Abundant low level moisture combined with an upper level disturbance north of the island to produce numerous showers over the east half of Puerto Rico mainly during the morning.
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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.
Abundant low level moisture combined with an upper level disturbance north of the island to produce numerous showers over the east half of Puerto Rico mainly during the morning.
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 May 18, 4:35 AM AST, 4 hours 5 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 435 AM AST TUE MAY 18 2010 .SYNOPSIS...UPPER LEVEL DISTURBANCES WILL CONTINUE TO MOVE MAINLY NORTH OF THE LOCAL ISLANDS THROUGH AT LEAST WEDNESDAY. THESE FEATURES WILL COMBINE WITH ABUNDANT LOW LEVEL MOISTURE TO INDUCE THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS THE FA DURING THE NEXT FEW DAYS. && .DISCUSSION...A MOIST AND UNSTABLE AIR MASS WILL CONTINUE ACROSS THE NORTHEAST CARIBBEAN UNTIL AT LEAST WEDNESDAY. IN FACT...THE DOPPLER RADAR DETECTED SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE U.S. VIRGIN ISLANDS...CULEBRA...VIEQUES AND ACROSS THE EASTERN AND SOUTHEASTERN SECTIONS OF PUERTO RICO OVERNIGHT AND EARLY THIS MORNING. THE GFS FORECAST SOUNDING INDICATED PWAT VALUES ABOVE 2.0 INCHES FOR THE NEXT FEW DAYS. LATEST MIMIC-TPW IMAGES ALSO SUGGEST THAT ABUNDANT TROPICAL MOISTURE WILL CONTINUE TO ADVECT ACROSS THE REGION FROM THE EAST AND SOUTHEAST TODAY AND TONIGHT. THUS...EXPECT ADDITIONAL PERIODS OF HEAVY RAINFALL AND URBAN AND SMALL STREAM FLOODING...WITH THE POTENTIAL FOR LOCALIZED FLASH AND RIVER FLOODING TODAY AND TONIGHT. A SHORT-LIVED DRY TREND IS EXPECTED BY LATE WEDNESDAY THROUGH AT LEAST EARLY THURSDAY...WITH MOISTURE INCREASING AGAIN LATE THURSDAY AND FRIDAY. A WEAK HIGH PRESSURE SYSTEM AT THE MIDDLE LEVELS OF THE ATMOSPHERE WILL AID TO INHIBIT THE DEVELOPMENT OF STORMS WITH HIGH ECHO TOPS TODAY. LOOKING WELL AHEAD...THE GFS DEVELOPS TWO AREAS OF LOW PRESSURE... ONE JUST TO THE NORTH OF PUERTO RICO AND THE OTHER OFF THE COAST OF CENTRAL AMERICA BY LATE FRIDAY. THE FIRST ONE WILL MOVE SLOWLY TO THE NORTH NORTHEAST...MAINTAINING A HUMID SOUTHEAST LOW LEVEL WIND FLOW ACROSS THE FA UNTIL THE UPCOMING WEEKEND. THE SECOND ONES WILL MOVE TO THE NORTHEAST FROM THE WESTERN CARIBBEAN ACROSS CUBA AND HISPANIOLA AS A STRONG LOW PRESSURE SYSTEM BY THE END OF THE MONTH. STAY TUNED. && .AVIATION...SHOWERS AND THUNDERSTORM WILL CONTINUE ACROSS TISX..TIST AND TJSJ AT LEAST UNTIL 18/14Z. INTERMITTENT PERIODS OF MVFR TO IFR CONDITIONS AND MOUNTAIN OBSCURATION WILL DEVELOP AFTER 18/17Z IN SHRA AND TSRA...OVER TJMZ...TJBQ. AFTER 19/01...MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS MOST OF THE TAF SITES. LLVL WIND FLOW WILL REMAIN ESE AT 10-20KTS...WITH SOME HIGHER GUSTS ESPECIALLY NEAR SHOWERS AND THUNDERSTORMS. && .MARINE...GENERALLY EXPECT WINDS OF 19 KNOTS OR LESS AND SEAS OF 6 FEET OR LESS ACROSS THE REGIONAL WATERS THROUGH AT LEAST WEDNESDAY. THERE IS A PRECAUTIONARY STATEMENT FOR MOST OF THE LOCAL COASTAL WATERS TODAY. && .PRELIMINARY POINT TEMPS/POPS... SJU 89 77 91 77 / 50 40 40 30 STT 87 78 88 80 / 50 40 40 30 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. && 71/72
HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 700 AM AST TUE MAY 18 2010 AMZ710>745-PRZ001>013-191100- 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- 700 AM AST TUE MAY 18 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER THE WEST AND INTERIOR SECTIONS OF PUERTO RICO THIS AFTERNOON. SOME RAINS COULD BE LOCALLY HEAVY AND MAY INDUCE URBAN AND SMALL STREAM FLOODING. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY AVAILABLE MOISTURE WILL COMBINE WITH DAYTIME HEATING AND OROGRPAHIC EFFECTS TO PRODUCE SCATTERED TO NUMEROUS SHOWERS WITH ISOLATED THUNDERSTORMS EACH AFTERNOON ACROSS THE WESTERN INTERIOR AND WEST SECTION OF PUERTO RICO. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE REQUIRED TODAY. AMZ715-725-VIZ001-002-191100- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 700 AM AST TUE MAY 18 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT SHOWER AND THUNDERSTORM ACTIVITY IS EXPECTED ACROSS THE LOCAL ISLANDS FROM TIME TO TIME. SOME RAINS COULD BE LOCALLY HEAVY AND MAY INDUCE URBAN AND SMALL STREAM FLOODING. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED AT THIS TIME.
The San Juan radar (TJUA), 32 km away, was scanning. The volume nearest the first event began at 12:40 UTC.
1 flash flood, 1 debris flow. Local standard time, as filed.
River Rio Blanco overflowed its banks, flooding road 31 near the Highway 22 exit.
A mudslide was reported across road 181, Km 12.0 in the municipality of San Lorenzo.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Puerto Rico in 2010Every state in 2010This day in weather historyWarnings in Puerto Rico, May 2010
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: 235320, 235321.