Deep moisture moisture and light trade wind flow resulted in a strong sea breeze and moisture convergence across the interior, north and west section of Puerto Rico during the afternoon which produced intense and slow moving showers.
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The episode as NWS SJU wrote it up.
Deep moisture moisture and light trade wind flow resulted in a strong sea breeze and moisture convergence across the interior, north and west section of Puerto Rico during the afternoon which produced intense and slow moving showers.
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 23, 10:41 AM AST, 1 hour 40 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JUAN PR 1041 AM AST SUN MAY 23 2010 .UPDATE...MOST OF THE SHOWER ACTIVITY WAS OCCURRING ACROSS THE OFFSHORE ATLANTIC WATERS THIS MORNING. SOME SHOWERS WERE EVIDENT ACROSS THE CARIBBEAN WATERS MOVING NORTH...APPROACHING THE SOUTHWEST COAST OF PUERTO RICO. WINDS ARE SHIFTING MORE TO THE SOUTH THIS MORNING...AND ARE SOUTHWEST ALREADY ACROSS THE U.S. VIRGIN ISLANDS. ACTIVE WEATHER IS EXPECTED FOR THIS AFTERNOON...AS DEEP MOISTURE WILL COMBINE WITH STRONG HEATING...AND LOCAL EFFECTS. SOME CHANGES WERE MADE TO FORECAST GRIDS REFLECTING THIS SCENARIO. && .AVIATION...ANOTHER DIURNAL INCREASE IN CLOUDINESS AND SHOWERS IS EXPECTED ACROSS THE NORTH...INTERIOR AND WESTERN SECTIONS OF PR. THIS SHOWER ACTIVITY WILL PRODUCE PERIODS OF MVFR/IFR CONDITIONS WITH MOUNTAIN OBSCURATIONS IN SHRA/TSRA MAINLY ACROSS TJMZ...TJBQ AND TJSJ DURING THE AFTERNOON HOURS. && .PREV DISCUSSION... /ISSUED 452 AM AST SUN MAY 23 2010/ SYNOPSIS...AT UPPER LEVELS...A TROUGH IS DIGGING SOUTH SOUTHEAST TOWARD THE DOMINICAN REPUBLIC AND A MODERATE JET IS WRAPPING AROUND THE TROUGH ABOUT 200 MILES TO THE NORTHWEST OF PUERTO RICO. THE JET WILL STRENGTHEN AND DRIFT NORTHWARD...BUT THE TROUGH WILL REMAIN THROUGH MOST OF THE WEEK KEEPING PUERTO RICO AND THE U.S. VIRGIN ISLANDS IN WEST SOUTHWEST FLOW. AT MID LEVELS...LOW PRESSURE WILL DEEPEN OVER THE SOUTHEAST BAHAMA ISLANDS AND MOVE NORTHWEST THROUGH MID-WEEK. A WEAK TROUGHINESS WILL REMAIN OVER THE WESTERN ATLANTIC THROUGH THE FOLLOWING WEEKEND. AT LOWER LEVELS...LOW PRESSURE WILL DEVELOP TODAY AND TUESDAY NORTH OF HISPANIOLA AS HIGH PRESSURE SAGS INTO THE TROPICAL ATLANTIC. BY WEDNESDAY LOW PRESSURE WILL MOVE TO A POSITION SOUTHEAST OF NORTH CAROLINA WHILE SOUTHEAST FLOW CONTINUES OVER THE LOCAL AREA. THE LOW WILL MOVE EAST THURSDAY AND FRIDAY PULLING A TROUGH ACROSS THE LOCAL AREA AND A CONSIDERABLE AMOUNT OF MOISTURE. MOISTURE WILL CONTINUE THROUGH MONDAY NIGHT AND GRADUALLY LEAVE THE AREA ON THE TUESDAY AFTER NEXT. DISCUSSION...SHOWERS HAVE INCREASED OVER THE ATLANTIC NORTHWEST OF THE LOCAL AREA AND HAVE CONTINUED IN THE CARIBBEAN SOUTHWEST OF SAINT THOMAS AND SOUTH OF PATILLAS INDICATING THE GRADUAL STRENGTHENING OF A LOW THAT HAS BEEN FORECAST TO DEVELOP NORTH OF THE AREA FOR SEVERAL DAYS NOW. THE MODELS ARE BEGINNING TO SHOW MORE CONSISTENCY IN THEIR SOLUTIONS FROM RUN TO RUN AND SUGGEST THAT SOUTH OR SOUTHEAST FLOW WILL CONTINUE AT LOW LEVELS THROUGH THE UPCOMING WEEK WHILE THE LOW PRESSURE DEEPENS NORTH OF HISPANIOLA. THIS WILL KEEP TEMPERATURES AT OR NEAR 90 DEGREES IN THE NORTHEAST COASTAL SECTIONS MIDDAY. THIS WILL ALSO PULL PLENTY OF MOISTURE ACROSS THE LOCAL AREA AND BRING CLOUDINESS AND SHOWERS EACH AFTERNOON WITH SOME RELIEF FROM THE ABOVE NORMAL MAXIMUMS. IN GENERAL TERMS MOISTURE APPEARS TO INCREASE THROUGH TUESDAY NIGHT AND THEN THERE IS AN INTERMISSION AFTER WEDNESDAY UNTIL A DEEP PLUME FROM THE SOUTHWEST MOVES EAST OVER THE AREA THURSDAY NIGHT AND FRIDAY. AT THIS TIME FRIDAY LOOKS LIKE THE WETTEST DAY OF THE WEEK WITH SATURDAY FOLLOWING WITH A CLOSE SECOND. WET WEATHER CONTINUES THROUGH THE END OF THE MONTH WITH THE NORTHWEST AND NORTHERN INTERIOR RECEIVING THE MOST RAIN...BUT