The interaction of a deep layered trough and a low pressure system across the Central Atlantic, generated a prevailing east northeast wind across the northern Caribbean basin. The interaction of these two features generated a very unstable environment across the local region producing scattered to numerous showers and thunderstorms along the northern portions of Puerto Rico.
Every event with a place to put it. Tap one for its entry below.
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 interaction of a deep layered trough and a low pressure system across the Central Atlantic, generated a prevailing east northeast wind across the northern Caribbean basin. The interaction of these two features generated a very unstable environment across the local region producing scattered to numerous showers and thunderstorms along the northern portions 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 Dec 9, 9:59 PM AST, 3 hours 56 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
959 PM AST FRI DEC 9 2011
.SYNOPSIS...TROUGH OF LOW PRES WILL MOVE ACROSS THE AREA TOMORROW
BEFORE IT WEAKENS SOUTH OF HISPANIOLA SUN. UPPER LEVEL RIDGE WILL
BUILD OVER THE AREA EARLY NEXT WEEK.
&&
.DISCUSSION...VERY WET WEATHER ON TAP NEXT 24 HRS FOR NORTHEAST PR
AS TROUGH OF LOW PRES MOVES ACROSS THE AREA. XPC HEAVY CONVECTION
TO MOVE ACROSS THE ATLC COASTAL WATERS AND SKIRT THE NORTHEAST
COAST. 2+ INCHES OF RAIN WHICH COULD COME DOWN IN A VERY SHORT
PERIOD OF TIME APPEAR MORE THAN LIKELY FOR NORTHEAST PR OVR THE
NEXT 24 HRS.
TROF MOVES INTO THE MONA PASSAGE BY SUN WITH SHARP DRYING NOW
EXPECTED FOR SUN. HAVE LOWERED POPS FOR SUN AND MON.
&&
.AVIATION...PREDOMINANT MVFR CONDITIONS WITH FREQ SHOWERS FOR
JSJ/USVI AND LEEWARD ISLANDS TERMINALS. WINDS WILL BE GUSTY WITH
GUSTS UP TO 30 KNOTS AT USVI AND JSJ TERMINALS.
&&
.MARINE...ROUGH SEAS NEXT 24 HRS DUE TO STRONG TRADES THAT WILL
GENERATE SEAS OF 7 TO 9 FEET.
&&
.CLIMATE...DAILY CLIMATE RECORD FOR SAN JUAN FOR DEC 10 IS 2.02
INCHES AND IS LIKELY TO FALL TOMORROW AS HEAVY RAINS OF 2+ INCHES
ARE EXPECTED. TOTAL FOR THE YEAR STANDS AT 84.29 INCHES AND 5.21
INCHES NEEDED TO BREAK THE ALL TIME RECORD OF 2010. THE RAIN
TOMORROW WILL PUT US SOLIDLY INTO THIRD PLACE. WHILE NOT LIKELY TO
RECEIVE FIVE INCHES THERE IS A SMALL CHANCE THAT COULD HAPPEN.
&&
.PRELIMINARY POINT TEMPS/POPS...
SJU 78 84 78 84 / 90 90 70 10
STT 78 81 78 81 / 80 80 70 10
&&
.SJU WATCHES/WARNINGS/ADVISORIES...
PR...SMALL CRAFT ADVISORY UNTIL MIDNIGHT AST SATURDAY NIGHT FOR NORTH
CENTRAL-SAN JUAN AND VICINITY.
SMALL CRAFT ADVISORY UNTIL 6 PM AST SATURDAY FOR MAYAGUEZ AND
VICINITY.
VI...NONE.
&&
11/64HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 604 AM AST FRI DEC 9 2011 AMZ710>745-PRZ001>013-101015- 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- 604 AM AST FRI DEC 9 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO 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 THE APPROACH OF AN UPPER LEVEL TROUGH AS WELL AS AN INCREASE IN MOISTURE WILL BRING MOIST AND UNSTABLE CONDITIONS ACROSS THE AREA THIS WEEKEND. THIS MAY RESULT IN PERIODS OF MODERATE TO HEAVY RAIN WHICH MAY LEAD TO AREAS OF URBAN AND SMALL STREAM FLOODING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED. AMZ715-725-VIZ001-002-101015- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 604 AM AST FRI DEC 9 2011 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 THE APPROACH OF AN UPPER LEVEL TROUGH AS WELL AS AN INCREASE IN MOISTURE WILL BRING MOIST AND UNSTABLE CONDITIONS ACROSS THE AREA THIS WEEKEND. THIS MAY RESULT IN PERIODS OF MODERATE TO HEAVY RAIN WHICH MAY LEAD TO AREAS OF URBAN AND SMALL STREAM FLOODING. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT ANTICIPATED.
The San Juan radar (TJUA), 32 km away, was scanning. The volume nearest the first event began at 05:56 UTC.
7 flash flood. Local standard time, as filed.
Creek flooded a small bridge in Barrio Palmarejo.
A car with the driver inside was swept away by the Cibuco river at road 647 near Barrio Candelaria. Driver was rescued by emergency managers.
Road 53 with intersection with road 3 was reported flooded and impassable.
Highway 2 was reported impassable near the border between the municipalities of Vega Baja and Vega Alta due to Cibuco river out of its banks.
Rio Grande de Manati was reported out of its banks flooding route 666 and 667.
Several houses were affected by Rio de la Plata in Barrio Galateo and Villa Josco.
Flooding was reported in Monte Casino, Quebrada Arenas affecting some residences. Also mudslides were reported in parts of Road 861 near Curva Herradura.
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, December 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: 355474, 355476, 353480, 355478, 354302, 353488, 353489.