101  
FXCA62 TJSJ 150900  
AFDSJU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN JUAN PR  
500 AM AST TUE JUL 15 2025  
   
KEY MESSAGES  
 
* HOT TEMPERATURES, HIGH HUMIDITY CONTENT, AND SOUTHEASTERLY WINDS  
WILL PROMOTE AN ELEVATED HEAT RISK ACROSS THE LOWER ELEVATIONS  
AND URBAN AREAS OF PUERTO RICO THROUGH THE END OF THE WEEK.  
 
* BACK TO BACK TROPICAL WAVES WILL INCREASE SHOWER AND THUNDERSTORM  
ACTIVITY TODAY AND TOMORROW.  
 
* A SAHARAN AIR LAYER WITH MODERATE TO HIGH CONCENTRATIONS OF  
SAHARAN DUST WILL PROMOTE HAZY SKIES AND POOR AIR QUALITY  
CONDITIONS ON THURSDAY AND FRIDAY.  
 
* INCREASING WINDS THROUGH MIDWEEK WILL PROMOTE CHOPPY SEAS AND A  
MODERATE RISK OF RIP CURRENTS ACROSS MOST EAST AND NORTHERN  
BEACHES OF THE ISLANDS.  
 
 
   
SHORT TERM...TODAY THROUGH THURSDAY  
 
AN INCREASE IN SHOWER FREQUENCY WAS SEEN OVERNIGHT ACROSS THE LOCAL  
ATLANTIC AND CARIBBEAN WATERS. THESE SHOWERS AFFECTED MAINLY THE  
ISLANDS OF ST. THOMAS AND ST. JOHN, WHERE DOPPLER RADAR ESTIMATED  
RAINFALL ACCUMULATIONS UP TO 0.50 INCHES. NONETHELESS, ST. CROIX AND  
EASTERN PUERTO RICO RECEIVED SOME SHOWERS WITH LIMITED  
ACCUMULATIONS. MINIMUM TEMPERATURES WERE FROM THE MID TO UPPER 70S  
ALONG THE COASTAL AND URBAN AREAS TO THE UPPER 60S TO LOW 70S ACROSS  
THE MOUNTAINS. WINDS WERE LIGHT FROM THE EAST-SOUTHEAST WITH LAND-  
BREEZE VARIATIONS.  
 
A BROAD SURFACE HIGH PRESSURE NORTH OF THE AREA WILL MAINTAIN A EAST-  
SOUTHEAST WIND FLOW TODAY. HOWEVER, WINDS WILL BECOME FROM THE EAST  
BY WEDNESDAY AS THE SURFACE HIGH MIGRATES EASTWARD. A TROPICAL WAVE  
THAT IS CURRENTLY CROSSING THE LESSER ANTILLES WILL APPROACH THE  
ISLANDS TODAY, INCREASING THE MOISTURE CONTENT WITH PRECIPITABLE  
WATER (PWAT) VALUES BETWEEN 1.80 TO 2.10 INCHES. A SECOND TROPICAL  
WAVE WITH ITS AXIS NEAR LONGITUDE 50W WILL ARRIVE INTO THE AREA BY  
WEDNESDAY BRINGING ADDITIONAL MOISTURE INTO THE AREA THROUGH  
THURSDAY. UNDER THE AFOREMENTIONED WEATHER PATTERN, SHOWERS AND  
THUNDERSTORMS ARE EXPECTED EACH DAY IN THE ISLANDS. DURING THE  
MORNING HOURS, SCATTERED SHOWERS WILL BE OBSERVED OVER THE U.S.  
VIRGIN ISLANDS AND EASTERN PUERTO RICO. THEN, AFTERNOON CONVECTIVE  
ACTIVITY IS LIKELY OVER PORTIONS OF CENTRAL AND WESTERN PUERTO RICO,  
AS WELL DOWNWIND FROM EL YUNQUE INTO THE SAN JUAN METROPOLITAN AREA  
AND ADJACENT MUNICIPALITIES. AT THIS TIME, THERE IS A LIMITED TO  
ELEVATED POTENTIAL TO OBSERVE PONDING OF WATER IN ROADS AND POORLY  
DRAINAGE AREAS, AS WELL AS LOCALIZED FLOODING IN URBAN AREAS, ROADS  
AND SMALL STREAMS.  
 
