815
FXCA62 TJSJ 122043
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
443 PM AST WED AUG 12 2020
SYNOPSIS
A TROPICAL WAVE CURRENTLY OVER THE AREA WILL MOVE
AWAY TONIGHT, WITH MUCH DRIER AIR EXPECTED TO MOVE IN WITH FAIR
WEATHER CONDITIONS EXPECTED. THIS RELATIVELY DRY AIR MASS WILL
PREVAIL ACROSS THE AREA THROUGH THE END OF THE WORK WEEK,
THEREFORE, SHOWER ACTIVITY WILL BE LIMITED. TROPICAL DEPRESSION
ELEVEN, FORECAST TO BECOME A TROPICAL STORM LATER TONIGHT, IS
STILL FORECAST TO PASS NORTH OF THE AREA DURING THE WEEKEND WITH
NO DIRECT IMPACTS EXPECTED AT THIS TIME.
SHORT TERM...TONIGHT THROUGH FRIDAY
THE SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH A TROPICAL
WAVE WILL CONTINUE TO LINGER ACROSS PORTIONS OF WESTERN PUERTO
RICO THROUGH THE EARLY EVENING HOURS BEFORE DISSIPATING COMPLETELY.
AS THE TROPICAL WAVE EXITS THE AREA TONIGHT, A MUCH DRIER AIR
MASS WILL MOVE IN. THEREFORE, FAIR WEATHER CONDITIONS ARE
EXPECTED. THIS RELATIVELY DRY AIR MASS IS EXPECTED TO PREVAIL
THROUGH THE END OF THE WORK WEEK, RESULTING IN LIMITED SHOWER
ACTIVITY. HOWEVER, PATCHES OF LOW-LEVEL MOISTURE WILL MOVE OVER
THE AREA FROM TIME TO TIME, WHICH COULD CAUSE SOME PASSING
SHOWERS TO DEVELOP ACROSS THE REGIONAL WATERS AND AFFECT PORTIONS
OF EASTERN PUERTO RICO AND THE USVI DURING THE OVERNIGHT AND
MORNING HOURS FOLLOWED BY THE DEVELOPMENT OF SOME AFTERNOON
CONVECTION ACROSS WESTERN PUERTO RICO.
PREV DISCUSSION
/ISSUED 429 AM AST WED AUG 12 2020/
LONG TERM...SATURDAY THROUGH THURSDAY
THE FORECAST FOR SATURDAY, AND, INDEED, THE REST OF THE WEEKEND
AND INTO MONDAY, IS QUITE DEPENDENT ON THE DEVELOPMENT AND
TRAJECTORY OF TROPICAL DEPRESSION ELEVEN. SHOULD THE SYSTEM
STRENGTHEN, AS IS PRESENTLY EXPECTED, IT WOULD BE LIKELY TO PULL
NORTHWARD, AWAY FROM ANOTHER TROPICAL WAVE, AS IT NEARS THE
CARIBBEAN. IN THIS SCENARIO, A DRY SLOT FORMS BETWEEN THE TROPICAL
CYCLONE AND THE WAVE. THAT BEING SAID, THERE DOES REMAIN SOME
UNCERTAINTY, AS WE ARE STILL SEVERAL DAYS OUT. A SHIFT IN THE
STRENGTH OR TRAJECTORY WOULD SHIFT THE TIMING AND LOCATION OF ANY
POSSIBLE DRY SLOT. A LESS LIKELY SCENARIO INVOLVES THE SYSTEM NOT
STRENGTHENING, OR BEING SHORT-LIVED. THIS HAS THE POTENTIAL TO
LEAD TO MORE MOISTURE BEING BROUGHT THROUGH THE AREA. WHILE THIS
CURRENTLY DOES NOT LOOK LIKELY, IT CANNOT BE FULLY RULED OUT.
