National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXCA62 TJSJ 090111
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
911 PM AST SUN DEC 8 2013

.UPDATE...MID TO UPPER LOW AND ASSOCIATED TROUGH JUST SOUTH OF
PUERTO RICO WILL CONTINUE TO MEANDER ACROSS THE EASTERN CARIBBEAN
THROUGH AT LEAST MID WEEK BEFORE FINALLY WEAKENING/FILLING DURING
THE LATTER PART OF THE WEEK. INDUCED SURFACE TROUGH AND ASSOCIATED
SURGE OF LOW TO MID LEVEL MOISTURE NOW MOVING ACROSS THE REGION
WILL CONTINUE TO RACE QUICKLY WESTWARD OVERNIGHT THROUGH MONDAY
MORNING. ENHANCED SHOWERS AND ISOLATED THUNDERSTORMS WILL THEREFORE
CONTINUE TO DEVELOP AND MOVE RAPIDLY ACROSS THE COASTAL WATERS AND
BRUSH PARTS OF THE ISLANDS STEERED BY THE STRONG EASTERLY TRADE
WIND FLOW. LATEST MODEL GUIDANCE CONTINUED TO SUGGEST A SOMEWHAT
DRIER WEATHER PATTERN DURING THE LATTER PART OF THE WORK WEEK WITH
A SLIGHT LOOSENING OF THE SURFACE PRESSURE GRADIENT AND DIMINISHING
EASTERLY TRADE WINDS BY THURSDAY. IN THE MEANTIME...EXPECT PASSING
LATE EVENING AND EARLY MORNING TRADE WINDS SHOWERS TO AFFECT PARTS
OF THE ISLANDS AND LOCAL WATERS FROM TIME TO TIME. THE ACTIVITY HOWEVER
WILL BE LESS FREQUENT AS IN RECENT DAYS WITH ONLY ISOLATED TO SCATTERED
SHOWERS ACTIVITY EXPECTED ACROSS THE ISLANDS EACH DAY. NO SIGNIFICANT
CHANGES MADE TO THE INHERITED FORECAST AT THIS TIME.

THE SHORT PERIOD NORTHEAST SWELL COMBINED WITH LOCAL GENERATED
WIND WAVES CONTINUED TO CREATE HAZARDOUS SURF CONDITIONS ALONG THE
NORTH AND NORTHEAST COASTS OF THE LOCAL ISLANDS. THEREFORE THE
HIGH SURF ADVISORY WILL REMAIN IN EFFECT AT LEAST UNTIL EARLY
MONDAY MORNING. FOR UPDATES...PLEASE REFER TO THE LATEST COASTAL
HAZARD MESSAGE ISSUED BY THE NATIONAL WEATHER SERVICE WFO SAN JUAN
PR.

&&

.AVIATION UPDATE...PASSING SHOWERS WILL AFFECT MOST TAF SITES OVERNIGHT. VFR
CONDITIONS ARE EXPECTED TO PREVAIL ACROSS MOST TAF SITES THROUGH AT
LEAST 09/12Z. BRIEF PERIODS OF MVFR CONDITIONS ARE EXPECTED OVER TNCM
AND TKPK IN SHRA. LOW LEVEL WINDS WILL CONTINUE MAINLY EAST
NORTHEAST AT 15 TO 20 KTS WITH GUST UP TO 30 KTS IN SHRA/TSRA.


&&

.MARINE UPDATE...RECENT INFO FROM THE LOCAL AND OFFSHORE BUOYS SUGGEST
WAVE HEIGHTS NOW AVERAGING 8 TO 10 FEET AT 9-11 SECS...WITH WIND
SPEEDS OF 20 TO 25 KTS AND GUSTS UP TO 32 KNOTS OVER THE OFFSHORE
ATLANTIC. SEAS ARE HOWEVER STILL EXPECTED TO GRADUALLY SUBSIDE TO
7 TO 9 FEET ON MONDAY BUT WIND CHOP WAVES WILL CONTINUE THROUGH
MID WEEK. SMALL CRAFT ADVISORIES WILL THEREFORE REMAIN IN EFFECT
THROUGH AT LEAST TUESDAY.

&&

.PREV DISCUSSION... /ISSUED 308 PM AST SUN DEC 8 2013/

SYNOPSIS...STRONG SURFACE HIGH PRESSURE OVER THE WESTERN ATLANTIC
WILL MAINTAIN THE WINDY CONDITIONS ACROSS THE FORECAST AREA THROUGH
AT LEAST TUESDAY. UPPER LOW JUST SOUTH OF PUERTO RICO WILL MEANDER
OVER THE NORTHEAST CARIBBEAN THROUGH MIDWEEK. A DECREASE IN CLOUD
AND SHOWER COVERAGE IS EXPECTED ON MONDAY AS A MID LEVEL HIGH
PRESSURE RIDGE WILL BUILD OVER THE WESTERN ATLANTIC...PROMOTING A
GENERALLY STABLE PATTERN ACROSS THE REGION MOST OF THE WORK WEEK.

