102
FXCA62 TJSJ 012025
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
425 PM AST WED JAN 1 2025
SYNOPSIS
LIMITED SHOWER ACTIVITY AND PLEASANT TEMPERATURES WILL CONTINUE
ACROSS THE REGION FOR THE NEXT FEW DAYS. BY NEXT WEEKEND,CONDITIONS
WILL BECOME MORE WET AND UNSTABLE WITH THE POTENTIAL APPROACH OF
ANOTHER COLD FRONT WITH A PRE- FRONTAL TROUGH NEAR THE REGION.
MARINE AND COASTAL CONDITIONS ARE EXPECTED TO DETERIORATE BY THE
WEEKEND AND EARLY NEXT WEEK DUE TO THE ARRIVAL OF ANOTHER LONG-
PERIOD NORTHEASTERLY SWELL.
SHORT TERM...TONIGHT THROUGH FRIDAY
DURING THE FIRST MORNING OF THE YEAR, PARTLY TO CLOUDY SKIES WERE
OBSERVED. MOSTLY CALM CONDITIONS ACROSS THE ISLANDS, EXCEPT FOR SOME
PASSING SHOWERS IN THE NORTHERN AND EASTERN PARTS OF PUERTO RICO.
THE SHOWERS MOVED WITH THE NORTHEAST WINDS, LEAVING NO SIGNIFICANT
ACCUMULATIONS, ACCORDING TO RADAR ESTIMATES. PLEASANT TEMPERATURES
PREVAILED ACROSS THE AREA, WITH SURFACE OBSERVATIONS RECORDING
MINIMUM TEMPERATURES IN THE LOW 70S ALONG THE COAST AND URBAN AREAS,
WHILE IN THE MOUNTAINS, TEMPERATURES WERE MOSTLY IN THE LOW 60S.
FOR THE REST OF TODAY, THERE IS A 50 TO 60% CHANCE OF SCATTERED
SHOWERS DEVELOPING, PRIMARILY AFFECTING THE WESTERN INTERIOR OF
PUERTO RICO. MEANWHILE, CLOUD COVER WILL GRADUALLY DECREASE,
STARTING FROM THE USVI, AS A DRIER AIR MASS MOVES OVER THE ISLANDS
FROM EAST TO WEST. THIS WILL LEAD TO MOSTLY STABLE CONDITIONS
TONIGHT.
THE REST OF THE SHORT-TERM PERIOD REMAINS WITHOUT SIGNIFICANT
CHANGES. SATELLITE-DERIVED PRODUCTS SHOW PRECIPITABLE WATER (PWAT)
VALUES RANGING BETWEEN BELOW NORMAL TO SEASONAL VALUES THROUGH
TOMORROW, AROUND 1.1 TO 1.5 INCHES. THE HIGH SURFACE PRESSURE IN THE
WESTERN ATLANTIC WILL CONTINUE TO PROMOTE E TO ENE WINDS. AS A
RESULT, TOMORROW WE SHOULD OBSERVE A SIMILAR PATTERN IN CONTRAST
WITH TODAY, WITH MIX OF CLOUDS AND SUNSHINE, PERIODS OF PASSING
SHOWERS IN THE MORNING AND WESTERN INTERIOR OF PUERTO RICO IN THE
AFTERNOON. BASED ON THE LATEST MODEL GUIDES, ACCUMULATIONS ARE NOT
EXPECTED TO BE SIGNIFICANT AS A MID TO UPPER LEVEL RIDGE WILL HOLD
ALOFT AND DYNAMICS ARE NOT FAVORABLE FOR DEEP CONVECTION. BY FRIDAY,
AN EVEN DRIER AIR MASS (0.8 TO 1.0 INCH OF PWAT) IS EXPECTED TO
REACH AND DOMINATE ACROSS THE LOCAL ISLANDS. PLEASANT TEMPERATURES
ARE EXPECTED TO PREVAIL THROUGHOUT THE WEEK.
LONG TERM...SATURDAY THROUGH WEDNESDAY
//..FROM PREVIOUS DISCUSSION..//
A COLD FRONT WILL DRIFT SLOWLY EASTWARD NEAR THE NORTHEAST
CARIBBEAN, INDUCING A PRE-FRONTAL TROUGH NEAR OR OVER PR/USVI
AROUND SATURDAY AFTERNOON INTO SUNDAY. AT THE SAME TIME, THE TRADE
WINDS WILL PROMOTE MOISTURE POOLING AND PLEASANT TEMPERATURES.
