Upper level trough west northwest of the local area and a broad surface trough across the eastern Caribbean combined with daytime heating and orographic effects to produce numerous showers with thunderstorms with areas of locally heavy rainfall.
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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.
Upper level trough west northwest of the local area and a broad surface trough across the eastern Caribbean combined with daytime heating and orographic effects to produce numerous showers with thunderstorms with areas of locally heavy rainfall.
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 19, 7:12 PM AST, 2 hours 9 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE SAN JUAN PR 712 PM AST MON SEP 19 2011 .UPDATE...A MASS OF CONVECTION IS MOVING NORTH OUT OF THE CARIBBEAN AND BRINGING VERY HEAVY SHOWERS AND THUNDERSTORMS. THIS FLOW HAS BEEN PULLED UP BY THE UPPER LEVEL LOW THAT CONTINUES TO THE NORTH OF THE AREA. && .DISCUSSION...AS CONVECTION WORKS ITS WAY THROUGH PUERTO RICO EXPECT IT TO DISSIPATE CONSIDERABLY BEFORE REACHING THE NORTH HALF OF THE ISLAND AND ALSO AFTER ABOUT 10 PM AST. HOWEVER IN THE MEANTIME THERE WILL BE A NUMBER OF AREAS WITH URBAN AND SMALL STREAM FLOODING IN SOUTH CENTRAL AND SOUTHEASTERN PUERTO RICO. ONLY A FEW HEAVY SHOWERS ARE EXPECTED IN THE U.S. VIRGIN ISLANDS. GENERAL SHOWER ACTIVITY SHOULD END AFTER 2 AM AST...BUT RETURN BEFORE NOON TO PUERTO RICO. && .AVIATION...AREAS OF MVFR AND IFR ARE MOVING THROUGH PUERTO RICO FROM THE SOUTH AND MOST MOUNTAINS WILL BE OBSCURED THROUGH THE NIGHT. && .PREV DISCUSSION... /ISSUED 306 PM AST MON SEP 19 2011/ SYNOPSIS...TUTT EXTENDS FROM THE SOUTHWEST ATLANTIC SOUTHWARD ACROSS THE REGION INTO THE SOUTHEAST CARIBBEAN. THIS WILL MAINTAIN A WEST TO SOUTHWEST WIND FLOW ACROSS THE AREA AND THEREFORE CONTINUE TO LIFT PATCHES OF MID TO UPPER LEVEL MOISTURE ACROSS THE REGION WHILE PROVIDING UPPER LEVEL INSTABILITY THROUGH AT LEAST TUESDAY. IN THE LOW LEVELS...BROAD SURFACE TROUGH ACROSS THE CENTRAL AND EASTERN CARIBBEAN AND HIGH PRESSURE RIDGE EXTENDING WEAKLY ACROSS THE NORTHEAST CARIBBEAN FROM THE EASTERN ATLANTIC WILL MAINTAIN A LIGHT TO MODERATE EAST TO SOUTHEAST WIND FLOW ACROSS THE LOCAL AREA FOR THE NEXT SEVERAL DAYS. THE HIGH PRESSURE RIDGE IS EXPECTED TO GRADUALLY BUILD ACROSS THE REGION THROUGH THE REST OF THE WEEK AS THE TROUGH ACROSS THE CARIBBEAN SHIFTS FURTHER WESTWARD. SATELLITE IMAGERY AND DOPPLER WEATHER RADAR SHOWED CONSIDERABLE AMOUNTS OF TROPICAL MOISTURE WITH AREAS OF ENHANCED SHOWERS AND THUNDERSTORMS BEING ADVECTED ACROSS PARTS OF THE ISLANDS AND SURROUNDING WATERS IN THE PREVAILING SOUTHEAST WIND FLOW. DISCUSSION...THE PRESENT LOW LEVEL PATTERN IN INDUCING LOW LEVEL CONVERGENCE ACROSS THE REGION. THIS COMBINED WITH THE PROXIMITY OF TUTT WILL CONTINUE TO HELP DESTABILIZE LOCAL AREA AND ALLOW FOR ENHANCED DIURNAL AND NOCTURNAL CONVECTION FOR THE NEXT FEW DAYS. EXPECT DAYTIME CONVECTION ACROSS THE ISLANDS TO DIMINISH DURING THE EARLY EVENING HOURS LEAVING MOSTLY CLEAR TO PARTLY CLOUDY SKIES OVERNIGHT. HOWEVER...SOME EARLY MORNING SHOWERS AND ISOLATED THUNDERSTORMS CAN BE EXPECTED ALONG THE EAST COASTAL SECTIONS OF PUERTO RICO...AS WELL AS OVER PARTS OF THE LOCAL ISLANDS AND THE REGIONAL WATERS. BY TUESDAY AFTERNOON TUTT IS TO PULL FURTHER NORTH AND WEST OF AREA WITH UPPER RIDGE OF HIGH PRESSURE TO THEN BECOME THE DOMINANT FEATURE. THEREFORE...EXPECT AFTERNOON CONVECTION TO BE MAINLY LOCALLY AND DIURNALLY INDUCED...WHICH WILL BE FOCUSED MAINLY ACROSS THE NORTH CENTRAL AND WEST SECTIONS OF PUERTO RICO...AS WELL AS OVER ISOLATED SPOTS IN THE VIRGIN ISLANDS. WIDESPREAD RAINFALL IS HOWEVER NOT EXPECTED. BY LATE WEDNESDAY THROUGH THURSDAY...ANOTHER SURGE OF MOISTURE IS EXPECTED AS AN EASTERLY PERTURBATION WILL MOVE ACROSS THE REGION...THIS WILL INCREASE THE CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS MAINLY DURING THE DAYTIME...SOME OF WHICH