESKS  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
204 PM EDT FRI OCT 27 2017  
 
TROPICAL STORM SELMA IS LOCATED AT 11.4N 89.5W...MAXIMUM SUSTAINED  
WINDS ARE 40 MPH...MINIMUM CENTRAL PRESSURE IS 1005 HPA. SELMA IS  
MOVING TO THE NORTH-NORTHWEST AT 05 MPH.  
 
TROPICAL DISCUSSION FROM OCT 27/12 UTC: A HIGH AMPLITUDE TROUGH  
OVER THE WESTERN ATLANTIC IS SUSTAINING A SURFACE FRONT ACROSS THE  
CENTRAL BAHAMAS-CENTRAL CUBA. THE TAIL OF THE FRONT IS TO RAPIDLY  
FRONTOLIZE DURING FRIDAY TO PRODUCE A FEW SHOWERS AND  
THUNDERSTORMS IN EASTERN CUBA WITH ACCUMULATIONS OF 05-10MM/DAY  
AND MAXIMA OF 15MM. ACROSS THE SOUTHEASTERN BAHAMAS EXPECTING  
00-05MM AND MAXIMA OF 10MM.  
 
THE NEXT SYSTEM OF INTEREST IS ANOTHER STRONG AND AMPLE UPPER  
TROUGH THAT IS FORECAST TO EXTEND ACROSS THE CENTRAL PLAINS OF THE  
USA-NORTHERN MEXICO ON FRIDAY...TO THE MISSISSIPPI  
VALLEY-NORTHWESTERN GULF OF MEXICO BY SATURDAY...TO THEN START  
LIFTING TO THE NORTHEAST ACROSS THE EAST COAST OF THE UNITED  
STATES. THIS TROUGH WILL REINFORCE THE CURRENT UPPER DIVERGENT  
PATTERN SET UP IN THE NORTHWESTERN CARIBBEAN/CUBA/BAHAMAS...AS IT  
PRESSES AGAINST THE UPPER RIDGE TO ITS SOUTHEAST...FORECAST TO  
EXTEND NEAR JAMAICA ON FRIDAY AND SATURDAY. AT LOW-LEVELS...THIS  
TROUGH WILL SUSTAIN A SURFACE COLD FRONT THAT WILL MOVE VERY  
RAPIDLY ACROSS THE GULF OF MEXICO. BY FRIDAY EVENING...THE FRONT  
WILL EXTEND ACROSS LOUISIANA INTO TAMAULIPAS. BY SATURDAY  
EVENING...THE FRONT WILL EXTEND ACROSS THE CENTRAL GULF INTO  
SOUTHERN VERACRUZ. BY SUNDAY EVENING THE FRONT WILL EXTEND ACROSS  
THE NORTHERN BAHAMAS...WESTERN CUBA...THE SOUTHERN YUCATAN  
PENINSULA...SOUTHERN VERACRUZ. BY MONDAY EVENING THE FRONT WILL  
MAKE IT TO THE SOUTHEASTERN BAHAMAS...CENTRAL CUBA...INTO THE  
SOUTHERN GULF OF HONDURAS/SOUTHERN BELIZE. THE FRONT IS FORECAST  
TO INTERACT WITH A BROAD AREA OF LOW PRESSURE IN THE NORTHWESTERN  
CARIBBEAN/GULF OF HONDURAS. THIS REGION IS ASSOCIATED WITH A LARGE  
AREA OF STRONG CONVECTION AND LOCALLY HEAVY RAINFALL. MODELS  
SUGGEST THIS SYSTEM MEANDERING TO THE NORTHEAST TO CROSS WESTERN  
CUBA ON SATURDAY...TO THEN INTERACT WITH THE AFOREMENTIONED  
SURFACE FRONT AND FORM A FRONTAL LOW ACROSS THE BAHAMAS ON SUNDAY.  
UNDER A FORMIDABLE UPPER DIVERGENT PATTERN...THIS WILL SUSTAIN  
VERY HEAVY RAINS IN THE REGION.  
 
