The combination of moisture advection and favorable upper level dynamics produced scattered showers with isolated strong thunderstorms mainly over the western interior and northwest sections 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.
The combination of moisture advection and favorable upper level dynamics produced scattered showers with isolated strong thunderstorms mainly over the western interior and northwest 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 23, 10:43 AM AST, 2 hours 16 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 1043 AM AST SUN SEP 23 2012 .UPDATE...MOSTLY CLEAR SKIES PREVAILED DURING THE MORNING HOURS ACROSS THE LOCAL REGION. ONLY FEW ISOLATED SHOWERS WERE DETECTED MAINLY ACROSS THE SURROUNDING COASTAL WATERS. COMPUTER MODEL GUIDANCE AS WELL AS SATELLITE ANALYSIS DEPICTED TWO TUTT LOWS...ONE ACROSS THE CENTRAL ATLANTIC JUST NORTH NORTHEAST OF THE FA AND ANOTHER ONE JUST OVER THE LESSER ANTILLES. BOTH UPPER LOW ACROSS ARE EXPECTED TO RETROGRADE SLOWLY WESTWARD APPROACHING TO THE LOCAL ISLANDS DURING THE NEXT FEW DAYS WHILE FILLING. THESE FEATURES WILL CONTINUE TO INFLUENCE THE WEATHER PATTERN ACROSS THE REGION UNTIL AT LEAST THE MIDDLE OF THE WEEK. SEVERAL LOW LEVEL REELECTIONS/PERTURBATIONS ASSOCIATED WITH THE AFOREMENTIONED LOWS WILL MOVE ACROSS THE LOCAL ISLANDS FROM TIME TO TIME DURING THE NEXT FEW DAYS...PRODUCING INTERVALS OF CLOUDINESS...SHOWERS AND THUNDERSTORMS...ACROSS THE LOCAL ISLANDS. PWAT VALUES WILL REMAIN IN THE RANGE 1.50-1.80 INCHES FOR THE FORECAST PERIODS. THESE PWAT VALUES DO NOT SUPPORT WIDESPREAD SHOWERS AND THUNDERSTORMS...BUT THE COMBINATION OF STRONG DIURNAL HEATING...LOCAL OROGRAPHIC EFFECTS AND MARGINAL FAVORABLE UPPER LEVEL DYNAMIC IS EXPECTED TO INDUCE FEW AREAS OF HEAVY SHOWERS AND THUNDERSTORMS...SPECIALLY ACROSS NORTHERN AND NORTHWEST SECTIONS OF PUERTO RICO EACH AFTERNOON. MODEL GUIDANCE SUGGESTS AN INCREASE IN MOISTURE MONDAY AND TUESDAY AS ANOTHER LOW LEVEL PERTURBATION MOVES ACROSS THE REGION. BY THE NEXT WEEKEND...MODELS INDICATED THAT A SURFACE LOW PRESSURE CENTER WILL DEVELOP SOUTH OF THE REGION...INDUCING A VERY DEEP MOIST AND UNSTABLE SOUTH SOUTHEAST WIND FLOW AND A GENERAL INCREASE IN MOISTURE ACROSS THE FA. STAY TUNED. && .AVIATION...AFTERNOON CONVECTION WILL DEVELOP AGAIN ACROSS CENTRAL...NORTH AND WEST PR FROM 23/16Z-23/22Z. AS A RESULT...BRIEF MVFR CONDITIONS WILL OCCUR NEAR OR OVER TJMZ AND TJBQ...WITH MOUNTAIN TOP OBSCURATIONS OVER INTERIOR PR. LATEST 23/12Z TJSJ SOUNDING INDICATED MAINLY EAST TO SOUTHEAST WINDS FROM THE SURFACE UP TO 20K FEET...BECOMING NORTHEASTERLY ABOVE. && .PREV DISCUSSION... /ISSUED 431 AM AST SUN SEP 23 2012/ SYNOPSIS...TUTT EXTENDING FROM THE CENTRAL ATLANTIC INTO THE EASTERN CARIBBEAN...WITH ASSOCIATED LOWS THE FIRST AND DEEPER NEAR 30N/60W AND THE SECOND LOW OVER THE LEEWARD ISLANDS...WILL CONTINUE TO DOMINATE THE LOCAL WEATHER PATTERN FOR THE NEXT FEW DAYS. DISCUSSION...AFOREMENTIONED TUTT AND ASSOCIATED LOWS WILL CONTINUE TO RETROGRADE WESTWARD WITH ITS AXIS REACHING THE LOCAL AREA MONDAY THROUGH TUESDAY. AS A RESULT...MOISTURE ADVECTION AND FAVORABLE UPPER LEVEL DYNAMICS ARE EXPECTED EARLY NEXT WORK WEEK WITH AN INCREASE IN AFTERNOON CONVECTION ACROSS CENTRAL AND SOUTHWEST PUERTO RICO TUESDAY AND WEDNESDAY SHIFTING TOWARDS NORTHWEST PUERTO RICO ON THURSDAY. MEANWHILE...AIR MASS DRIES OUT SIGNIFICANTLY TODAY AND MONDAY...BUT LOCAL EFFECTS AND DIURNAL HEATING WILL INDUCE SPOTTY CONVECTION ACROSS CENTRAL AND WEST PUERTO RICO BOTH DAYS. MODEL