WILL AGAIN PRODUCE LOCALLY HEAVY RAINFALL AT TIMES. BY LATE FRIDAY AND INTO THE INTO THE UPCOMING WEEKEND...A TROPICAL WAVE STILL WAY OUT IN THE ATLANTIC AND EAST OF THE ISLANDS...IS FORECAST TO APPROACH THE LESSER ANTILLES LATE FRIDAY...THEN MOVE ACROSS THE EASTERN CARIBBEAN SATURDAY THROUGH SUNDAY. THIS WAVE STILL HAS A LONG WAY TO GO BEFORE REACHING THE ISLANDS...BUT SO FAR ALL MODELS AGREE THAT IS WILL BRING A SIGNIFICANT INCREASE IN TROPICAL ITCZ MOISTURE AND THUS INCREASE THE POTENTIAL FOR ACTIVE WEATHER OVER THE WEEKEND AND INTO THE FOLLOWING WEEK. STAY TUNED FOR MORE INFO AS THIS UNFOLDS WITH TIME. AVIATION...SHOWERS WILL CONTINUE TO DEVELOP THROUGH 20/22Z OVER THE INTERIOR OF PUERTO RICO. THIS WILL OBSCURE SOME HIGHER MOUNTAINS BUT TAF SITES IN PR AND ELSEWHERE IN THE AREA ARE EXPECTED TO REMAIN VFR...EXCEPT FOR TEMPO MVFR/IFR IN TJBQ. LLVL WINDS ARE GENERALLY EASTERLY AT 15 KNOTS BELOW 10 THOUSAND FEET. && .PRELIMINARY POINT TEMPS/POPS... SJU 76 88 77 90 / 60 30 30 30 STT 77 87 78 90 / 60 50 40 40 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. && 11/12
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN JUAN PR 448 AM AST MON SEP 19 2011 AMZ710>745-PRZ001>013-201030- 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- 448 AM AST MON SEP 19 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT ATLANTIC COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT AN UPPER LEVEL LOW LOCATED JUST NORTH OF PUERTO RICO EARLY THIS MORNING...WILL CONTINUE TO WEAKEN AND LIFT NORTH THROUGH TONIGHT. HOWEVER...THIS FEATURE WILL COMBINE WITH A MOIST AND UNSTABLE AIR MASS AND LOCAL EFFECTS TODAY...TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE LOCAL ISLANDS. PERIODS OF HEAVY RAIN...LIGHTNING...BRIEF STRONG AND GUSTY WINDS AND AT LEAST SOME MINOR LOW LYING FLOODING ARE EXPECTED IN A FEW LOCATIONS. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY LINGERING MOISTURE AND INSTABILITY WILL COMBINE WITH LOCAL EFFECTS THROUGH AT LEAST MIDWEEK...TO PRODUCE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER PARTS OF THE LOCAL ISLANDS EACH DAY. ADDITIONAL PERIODS OF HEAVY RAIN...LIGHTNING...BRIEF GUSTY WINDS AND AT LEAST SOME MINOR LOW LYING FLOODING ARE POSSIBLE. .SPOTTER INFORMATION STATEMENT... REPORTS OF HEAVY RAIN...FLOODING OR OTHER HAZARDOUS WEATHER WOULD BE GREATLY APPRECIATED. AMZ715-725-VIZ001-002-201030- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 448 AM AST MON SEP 19 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT AN UPPER LEVEL LOW LOCATED JUST NORTH OF PUERTO RICO EARLY THIS MORNING...WILL CONTINUE TO WEAKEN AND LIFT NORTH THROUGH TONIGHT. HOWEVER...THIS FEATURE WILL COMBINE WITH A MOIST AND UNSTABLE AIR MASS AND LOCAL EFFECTS TODAY...TO PRODUCE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE LOCAL ISLANDS. PERIODS OF HEAVY RAIN...LIGHTNING...BRIEF STRONG AND GUSTY WINDS AND AT LEAST SOME MINOR LOW LYING FLOODING ARE EXPECTED IN A FEW LOCATIONS. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY LINGERING MOISTURE AND INSTABILITY WILL COMBINE WITH LOCAL EFFECTS THROUGH AT LEAST MIDWEEK...TO PRODUCE SCATTERED SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM OR TWO OVER PARTS OF THE LOCAL ISLANDS EACH DAY. ADDITIONAL PERIODS OF HEAVY RAIN... LIGHTNING...BRIEF GUSTY WINDS AND AT LEAST SOME MINOR LOW LYING FLOODING ARE POSSIBLE. .SPOTTER INFORMATION STATEMENT... REPORTS OF HEAVY RAIN...FLOODING OR OTHER HAZARDOUS WEATHER WOULD BE GREATLY APPRECIATED.
The San Juan radar (TJUA), 68 km away, was scanning. The volume nearest the first event began at 01:18 UTC.
1 flash flood. Local standard time, as filed.
Rio Grande de Arecibo was reported out of its banks near the Guanico sector and near University of Puerto Rico Campus in Utuado.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2011Every state in 2011This day in weather historyWarnings in Puerto Rico, September 2011
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: 350189.