IN TERMS OF ACCUMULATIONS...ON FRIDAY...LARGEST AMOUNTS WILL  
CLUSTER BETWEEN NORTHERN HONDURAS/NORTHEASTERN NICARAGUA NORTH  
INTO WESTERN CUBA/CAYMAN ISLANDS WHERE EXPECTING 25-50MM/DAY AND  
MAXIMA O9F 75-125MM. BY SATURDAY-SUNDAY...LARGEST AMOUNTS WILL  
CLUSTER ACROSS WESTERN CUBA AND IN THE NORTHERN BAHAMAS WHERE  
EXPECTING SIMILAR ACCUMULATIONS. IN THE CAYMAN ISLANDS EXPECTING  
15-30MM/DAY AND MAXIMA OF 40-80MM. ALSO IN ASSOCIATION WITH THE  
FRONT...ENHANCE OROGRAPHIC UPLIFT IN NORTHERN SLOPES OF CENTRAL  
AMERICA WILL SUSTAIN ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF  
20-40MM. DURING SUNDAY0MONDAY...LARGEST ACCUMULATIONS ARE TO  
CLUSTER IN THE NORTHERN BAHAMAS...WHERE EXPECTING 15-20MM/DAY AND  
MAXIMA OF 35-70MM. ALSO...UNDER THE INFLUENCE OF STRONG  
NORTHERLIES...EXPECTING SIMILAR ACCUMULATIONS IN THE SOUTHERN GULF  
OF HONDURAS AND NORTHERN HONDURAS. IN SOUTHERN MEXICO INTO  
SOUTHERN BELIZE EXPECTING 10-15MM/DAY AND MAXIMA OF 20-35MM. THE  
PREFRONTAL TROUGH WILL ALSO STIMULATE PRECIPITATION IN  
JAMAICA/SOUTHEASTERN CUBA ON SATURDAY...WHERE EXPECTING  
10-15MM/DAY AND MAXIMA OF 20-35MM. IN THE CENTRAL AND  
SOUTHEASTERN BAHAMAS EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM.  
ALSO IN ASSOCIATION WITH PRE-FRONTAL TROUGH AND NORTHERLY WINDS AT  
LOW-LEVELS...DEVELOPING IN THE WESTERN CARIBBEAN ON  
SUNDAY...EXPECTING SCATTERED THUNDERSTORMS DEVELOPMENT IN SOUTHERN  
HONDURAS AND MOST OF NICARAGUA ON SUNDAY...WITH ACCUMULATIONS OF  
10-15MM/DAY AND MAXIMA OF 20-35MM.  
 
TROPICAL STORM SELMA HAS FORMED IN THE EASTERN PACIFIC. THE NHC IS  
FORECASTING THE STORM TO MAKE LANDFALL NEAR SOUTHWESTERN EL  
SALVADOR/SOUTHEASTERN GUATEMALA ON SATURDAY. THIS WILL SUSTAIN  
LOCALLY HEAVY RAINFALL...WITH ACCUMULATIONS OF 25-50MM/DAY AND  
MAXIMA OF 75-150MM DURING SATURDAY-SUNDAY. AMOUNTS ARE TO DECREASE  
RAPIDLY AFTER.  
 
