Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 300233
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1033 PM AST FRI AUG 29 2014

.UPDATE...30/00Z SOUNDING CAME IN FAIRLY WET AND JUST ABOVE 2
INCHES IN PRECIPITABLE WATER. WINDS HAVE ALSO DIMINISHED
CONSIDERABLY AT LOWER LEVELS. RADAR SHOWS INCREASING SMALL SHOWERS
ACROSS ALL WATERS EXCEPT IN THE LEE OF PUERTO RICO WITH A FEW
SHOWERS MOVING INLAND AS OF 10 PM AST.


&&

.DISCUSSION...FORECAST SOUNDING FROM THE GFS FOR TOMORROW SHOWS
PRECIPITABLE WATER DECREASING WITH MOST OF THE DECREASE AROUND 20
KFT. THE CURRENT 30/00Z SOUNDING...HOWEVER WAS CONSIDERABLY DRIER
THAN THE FORECAST SOUNDING AT THIS HEIGHT AND SO MUST CONSIDER
THAT THIS DRYING HAD ALREADY OCCURRED AND THAT CURRENT INCREASE IN
SHOWER ACTIVITY...THOUGH AS EXPECTED...IS OCCURRING IN THIS
ALREADY SOMEWHAT DRIER ATMOSPHERE. THIS INDICATES THAT SHOWER
ACTIVITY WILL RETURN TO THE AREA EARLY THIS MORNING AS MOISTURE
FORECAST BY THE NAM MOVES IN FROM THE EAST...BUT ALSO THAT
INSTABILITY PRESENT AND TOMORROW`S HEATING WILL TRIGGER ANOTHER
ROUND OF SHOWERS AND SOME THUNDERSTORMS. HAVE BUMPED POPS A LITTLE
HIGHER IN LIGHT OF THIS. NO CHANGE TO PREVIOUS THINKING EXCEPT
THAT EASTERN PUERTO RICO MAY RECEIVE MORE RAINFALL THAN PREVIOUSLY
EXPECTED.

&&

.AVIATION...SHRA ACTIVITY IS EXPECTED TO INCREASE OVERNIGHT ACROSS
THE LOCAL AREA. VCSH EXPECTED ACROSS ALL TAF SITES THROUGH THE
PERIOD. TONIGHT...WINDS WILL BE LIGHT AND VARIABLE ACROSS THE PR
TERMINALS WHILE THE USVI/BVI SHOULD REMAIN LIGHT AND EASTERLY. WINDS
BECOMING EASTERLY THROUGH THE TERMINALS WITH SEA BREEZE VARIATIONS
AFTER 30/13Z. NMRS SHRA ISOLD/TSRA EXPECTED ACROSS CENTRAL PR AFTER
30/18Z...TSRA IN AND AROUND TJMZ IS POSSIBLE. MTN OBSCURATIONS
WILL INCREASE THROUGH THE PERIOD.

&&

.MARINE...WINDS WILL INCREASE DURING THE DAY SOMEWHAT TOMORROW AND
EXERCISE CAUTION AREAS WILL BE RE-INTRODUCED INTO THE FORECAST
SATURDAY...MAINLY IN THE ATLANTIC WATERS AND THE MONA PASSAGE.


&&

.PREV DISCUSSION... /ISSUED 303 PM AST FRI AUG 29 2014/

SYNOPSIS...RIDGE PATTERN WILL BUILD ACROSS THE LOCAL AREA DURING
THE UPCOMING WEEKEND AS TUTT LOW...NOW LOCATED NORTH OF THE ISLANDS...
MOVES WESTWARD. AN INDUCED SURFACE TROUGH WILL CONTINUE TO MOVE
ACROSS THE EASTERN CARIBBEAN TONIGHT AND SATURDAY. A PAIR OF
TROPICAL WAVES WILL MOVE ACROSS THE LOCAL ISLANDS NEXT WORKWEEK.