BY THURSDAY, TRAILING MOISTURE FROM A DEPARTING TROPICAL WAVE WILL  
CONTINUE TO ENHANCE THE DEVELOPMENT OF SHOWERS AND ISOLATED  
THUNDERSTORMS ACROSS THE ISLANDS DURING THE DAY. HOWEVER, A DENSE  
SAHARAN AIR LAYER (SAL) WITH MODERATE TO HIGH CONCENTRATIONS OF DUST  
PARTICLES WILL REACH THE NORTHEASTERN CARIBBEAN AND GRADUALLY MOVING  
ACROSS THE REGION. THEREFORE, HAZY SKIES, REDUCED VISIBILITY, AND  
POOR AIR QUALITY CONDITIONS ARE ANTICIPATED THROUGH AT LEAST THE  
WEEKEND.  
 
HOT TEMPERATURES WILL CONTINUE TO PERSIST ALL WEEK, WITH MAXIMUM  
TEMPERATURES REACHING UPPER 80S TO LOW 90S ALONG THE COASTAL AND  
URBAN AREAS EACH DAY. HEAT INDICES ARE EXPECTED TO BE ABOVE THE 100  
DEGREES FAHRENHEIT EACH DAY AS WELL, WITH THURSDAY BEING THE WARMEST  
DAY. TODAY, THERE IS A HEAT ADVISORY IN EFFECT FOR ALL COASTAL AREAS  
OF PUERTO RICO, INCLUDING THE CAGUAS VALLEY FROM 10 AM TO 4 PM AST.  
RESIDENTS AND VISITORS, PLEASE BE AWARE OF THESE CONDITIONS AND PLAN  
ACCORDINGLY IF PLANNING TO DO OUTDOOR ACTIVITIES UNDER SUN EXPOSURE.  
   
LONG TERM...FRIDAY THROUGH TUESDAY  
 
HAZY SKIES, REDUCED VISIBILITY, AND POOR AIR QUALITY CONDITIONS WILL  
CONTINUE THROUGH FRIDAY DUE TO A LINGERING SAHARAN AIR LAYER.  
WINDS WILL ACQUIRE A NORTHEASTERLY COMPONENT AS A BROAD TUTT-  
INDUCED TROUGH APPROACHES THE EASTERN CARIBBEAN. THE COMBINATION  
OF THE LIMITED MOISTURE CONTENT WITH DAYTIME HEATING AND THE SEA  
BREEZE CONVERGENCE WILL TRIGGER AFTERNOON SHOWERS WITH ISOLATED  
THUNDERSTORMS OVER THE SOUTHWEST QUADRANT OF PR. AN ADVECTIVE  
WEATHER PATTERN AT NIGHT WILL THEN PROMOTE SHOWERS ACROSS THE  
LOCAL WATERS AND OVER PORTIONS OF THE USVI AND NORTHEASTERN PR.  
 
THE TUTT-LOW AND THE INDUCED LOW-LEVEL TROUGH ARE EXPECTED TO  
MOVE ACROSS THE NORTHEASTERN CARIBBEAN THROUGH THE WEEKEND. THIS  
WILL BRING AN INCREASE IN SHOWER ACTIVITY ONCE AGAIN ACROSS THE  
ISLANDS. A TROPICAL WAVE IS EXPECTED TO MOVE ACROSS THE REGION ON  
MONDAY, FOLLOWED BY ANOTHER SAL EVENT ON TUESDAY. IN GENERAL,  
THESE WEATHER FEATURES WILL ENHANCE THE EARLY MORNING CONVECTION  
BETWEEN THE USVI AND EASTERN SECTIONS OF PR, FOLLOWED BY AFTERNOON  
THUNDERSTORMS OVER PORTIONS OF THE INTERIOR AND WESTERN PR. EVEN  
THOUGH THE SAL IS EXPECTED TO BRING HAZY SKIES AND DRIER MID-LEVEL  
AIR, THE PRECIPITABLE WATER CONTENT IS FORECAST TO RANGE BETWEEN  
NORMAL TO ABOVE NORMAL LEVELS THROUGH THE END OF THE LONG-TERM  
PERIOD.  
 
