Debris Flows and Flooding in Puerto Rico, March 4 to 5, 2009

Name: Debris Flows and Flooding in Puerto Rico, March 4 to 5, 2009
Start: 2009-03-04T14:57
End: 2009-03-05T20:50
Location: Puerto Rico

March 4 to 5, 2009 · NWS SJU · 8 events in 7 counties and zones

A slow moving frontal boundary extending from the Central Caribbean northeastward across the Mona Passage combined with favorable mid to upper level atmospheric conditions to produce heavy rain and thunderstorms across the local islands.

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: 8

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 Mar 4, 11:40 AM AST, 3 hours 17 minutes earlier.

Area forecast discussion, Mar 4, 11:40 AM AST, 3 hours 17 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1140 AM AST WED MAR 4 2009

.UPDATE...MORNING SOUNDING REVEALED A STRONG CAP THAT WAS NOT WELL
FORECAST BY THE MODELS YDAY AND NOT INITIALIZED WELL BY THE MODELS
TODAY EITHER. SOUNDING AND VWP SHOW WIND FLOW IS ALMOST NON
EXISTENT FROM THE SFC TO 10KFT. IT DOES APPEAR FROM RECENT RADAR
IMAGERY WHICH INDICATES SHOWERS ALREADY AFFECTING THE NORTHEAST
THAT THE CAP MAY BE WEAKENING SOMEWHAT AND THAT FURTHER HEATING
MAY BE ABLE TO BREAK THROUGH THE CAP LATER THIS AFTERNOON ESPECIALLY
IF WE REACH UPPER 80S LIKE WE DID YESTERDAY (88F AT JSJ YDAY) EVEN
WITH ALL THE CLOUD CVR. GIVEN THE UNCERTAINTY IN THE SHORT TERM
AND MY LVL OF CONFIDENCE NOT ALL THAT HIGH AM HESITANT TO MAKE
ANY CHANGES ATTM. ONE THING THAT AM CONFIDENT ABOUT IS THAT WITH
THE WIND FLOW SO WEAK AND ERRATIC EXPECT SHRAS TO BE RANDOM WITH
ERRATIC MOTION WITHOUT ANY AREAS BEING FAVORED OTHER THAN OTHERS.

&&

.AVIATION...MVFR POSSIBLE WITH ANY HVY SHRAS.

&&

.PREV DISCUSSION... /ISSUED 554 AM AST WED MAR 4 2009/

SYNOPSIS...A SLOW MOVING FRONTAL BOUNDARY EXTENDING FROM THE
CENTRAL CARIBBEAN NORTHEASTWARD ACROSS THE MONA PASSAGE AND
CONTINUING NORTHEASTWARD ACROSS THE NORTHWESTERN ATLANTIC THIS
MORNING...WILL MOVE TO THE SOUTHEAST ACROSS THE REGION LATE TODAY
AND TONIGHT. STRONG HIGH PRESSURE SYSTEM WILL BUILD ACROSS THE
REGION BEHIND THE FRONTAL BOUNDARY THURSDAY AND FRIDAY...
INCREASING THE LOCAL WINDS AND BRINGING A RETURN TO A MORE DRY
WEATHER PATTERN.

DISCUSSION...LATEST SATELLITE IMAGES EARLY THIS MORNING INDICATED
ABUNDANT MID TO HIGH LEVEL CLOUDINESS STREAMING FROM THE SOUTHWEST
TO THE NORTHEAST ACROSS THE FA. AT THE SAME TIME...LATEST RADAR
OBSERVATIONS DEPICTED SCATTERED TO NUMEROUS SHOWERS ACTIVITY
ACROSS THE SURROUNDING COASTAL WATERS AND ACROSS THE EASTERN AND
SOUTHEASTERN SECTIONS OF PUERTO RICO WITH MAXIMUM ECHO TOPS OF
AROUND 20K FEET.

THE MOISTURE ASSOCIATED WITH CONVERGENCE ALONG THE LOW LEVEL FRONTAL
ZONE...WILL BRING UNSTABLE WEATHER CONDITIONS TO THE REGION TODAY AND
THURSDAY...AND BOTH THE GFS AND THE NAM MODELS SUGGEST THAT SOME
MOISTURE WILL LINGER ACROSS THE REGION UNTIL EARLY FRIDAY. THERE
WILL BE SUFFICIENT MOISTURE AVAILABILITY TO PRODUCE GOOD SHOWERS
ACTIVITY DURING THOSE DAYS. HOWEVER...DUE TO THE HEAVY MID TO
UPPER LEVEL CLOUDINESS ACROSS THE REGION AND ONLY MARGINAL UPPER
LEVEL DYNAMIC...NO SIGNIFICANT VERTICAL DEVELOPMENT ARE EXPECTED
AT THIS TIME. AT THIS MOMENT NO WIDESPREAD PCPN IS EXPECTED
ACROSS THE REGION FOR TODAY AND THE WEATHER EXPECTED FOR THE NEXT
FEW DAYS COULD BE HANDLE WITH SOME SPECIAL PRODUCTS LIKE NOWCAST
AND FLS AND FOR THOSE REASONS THE FLASH FLOOD WATCH WAS CANCELLED
EARLY THIS MORNING.

