771
FXCA62 TJSJ 201058
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
658 AM AST WED NOV 20 2024
UPDATE
BUOY 41043, ABOUT 170 NM NE OF SAN JUAN INDICATED A 7 FT SWELL AT
11-13 SECONDS. THE LOCAL SAN JUAN AND NORTHERN VIEQUES BUOYS ARE
CURRENTLY INDICATING SEAS AT 5 FT AT 10 SECONDS. THEREFORE, THE HIGH
RIP CURRENT RISK (CFWSJU) IS NOW IN EFFECT FOR ALL NORTHERN
BEACHES OF PUERTO RICO, FROM AGUADILLA TO FAJARDO, AND CULEBRA
THROUGH AT LEAST 6 AM THURSDAY MORNING.
AVIATION...
(12Z TAFS)
MAINLY VFR CONDITIONS ARE FORECAST TO PREVAIL ACROSS THE TERMINALS.
VCSH WILL BE BROUGHT IN BY NORTHEASTERLY FLOW AT TIMES. -RA
POSSIBLE AT TISX/TJSJ/TJBQ. AFTER 18Z, CONVECTIVE VCSH ALSO
POSSIBLY AFFECTING TJPS. BELOW FL050, NE WINDS WILL BE UP TO
AROUND 12 KTS WITH HIGHER GUSTS AND SEA BREEZE VARIATIONS.
PREV DISCUSSION
/ISSUED 540 AM AST WED NOV 20 2024/
SYNOPSIS...HIGH PRESSURE WILL FORM IN THE WESTERN TROPICAL
ATLANTIC DURING THE LATTER PART OF THE WEEK AS A DISTANT LOW PULLS
NORTHEAST AND THE COOL AIR BEHIND THE FRONT WARMS. DRIER WEATHER
WITH ONLY A FEW SHOWERS ARE EXPECTED THROUGH FRIDAY THEN BETTER
MOISTURE ON SOUTH TO SOUTHEAST FLOW WILL RETURN TO THE AREA
INCREASING SHOWERS AND THE CHANCE OF THUNDERSTORMS.
SHORT TERM...TODAY THROUGH FRIDAY...
DURING THE OVERNIGHT HOURS, SATELLITE DERIVED PRECIPITABLE WATER
(PWAT) VALUES OVER PUERTO RICO WERE AROUND 1.09 TO 1.2 INCHES, WELL
BELOW NORMAL TO BELOW NORMAL, WITH THE HIGHER VALUES OVER EASTERN
PR. BELOW NORMAL PWAT VALUES WERE ALSO OBSERVED OVER THE USVI WITH
UP TO 1.30 TO 1.35 IN. SINCE MIDNIGHT, COLD AIR ADVECTION PROMOTED
LIGHT TO LOCALLY MODERATE SHOWERS UNDER NE WINDS, MAINLY ACROSS
NORTHERN AND EASTERN PUERTO RICO, VIEQUES, ST. THOMAS AND ST. CROIX.
THESE SHOWERS LEFT, A RADAR ESTIMATED, 0.20 TO 0.25 INCHES OVER
VIEQUES, EASTERN ST. CROIX AND ISOLATED AREAS OF NE PR. REPORTED
LOWS WERE IN THE LOW TO MID 60S AT HIGHER ELEVATIONS OF PUERTO RICO
AND IN THE MID 70S TO AROUND 80 OVER LOWER ELEVATIONS OF THE ISLANDS.
CURRENT MODEL GUIDANCE HAS PWAT VALUES OF 0.9 TO 1.3 INCHES OVER THE
ISLANDS THROUGH THURSDAY, WELL BELOW TO BELOW NORMAL VALUES FOR THIS
TIME OF THE YEAR. NORTHEASTERLY FLOW WILL CONTINUE TODAY, BRINGING
COOL AND RELATIVELY DRY AIR OVER THE REGION. ADVECTIVE SHOWERS WILL
STILL MOVE IN OVER WINDWARD SECTORS AT TIMES. A POLAR TROUGH WILL
EXIT THE EASTERN COAST OF THE U.S WHILE A SURFACE HIGH WILL
GRADUALLY MOVE OVER THE CENTRAL ATLANTIC FROM OUR NORTHWEST,
PROMOTING WINDS TO GRADUALLY VEER TO BECOME MORE EASTERLY TONIGHT,
SOUTHEASTERLY TOMORROW AFTERNOON, AND THEN SOUTHERLY BY FRIDAY.
INCREASING MOISTURE WILL THEN BE EXPERIENCED FRIDAY WITH PWAT VALUES
CLIMBING BACK TO LOW END NORMAL VALUES. THE CHANGE IN WIND WILL
BRING IN A MOISTURE PLUME FROM THE EAST AND SOUTH, INCREASING THE
POTENTIAL FOR SHOWERS AND SETTING THE STAGE FOR A WETTER LONG TERM
PERIOD. THE PRESSURE GRADIENT WILL BE WEAK, PROMOTING LIGHT WIND
FLOW. BY FRIDAY, SOUTHERLY FLOW WILL PULL MOISTURE FROM THE
CARIBBEAN SEA INTO THE ISLANDS, INCREASING PWAT VALUES BACK TO
AROUND AND ABOVE 2 INCHES IN THE AFTERNOON/EVENING. MID TO UPPER
LEVEL RIDGING WILL MAINTAIN A TRADE WIND CAP INVERSION AROUND 800
MB, WITH ALL THE LOW LEVEL MOISTURE TRAPPED BELOW THIS LEVEL,
THROUGH FRIDAY AFTERNOON WHEN DEEP MOISTURE MOVES INTO THE REGION.
