An area of low pressure located over Hispaniola, produced favorable atmospheric conditions to produced scattered to numerous with strong thunderstorms. These strong thunderstorms produced small hail and torrential rainfall mainly over the western interior and west sections of Puerto Rico.
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The episode as NWS SJU wrote it up.
An area of low pressure located over Hispaniola, produced favorable atmospheric conditions to produced scattered to numerous with strong thunderstorms. These strong thunderstorms produced small hail and torrential rainfall mainly over the western interior and west sections of Puerto Rico.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS San Juan, PR wrote its last area forecast discussion before the first event at Sep 1, 2:51 PM AST, 9 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 251 PM AST SUN SEP 1 2013 .SYNOPSIS...A LOW OVER HISPANIOLA WILL BE DISPLACED BY HIGH PRESSURE MOVING IN FROM THE EAST SOUTHEAST AND IT WILL HAVE A STRONG PRESENCE JUST NORTH OF THE MONA PASSAGE BY THURSDAY. THIS HIGH WILL DRIFT OVER THE WINDWARD PASSAGE BY SUNDAY OF NEXT WEEK BUT WILL CONTROL THE WEATHER OVER THE ENTIRE EASTERN AND CENTRAL CARIBBEAN. AT MID LEVELS...HIGH PRESSURE JUST NORTHEAST OF THE BAHAMA ISLANDS WILL DISSIPATE SLOWLY LATE THIS WEEK. AN INVERTED TROUGH OVER THE WESTERN TROPICAL ATLANTIC NEAR 57 WEST WILL MOVE ACROSS THE LESSER ANTILLES MONDAY NIGHT AND SOUTH OF THE U.S. VIRGIN ISLANDS AND PUERTO RICO TUESDAY NIGHT. THIS TROUGH WILL BE OVER THE WESTERN CARIBBEAN BY THURSDAY. A LOW WILL DEVELOP 1700 MILES EAST NORTHEAST OF SAINT THOMAS FRIDAY AND FORM A TROUGH IN THE WESTERN TROPICAL ATLANTIC BY TUESDAY OF THE FOLLOWING WEEK. AT LOWER LEVELS...A TROPICAL WAVE IS A STRENGTHENING JUST EAST OF THE WINDWARD ISLANDS AND WILL MOVE INTO THE SOUTHEASTERN CARIBBEAN TONIGHT. ALTHOUGH IT HAS SOME CHANCE FOR DEVELOPMENT...IT IS EXPECTED TO MOVE THROUGH THE CARIBBEAN SOUTH OF THE FORECAST AREA AS A STRONG WAVE OR A TROPICAL DEPRESSION...INCREASING MOISTURE THROUGH TUESDAY NIGHT. HIGH PRESSURE SLOWLY RETURNS TO THE NORTHEAST CARIBBEAN WEDNESDAY THROUGH FRIDAY. SOUTHEAST FLOW WILL PREVAIL ACROSS THE AREA AFTER THE WAVE PASSAGE INTO NEXT WEEK. && .DISCUSSION...STRONG THUNDERSTORMS DEVELOPED IN THE MAYAGUEZ AREA AND ALONG THE CORDILLERA CENTRAL FROM PENUELAS TO SABANA GRANDE EARLY IN THE AFTERNOON WITH SOME MINOR FLOODING AS OF 2:30 PM AST. THESE THUNDERSTORMS ARE EXPECTED TO BEFORE SUNSET. SHOWER ACTIVITY SHOULD BE MINIMAL OVERNIGHT. MOISTURE CIRCULATING AROUND A HIGH PRESSURE AT 700 MB WILL MOVE ACROSS THE AREA FROM THE NORTH ON MONDAY...INCREASING THE CHANCES OF SHOWERS...MAINLY ACROSS THE NORTHEASTERN TWO THIRDS OF THE PUERTO RICO. ON TUESDAY THE MOISTURE FROM THE WAVE WILL MOVE ACROSS THE FORECAST AREA WITH SHOWERS AND THUNDERSTORMS. AT THIS TIME MODELS DO NOT SHOW TROPICAL CYCLONE FORMATION THOUGH SATELLITE IMAGERY SUGGESTS THAT THERE IS CERTAINLY SOME POSSIBILITY. NEVERTHELESS... THE LOW PRESSURE THAT WOULD BE ITS SEED IS QUITE ELONGATED AT THIS TIME AND IT IS ENTERING AN AREA THAT TYPICALLY WORKS AGAINST SUCH FORMATION. THEREFORE WILL GO WITH THE CONSENSUS OF FORECASTERS HERE...AND AT THE HURRICANE CENTER...AND THE MAJORITY OF THE MODELS AND SHOW A STRONG TROPICAL WAVE PASSING TUESDAY AND TUESDAY NIGHT...MAINLY SOUTH OF THE AREA. THIS WILL BRING HEAVY RAIN TO MANY AREAS TUESDAY AND TUESDAY NIGHT. THE GFS SHOWS RELATIVE HUMIDITY AT 850 MB WEAKENING ON WEDNESDAY ALTHOUGH IN GENERAL MOIST FLOW CONTINUES FROM THE SOUTHEAST AND SOUTH AND SO NOW EXPECT BEST RAINS ON TUESDAY. NOT WITHSTANDING...THERE IS A GOOD POSSIBILITY THAT STRONG SHOWERS AND THUNDERSTORMS COULD CONTINUE INTO WEDNESDAY. AT THIS TIME IT IS TOO EARLY TOO PUT OUT A FLASH FLOOD WATCH DUE TO THE UNCERTAINTY OF THE DEVELOPMENT OF THE TROPICAL WAVE PASSING THROUGH THE CARIBBEAN AND ITS PATH IF IT DOES DEVELOP. WE WILL