954
FXCA62 TJSJ 010852
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
452 AM AST WED JAN 1 2025
SYNOPSIS
THE WINTER ADVECTIVE PATTERN WILL PROMOTE PLEASANT TEMPERATURES
WITH OCCASIONAL PASSING SHOWERS THROUGHOUT THE BEGINNING OF 2025.
SHOWER ACTIVITY WILL AFFECT MAINLY PR AND THE USVI'S WINDWARD
LOCATIONS. BY NEXT WEEKEND, INSTABILITY AND RAINFALL ACTIVITY WILL
INCREASE SLIGHTLY TO MODERATELY DUE TO THE POTENTIAL APPROACH OF
ANOTHER COLD FRONT WITH A PRE-FRONTAL TROUGH NEAR THE NORTHEAST
CARIBBEAN. ANOTHER LONG-PERIOD NORTHEASTERLY SWELL WILL
DETERIORATE THE MARINE AND COASTAL CONDITIONS BY THE WEEKEND AND
EARLY NEXT WEEK. NEXT WEEK'S WEATHER WILL BE TIGHT TO THE FINAL
POSITION OF THE COLD FRONT THAT WILL LINGER NEAR THE NORTHEAST
CARIBBEAN.
SHORT TERM...TODAY THROUGH FRIDAY
A SHOWERY BEGINNING OF THE YEAR WAS OBSERVED AS PATCHES OF MOISTURE
MOVED ACROSS THE REGION. THIS PATTERN PREVAILED ALL NIGHT JUST
BEFORE NEW YEAR'S, WITH STATIONS IN EASTERN PUERTO RICO REPORTING
ACCUMULATIONS UP TO 0.25 INCHES AND THE STATION IN CULEBRA OBSERVED
APPROXIMATELY 0.33 INCHES. TEMPERATURES REMAINED SLIGHTLY HIGHER
THAN YESTERDAY, AS STATIONS IN URBAN AND COASTAL AREAS REPORTED LOW
TO MID 70S WHILE THE INTERIOR REMAINED IN THE LOW TO MID 60S WITH
LOCALIZED AREAS DROPPING TO LOW 50S.
THE CURRENT RADAR LOOP AND VAD WIND PROFILE SHOW NE WINDS BRINGING A
FEW PASSING SHOWERS ACROSS THE LOCAL WATERS AND WINDWARD SECTIONS.
SATELLITE-DERIVED PRODUCTS SHOW PRECIPITABLE WATER (PWAT) VALUES
BETWEEN 1.1 - 1.4 INCHES AS EXPECTED BY MODEL GUIDANCE. THE HIGH
SURFACE PRESSURE IN THE WESTERN ATLANTIC AND THE LOW SURFACE
PRESSURE IN THE CENTER ATLANTIC WILL KEEP PROMOTING NE TO ENE
WINDS AS THE HIGH PRESSURE BUILDS IN THE CENTRAL ATLANTIC MAKING
WAY FOR A FRONTAL SYSTEM JUST EAST OF CONUS MOVING SOUTHEASTWARD
NEAR HISPANIOLA. PATCHES OF MOISTURE WILL MOVE ACROSS THE LOCAL
ISLANDS TODAY AND TOMORROW, INCREASING FROM BELOW NORMAL TO
SEASONAL PWAT VALUES. THE ADVECTIVE PATTERN WILL PREVAIL, WITH MIX
IN CLOUDS AND PERIODS OF PASSING SHOWERS IN THE MORNING AND
DURING THE NIGHT HOURS FOR NORTHERN AND EASTERN PUERTO RICO,
VIEQUES, CULEBRA, AND THE U.S. VIRGIN ISLANDS. SHALLOW CONVECTION
IN THE AFTERNOON IS ANTICIPATED IN SOUTHWESTERN PUERTO RICO,
INCREASING RISK OF FLOODING. RAINFALL ACCUMULATIONS ARE LIKELY TO
PROMOTE PONDING OF WATER IN ROADWAYS, URBAN, AND POORLY DRAINED
AREAS.
MORE STABLE CONDITIONS ARE EXPECTED ON FRIDAY AS MODEL SOLUTIONS
AGREE THAT A MASS OF DRIER AIR WILL REACH THE LOCAL ISLANDS.
HOWEVER, MOISTURE CONTENT WILL GRADUALLY INCREASE IN THE NIGHT. THE
FRESHER TEMPERATURES WILL CONTINUE ACROSS THE REGION FOR THE SECOND
PART OF THE WORKWEEK INTO THE WEEKEND.
LONG TERM...SATURDAY THROUGH WEDNESDAY
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
(06Z TAFS)
MOSTLY VFR CONDS FOR ALL TERMINALS IN NYD. FU AND -RA
WILL PREV FOR TJSJ BTW 04-08Z. EXPECT NE-ENE WINDS AT 5-12 KT WITH
SEA BREEZE VARIATIONS THROUGH THE DAY. PATCHES OF MOISTURE WILL
PROMOTE SHRA AND VCSH FOR MOST TAF SITES BTW 01/12-01/22Z,
RESULTING IN BKN-OVC CIGS AND REDUCED VIS.
MARINE
MODERATE NORTHEAST WINDS IN PLACE FOR EARLY THIS WEEK UNDER 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.
CLIMATE
THE YEAR 2024 WILL END AS THE WARMEST YEAR ON RECORD FOR THE SAN
JUAN AREA CLIMATE SITE. THESE RECORDS DATE BACK TO 1898.
ADDITIONALLY, DECEMBER 2024 WILL END AS THE SECOND WARMEST DECEMBER
ON RECORD AS WELL, FOR THE SAN JUAN AREA SITE, AND ALSO FOR HENRY E.
ROHLSEN IN SAINT CROIX.
FOR THE SAN JUAN AREA SITE, IT WILL END ALSO AS THE EIGHT WETTEST ON
RECORD, WITH 78.93 INCHES COLLECTED.
SJU WATCHES/WARNINGS/ADVISORIES
PR...NONE.
VI...NONE.
AM...NONE.
SHORT TERM/AVIATION...MNG
SYNOPSIS/LONG TERM/MARINE/BEACH FORECAST....CAM
CLIMATE...ERG
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