AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
927 PM AST THU JUL 7 2011

.UPDATE...SURFACE TROUGH/TROPICAL WAVE AND ASSOCIATED DEEP LAYERED
MOISTURE WHICH CONTINUED TO AFFECT THE REGION THIS EVENING...IS
EXPECTED TO QUICKLY MOVE WEST NORTHWEST AND EXIT THE REGION DURING
THE OVERNIGHT HOURS. LATEST SATELLITE DERIVED MIMIC TPW PRODUCT
AND TJSJ 00Z UPPER AIR SOUNDING SUGGESTED THAT PRECIPITABLE WATER
REMAINED WELL ABOVE 2.00 INCHES. ALSO...THE MID TO UPPER LEVEL
TROUGH/TUTT IS EXPECTED TO CONTINUE TO LINGER ACROSS THE NORTHEAST
CARIBBEAN. CONVECTIVE ACTIVITY OVER LAND AND ACROSS THE LOCAL
WATERS HAVE CONTINUED TO SLOWLY DIMINISH DURING THE EVENING HOURS.
HOWEVER...STILL EXPECT SUFFICIENT INSTABILITY AND MOISTURE CONTENT
FOR ANOTHER ROUND OF ACTIVITY WEATHER BY EARLY MORNING AND CONTINUING
THROUGH AT LEAST EARLY SATURDAY...AS THE TROPICAL WAVE MENTIONED IN
PREVIOUS DISCUSSION...ENTERS THE EASTERN CARIBBEAN AND MOVES ACROSS
THE REGION. THEREFORE ONLY MINOR ADJUSTMENTS MADE TO INHERITED FORECAST
BASED ON LATEST SATELLITE IMAGERY AND GFS MODEL GUIDANCE WHICH SO FAR
INITIALIZED WELL.

EXPECT THE ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ACROSS
THE REGIONAL WATERS AND THE MODERATE TO FRESH TRADE WINDS TO MAINTAIN
HAZARDOUS CONDITIONS ACROSS PARTS OF THE LOCAL WATERS AT LEAST THROUGH
THE EARLY MORNING HOURS. THEREFORE...SMALL CRAFT ADVISORIES AND PRECAUTIONARY
STATEMENTS WILL REMAIN IN EFFECT DURING THAT TIME FRAME. PLEASE REFER
TO LATEST COASTAL WATERS FORECAST AND MARINE WEATHER STATEMENTS.

&&

.AVIATION...PREVAILING VFR CONDITIONS ARE EXPECTED ACROSS MOST TAF
SITES THROUGH AT LEAST 08/12Z. PERIODS OF MVFR CONDITIONS CAN BE
EXPECTED ACROSS TKPK AND TNCM IN SHRA OVERNIGHT. AFTER 08/12Z MOISTURE
WILL INCREASE WITH MVFR OR EVEN IFR CONDITIONS AND LOCAL MOUNTAIN
OBSCURATIONS EXPECTED OVER THE LOCAL TAF SITES THROUGHOUT THE DAY IN
SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS. LATEST
08/00Z TJSJ SOUNDING INDICATED EAST SOUTHEAST WINDS OF 20KT OR LESS
FROM THE SURFACE UP TO 20K FEET...BECOMING SOUTHWESTERLY AND
STRONGER ABOVE.

&&

.PREV DISCUSSION... /ISSUED 327 PM AST THU JUL 7 2011/

SYNOPSIS...
A SURGE OF TRADE WIND MOISTURE WILL QUICKLY MOVE ACROSS THE AREA
TONIGHT...BRINGING PERIODS OF HAZARDOUS WEATHER TO THE LOCAL
WATERS. IN ADDITION...A TROPICAL WAVE IS FORECAST TO MOVE ACROSS
THE LOCAL WATERS LATE TONIGHT THROUGH SATURDAY...INCREASE THE
SHOWER AND THUNDERSTORM ACTIVITY AS WELL AS THE CHANCES FOR
HAZARDOUS WINDS AND SEAS.

DISCUSSION...SCATTERED TO LOCALLY NUMEROUS SHOWERS AND
THUNDERSTORMS AFFECTED THE EASTERN PORTIONS OF PUERTO RICO
GENERATING RAINFALL ACCUMULATIONS OF BETWEEN 2 TO 4 INCHES.
ALTHOUGH MOST OF THESE SHOWERS WERE FAST MOVERS...REPORTS OF
TORRENTIAL RAINFALL WERE RECEIVED FROM THE PUBLIC. SHOWERS AND
THUNDERSTORMS WILL CONTINUE TO GENERATE OVER THE LOCAL EASTERN
WATERS WITH SOME AFFECTING THE U.S. VIRGIN ISLAND LATE IN THE
EVENING AND THE EASTERN PUERTO RICO EARLY FRIDAY MORNING.

A TUTT REFLECTION AT LOW LEVEL COMBINED WITH AN ARE OF HIGH
MOISTURE CONTENT OVER THE REGION HAVE INCREASE SIGNIFICANTLY THE
SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE LOCAL FORECAST
AREA...MAINLY OVER THE EASTERN HALF OF PUERTO RICO. THE MIMIC TPW
PRODUCT IS SHOWING THAT THIS LARGE SURGE OF MOISTURE TO ONLY
STARTING TO MOVER THE LOCAL AREA AND THIS HIGH CONTENT MOISTURE
AREA WILL BE OVER THE REGION FOR THE NEXT FEW DAYS. A TROPICAL
WAVE NOW LOCATED OVER THE LEEWARD WILL CONTINUE TO MOVE WEST AND
ENTER OUR LOCAL WATERS LATER TONIGHT. THIS FEATURE IN COMBINATION
WITH THE LARGE AMOUNT OF MOISTURE WILL CONTINUE TO DEVELOP SHOWERS
AND THUNDERSTORMS ACROSS THE LOCAL FORECAST AREA...MAINLY THE
EASTERN PORTIONS OF PUERTO RICO AND ADJACENT ISLANDS.

AVIATION...MVFR CONDITIONS AND LOCAL MOUNTAIN OBSCURATIONS WILL
CONTINUE ACROSS THE AREA AS THE LEADING EDGE OF A TROPICAL WAVE
MOVES THROUGH THE LEEWARD AND U.S. VIRGIN ISLAND THRU FRIDAY. GUSTY
SFC WINDS NR TSTMS MAY REACH 30 KTS. SIMILAR CONDS WILL SPREAD
ACROSS PUERTO RICO AFT 08/18Z WITH LOCAL IFR IN +SHRA. AREAS OF MVFR
WILL PERSIST BEYOND 08/06Z IN PR.

MARINE...MARINERS SHOULD MONITOR OUR LOCAL MARINE PRODUCTS AS
UNSTABLE CONDITIONS DUE TO THE INTERACTIONS OF A TUTT REFLECTION
AND A TROPICAL WAVE WILL BE FUEL BY A HIGH MOISTURE CONTENT ACROSS
THE LOCAL WATERS THROUGH AT LEAST LATE SATURDAY. AN INCREASE ON
WINDS IS FORECAST FOR TONIGHT GENERATING CHOPPY CONDITIONS ACROSS
THE LOCAL WATERS...THEREFORE SMALL CRAFT ADVISORIES WILL BE IN
EFFECT AFTER 6 PM THIS EVENING FOR THE OFFSHORE ATLANTIC AND
CARIBBEAN WATERS INCLUDING THE ANEGADA PASSAGE.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  77  86  77  89 /  50  60  50  40
STT  78  86  78  90 /  60  60  50  40

&&

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

$$