LIKEWISE LOW LEVEL MOISTURE ITSELF, AS WELL AS 925MB
TEMPERATURES, ARE FORECAST TO BE BELOW NORMAL UNTIL FRIDAY WHEN
THEY CLIMB BACK UP. BEFORE FRIDAY, 500 MB TEMPERATURES WILL BE
PRETTY WARM, DIMINISHING DEEP CONVECTIVE ACTIVITY POSSIBILITIES,
HOWEVER LOCAL EFFECTS CAN HELP PRODUCE LIMITED AFTERNOON
CONVECTION OVER THE INTERIOR. COLD AIR ADVECTION WILL ALSO PROMOTE
SHOWERS OVER NORTHERN AND EASTERN REGIONS. HIGHS WILL BE IN THE
THE MID TO UPPER 80S TODAY ACROSS MOST COASTAL AREAS OF THE
ISLANDS, EXCEPT IN SOUTHERN PR WHERE IT CAN REACH THE LOW 90S.
LIMITED TO ELEVATED EXCESSIVE RAINFALL RISKS AND AND AN INCREASED
POTENTIAL FOR THUNDERSTORMS WILL BE PRESENT FOR THE SECOND HALF OF
THE WORKWEEK, ESPECIALLY ON FRIDAY WITH ALL OF THE COLUMNAR
MOISTURE OVER THE REGION. THIS WET PATTERN WILL CONTINUE INTO THE
LONG TERM FORECAST PERIOD.
LONG TERM...SATURDAY THROUGH WEDNESDAY...
HIGH PRESSURE AT UPPER LEVELS DOMINATES THE LONG PERIOD DESPITE
THE PASSAGE OF AN UPPER LEVEL TROUGH SATURDAY EVENING WELL TO THE
NORTH OF THE AREA. THE ASSOCIATED SOUTHWESTERLY JET STREAM WILL
LIKELY NEVER GET PAST CUBA. AT MID LEVELS HIGH PRESSURE BECOMES
ENTRENCHED ABOUT 1000 MILES EAST NORTHEAST OF SAN JUAN, PUERTO
RICO AND MOVES VERY LITTLE. AS THE FLOW AROUND THIS HIGH IS FROM
THE SOUTH MODEST MOISTURE WILL BE BROUGHT UP OUT OF THE CARIBBEAN
DURING THE PERIOD. PEAK MOISTURE WILL BE SEEN LATE SUNDAY NIGHT
AND MONDAY MORNING. AT THE SURFACE HIGH PRESSURE NORTHEAST OF THE
AREA--MUCH WHERE THE MID LEVEL HIGH IS ALSO--KEEPS FLOW SOUTHERLY.
A WEAK WAVE PASSING TO THE WEST OVER THE CARIBBEAN BEGINS TO
AMPLIFY SOUTH OF JAMAICA AND FLOW TURNS SOUTHEASTERLY FOR THE
REMAINDER OF THE PERIOD. WHILE THIS DOES BRING IN SOME MOISTURE,
FLOW IS NEVER PARTICULARLY MOIST AT ANY ONE LEVEL BUT PRECIPITABLE
WATER VALUES REMAIN ABOVE TWO INCHES EXCEPT FOR A 24 HOUR PERIOD
FROM EARLY TUESDAY TO EARLY WEDNESDAY WHEN AIR FROM THE MID
ATLANTIC IS BROUGHT BACK IN AROUND THE HIGH PRESSURE EAST
NORTHEAST OF THE AREA. WHILE THE LOW PRESSURE EXPECTED TO FORM
OVER THE CENTRAL CARIBBEAN WILL NOT DIRECTLY AFFECT PUERTO RICO
OR THE U.S. VIRGIN ISLANDS, PERIODS OF SHOWERS WILL KEEP THE AREA
WET. AT THIS TIME THIS DOES NOT APPEAR TO GENERATE EXPECTATIONS
FOR ANYTHING MORE THAN PONDING OF ROADS AND SOME STREAM RISES.
AVIATION...
(06Z TAFS)
MAINLY VFR CONDITIONS ARE FORECAST TO PREVAIL ACROSS THE TERMINALS.
VCSH WILL BE BROUGHT IN BY NORTHEASTERLY FLOW AT TIMES. AFTER 18Z,
CONVECTIVE VCSH ALSO POSSIBLY AFFECTING TJPS. BELOW FL050, NE WINDS
WILL BE UP TO AROUND 12 KTS WITH HIGHER GUSTS AND SEA BREEZE
VARIATIONS.
MARINE...SEAS WERE RISING AT THE OUTER BUOY (41043) AND THESE
SWELL WERE ABOUT 5 HOURS AWAY FROM PUERTO RICO'S NORTHERN COAST
AND CULEBRA, HOWEVER SEAS HAVE LEVELED OFF FOR THE MOMENT SO, FOR
NOW, SEAS OF NO MORE THAN 5-6 FEET IN AREAS EXPOSED TO NORTHERLY
SWELL ARE EXPECTED THROUGH SUNDAY. ANOTHER SWELL WILL MOVE IN ON
MONDAY THAT MAY BRING SMALL CRAFT CONDITIONS.
BEACH FORECAST...THERE IS A HIGH RISK OF RIP CURRENTS TONIGHT
FOR THE SAN JUAN ZONE, THE FAJARDO ZONE, AND CULEBRA. OTHERWISE
MODERATE OR LOW RISK OF RIP CURRENTS WILL BE FOUND UNTIL SUNDAY
NIGHT. THEN, SWELL FROM BEYOND THE ANEGADA PASSAGE WILL BRING A
HIGH RISK TO SAINT CROIX AND LATER TO NORTHWEST AND NORTH CENTRAL
PUERTO RICO ON TUESDAY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR PRZ001-002-005-
008-012.
VI...NONE.
AM...NONE.
UPDATE...DSR
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page