DISCUSSION...AS INDUCED SURFACE TROUGH CONTINUES TO MOVE ACROSS
THE EASTERN CARIBBEAN TONIGHT AND SATURDAY...DEEP TROPICAL
MOISTURE FROM THE ITZC WILL CONTINUE TO BE LIFTED NORTHWARDS
ACROSS LOCAL ISLANDS. THEREFORE STILL EXPECT TRADE WIND SHOWERS
ACROSS WINDWARD AREAS TONIGHT AND SATURDAY MORNING. RIDGE ALOFT
WILL BUILD OVER THE AREA AS THE AFOREMENTIONED TUTT LOW MOVES
FURTHER WEST DURING THE WEEKEND. HOWEVER DUE TO THE PROXIMITY OF
THIS FEATURE...SHOWERS AND THUNDERSTORMS WERE INCLUDED IN THE
FORECAST FOR SATURDAY AFTERNOON. UNDER THE PREVAILING EASTERLY
WIND FLOW...MOST AFTERNOON ACTIVITY WILL BE FOCUSED ACROSS THE
CORDILLERA AND WEST PUERTO RICO.

LATEST MODEL GUIDANCE INDICATED A DECREASING TREND IN PRECIPITABLE
WATER OVER THE NEXT FEW DAYS. THIS TREND COMBINED WITH BUILDING
UPPER LEVEL RIDGE SHOULD RESULT IN A MORE TYPICAL WEATHER PATTERN
WITH A FEW TRADE WIND SHOWERS ACROSS WINDWARD AREAS IN THE MORNING
FOLLOWED BY SOME AFTERNOON CONVECTION ACROSS WESTERN PUERTO RICO.
THEREFORE...SO FAR LOOKING FOR GRADUALLY IMPROVING CONDITIONS ON
SUNDAY AND MONDAY. THERE IS A PAIR OF TROPICAL WAVE ACROSS THE
CENTRAL TROPICAL ATLANTIC THAT AREA EXPECTED TO MOVE ACROSS THE
EASTERN CARIBBEAN BY THE MID AND LATER PART OF NEXT WORKWEEK.

AVIATION...WINDS WILL REMAIN GENERALLY EASTERLY AT AROUND 10 KNOTS
WITH SHRA/TSRA DEVELOPING ACROSS NORTHERN SECTIONS OF PR WITH MTN
OBSCURATIONS TIL AROUND 29/22Z. THESE STORMS ARE MOVING TO THE NORTH
DUE TO THE STEERING FLOW FROM THE SOUTH ABOVE 20KFT. VFR AFT 29/22Z
FOR ALL TAF SITES WITH VCSH POSSIBLE FOR THE LOCAL ISLANDS AND TJSJ.

MARINE...A MODERATE TO LOCALLY FRESH TRADE WIND FLOW WILL CONTINUE
TO PREVAIL ACROSS THE LOCAL WATERS THROUGH EARLY NEXT WEEK. AN
INDUCED SURFACE TROUGH WILL CONTINUE MOVE ACROSS THE EASTERN CARIBBEAN
TONIGHT AND SATURDAY. THIS WILL CONTINUE TO ENHANCE SHOWER AND
ISOLATED THUNDERSTORM ACTIVITY ACROSS PARTS OF THE COASTAL WATERS.

IN TERMS OF SEAS...SEAS ACROSS THE LOCAL WATERS WILL CONTINUE TO
SUBSIDE TONIGHT AND THROUGH THE UPCOMING WEEKEND. HOWEVER...SMALL
CRAFT OPERATORS SHOULD CONTINUE EXERCISE CAUTION ACROSS THE OFFSHORE
ATLANTIC DUE TO SEAS OF UP TO 6 FEET. ELSEWHERE SEAS WILL BE 5
FEET OR LESS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  78  89  78  89 /  10  50  40  30
STT  78  89  79  88 /  40  50  50  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

25/12





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