The combination of an upper level trough with strong daytime heating and orographic effects, produced numerous showers with thunderstorms which led to heavy rainfall across the southwest 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.
The combination of an upper level trough with strong daytime heating and orographic effects, produced numerous showers with thunderstorms which led to heavy rainfall across the southwest 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 Aug 24, 3:12 PM AST, 1 hour 22 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 312 PM AST MON AUG 24 2009 .SYNOPSIS...AT UPPER LEVELS...A STRONG UPPER LEVEL LOW IS NORTH OF SAINT MARTIN BUT IS RETREATING NORTH. A WEAKER LOW WILL FORM AT THE BASE OF THIS LOW TONIGHT AND MOVE WEST SOUTHWEST AT ABOUT 10 KNOTS...AND WILL BE OVER HAITI BY WEDNESDAY MORNING. DURING THE REST OF THE WEEK HIGH PRESSURE WILL FORM TO THE NORTH...BUT ANOTHER WEAK LOW WILL ALSO FORM TO THE NORTHEAST BY THE WEEKEND. AT MID LEVELS...HIGH PRESSURE REMAINS ANCHORED ACROSS THE ATLANTIC MOVING AROUND 35 NORTH 50 WEST UNTIL NEXT WEEK. A TROUGH OVER THE EASTERN CARIBBEAN TODAY WILL MOVE WEST...A WEAK LOW WILL FORM IN THE APEX OF THE TROUGH NORTH OF PUERTO RICO AND MOVE NORTHWEST TUESDAY THROUGH THURSDAY. TROUGHING IN THE MID TROPICAL ATLANTIC TODAY WILL MOVE WEST ACROSS THE LOCAL AREA SATURDAY NIGHT AND SUNDAY...WITH HIGH PRESSURE FOLLOWING. AT LOWER LEVELS...A TROPICAL WAVE WILL MOVE INTO AN AREA ALREADY ACTIVE WITH CONVECTION FROM THE UPPER LEVEL LOW TUESDAY MORNING. MOISTURE WILL STREAM INTO THIS SYSTEM THROUGH WEDNESDAY MORNING KEEPING THE LOCAL AREA WET. MOISTURE RETURNS THURSDAY THROUGH SATURDAY...AND ANOTHER TROPICAL WAVE MOVES INTO THE AREA ON MONDAY NEXT WEEK. && .DISCUSSION...GOOD MOISTURE WITH PRECIPITABLE WATER MOVING UP THROUGH TWO INCHES HAS REACTED TO THE STRONG DAYTIME HEATING AND AN UNSTABLE SOUNDING AND PRODUCED SCATTERED THUNDERSTORMS WITH FREQUENT AND COPIOUS LIGHTNING. SOME RAIN AMOUNTS HAVE EXCEEDED 3 INCHES IN MARICAO ACCORDING TO NWS RADAR AND SEVERAL FLSS HAVE BEEN ISSUED. THE WAVE IS STILL BEING STRONGLY DEVELOPED BY THE NAM AND THE FORECAST THAT IT IS PRODUCING IS STRONGLY DISTORTED BY THIS CYCLOGENESIS TO OUR NORTH. THEREFORE HAVE HAD TO RELY ALMOST COMPLETELY ON THE GFS. BOTH MODELS RIGHTLY BRING AND KEEP PRECIPITATION MAXIMUMS TO OUR NORTH AND THIS IS WHERE THE HEAVIEST RAINFALL WILL BE. EXPECT CONSIDERABLE ACTIVITY INCLUDING THUNDERSTORMS ACROSS PUERTO RICO BEGINNING TONIGHT AND CONTINUING THROUGH EARLY WEDNESDAY AND POSSIBLY BEYOND DEPENDING ON HOW MUCH THE LOW PRESSURE DEVELOPS TO OUR NORTH. ALSO THE TRANSLATION OF THE UPPER LEVEL LOW TO THE WEST SOUTHWEST WILL BE QUITE FAVORABLE FOR THUNDERSTORMS AND GOOD ACTIVITY TUESDAY. SOME FLOODING MAY BE POSSIBLE BUT IT IS STILL TOO EARLY TO TELL WHERE. SURFACE WINDS TUESDAY WERE SOUTHEAST TO SOUTH SOUTH EAST IN THE MODEL RUNS AND THE EXACT DIRECTION WILL BE CRITICAL. THE GFS ALSO NOTES GOOD MOISTURE AT 700 MB BEGINNING THURSDAY AFTER THIS SYSTEM PASSES SO CANNOT RULE OUT A FAIRLY MOIST SERIES OF AFTERNOONS THURSDAY THROUGH SATURDAY. && .AVIATION...OVERALL VFR CONDITIONS ARE EXPECTED ACROSS THE LOCAL TAF SITES FOR THE NEXT 18 TO 24 HOURS. HOWEVER...TJMZ MAY EXPERIENCE BRIEF MVFR CONDITIONS AS SHOWERS AND THUNDERSTORMS MOVE ACROSS THE AIRPORT BETWEEN 19Z TO 21Z. LATER TONIGHT INTO THE OVERNIGHT HOURS...U.S. VIRGIN ISLANDS TAF SITES...AND TNCM AND TKPK MAY ALSO EXPERIENCE BRIEF MVFR AND EVEN IFR CONDITIONS AS SQUALL LINES MOVES ACROSS THE EASTERN CARIBBEAN TOWARD THE EAST...RESULTING IN LOW VISIBILITIES AND CEILINGS AS WELL AS MOUNTAIN OBSCURATIONS. && .MARINE...SEAS ARE EXPECTED TO HOLD AT JUST 7 FEET IN THE NORTHEAST PORTION OF THE FORECAST AREA FOR THE NEXT 30 OR SO HOURS. THEN EXPECT SEAS TO DIE DOWN A BIT. WINDS SHOULD BE MINIMAL ON TUESDAY AND THEN RETURN CLOSER TO SEASONAL NORMALS. && .PRELIMINARY POINT TEMPS/POPS... SJU 77 88 78 88 / 50 70 50 50 STT 79 88 80 89 / 50 50 60 60 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...SCA...AMZ710. VI...SCA...AMZ710. && 17/12
HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 600 AM AST MON AUG 24 2009 AMZ710>745-PRZ001>013-251000- 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- 600 AM AST MON AUG 24 2009 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...TUESDAY THROUGH SUNDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED. AMZ715-725-VIZ001-002-251000- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 600 AM AST MON AUG 24 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...TUESDAY THROUGH SUNDAY 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.
1 heavy rain. Local standard time, as filed.
Low lying areas of road 319 and 114 were reported flooded by River Guanajibo and River Rosario. The San Jose Lavadero street was reported flooded.
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, August 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: 183862.