GUIDANCE CONTINUES TO SUGGEST A WET/ACTIVE WEATHER PATTERN FOR THE END OF THE WORK WEEK INTO THE UPCOMING WEEKEND AS A BROAD SURFACE TROUGH DEVELOPS ACROSS THE CENTRAL CARIBBEAN. AVIATION...AN ISOLD TSRA POSSIBLE AT JBQ AND JMZ THIS AFTERNOON BUT PROB TOO LOW TO HAVE EITHER A VCTS OR PROB30 GROUP. OTHERWISE...VFR CONDITIONS AT ALL OTHER TAF SITES WITH NO SIG WX. ONSHORE SFC WINDS 15G20KT DURING THE DAY BCMG L/V AFTER SUNSET. MARINE...PULSES OF NORTHEAST SWELLS WILL AFFECT THE ATLANTIC COASTAL WATERS THROUGH MID NEXT WEEK. HOWEVER...TRANQUIL MARINE CONDITIONS EXPECTED TO PREVAIL TODAY WITH SEAS UP TO 5 FEET AND WINDS OF 17 KNOTS OR LESS. CLIMATE...AT THE SAN JUAN AREA...SEPTEMBER 2012 CURRENTLY RANKS AS THE DRIEST SEPTEMBER ON RECORD WITH ONLY 0.45 INCHES SO FAR. IN TERMS OF TEMPERATURES...SEPTEMBER 2012 REMAINS ON PACE TO BE THE WARMEST SEPTEMBER ON RECORD. THE AVERAGE TEMPERATURE SO FAR HAS BEEN 85.1 DEGREES. THE WARMEST SEPTEMBER ON RECORD WAS SEPTEMBER 1995 WITH AN AVERAGE TEMPERATURE OF 84.9 DEGREES. IN ADDITION...SEPTEMBER 2012 CURRENTLY RANKS AS THE THIRD HOTTEST MONTH OF ANY YEAR...TYING JUNE AND JULY 1980. THE HOTTEST MONTH EVER WAS JUNE 2012 WITH AN AVERAGE TEMPERATURE OF 85.7 DEGREES. AT CYRIL E. KING AIRPORT/SAINT THOMAS...SEPTEMBER 2012 CURRENTLY RANKS AS THE DRIEST SEPTEMBER ON RECORD WITH 0.76 INCHES SO FAR. && .PRELIMINARY POINT TEMPS/POPS... SJU 91 80 91 79 / 0 10 10 20 STT 90 82 90 81 / 0 10 10 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. COASTAL WATERS...NONE. && 72/06
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN JUAN PR 441 AM AST SUN SEP 23 2012 AMZ710>745-PRZ001>013-241000- 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- 441 AM AST SUN SEP 23 2012 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT ATLANTIC COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY AN UPPER LEVEL TROUGH IS FORECAST TO DROP SOUTH INTO THE CENTRAL CARIBBEAN MID WEEK AND INTERACT FAVORABLY WITH A BROAD AREA OF LOW PRESSURE LOCATED NORTH OF COLOMBIA AND PANAMA. THE UPPER LEVEL TROUGH WILL INDUCE AN INVERTED SURFACE TROF PATTERN ACROSS THE CENTRAL CARIBBEAN AND ALSO ALLOW DEEP MOISTURE TO BE LIFTED NORTHWARD INTO OUR AREA. THE INVERTED SURFACE TROF WILL BECOME FOCUS FOR SHOWERS AND THUNDERSTORMS WHICH COULD BECOME OR GROW INTO A LARGE THUNDERSTORM COMPLEX. PERIODS OF HEAVY RAINFALL APPEAR POSSIBLE STARTING FRIDAY AFTERNOON THROUGH SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY. AMZ715-725-VIZ001-002-241000- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 441 AM AST SUN SEP 23 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. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY AN UPPER LEVEL TROUGH IS FORECAST TO DROP SOUTH INTO THE CENTRAL CARIBBEAN MID WEEK AND INTERACT FAVORABLY WITH A BROAD AREA OF LOW PRESSURE LOCATED NORTH OF COLOMBIA AND PANAMA. THE UPPER LEVEL TROUGH WILL INDUCE AN INVERTED SURFACE TROF PATTERN ACROSS THE CENTRAL CARIBBEAN AND ALSO ALLOW DEEP MOISTURE TO BE LIFTED NORTHWARD INTO OUR AREA. THE INVERTED SURFACE TROF WILL BECOME FOCUS FOR SHOWERS AND THUNDERSTORMS WHICH COULD BECOME OR GROW INTO A LARGE THUNDERSTORM COMPLEX. PERIODS OF HEAVY RAINFALL APPEAR POSSIBLE STARTING FRIDAY AFTERNOON THROUGH SATURDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY. ROSA
The national radar mosaic for the moment the first event began.
1 funnel cloud. Local standard time, as filed.
A funnel cloud was reported in the municipality of San Sebastian.
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: 413858.