ALL AREAS SHOULD HAVE GOOD RAINS BY THE END OF MAY. AT THIS TIME THERE APPEARS TO BE SOME WEAKNESS IN THE MID LEVEL MOISTURE THAT KEEPS CONVECTION FROM BECOMING MORE INTENSE. WEST WINDS AT UPPER LEVELS ARE ALSO SHEARING OFF THE MOISTURE AS CLOUDS RISE DURING THE AFTERNOONS AND CUTTING OFF THE HEAT SOURCE IN THE SUBSEQUENT SHADOW WHICH IS NEEDED FOR FURTHER DEVELOPMENT. THUS RAINS ARE LIMITED AND FLOODING IS ONLY LOCAL. THE CULEBRINAS ROSE TO WITHIN INCHES OF FLOOD STAGE EARLY SUNDAY MORNING. IT APPEARS THAT MUCH BETTER MOISTURE IS ALMOST UNAVOIDABLE LATE THURSDAY AND ALL DAY FRIDAY AND FLOODING COULD BE WIDESPREAD THEN. IN THE MEANTIME CONDITIONS IN THE NORTHWEST WILL DETERIORATE SLOWLY THROUGH MID-WEEK WITH MUDSLIDES BECOMING MORE FREQUENT IN THE MOUNTAINOUS AREAS. AS THIS WET SCENARIO BECOMES MORE CERTAIN FURTHER STATEMENTS WILL BE ISSUED. AVIATION... VFR CONDITIONS WILL PREVAIL ACROSS MOST OF THE TAF SITES. ANOTHER DIURNAL INCREASE IN CLOUDINESS AND SHOWERS IS EXPECTED ACROSS THE NORTH...INTERIOR AND WESTERN SECTIONS OF PR. THIS SHOWER ACTIVITY WILL PRODUCE TEMPO PERIODS OF MVFR/IFR CONDITIONS IN SHRA/TSRA MAINLY ACROSS TJMZ...TJBQ AND TJSJ DURING AFTERNOON HOURS. MOST OF THE CENTRAL MOUNTAIN TOPS WILL BECOME OBSCURED BY 23/17Z. LATEST TJSJ SOUNDING AT 23/00Z INDICATED LIGHT AND VARIABLE WINDS BETWEEN SFC TO 13 KFT...AND THEN STRONGER WESTERLY WINDS ABOVE 13 KFT. MARINE...DUE TO LIGHT WINDS SEAS HAVE REMAINED BELOW SMALL CRAFT ADVISORY LEVELS AND ARE EXPECTED TO DO SO THROUGH THE END OF THE MONTH. LOCAL CONDITIONS LATER IN THE WEEK MAY DETERIORATE DUE TO ISOLATED TO SCATTERED THUNDERSTORMS AND VERY HEAVY RAIN. && .PRELIMINARY POINT TEMPS/POPS... SJU 92 78 92 78 / 60 50 30 30 STT 88 79 88 79 / 40 40 30 50 && .SJU WATCHES/WARNINGS/ADVISORIES... PR...NONE. VI...NONE. && 71/64
HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS NATIONAL WEATHER SERVICE SAN JUAN PR 612 AM AST SUN MAY 23 2010 AMZ710>745-PRZ001>013-241015- 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- 612 AM AST SUN MAY 23 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT DEEP MOISTURE AND LIGHT TRADE WIND FLOW WILL RESULT ONCE AGAIN IN STRONG SEA BREEZE AND MOISTURE CONVERGENCE ACROSS THE INTERIOR...NORTH AND WESTERN SECTIONS OF PUERTO RICO THIS AFTERNOON. THIS STRONG CONVECTION WILL PRODUCE INTENSE AND SLOW MOVING SHOWERS. THESE SHOWERS WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL...THEREFORE URBAN AND SMALL STREAM FLOODING WILL ALSO BE LIKELY IN ISOLATED AREAS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY AVAILABLE MOISTURE WILL COMBINE WITH DAYTIME HEATING AND LOCAL EFFECTS TO PRODUCE SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS EACH AFTERNOON ACROSS THE WESTERN INTERIOR AND WEST SECTIONS OF PUERTO RICO EACH AFTERNOON. .SPOTTER INFORMATION STATEMENT... AMZ715-725-VIZ001-002-241015- ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX- NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS- 612 AM AST SUN MAY 23 2010 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND THE ADJACENT COASTAL WATERS. .DAY ONE...TODAY AND TONIGHT A MOIST AND UNSTABLE WEATHER PATTERN IS EXPECTED TO CONTINUE ACROSS THE ISLANDS. 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...MONDAY THROUGH SATURDAY MOISTURE WILL CONTINUE ACROSS THE REGION THROUGH EARLY NEXT WEEK...LEADING TO THE DEVELOPMENT OF SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE LOCAL ISLANDS. .SPOTTER INFORMATION STATEMENT...
The San Juan radar (TJUA), 32 km away, was scanning. The volume nearest the first event began at 16:18 UTC.
2 flash flood. Local standard time, as filed.
A flooded home and road was reported in the University Gardens sector of Rio Piedras.
Magnolia Avenue was reported flooded in front of Nieves Refrigeration company .
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: 235323, 235326.