ALONG WITH THE FRONT, A MID-TO UPPER-LEVEL TROUGH WILL NEAR THE
ISLANDS, INCREASING LOCAL INSTABILITY OVER THE WEEKEND AND NEXT
WEEK. GIVEN THIS WEATHER PATTERN, WE CAN ANTICIPATE AN INCREASE IN
SHOWER ACTIVITY AND A SLIGHT TO MODERATE CHANCE OF ISOLATED TO
SCATTERED THUNDERSTORMS. STILL, THE GLOBAL MODELS SHOW SOME
DISCREPANCY IN THE AMOUNT OF PRECIPITATION THAT OUR REGION WILL
EXPERIENCE.
THE GFS MODEL INDICATES THAT THE FRONTAL BOUNDARY MAY LINGER NORTH
OF NEAR THE ISLANDS, INFLUENCED BY ONE HIGH PRESSURE SYSTEM OVER
THE CENTRAL ATLANTIC AND ANOTHER SURFACE HIGH TRAILING BEHIND THE
FRONT. IN CONTRAST, THE ECMWF MODEL SUGGESTS FRONTAL PASSAGE
(FROPA) LATE SUNDAY NIGHT OR EARLY MONDAY MORNING. THESE
SCENARIOS SUGGEST TWO POSSIBLE OUTCOMES FOR EARLY NEXT WEEK:
SHOWERY CONDITIONS PER THE GFS OR DRIER, WINDY AND COOLER
CONDITIONS, ACCORDING TO THE ECMWF. WE WILL CONTINUE TO MONITOR
AND ASSESS THIS POTENTIAL AS THE FORECAST EVOLVES.
PULSES OF A LONG PERIOD NORTHEASTERLY SWELL WILL CREATE LIFE-
THREATENING RIP CURRENTS DUE TO DANGEROUS BREAKING WAVES ALONG THE
EXPOSED NORTH AND EAST-FACING BEACHES IN PR AND THE USVI FROM
FRIDAY TO SUNDAY. THE HAZARDOUS COASTAL CONDITIONS COULD EXTENT
FROM MONDAY ONWARD AS ANOTHER NORTH-TO-NORTHWEST LONG PERIOD SWELL
ARRIVES FROM THE ATLANTIC OCEAN.
AVIATION
VFR CONDITIONS WILL PERSIST FOR THE PERIOD ACROSS ALL
TAF SITES. WINDS WILL CONTINUE FROM THE E-NE WITH SEA BREEZE
VARIATION AND GUSTY WINDS. VCSH ARE FORECAST FOR TJSJ AND TIST.
WINDS WILL DIMINISH AT 01/23Z BECOMING MORE VRB.
MARINE
MODERATE NORTHEAST WINDS WILL CONTINUE TO PREVAIL THIS WEEK UNDER THE
INFLUENCE OF A SURFACE HIGH PRESSURE IN THE WESTERN ATLANTIC AND
SURFACE LOW OVER THE CENTRAL ATLANTIC. ANOTHER FRONT FROM THE EASTERN
US COAST WILL MOVE INTO THE WESTERN ATLANTIC BY MIDWEEK, APPROACHING
THE NORTHEAST CARIBBEAN BY THE WEEKEND. ANOTHER LONG- PERIOD
NORTHERLY SWELL WILL PROMOTE HAZARDOUS SEAS BY THE END OF THIS WEEK
THROUGH THE WEEKEND.
BEACH FORECAST
PULSES OF A FADING NORTHEASTERLY SWELL, MOVING ACROSS THE ATLANTIC
WATERS AND CARIBBEAN PASSAGES, WILL PROMOTE A MODERATE RISK OF RIP
CURRENTS ALONG THE NORTH AND EAST-FACING BEACHES OF PR/USVI,
INCLUDING CULEBRA. MEANWHILE, THE SOUTHERN PROTECTED BEACHES OF PR
REMAIN UNDER A LOW RISK OF RIP CURRENTS.
COASTAL CONDITIONS WILL DETERIORATE AGAIN AROUND FRIDAY THROUGH
THE WEEKEND WITH THE ARRIVAL OF ANOTHER LONG-PERIOD NORTHERLY
SWELL.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM...LIS/DSR
LONG TERM...CAM
PUBLIC DESK/UPPER AIR...GRS
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