Ample low level moisture combined with favorable upper level conditions associated with an upper level low, produced numerous showers and thunderstorms during this time period every afternoon, affecting the western interior, west and northwest sections 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.
Ample low level moisture combined with favorable upper level conditions associated with an upper level low, produced numerous showers and thunderstorms during this time period every afternoon, affecting the western interior, west 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 20, 2:56 PM AST, 6 hours 28 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 256 PM AST SUN SEP 20 2009 .SYNOPSIS...AN UPPER LEVEL LOW COMBINED WITH DEEP LOW LEVEL MOISTURE...WILL INCREASE THE SHOWER AND THUNDERSTORM COVERAGE ACROSS THE LOCAL REGION. && .DISCUSSION...SHOWERS AND THUNDERSTORMS DEVELOPED EARLIER THAN NORMAL ACROSS THE EASTERN INTERIOR AND ACROSS THE SAN JUAN METROPOLITAN AREA. ANOTHER AREA OF HEAVY SHOWERS AND THUNDERSTORMS DEVELOPED OVER THE WESTERN INTERIOR SECTIONS. MOST OF THESE SHOWERS AND THUNDERSTORMS WILL DISSIPATED OR MOVE OVER THE LOCAL ATLANTIC WATER AND LINGER THROUGH LATE EVENING. ALTHOUGH THE GFS MODEL SUGGEST A SLIGHT DECREASE ON MOISTURE A SIMILAR UPPER LEVEL CONDITIONS WILL PREVAIL OVER THE LOCAL AREA THROUGH MONDAY. THEREFORE EXPECT MORE AFTERNOON SHOWERS AND THUNDERSTORMS TO DEVELOP OVER THE INTERIOR AND NORTHERN SECTIONS OF PUERTO RICO. THE NAM MODEL SUGGEST THE DEVELOPMENT OF A LOW LEVEL LOW OVER THE ATLANTIC WATER JUST NORTH OF PUERTO RICO. THIS WEATHER FEATURE IS ASSOCIATED TO A SURFACE REFLECTION OF THE UPPER LEVEL LOW. THEREFORE EXPECT MORE ACTIVE WEATHER TO OCCUR ON TUESDAY AND WEDNESDAY. && .AVIATION...MVFR OR EVEN IFR CONDITIONS ARE EXPECTED TO CONTINUE ACROSS TJMZ...TJBQ AND TJSJ UNTIL 20/2200Z. BRIEF PERIODS OF MVFR CONDITIONS ARE ALSO EXPECTED ACROSS TIST UNTIL 20/2200Z. EXPECT PREVAILING VFR CONDITIONS ACROSS THE LOCAL ISLANDS AND AT MOST LOCAL TAF SITES AFTER 20/2200Z...BUT PASSING SHRA THIS EVENING WILL RESULT IN A POSSIBLE BRIEF MVFR CEILING. ON MONDAY ANOTHER DAY OF ACTIVE CONVECTION WITH MVFR/IFR LIKELY OVER TJMZ AND TJBQ WITH TSRA 18-21Z. VCTS ALSO LIKELY TJSJ...TIST AND TISX SAME TIMES. && .MARINE...MODELS ARE SUGGESTING EVEN SMOOTHER CONDITIONS FOR THE INCOMING WEEK. && .PRELIMINARY POINT TEMPS/POPS... SJU 77 88 77 87 / 30 40 40 60 STT 79 88 78 87 / 30 30 40 50 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. && 72/10
HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 515 AM AST SUN SEP 20 2009 AMZ710>745-PRZ001>013-211000- 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- 515 AM AST SUN SEP 20 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT SCATTERED TO NUMEROUS SHOWERS AND ISOLATED TO SCATTERED THUNDERSTORMS WILL OCCUR AGAIN TODAY...ESPECIALLY OVER THE CENTRAL AND WESTERN INTERIOR...WEST...NORTHWEST AND NORTH CENTRAL SECTIONS OF PUERTO RICO THIS AFTERNOON. ALTHOUGH NO WIDESPREAD FLOODING IS EXPECTED...A FEW LOCATIONS WILL RECEIVE ENOUGH RAINFALL TO RESULT IN URBAN AND SMALL STREAM FLOODING...WITH THE POTENTIAL FOR LOCALIZED FLASH OR RIVER FLOODING...PARTICULARLY ALONG THE RIO CULEBRINAS AND RIO GRANDE DE ARECIBO AND THEIR TRIBUTARIES. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE REQUIRED. AMZ715-725-VIZ001-002-211000- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 515 AM AST SUN SEP 20 2009 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...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED.
The national radar mosaic for the moment the first event began.
2 debris flow, 1 flood. Local standard time, as filed.
Road 418, Coloso sector was flooded by Culebrinas River.
Road 495 sector Humatas, tree downed and blocked the roadway. A mudslide was reported also at Road 402 in the municipality of Anasco.
Landslide was reported at road 435, Km 3.6 in the municipality of San Sebastian. Power lines downed due to downed tree at road 455.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2009Every state in 2009This day in weather historyWarnings in Puerto Rico, September 2009
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: 190184, 190185, 190186.