Area Forecast Discussion
Issued by NWS San Juan, PR

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000
FXCA62 TJSJ 291506
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1106 AM AST TUE JUL 29 2014

.UPDATE...ISOLATED TO WIDELY SCATTERED SHOWERS WILL CONTINUE TO
MOVE QUICKLY NORTHWESTWARD ACROSS THE U.S. VIRGIN ISLANDS AND
PUERTO RICO DURING THE MORNING HOURS. 12Z SJU SOUNDING INDICATED
HIGHER PW VALUES THAN 24 HOURS AGO AND THIS COULD BE RESPONSIBLE FOR THE
SHOWER ACTIVITY THIS MORNING. THE PROXIMITY OF A TUTT LOW TO THE
NORTH OF THE LOCAL AREA...IN COMBINATION WITH DIURNAL HEATING AND
OTHER LOCAL EFFECT...COULD RESULT IN SCATTERED
SHOWERS/THUNDERSTORMS DEVELOPING ACROSS INTERIOR/NORTHWEST
SECTIONS OF PUERTO RICO THIS AFTERNOON. LIGHT WIND FLOW ALOFT
COULD RESULT IN VERY SLOW MOTION OF ANY SHOWER/THUNDERSTORM THAT
DEVELOPS...WHICH IN TURN...COULD LEAD TO LOCALLY HEAVY RAIN IN
SOME AREAS. CURRENT FORECAST PACKAGE ADDRESSES THIS QUITE
WELL...THEREFORE NO CHANGES WILL MADE AT THIS TIME.

&&

.AVIATION...OBSCD MTN AND BRIEF MVFR CIGS ARE EXPECTED BETWEEN
29/16-21Z DUE SHRA/TSRA DEVELOPING ACROSS THE CENTRAL INTERIOR AND
NORTHWESTERN SECTION OF PR AFFECTING TJBQ AND TJMZ WITH VCTS
POSSIBLE AT JSJ. E-SE WINDS 5-15 KTS BELOW 5 KFT.

&&

.MARINE...A LIGHT TO MODERATE SOUTHEAST WIND FLOW WILL CONTINUE
ACROSS THE COASTAL WATERS THIS AFTERNOON WITH SEAS AT OR BELOW 4
FEET FOR THE MOST PART. WINDS COULD VARIABLE ALONG THE COAST AS
LOCAL SEA BREEZES DEVELOP.


&&

.PREV DISCUSSION... /ISSUED 618 AM AST TUE JUL 29 2014/

SYNOPSIS...SURFACE HIGH PRESSURE ACROSS THE WEST CENTRAL
ATLANTIC IS STILL EXPECTED TO SLOWLY RETREAT NORTH AND INTO THE
NORTHWESTERN ATLANTIC BY THURSDAY MORNING WHICH WILL GRADUALLY
RELAX THE PRESSURE GRADIENT OVER THE LOCAL AREA. TUTT LOW NORTH OF
THE LOCAL ISLANDS IS EXPECTED TO REMAIN FAIRLY STATIONARY BUT
WEAKEN OVER THE NEXT FEW DAYS. SHOWERS AND THUNDERSTORMS POSSIBLE
ACROSS THE NORTHWESTERN QUADRANT OF PR THIS AFTERNOON.

DISCUSSION...ISOLATED TO SCATTERED PASSING SHOWERS ACROSS THE
LOCAL WATERS OVERNIGHT...SOME OF THEM BRIEFLY OVER THE USVI AND
EASTERN PR LEFT MINIMAL ACCUMULATIONS. THE OVERALL PATTERN IS
EXPECTED TO REMAIN FAIRLY SIMILAR FOR THE NEXT SEVERAL DAYS WITH
SHOWERS AND THUNDERSTORMS DEVELOPING MAINLY ACROSS THE
NORTHWESTERN QUADRANT OF PUERTO RICO IN THE AFTERNOON
HOURS...WHILE OVERNIGHT AND IN THE MORNING HOURS ISOLATED TO
SCATTERED PASSING SHOWERS ARE EXPECTED.

ACCORDING TO THE NATIONAL HURRICANE CENTER...A TROPICAL WAVE ROUGHLY
AROUND 10 NORTH AND 37 WEST...OR AROUND 1000 MILES TO THE WEST SOUTHWEST
OF THE CAPE VERDE ISLANDS...HAS A 70 PERCENT OF DEVELOPING IN TO A
TROPICAL CYCLONE IN THE NEXT 48 HOURS AND A 70 PERCENT WITHIN THE
NEXT 5 DAYS. AT THIS TIME IT IS STILL A BIT EARLY TO PRECISE JUST HOW
MUCH OR EVEN IF THIS WAVE WILL AFFECT THE LOCAL AREA AS A WAVE OR
TROPICAL CYCLONE...IF AT ALL. THERE IS A FAIR AMOUNT OF UNCERTAINTY
AT THE TIME AND THERE ARE SOME DIFFERENCES IN THE SOLUTION OF THE
GLOBAL MODELS. GFS MODEL DEVELOPS IT INTO A TROPICAL CYCLONE AND
TRACKS IT TO THE NORTHEAST OF THE LOCAL ISLANDS...WHILE THE ECMWF
MODEL DEVELOPS IT INTO A WEAK TROPICAL CYCLONE BUT TRACKS
IT FURTHER SOUTH THAN THE GFS...AND CLOSER TO THE OUR LOCAL AREA.
WE ARE OBSERVING THE TROPICAL WAVE CLOSELY AND ITS EVOLUTION...BUT
IT IS QUITE EARLY TO PRECISE HOW OR EVEN IF THIS WILL AFFECT THE
LOCAL AREA.

AVIATION...VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH THE
FCST PERIOD WITH VCSH AT JSJ/IST/ISX AND NCM IN THE MORNING HOURS.
BETWEEN 29/16-21Z OBSCD MTN AND BRIEF MVFR CIGS ARE EXPECTED DUE
SHRA/TSRA DEVELOPING ACROSS THE CENTRAL INTERIOR AND NORTHWESTERN
SECTION OF PR AFFECTING TJBQ AND TJMZ WITH VCTS POSSIBLE AT JSJ.
E-SE WINDS 5-15 KTS BELOW 5 KFT.

MARINE...

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  88  77  89  77 /  30  20  20  20
STT  88  78  89  78 /  30  20  20  20

&&

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

$$

08/71





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