IN THE EASTERN CARIBBEAN...AN INTENSE TUTT-LOW CONTINUES  
RETROGRESSING VERY SLOWLY JUST TO THE NORTH OF THE VENEZUELAN  
COAST...WHILE AN UPPER RIDGE BUILDS TO ITS NORTH FROM JAMAICA/GULF  
OF HONDURAS ON FRIDAY...TO EXTEND TO THE NORTH OF HISPANIOLA BY  
SUNDAY. AS THE RIDGE BUILDS...THE TUTT WILL CONTINUE DISPLACING TO  
THE WEST. BY SUNDAY IT IS FORECAST TO CENTER JUST TO THE NORTH OF  
THE GUAJIRA PENINSULA. AT LOW-LEVELS...A TUTT-INDUCED WAVE WILL  
CONTINUE ENHANCING PRECIPITATION IN THE NORTHEASTERN CARIBBEAN  
(SEE BELOW). EXPECTING ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF  
20-30MNM WITH THIS WAVE. PRECIPITATION WILL CLUSTER ACROSS THE  
LEEWARD ISLANDS-PUERTO RICO AND THE VI ON FRIDAY-SATURDAY...ACROSS  
THE VIRGIN ISLANDS INTO THE EASTERN DOMINICAN REPUBLIC ON  
SATURDAY-SUNDAY...AND ACROSS EASTERN HISPANIOLA ON SUNDAY-MONDAY.  
THE TUTT WILL ALSO INFLUENCE PRECIPITATION IN NORTHERN SOUTH  
AMERICA...WHERE TWO TROPICAL WAVES ARE PROPAGATING WESTWARD  
(SEE-BELOW). THE WAVES ARE FORECAST TO STRUGGLE AS THEY MOVE WEST  
OF 75W...GIVEN THE COMPLEX SYNOPTIC PATTERN IN PLACE IN THE  
WESTERN CARIBBEAN. YET...THEY WILL PROVIDE SUFFICIENT FORCING TO  
SUSTAIN MODERATE RAINFALL AMOUNTS IN WESTERN VENEZUELA AND  
ESPECIALLY COLOMBIA. THROUGH EARLY SATURDAY...LARGEST  
ACCUMULATIONS ARE TO CLUSTER ACROSS CENTRAL AND NORTHWESTERN  
COLOMBIA WHERE EXPECTING 15-20MM/DAY AND MAXIMA OF 25-50MM. EAST  
ACROSS VENEZUELA...EXPECTING 05-10MM/DAY AND MAXIMA OF 15-20MM.  
DURING SATURDAY-SUNDAY...LARGEST ACCUMULATIONS ARE TO CLUSTER IN  
MOST OF NORTHERN AND WESTERN COLOMBIA WHERE EXPECTING 15-20MM/DAY  
AND MAXIMA OF 30-60MM. DURING SUNDAY-MONDAY...LARGEST AMOUNTS WILL  
CONTINUE CLUSTER ONCE AGAIN IN COLOMBIA...WHERE EXPECTING  
15-20MM/DAY AND MAXIMA OF 25-50MM.  
 
TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC:  
INITIAL 24 36 48 60 72 84 96 TYPE SOF  
45W 47W 49W 51W 53W 55W 57W 58W TW 12N  
66W 67W 68W 69W 70W 71W DISSIPATES TUTT INDCD 22N  
66W 67W 70W 72W 74W 76W 77W 78W TW 12N  
74W 76W 78W DISSIPATES TW 16N  
 
A TROPICAL WAVE IS INITIALIZED AT 45W AND TO THE SOUTH OF 13N.  
THIS WAVE WILL APPROACH THE GUIANAS ON SATURDAY WITH LITTLE  
EFFECTS IN PRECIPITATION. IT WILL SUSTAIN MAXIMA OF 15MM.  
 
TO THE NORTH...UNDER THE INFLUENCE OF THE TUTT IN THE EASTERN  
CARIBBEAN/VENEZUELA...A TUTT-INDUCED WAVE IS INITIALIZED AT 66W  
AND TO THE SOUTH OF 20N. THIS WAVE IS SUSTAINING RAINFALL  
ACCUMULATIONS OF 10-15MM/DAY AND MAXIMA OF 20-30MM AS IT  
PROPAGATES FROM PUERTO RICO ON FRIDAY...TO CENTRAL HISPANIOLA BY  
SUNDAY.  
 
TROPICAL WAVE ALONG 66W AND SOUTH OF 12N...WILL ENHANCE ACTIVITY  
ACROSS NORTHERN SOUTH AMERICA IN INTERACTION WITH THE TUTT. THIS  
WILL ASSOCIATE WITH RAINFALL AMOUNTS OF 05-10MM/DAY AND MAXIMA OF  
15-20MM IN VENEZUELA ON FRIDAY-SATURDAY...15-20MM/DAY AND MAXIMA  
OF 30-60MM IN COLOMBIA ON SATURDAY-SUNDAY...AND 15-20MM/DAY AND  
MAXIMA OF 25-50MM IN COLOMBIA ON SUNDAY-MONDAY.  
 
A TROPICAL WAVE AT 74W...IS LOSING DEFINITION AS IT ENTERS THE  
BROAD CYCLONIC CIRCULATION PATTERN IN THE WESTERN CARIBBEAN. IT  
WILL STILL AID CONVECTIVE DEVELOPMENT IN WESTERN AND NORTHWESTERN  
COLOMBIA ON FRIDAY-SATURDAY...WHERE IT WILL SUSTAIN 15-20MM/DAY  
AND MAXIMA OF 25-50MM.  
 
GUY...NMS (BELIZE)  
PECK...MS (JAMAICA)  
DAVISON/GALVEZ...WPC (USA)  

 
 
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