DISCUSSION...ABUNDANT MOISTURE EMBEDDED IN THE STRONG NORTHEAST
FLOW HAS RESULTED SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
ACROSS THE LOCAL ISLANDS TODAY. THE RAPID MOVEMENT OF THESE SHOWERS
HAVE LIMITED THE RAINFALL ACCUMULATION OVER LAND AREAS. AN UPPER
LEVEL LOW JUST SOUTH OF THE LOCAL AREA HAS ALSO CONTRIBUTED TO THE
INCREASE IN CLOUD COVER AND THE THUNDERSTORM ACTIVITY IN THE CARIBBEAN
WATERS. THIS UPPER LOW HAS MOVED LITTLE SINCE YESTERDAY...AND
LATEST MODEL GUIDANCE HAS IT LINGERING NEAR THE ISLANDS THROUGH
MIDWEEK WHILE SLOWLY FILLING.

A MID LEVEL RIDGE WILL SPREAD AND BUILD OVER THE WESTERN ATLANTIC
OVER THE NEXT 24 HOURS. THIS MID-LEVEL RIDGE WILL FAVOR A GENERALLY
SUBSIDENT PATTERN ACROSS THE NORTHEAST CARIBBEAN...LIMITING THE SHOWER
COVERAGE OVER THE NEXT SEVERAL DAYS. HOWEVER...A TIGHT PRESSURE GRADIENT
ASSOCIATED WITH THE STRONG SURFACE RIDGE NORTH OF THE AREA WILL KEEP
THE BRISK EAST TO NORTHEAST WIND FLOW ACROSS THE EASTERN CARIBBEAN
RESULTING IN AN INCREASE IN NIGHT TIME/EARLY MORNING SHOWERS ACROSS
THE EAST AND NORTHEAST PORTIONS OF PR AND THE USVI. ANY AFTERNOON
CONVECTION THAT DEVELOPS SHOULD BE MOSTLY SHALLOW AND DEVELOP FARTHER
DOWNWIND DUE TO THE STRONGER FLOW.

AVIATION...BRIEF PERIODS OF MVFR CONDITIONS ARE EXPECTED OVER
TNCM/TKPK AND TJPS/TIST/TISX FROM TIME TO TIME IN SHRA AND ISOLATED
TSRA THROUGH THE EVENING HOURS. ELSEWHERE...MOSTLY VFR CONDITIONS
ARE EXPECTED TO PREVAIL. LOW LEVEL WINDS WILL CONTINUE MAINLY EAST
NORTHEAST AT 15 TO 20 KTS WITH GUST UP TO 30 KTS IN SHRA/TSRA.

MARINE...THE COMBINATION OF A SHORT-PERIOD NORTHEAST SWELL AND
LOCALLY GENERATED WIND WAVES WILL CONTINUE TO PRODUCE HAZARDOUS
SEAS ACROSS THE REGIONAL WATERS AT LEAST TUESDAY. WAVE HEIGHTS
HAVE AVERAGED 8-11 FEET AT 9-11 SECS SINCE THIS MORNING. LOOKS
LIKE THE SEAS HAVE PEAKED THIS MORNING AND ARE EXPECTED TO GRADUALLY
SUBSIDE TO 7 TO 9 FEET ON MONDAY. HIGH SURF ADVISORY AND A SMALL
CRAFT ADVISORY REMAIN IN EFFECT THROUGH AT LEAST MONDAY AND TUESDAY...
RESPECTIVELY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  85  74  84 /  30  30  40  40
STT  75  87  77  86 /  30  30  30  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...HIGH SURF ADVISORY UNTIL 6 AM AST MONDAY FOR CULEBRA-NORTH
     CENTRAL-NORTHEAST-NORTHWEST-SAN JUAN AND VICINITY-SOUTHEAST-
     VIEQUES-WESTERN INTERIOR.

VI...HIGH SURF ADVISORY UNTIL 6 AM AST MONDAY FOR ST CROIX-ST.
     THOMAS/ST. JOHN/ADJACENT ISLANDS.

COASTAL WATERS...
     SMALL CRAFT ADVISORY UNTIL 3 PM AST MONDAY FOR COASTAL WATERS OF
     SOUTHERN PUERTO RICO OUT 10 NM.

     SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST TUESDAY NIGHT FOR
     ANEGADA PASSAGE SOUTHWARD TO 17N-ATLC WATERS OF PUERTO RICO
     AND USVI FROM 10NM TO 19.5N-CARIBBEAN WATERS OF PUERTO RICO
     FROM 10 NM TO 17N-COASTAL WATERS OF NORTHERN PUERTO RICO
     OUT 10 NM-COASTAL WATERS OF NORTHERN USVI AND CULEBRA OUT
     10 NM-COASTAL WATERS OF NORTHWESTERN PUERTO RICO OUT 10 NM-
     COASTAL WATERS OF SOUTHERN USVI VIEQUES AND EASTERN PUERTO
     RICO OUT 10 NM-MONA PASSAGE SOUTHWARD TO 17N.

&&

$$

71/09