Debris Flow and Heavy Rain in Puerto Rico, April 18 to 19, 2009

Name: Debris Flow and Heavy Rain in Puerto Rico, April 18 to 19, 2009
Start: 2009-04-18T21:11
End: 2009-04-19T01:47
Location: Puerto Rico

April 18 to 19, 2009 · NWS SJU · 3 events in 2 counties and zones

Shower activity was further enhanced by a pre-frontal trough that formed across Puerto Rico on the 19th of the month, when the most significant rainfall fell, resulting in localized flooding across various sectors of the island. 40 , which fell in Negro Corozal.

Where it happened

Every event with a place to put it. Tap one for its entry below.

Tornadoes
Tropical storms and surge
Floods
Wind
Hail
Winter weather
Heat and drought
Cold
Fire, smoke and dust
Marine and coastal
Other

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 3

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.

What happened

The episode as NWS SJU wrote it up.

What forecasters said that day

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 Apr 18, 1:54 PM AST, 7 hours 17 minutes earlier.

Area forecast discussion, Apr 18, 1:54 PM AST, 7 hours 17 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
154 PM AST SAT APR 18 2009

.DISCUSSION...COLD FRONT/SHEAR LINE TRAILING FROM SURFACE LOW IN
THE N ATLC DEEP INTO THE SW ATLC CURRENTLY NEAR HISPANIOLA.
ACCOMPANYING U/L LOW DIGGING A FEW HUNDRED MILES OFF THE GEORGIA
COAST WITH AXIS EXTENDING JUST NORTH OF HISPANIOLA ATTM. U/L
FEATURE PROVIDING WEAK U/L SUPPORT WITH 500 VORT MAX ABOUT 300
MILES NORTH OF PUERTO RICO. THIS WILL TRAIL SOME MID TO U/L
MOISTURE AND WEAK VORT ADVECTION OVERHEAD LATE THIS AFTERNOON AND
THIS EVENING. VERY WEAK WINDS IN PRE FRONTAL TROUGH AREA OVER
LOCAL AREA ENSURING VERY SLOW STORM MOTION WITH CELLS OVER WESTERN
PR THIS AFTERNOON. THIS WILL PRESENT THE BIGGER PROBLEM THIS
AFTERNOON IN TERMS OF HEAVY RAIN. RAINFALL IS OCCURRING IN THE SAME
PLACES AS YESTERDAY...AND WILL LIKELY BE IN THE SAME AREAS OF THE
WEST/W INTERIOR EACH AFTERNOON FOR THE NEXT FEW DAYS. WILL KEEP AN
EYE ON RIVERS AS SOILS IN THE AREA BECOME MORE MOIST. HOWEVER...NO
PROBLEMS AS OF YET AS RIVERS HAVE BEEN RUNNING AT LOW OR NORMAL
LEVELS FOR SOME TIME.

U/L WAVE PASSES EAST OF THE ISLAND TONIGHT...LEAVING A DRIER UPPER
AIR MASS IN PLACE FOR THE NEXT SEVERAL DAYS. DONT KNOW THAT THIS
WILL MAKE MUCH OF A DIFFERENCE AS MAIN PLAYER IN AFT CONVECTION
WILL BE HEATING EACH DAY THIS FORECAST CYCLE. ATMOSPHERE NOW
UNSTABLE ENOUGH TO LIKELY SUPPORT AN ISOLATED THUNDERSTORM EACH
AFTERNOON IN THE AREAS OF GREATEST SEA BREEZE FORCING...MOVING
SLIGHTLY EACH DAY IN ACCORDANCE WITH LOW LEVEL WIND FLOW.

AS U/L HIGH PRESSURE BUILDS OVERHEAD STARTING EARLY NEXT
WEEK...WEAK REMNANTS OF FRONTAL/SHEAR LINE WILL PROVIDE SOME
MOISTURE UP TO THE 700MB LEVEL...WITHOUT ANY U/L SUPPORT FOR THE
UPCOMING WEAK. THE THEME WILL BE SCT SHOWERS/ISO THUNDER IN THE
WEST EACH AFTERNOON WITH LITTLE TO NO SHOWER ACTIVITY ALL OTHER AREAS.