EITHER WAY, IT DOES LOOK TO BE A FAIRLY RAINY WEEKEND,
INCREASINGLY SO AS WE MOVE INTO SUNDAY. WIDESPREAD SHOWERS ARE
LIKELY BY SUNDAY, WITH ISOLATED TO LOCALLY SCATTERED
THUNDERSTORMS. CONDITIONS ALOFT ARE EXPECTED TO BE MORE FAVORABLE
FOR CONVECTIVE ACTIVITY, BUT NOT VERY FAVORABLE. THIS WILL STILL
HELP CONTRIBUTE TO THE AFTERNOON SHOWERS AND THUNDERSTORMS,
THOUGH.
MOISTURE WILL REMAIN IN THE AREA FOR MONDAY, WHEN THERE WILL LIKELY
BE A CONTINUATION OF SUNDAY, THOUGH SLIGHTLY WEAKER IN TERMS OF
ACTIVITY. DYNAMIC FORCING ALOFT REMAINS RELATIVELY WEAK, AND ITS
INFLUENCE WILL WANE SOMEWHAT. DECREASING MOISTURE IS EXPECTED DURING
THE EVENING AND INTO THE NIGHT. AND BY TUESDAY, CONDITIONS ALOFT
WILL BECOME DECREASINGLY FAVORABLE FOR CONVECTION, WITH DRYING
FORECAST FOR THE MID-LEVELS. A LARGE, BUT WEAK, DEVELOPING
DISTURBANCE WILL HELP BRING ADDITIONAL MOISTURE INTO THE AREA ON
TUESDAY INTO WEDNESDAY; MOISTURE LEVELS WILL BE NEAR-NORMAL LEVELS,
CLIMATOLOGICALLY SPEAKING. A TYPICAL PATTERN OF AFTERNOON SHOWERS IN
THE WEST AND PASSING SHOWERS OVERNIGHT AND INTO THE MORNING IN THE
EAST WILL PREVAIL THROUGH MIDWEEK. FURTHER DRYING IS EXPECTED
WEDNESDAY NIGHT INTO THURSDAY, WHICH WILL ACT TO INHIBIT SOME OF THE
TYPICAL SHOWER ACTIVITY ACROSS THE LOCAL ISLANDS.
AVIATION
TROPICAL WAVE MOVING ACROSS THE REGION WILL CONTINUE TO
BRING SHRA/TSRA TO THE LOCAL FLYING AREA AT LEAST TIL 12/23Z. THIS
WILL CAUSE VCSH/VCTS IN AND AROUND THE ISLANDS AS WELL AS OVR THE
LOCAL FLYING AREA. SCT-BKN LYRS NR FL025...FL050...FL100 TIL 13/00Z.
BRIEF MVFR PSBL AT TJSJ/TJBQ/TJMZ AND EN ROUTE BETWEEN ISLANDS WITH
SHRA/ISOLD TSRA. SFC WNDS FM E-SE 10-15 KTS WITH OCNL HIR GUST WITH
SHRA/ISOLD TSRA. WNDS BCMG FM ESE 10 KTS OR LESS AFT 12/23Z.
MARINE
MODERATE TO FRESH EASTERLY WINDS BETWEEN 15 AND 20 KNOTS
WILL CONTINUE TO RESULT IN SEAS OF BETWEEN 3 AND 6 FEET ACROSS THE
REGIONAL WATERS, WITH THE HIGHEST SEAS EXPECTED ACROSS THE
OFFSHORE WATERS. TROPICAL DEPRESSION ELEVEN, CURRENTLY LOCATED
OVER THE CENTRAL TROPICAL ATLANTIC, IS FORECAST TO MOVE NORTH OF
THE LOCAL AREA DURING THE UPCOMING WEEKEND. THIS COULD GENERATE
SOME HAZARDOUS SEAS, MAINLY ACROSS THE OFFSHORE ATLANTIC WATERS. A
MODERATE RISK OF RIP CURRENTS IS EXPECTED FOR SEVERAL OF THE
LOCAL BEACHES OF THE ISLANDS, EXCEPT ACROSS THE WESTERN COAST OF
PUERTO RICO, THROUGH THURSDAY.
PRELIMINARY POINT TEMPS/POPS
SJU 80 90 80 89 / 40 20 20 40
STT 81 90 80 91 / 40 20 20 40
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...DSR
LONG TERM....GL
PUBLIC DESK...LIS
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