Low level moisture combined with strong daytime heating and orographic effects produced scattered to numerous showers with isolated thunderstorms over the western interior section of Puerto Rico.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS SJU wrote it up.
Low level moisture combined with strong daytime heating and orographic effects produced scattered to numerous showers with isolated thunderstorms over the western interior section 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 28, 3:19 PM AST, 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 319 PM AST FRI SEP 28 2012 .SYNOPSIS...HIGH PRESSURE SYSTEM WILL REMAIN OVER THE REGION THROUGH AT LEAST MID NEXT WEEK. UPPER LEVEL TROUGH LOCATED NORTHEAST OF THE LESSER ANTILLES...WILL MOVE WEST NEXT FEW DAYS. && .DISCUSSION...SHOWERS WITH ISOLATED STRONG THUNDERSTORMS DEVELOPED THIS AFTERNOON OVER THE CORDILLERA CENTRAL. THE HEAVIEST RAINFALL OCCURRED OVER THE WESTERN INTERIOR SECTION OF PUERTO RICO WITH OVER THREE INCHES PER HOUR REPORTED IN THE MUNICIPALITY OF LARES. THIS ACTIVITY WAS ASSOCIATED WITH THE COMBINATION OF DAYTIME HEATING...WITH AVAILABLE MOISTURE AND OROGRAPHIC EFFECTS. THIS ACTIVITY WILL DISSIPATED NEAR SUNSET. THE SAME WEATHER PATTERN...WITH SHOWERS AND THUNDERSTORMS ARE EXPECTED EACH AFTERNOON NEXT FEW DAYS. AN UPPER LEVEL RIDGE WILL CONTINUE TO DOMINATE THE REGION THROUGH AT LEAST MID NEXT WEEK. THIS WILL MAINTAIN MOSTLY SUNNY SKIES DURING THE MORNING HOURS ACROSS THE LOCAL ISLANDS...WITH ONLY PASSING SHOWERS EXPECTED. AN UPPER LEVEL TROUGH LOCATED NORTHEAST OF THE AREA...WILL MOVE SLOWLY WEST NEXT FEW DAYS. THIS TROUGH IS EXPECTED TO MOVE IN A MORE FAVORABLE AREA FOR SHOWER DEVELOPMENT LOCALLY...MID NEXT WEEK. IN THE LONG TERM...NO SIGNIFICANT WEATHER EVENTS ARE FORECAST TO AFFECT THE REGION. && .AVIATION...AFTERNOON SHRA/TSRA ACROSS THE NW SECTIONS OF PUERTO RICO WILL AFFECT THE AREAS AROUND TJBQ...THEREAFTER...VFR CONDITIONS WILL PREVAIL ACROSS ALL TAF SITES THIS EVENING AND OVERNIGHT. WINDS WILL BECOME LIGHT AND VARIABLE TONIGHT AT THE SURFACE. SHRA/TSRA ARE ONCE AGAIN EXPECTED TOMORROW AFTERNOON ACROSS THE INTERIOR....NORTHERN...AND NORTHWESTERN PR. && .PRELIMINARY POINT TEMPS/POPS... SJU 78 90 79 90 / 0 50 0 20 STT 78 88 79 89 / 30 30 20 20 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. COASTAL WATERS...NONE. && 25/71
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN JUAN PR 452 AM AST FRI SEP 28 2012 AMZ710>745-PRZ001>013-290900- 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- 452 AM AST FRI SEP 28 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT ATLANTIC COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT ISOLATED THUNDERSTORMS WILL BE POSSIBLE DURING THE AFTERNOON. THE MAIN IMPACTS WILL BE DANGEROUS CLOUD TO GROUND LIGHTNING STRIKES AND LOCALIZED HEAVY RAINS. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... AMZ715-725-VIZ001-002-290900- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 452 AM AST FRI SEP 28 2012 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 AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE SAN JUAN PR 229 PM AST FRI SEP 28 2012 PRC027-065-071-081-115-131-141-281930- HATILLO PR-LARES PR-UTUADO PR-SAN SEBASTIAN PR-ISABELA PR-CAMUY PR- QUEBRADILLAS PR- 229 PM AST FRI SEP 28 2012 AT 220 PM AST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 3 MILES SOUTHEAST OF LARES...MOVING NORTHWEST AT 10 MPH. THIS THUNDERSTORM IS CAPABLE OF PRODUCING STRONG WINDS UP TO 40 MPH...TORRENTIAL RAINFALL AND DANGEROUS LIGHTNING. INTENSE LIGHTNING IS REPORTED WITH THIS STORM. IF OUTDOORS...STAY AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES. MOVE INDOORS IF POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND DOORS AND AVOID USING TELEPHONES UNLESS IT IS AN EMERGENCY. TRY TO UNPLUG UNNECESSARY ELECTRICAL APPLIANCES BEFORE THE THUNDERSTORM APPROACHES. CASTRO
COMUNICADO ESPECIAL SOBRE LAS CONDICIONES DEL TIEMPO SERVICIO NACIONAL DE METEOROLOGIA SAN JUAN PR 229 PM AST VIERNES 28 DE SEPTIEMBRE DE 2012 PRC027-065-071-081-115-131-141-281930- HATILLO PR-LARES PR-UTUADO PR-SAN SEBASTIAN PR-ISABELA PR-CAMUY PR- QUEBRADILLAS PR- 229 PM AST VIERNES 28 DE SEPTIEMBRE DE 2012 A LAS 2:20 PM AST...EL RADAR DOPPLER DEL SERVICIO NACIONAL DE METEOROLOGIA INDICO UNA FUERTE TRONADA A 3 MILLAS AL SURESTE DE LARES...MOVIENDOSE HACIA EL NOROESTE A 10 MPH. ESTA TRONADA ES CAPAZ DE PRODUCIR VIENTOS FUERTES HASTA DE 40 MPH...LLUVIAS TORRENCIALES Y RELAMPAGOS PELIGROSOS. SE HAN REOPORTADO INTENSOS RELAMPAGOS CON ESTA TORMENTA ELECTRICA. DE VERSE AL DESCUBIERTO MANTENGASE ALEJADO DE OBJETOS ALTOS COMO ARBOLES. DE SER POSIBLE...PROTEJASE MANTENIENDOSE DENTRO DE ALGUNA ESTRUCTURA. CUANDO ESTE ADENTRO...MANTENGASE ALEJADO DE LAS VENTANAS Y PUERTAS Y EVITE UTILIZAR EL TELEFONO A MENOS QUE SEA UNA EMERGENCIA. TRATE DE DESCONECTAR LOS ENSERES ELECTRICOS QUE NO ESTE UTILIZANDO ANTES QUE SE APROXIME LA TRONADA. CASTRO/SANCHEZ
The San Juan radar (TJUA), 90 km away, was scanning. The volume nearest the first event began at 19:25 UTC.
1 flash flood. Local standard time, as filed.
Rio Guajataca in Lares went above flood stage with sensor indicating 16.27 feet. Flood stage is 13 feet. Minor flooding was reported near Barrio Seburuquillo.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2012Every state in 2012This day in weather historyWarnings in Puerto Rico, September 2012
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: 414008.