MEANWHILE, A DEEP LAYER RIDGE BUILDING FROM THE CENTRAL ATLANTIC  
INTO THE NORTHEASTERN CARIBBEAN WILL PUSH FURTHER WEST AND AWAY OF  
THE AREA THE TROUGH PATTERN AND PROMOTE SOUTHEASTERLY WINDS BY  
SATURDAY AFTERNOON. THIS MOIST SOUTHEAST FLOW WILL PREVAIL THROUGH  
AT LEAST TUESDAY, AND HOT TEMPERATURES ARE EXPECTED EACH DAY.  
LIKELY TRIGGERING HEAT ADVISORY CONDITIONS ACROSS MOST COASTAL  
AREAS OF PR.  
 
 
   
AVIATION  
 
(06Z TAFS)  
 
MAINLY VFR CONDS WILL PREVAIL ACROSS ALL TERMINALS DURING THE FCST  
PERIOD. A TROPICAL WAVE WILL ARRIVE TODAY INCREASING SHRA/TSRA  
ACROSS THE ISLANDS, AFFECTING THE TJSJ/TIST/TISX AFT 15/13-14Z AND  
TJBQ/TJPS AFT 15/17-18Z. BRIEF MVFR CIGS POSSIBLE BTW 15/17-23Z. ESE  
WINDS EXPECTED BTW 15-20 KT WITH SEA BREEZE VARIATIONS AND HIGHER  
GUSTS AFT 15/13Z.  
 
 
   
MARINE  
 
A SURFACE HIGH PRESSURE WILL STRENGTHEN OVER THE WESTERN ATLANTIC  
EARLY THIS WEEK. BACK TO BACK TROPICAL WAVES WILL MOVE ACROSS THE  
LOCAL WATERS TODAY AND ON WEDNESDAY. THEREFORE, MODERATE TO  
LOCALLY FRESH TRADES AND CHOPPY SEAS ARE EXPECTED ACROSS THE  
REGIONAL WATERS THROUGH MIDWEEK. INCREASING SHOWER AND  
THUNDERSTORM ACTIVITY IS EXPECTED WITH THE PASSAGE OF THE TROPICAL  
WAVES. HAZY CONDITIONS DUE TO SAHARAN DUST ARE EXPECTED ON  
THURSDAY AND FRIDAY.  
 
 
   
BEACH FORECAST  
 
THERE IS A MODERATE RISK OF RIP CURRENTS FOR THE NORTH AND EAST  
FACING BEACHES OF PUERTO RICO, CULEBRA, VIEQUES, AND ST. CROIX.  
LIFE-THREATENING RIP CURRENTS OFTEN OCCUR IN THE VICINITY OF  
GROINS, JETTIES, REEFS, AND PIERS. THE POTENTIAL FOR ISOLATED  
THUNDERSTORM DEVELOPMENT WILL INCREASE TODAY AND TOMORROW ACROSS  
MOST COASTAL AREAS DUE TO PASSING TROPICAL WAVES.  
 
 
   
SJU WATCHES/WARNINGS/ADVISORIES  
 
PR...HEAT ADVISORY FROM 10 AM THIS MORNING TO 4 PM AST THIS AFTERNOON  
FOR PRZ001>005-007-008-010-011.  
 
VI...NONE.  
AM...NONE.  
 
 
 
 
SHORT...GRS  
LONG...DSR  
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab PR Page
Main Text Page