BY FRIDAY AND SATURDAY...THE EXPECTED MODERATE TO STRONG
PREVAILING NORTHERLIES WILL TRANSPORT PATCHES OF LOW LEVEL
MOISTURE AND BRING PERIODS OF CLOUDINESS AND SHOWERS TO THE LOCAL
ISLANDS ESPECIALLY DURING THE OVERNIGHT AND EARLY MORNING
HOURS...FOLLOWED BY A SHIFT IN THE SHOWER ACTIVITY DURING THE
AFTERNOONS...ALONG THE INTERIOR AND SOUTHERN SLOPES OF PUERTO
RICO. STRONG HIGH PRESSURE WILL QUICKLY BUILD ACROSS LOCAL AREA
BEHIND THE FRONTAL BOUNDARY. THIS WILL RESULT IN A GRADUAL
CLEARING AND A DECREASE IN CLOUD COVER AND MOSTLY DRY CONDITIONS
FOR THE UPCOMING WEEKEND. LOOKING WELL AHEAD...THE GFS MODEL
GUIDANCE SUGGESTS THAT A SURFACE TO MID LEVEL LOW WILL DEVELOP
NORTHEAST OF PUERTO RICO BY THE UPCOMING WEEKEND. THIS FEATURE
WILL MOVE SLOWLY TO THE SOUTH SOUTHWEST APPROACHING TO THE REGION
BY THE FIRST PART OF THE UPCOMING WORK WEEK...INCREASING THE
CLOUDINESS AND SHOWERS ACROSS THE FA.

AVIATION...MOSTLY VFR CONDITIONS ARE EXPECTED ACROSS TNCM...
TKPK...TJMZ AND TJBQ DURING THE REST OF THE MORNING HOURS. BRIEF
PERIODS OF MVFR CONDITIONS ARE EXPECTED ACROSS TISX...TIST...TJSJ
AND TJPS UNTIL AT LEAST 04/1500Z AS MID TO HIGH LEVEL CLOUDS AND A
FEW EMBEDDED SHOWERS STREAM ACROSS THESE TAF SITES. EXPECT WETTER
CONDITIONS THIS AFTERNOON AND TONIGHT...WITH INTERMITTENT MVFR
CEILINGS AND VSBYS IN A PASSING SHRA OR TSRA ACROSS ALL THE PR
TAF SITES AFTER 04/1900Z...AND SPREADING ACROSS THE VI LATER IN
THE NIGHT.

MARINE...SEAS UP TO 6 FEET AND WINDS UP TO 17 KNOTS WILL
CONTINUE ACROSS THE LOCAL COASTAL WATERS UNTIL AT LEAST THIS
AFTERNOON. A HIGH PRESSURE SYSTEM WILL MOVE ACROSS THE EASTERN
UNITED STATES SEABOARD BY THURSDAY. THIS HIGH PRESSURE WILL PUSH THE
REMNANTS OF A FRONTAL BOUNDARY ACROSS THE LOCAL SOUTHERN WATERS.
THIS HIGH PRESSURE WILL ALSO GENERATE SEAS OF AT LEAST 7 FEET
BEGINNING TONIGHT AND INCREASING THROUGH SATURDAY. A SIGNIFICANT
INCREASE IN NORTHEAST WINDS ARE ALSO EXPECTED ACROSS THE REGIONAL
COASTAL WATERS...AFTER THE PASSAGE OF THE FRONTAL BOUNDARY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  84  73  82  73 /  70  60  70  70
STT  81  72  80  72 /  40  40  40  50

&&

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

64

Hazardous weather outlook, Mar 4, 6:19 AM AST, 8 hours 38 minutes before

HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN
ISLANDS
NATIONAL WEATHER SERVICE SAN JUAN PR
619 AM AST WED MAR 4 2009

AMZ710>745-PRZ001>013-051030-
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-
619 AM AST WED MAR 4 2009