RE- EVALUATE THIS SITUATION ON MONDAY AND DECIDE IF SUFFICIENT RAIN POTENTIAL EXISTS FOR FLASH FLOODING. WOULD EXPECT MANY AREAS OF URBAN AND SMALL STREAM FLOODING TO DEVELOP TUESDAY THROUGH WEDNESDAY WITH IMPROVEMENT ON THURSDAY. MOISTURE CONTINUES RICH OVER THE AREA AND REAL DRYING IS NOT DEPICTED IN THE GFS MODEL UNTIL MONDAY OF NEXT WEEK. HENCE SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS EACH DAY THURSDAY THROUGH SUNDAY OVER PORTIONS OF PUERTO RICO ARE EXPECTED...WITH ISOLATED SHOWERS...PERHAPS SCATTERED AT TIMES IN THE U.S. VIRGIN ISLANDS. && .AVIATION... AFTERNOON CONVECTION CONTINUING OVER SW PR...WILL RESULT IN VCTS IN AND AROUND TJMZ AND TJPS BETWEEN 01/19-22Z. THIS FLOW WILL FOCUS THE SHRA/TSRA ACTIVITY OVER SW PR BETWEEN OF TJPS AND TJMZ...MOST OF THESE SHOWERS WILL DISSIPATE AT AROUND SUNSET. WINDS WILL BE FROM ENE AT 10 TO 15 KTS. VFR CONDITIONS EXPECTED AT ALL TAF SITES THROUGH THE OVERNIGHT FORECAST PERIOD. && .MARINE...THE MODELS ARE SHOWING STRENGTHENING WINDS OVER THE AREA WITH THE PASSAGE OF THE TROPICAL WAVE AND SEAS OF OVER 5 FEET WERE SEEN FOR A WHILE AT BUOY 42060 SOUTHEAST OF THE FORECAST AREA TODAY. HAVE INCREASED WINDS IN THE FORECAST...BUT CURRENTLY HOLDING WINDS AT OR BELOW 21 KNOTS. SHOULD ANY FURTHER DEVELOPMENT BE OBSERVED WITH INVEST 97L...THE WAVE NOW APPROACHING THE CARIBBEAN...WILL HAVE TO PUT UP SMALL CRAFT ADVISORIES FOR BOTH WINDS AND SEAS AS EARLY AS MONDAY NIGHT. CONDITIONS SHOULD IMPROVE AFTER WEDNESDAY. && .PRELIMINARY POINT TEMPS/POPS... SJU 80 89 77 87 / 40 60 60 70 STT 80 89 78 89 / 40 40 60 70 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. COASTAL WATERS...NONE. && 10/12
HAZARDOUS WEATHER OUTLOOK...CORRECTED NATIONAL WEATHER SERVICE SAN JUAN PR 508 AM AST SUN SEP 1 2013 AMZ710>745-PRZ001>013-020915- SAN JUAN AND VICINITY-NORTHEAST-SOUTHEAST-EASTERN INTERIOR- NORTH CENTRAL-CENTRAL INTERIOR-PONCE AND VICINITY-NORTHWEST- WESTERN INTERIOR-MAYAGUEZ AND VICINITY-SOUTHWEST-CULEBRA-VIEQUES- THE NEARSHORE AND OFF SHORE ATLANTIC AND CARIBBEAN COASTAL WATERS- 508 AM AST SUN SEP 1 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT ATLANTIC COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT AN UPPER LEVEL TROUGH JUST WEST OF PUERTO RICO WILL HELP TRIGGER SHOWERS AND THUNDERSTORMS ACROSS PORTIONS OF THE LOCAL ISLANDS. LOCALIZED AREAS OF HEAVY RAINFALL AND SOME FLOODING IN URBAN AREAS AND SMALL STREAMS ARE POSSIBLE OVER THE WEST INTERIOR AND SOUTHWEST SECTIONS OF PUERTO RICO THIS AFTERNOON. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY A VIGOROUS TROPICAL WAVE EAST OF THE LESSER ANTILLES...WILL MOVE WESTWARD OVER THE NEXT SEVERAL DAYS. THIS WAVE WILL LIKELY BRING A SIGNIFICANT INCREASE IN CLOUDS AND SHOWER ACTIVITY ACROSS THE LOCAL ISLANDS BETWEEN TUESDAY AND WEDNESDAY. URBAN AND SMALL STREAM FLOODING IS EXPECTED AND FLASH FLOODING CANNOT BE RULED OUT AT THIS TIME. .SPOTTER INFORMATION STATEMENT... RAINFALL REPORTS OF TWO INCHES OR MORE AND/OR FLOODING REPORTS WOULD BE GREATLY APPRECIATED. AMZ715-725-VIZ001-002-020915- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 508 AM AST SUN SEP 1 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY A VIGOROUS TROPICAL WAVE EAST OF THE LESSER ANTILLES...WILL MOVE WESTWARD OVER THE NEXT SEVERAL DAYS. THIS WAVE WILL LIKELY BRING A SIGNIFICANT INCREASE IN CLOUDS AND SHOWER ACTIVITY ACROSS THE LOCAL ISLANDS BETWEEN TUESDAY AND WEDNESDAY. THIS IS LIKELY TO CAUSE URBAN AND GUT FLOODING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.
The San Juan radar (TJUA), 110 km away, was scanning. The volume nearest the first event began at 19:02 UTC.
1 hail. Local standard time, as filed.
Pea size hail was reported at Mayaguez area, near downtown.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2013Every state in 2013This day in weather historyWarnings in Puerto Rico, September 2013
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 477648.