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Tropical Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1147Z Nov 18, 2014)
 
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TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
647 AM EST TUE NOV 18 2014

PRELIMINARY DISCUSSION FOR PUERTO RICO AND THE USVI. HIGH
AMPLITUDE TROUGH OVER NORTH AMERICA IS LIFTING OVER BROAD CELL OF
THE SUBTROPICAL RIDGE TO THE EAST. THE RIDGE ORIGINATES OVER THE
CARIBBEAN BASIN AND EXTENDS TO THE NORTHEAST INTO THE WESTERN
ATLANTIC. A TUTT LIES TO THE EAST...WITH AXIS SOUTHWEST TO THE
LESSER ANTILLES. PUERTO RICO AND THE USVI...MEANWHILE... REMAIN ON
THE CONVERGENT/SUBSIDENT SIDE OF THE RIDGE-TUTT. AT LOW LEVELS...A
POLAR FRONT EXITED THE EASTERN SEABOARD OF THE USA...WHILE A BROAD
RIDGE REMAINS OVER THE CENTRAL-WESTERN ATLANTIC. THIS FAVORS A
BRISK EASTERLY FLOW ACROSS THE EASTERN CARIBBEAN ISLES.

MID/UPPER LEVEL RIDGE...ALTHOUGH PRESSURED BY POLAR TROUGH...IS TO
HOLD OVER THE FORECAST AREA DURING THE NEXT FEW DAYS. BUT LATER ON
THURSDAY/EARLY ON FRIDAY IT IS TO WEAKEN ENOUGH TO ALLOW TUTT TO
RETROGRESS ACROSS THE LESSER ANTILLES TO THE EASTERN CARIBBEAN.
MODELS THEN DIVERGE ON HOW FAR WEST THE TUTT IS TO MOVE...WITH THE
UKMET/ECMWF FAVORING A BRIEF/WEAKER INCURSION THAN WHAT THE GFS
SUGGESTS. MEANWHILE...SUBSIDENCE ENVELOPING THE FORECAST AREA IS
EXPECTED TO PERSIST FOR AT LEAST THE NEXT 72-84 HRS. AT LOW
LEVELS...POLAR FRONT IS TO STALL ACROSS THE NORTHWEST
BAHAMAS-WESTERN CUBA LATER ON WEDNESDAY...AND IT IS EXPECTED TO
REMAIN FAR TO THE NORTH AS IT LIFTS OVER THE SUBTROPICAL RIDGE.
RIDGE PATTERN IS TO BRIEFLY WEAKEN ON THURSDAY-FRIDAY...BUT
ANOTHER RIDGE ROLLS FROM THE WEST INTO THE WESTERN NORTH ATLANTIC.
THESE ARE TO CONTINUE FAVORING BRISK EASTERLY WINDS ACROSS THE
FORECAST AREA DURING THE NEXT SEVERAL DAYS.

DURING SHORT RANGE PERIOD EXPECTING FAIR WEATHER CONDITIONS TO
PREVAIL...WITH TRADE WIND SHOWERS TO AFFECT THE VIRGIN
ISLES-EASTERN/NORTHEASTERN PUERTO RICO FROM TIME-TO-TIME. DURING
MEDIUM RANGE PERIOD...THE MODELS DIVERGE ON IMPACT TUTT IS GOING
TO HAVE ACROSS THE FORECAST AREA. AS PREVIOUSLY INDICATED THE GFS
IS THE MOST BULLISH WITH THIS FEATURE...AS IT HAS BEEN DURING MOST
OF THE SUMMER. SO UNCERTAINTY IS HIGH AND CONFIDENCE IN THE
FORECAST IS LOW. IN THIS PATTERN...PERSISTENCE SEEMS TO BE THE
SAFEST BET.

DISCUSSION FROM NOVEMBER 17/00UTC:

TROPICAL/EASTERLY WAVES INITIALIZED AT 12UTC
INITIAL  24     36     48     60     72     84     96     TYPE
31W     34W    37W    40W    42W    44W     46W   48W     TW
57W     59W    62W    64W    66W    69W     72W   75W     TW

JN BAPTISTE...MS (SAINT LUCIA)
MEDINA...ONAMET (REPUBLICA DOMINICANA)
DAVISON...WPC (USA)