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

.DAY ONE...TODAY AND TONIGHT
AN APPROACHING COLD FRONT AND A MOIST AIR MASS AHEAD OF IT WILL
TRIGGER INSTANCES OF URBAN AND SMALL STREAM FLOODING ACROSS
EASTERN AND CENTRAL PUERTO RICO TODAY AND TONIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY
URBAN AND SMALL STREAM FLOODING ARE POSSIBLE ACROSS AREAS OF
EASTERN AND CENTRAL PUERTO RICO THURSDAY AND THURSDAY NIGHT MAINLY
ACROSS EASTERN AND CENTRAL PUERTO RICO NORTH OF THE CORDILLERA
CENTRAL. OVER THE ATLANTIC WATERS AND PASSAGES TO THE CARIBBEAN...
SEAS WILL RISE ABOVE 10 FEET EARLY FRIDAY MORNING AND CONTINUE
THROUGH TUESDAY. HIGH SURF ALONG THE NORTHWEST THROUGH NORTHEAST
COASTS WILL BE POSSIBLE FRIDAY THROUGH MONDAY.

.SPOTTER INFORMATION STATEMENT...SURF REPORTS ARE SOLICITED
BEGINNING FRIDAY.

AMZ715-725-VIZ001-002-051030-
ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX-
NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS-
619 AM AST WED MAR 4 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.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY
OVER THE ATLANTIC WATERS AND PASSAGES TO THE CARIBBEAN...
SEAS WILL RISE ABOVE 10 FEET EARLY FRIDAY MORNING AND CONTINUE
THROUGH TUESDAY. HIGH SURF ALONG THE NORTHWEST THROUGH NORTHEAST
COASTS OF THE NORTHERN VIRGIN ISLANDS WILL BE POSSIBLE FRIDAY
THROUGH MONDAY.

.SPOTTER INFORMATION STATEMENT...SURF REPORTS ARE SOLICITED
BEGINNING FRIDAY.

The radar

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

Open the radar archive at this moment

Event by event

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

Heavy Rain, Ponce

When: March 4, 2:57 PM AST to 3:57 PM AST
Where: Ponce County, 2.21 mi SE of Ponce
Reported by: Emergency Manager
Coordinates: 18.032, -66.593

Road 14 in front of Saint Lucas Hospital was reported flooded.

Heavy Rain, Ponce

When: March 4, 3:26 PM AST to 4:26 PM AST
Where: Ponce County, 2.99 mi SW of Ponce
Reported by: Emergency Manager
Coordinates: 18.018, -66.651

Heavy rain and urban flooding was reported at the Sabanetas sector in the municipality of Ponce.

Debris Flow, Ponce and Vicinity

When: March 4, 7:20 PM AST
Where: Ponce and Vicinity forecast zone
Reported by: Emergency Manager

A mudslide was reported along road 132, km 18.8 in the municipality of Ponce.

Heavy Rain, Gurabo

When: March 4, 7:50 PM AST
Where: Gurabo County, Gurabo
Reported by: Emergency Manager
Coordinates: 18.270, -65.970

Small stream flooding was reported along road 174 in the municipality of Gurabo.

Heavy Rain, Cidra

When: March 4, 7:50 PM AST to 8:50 PM AST
Where: Cidra County, Cidra
Reported by: Emergency Manager
Coordinates: 18.170, -66.150

Heavy rain and urban flooding was reported in the municipality of Cidra.

Debris Flow, San Juan and Vicinity

When: March 5, 1:15 PM AST
Where: San Juan and Vicinity forecast zone
Reported by: Emergency Manager

A mudslide was reported in Bo. Guaraguao Road 174, in the municipality of Bayamon.

Flood, Vega Alta

When: March 5, 3:30 PM AST to 6:30 PM AST
Where: Vega Alta County, 1.63 mi SW of Vega Alta to 1.64 mi SW of Vega Alta
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 18.401, -66.344

Small stream was reported overflowing its banks along road 620 in the municipality of Vega Alta.

Flood, Barceloneta

When: March 5, 6:50 PM AST to 8:50 PM AST
Where: Barceloneta County, 1.51 mi E of Barceloneta
Cause: Heavy Rain
Reported by: Emergency Manager
Coordinates: 18.427, -66.527

Small stream flooding was reported in Barrio Cachete, along the intersection of roads 666 and 667 in the municipality of Barceloneta.

What these are

Heavy Rain: Rainfall totals unusual for the place and season that did not produce a flood.
Debris Flow: A fast-moving slurry of mud, rock and debris, usually on a slope soaked by heavy rain or stripped by a fire.
Flood: Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.

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, March 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: 160918, 160968, 159093, 159094, 159095, 160974, 159096, 159097.