Area Forecast Discussion

Received: Sun Aug 28 13:15:37 AST 2011


000
FXCA62 TJSJ 281528
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1128 AM AST SUN AUG 28 2011

.UPDATE...SHOWERS AND THUNDERSTORMS HAVE MOVED IN AND AFFECTED THE
SOUTH AND EASTERN PORTIONS OF PUERTO RICO AS WELL AS
VIEQUES...CULEBRA... AND SAINT THOMAS/SAINT JOHN. THE USGS RIVER
SENSORS HAVE YET TO INDICATE ANY SIGNIFICANT RISES IN THE RIVER
LEVELS WITH THIS ACTIVITY.

THE POPS WERE INCREASED AND THE GRIDS WERE TWEAKED SLIGHTLY TO
INCREASE SHOWER AND THUNDERSTORM COVERAGE. OTHERWISE...WE STILL
EXPECT SCATTERED SHOWERS AND THUNDERSTORMS TO CONTINUE INTO THE
EVENING HOURS.


&&

.AVIATION...MAINLY VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS 
MOST TAF SITES. MVFR CONDITIONS WILL DEVELOP IN WESTERN...SOUTHERN...AND
CENTRAL PUERTO RICO AND IN ISOLD SHRA AND TSRA AFT 28/16Z. EXPECT
MTN OBSCURATIONS AFT 28/17Z IN PR. WINDS ARE MAINLY SOUTHEAST AT
15 KTS OR LESS BELOW 10 KFT.

&&

.PREV DISCUSSION... /ISSUED 444 AM AST SUN AUG 28 2011/ 

SYNOPSIS...SURFACE HIGH PRESSURE RIDGE EXTENDING SOUTHWEST ACROSS
THE NORTHEAST CARIBBEAN FROM THE CENTRAL ATLANTIC...WILL GRADUALLY
BUILD ACROSS THE REGION OVER THE NEXT SEVERAL DAYS. THIS WILL INCREASE
THE EAST TO SOUTHEAST TRADE WIND FLOW ACROSS THE LOCAL AREA AT LEAST
THROUGH WEDNESDAY BEFORE DECREASING AGAIN BY THE LATTER PART OF
THE UPCOMING WEEK. TUTT AND ASSOCIATED LOW NOW SAGGING SOUTHWARDS
ACROSS PUERTO RICO AND THE VIRGIN ISLANDS INTO THE EASTERN CARIBBEAN...
WILL CONTINUE TO RETROGRESS TOWARDS THE WEST NORTHWEST BY MONDAY...WHERE
IT WILL GRADUALLY FILL.THE TUTT IS SUPPORTED BY A WEAK LOW LEVEL TROUGH
NOW MOVING ACROSS THE AREA.

DISCUSSION...SHOWERS WILL BE LIMITED TO MAINLY THE EAST AND SOUTHEAST
COASTAL SECTIONS OF PUERTO RICO AND PARTS OF THE VIRGIN ISLANDS DURING
THE EARLY MORNING. HOWEVER...EXPECT A GRADUAL INCREASE IN CLOUDINESS
WITH SHOWERS AND ISOLATED THUNDERSTORMS LATER IN THE DAY ACROSS THE
ISLANDS DUE TO THE PROXIMITY OF THE TUTT LOW AND ASSOCIATED TROUGH.
THESE TWO FEATURES WILL QUICKLY MOVE WESTWARD DURING THE NEXT 24
HOURS OR SO...AND BRING A QUICK SURGE OF TROPICAL MOISTURE ACROSS
THE REGION...AND CONSEQUENTLY CAUSE A RAPID RISE IN PWAT VALUES.
SATELLITE IMAGERY AND PRECIPITABLE WATER ANALYSIS ALREADY DEPICTED
THIS SURGE OF MOISTURE SLOWLY ENTERING THE REGION FROM THE SOUTHEAST.
THE INCREASING MOISTURE COMBINED WITH LOCAL AND DIURNAL EFFECTS
WILL LEAD TO PERIODS OF ENHANCED SHOWERS AND ISOLATED THUNDERSTORMS
LATER IN THE DAY AND POSSIBLY THROUGH MONDAY AFTERNOON. SOME OF
THE RAINFALL WILL BE LOCALLY HEAVY AT TIMES...ESPECIALLY DURING
THE AFTERNOON OVER THE INTERIOR...AND WEST TO NORTHWEST SECTIONS
OF OF PUERTO RICO. ISOLATED THUNDERSTORMS WILL ALSO BE POSSIBLE
OVER PORTIONS OF THE VIRGIN ISLANDS...BUT WIDESPREAD RAINFALL IS
NOT ANTICIPATED OVER THE ISLANDS.

ALTHOUGH AN OVERALL DRIER WEATHER PATTERN IS EXPECTED FOR MOST OF
THE UPCOMING WORK WEEK...EXPECT WEAK EASTERLY PERTURBATIONS TO MOVE
ACROSS THE REGION FROM TIME TO TIME. THIS WILL RESULT IN PERIODS
OF CLOUDINESS...WITH MOSTLY ISOLATED SHOWERS AND/OR THUNDERSTORMS
ACROSS THE FORECAST AREA. THEREFORE BRIEF PERIODS OF DIURNALLY
INDUCED AND NOCTURNAL CONVECTION WILL REMAIN LIKELY EACH DAY WITH
NO SIGNIFICANT WEATHER FEATURE EXPECTED FOR THE NEXT SEVERAL DAYS.

AVIATION...MAINLY VFR CONDITIONS ARE EXPECTED TO PREVAIL ACROSS
MOST TAF SITES THROUGH 28/16Z. MVFR CONDITIONS WILL DEVELOP IN
WESTERN AND CENTRAL PUERTO RICO AND IN ISOLD SHRA AND TSRA OVER
LOCAL WATERS AFT 28/16Z. EXPECT MTN OBSCURATIONS AFT 28/17Z IN PR.
WINDS ARE MAINLY SOUTHEAST AT 10 KTS OR LESS BELOW 10 KFT...VARIABLE
LESS THAN 10 KTS UP TO 23 KFT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  78  90  78 /  40  30  30  20 
STT  89  79  90  80 /  30  40  40  30 

&&

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

$$

25/06