&&

.AVIATION...IN GENERAL...VFR CONDITIONS WILL PREVAIL ACROSS THE LOCAL
TAF SITES DURING THE FORECAST PERIOD EXCEPT FOR SOME CONVECTION
ACROSS PARTS OF THE CENTRAL...WEST AND NORTHWEST SECTIONS OF PUERTO
RICO THIS AFTERNOON. THESE SHOWERS AND ISOLATED THUNDERSTORMS WILL
RESULT IN BRIEF PERIODS OF MVFR CONDITIONS BTWN 18-22Z MAINLY IN AND
AROUND TJBQ AND TJMZ. NO OTHER OPERATIONAL IMPACT EXPECTED.

&&

.MARINE...LONG PERIOD SWELLS COMING IN FROM THE NW THIS EVENING AT
AROUND 12 TO 13 SECONDS...BUT ONLY PACKING ABOUT 7 FOOT SEAS IN
THE OFFSHORE ATLC. THIS WILL MARGINALLY INCREASE SEAS NORTH OF
THE AGUADILLA AND ARECIBO AREAS...WELL OFFSHORE...BUT ALL OTHER
AREAS WILL CONTINUE TO ENJOY TRANQUIL SEAS FOR THE NEXT FEW
DAYS...REMAINING UNDER SCA CRITERIA.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  74  85  74  85 /  20  30  30  40
STT  74  83  74  83 /  20  30  30  30

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
&&

15/93

Hazardous weather outlook, Apr 18, 5:45 AM AST, 15 hours 26 minutes before

HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN
ISLANDS
NATIONAL WEATHER SERVICE SAN JUAN PR
545 AM AST SAT APR 18 2009

AMZ710>745-PRZ001>013-190945-
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-
545 AM AST SAT APR 18 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE
ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT

DAYTIME HEATING...LOCAL TERRAIN EFFECTS AND GOOD UPPER LEVEL
DYNAMIC PROVIDED BY AN APPROACHING UPPER TROUGH...WILL INDUCE
THE DEVELOPMENT OF AFTERNOON SHOWERS AND ISOLATED THUNDERSTORMS
ESPECIALLY ACROSS WESTERN AND INTERIOR SECTIONS OF PUERTO RICO.
SOME SHOWERS MAY BE LOCALLY HEAVY AT TIME AND MAY LEAD TO MINOR
URBAN AND SMALL STREAM FLOODING IN ISOLATED SPOTS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED AT THIS TIME.

AMZ715-725-VIZ001-002-190945-
ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX-
NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS-
545 AM AST SAT APR 18 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...SUNDAY THROUGH FRIDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

2 heavy rain, 1 debris flow. Local standard time, as filed.

Debris Flow, Mayaguez and Vicinity

When: April 18, 9:11 PM AST
Where: Mayaguez and Vicinity forecast zone
Reported by: Emergency Manager

A landslide was reported at Barrio Quebrada Grande, Santa Ana sector, road 348 interior in Mayaguez.

Heavy Rain, San Juan

When: April 18, 11:13 PM AST to April 19, 1:00 AM AST
Where: San Juan County, 7.1 mi NNW of San Juan
Reported by: Emergency Manager
Coordinates: 18.466, -66.110

Road flooding was reported in front of the Tax Building in Old San Juan, near the bus terminal.

Heavy Rain, San Juan

When: April 19, 12:47 AM AST to 1:47 AM AST
Where: San Juan County, 5.04 mi NNW of San Juan
Reported by: Emergency Manager
Coordinates: 18.449, -66.076

Road flooding was reported in Santurce, near parada 18 Texaco gas station.

What these are

Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Puerto Rico in 2009 Every state in 2009 This day in weather history Warnings in Puerto Rico, April 2009

Sources

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: 168925, 168926, 168927.