Name: Flash Flooding in Puerto Rico, May 10, 2001
Start: 2001-05-10T15:00
End: 2001-05-10T18:00
Location: Puerto Rico

The toll

Deaths: 0
Injuries: 0
Property damage: $50,000
Crop damage: None recorded
Events: 2

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.

Daytime heating in combination with local sea breeze influences caused numerous showers and thunderstorms across the west and northwest sections of Puerto Rico. Previous rains saturated the ground and many areas experienced flash flooding. In Mayaguez, two cars were swept away by water when a stream went out of its banks. They were later rescued unharmed. Other stream went out of their banks flooding nearby areas. In addition, two bridges suffered damages by the waters and many streets were covered by water or mudslides. Other rivers in San German, Hormigueros and Aguada went out of their banks.

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 May 10, 2:36 PM AST, 24 minutes earlier.

Area forecast discussion, May 10, 2:36 PM AST, 24 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
200 PM AST THU MAY 10 2001

LOW NORTH OF PUERTO RICO NEAR 35N WILL CONTINUE TO PULL TO THE NORTH
WILL THE WEEKEND. THIS HAS ALLOWED THE RIDGE TO MOVE NORTHWARD AND A
MORE EASTERLY WINDS. THIS EASTERLY FLOW WILL ONLY BE TEMPORARY. AS
THE LOW PULLS NORTHWARD HIGH PRESSURE ACROSS THE EASTERN U.S. WILL
MOVE EASTWARD WITH A WEAKNESS BETWEEN THE HIGH LEAVING THE EAST
COAST AND A HIGH TO OUR NORTHEAST.  THIS WILL RESULT IN TROUGH
EXTENDING FROM AROUND 30N60W SOUTHWEST TO THE YUCATAN. GUIDANCE
CONTINUES TO DEVELOP A LOW NEAR CUBA BY SATURDAY AND 18Z AS THE HIGH
WEAKENS AND ANOTHER LOW PRESSURE CENTER MOVES OF THE EAST COASTS OF
THE U.S.

THIS WILL AGAIN RESULT IN A SOUTHEAST TO SOUTH WIND FLOW ACROSS THE
REGION. WHAT WILL ALSO ADD TO THE FORECAST PROBLEM IS A LOW LEVEL
TROUGH ALONG 58W WHICH APPEARS TO BE A BREAK-AWAY REFLECTION OF A
UPPER LOW TO THE EAST. THIS LOW LEVEL FEATURE MAY BE MASKED IN THE
PREDOMINANT FLOW BY THE TIME ITS GETS HERE BUT LOCAL REGION SHOULD
SEE A SIGNIFICANT DRYING FROM FRIDAY AFTERNOON  THROUGH AROUND
MIDNIGHT...BUT A DISTINCT INCREASE AND SHIFT TO THE WIND FLOW AFTER
MIDNIGHT AS THE LOW LEVEL TROUGH PASSES MAINLY SOUTH THE AREA ON
SATURDAY. BELIEVE THAT OTHER THAN DIURNAL PATTERNS ON FRIDAY...
SATURDAY MORNING WILL BRING THE MOST RAINFALL FOR THE U.S. VIRGIN
ISLANDS SATURDAY AFTERNOON AND ACROSS PUERTO RICO FROM SATURDAY
MORNING THROUGH LATE SATURDAY NIGHT. WITH THIS BEING SAID EXCEPT FOR
A SHORT PERIODS OF SUN WE WILL SHOULD NOT SEE MOSTLY CLOUD FREE
SKIES TILL LATE SATURDAY NIGHT OR SUNDAY.

WILL NOT DROP HSA AT THIS TIME. PREVIOUS FORECASTER LOOKS TO BE ON
MARK WITH A SHIP JUST NORTH OF AREA REPORTING A NORTH 10 SECOND
SWELL OF 11 OR 12 FT.

EQUIPMENT: NO PROBLEMS AT THIS TIME.

.PRELIMINARY NUMBERS...
SJU EE 075/085 077/087 076 07333
STT EE 075/086 078/086 077 07344=

.SJU...
.PR...SCA AMZ750-770-773-750. HSA PRZ001-002-005-008-010-012-013-
      AMZ750-770-773. FFA W PR FT 22Z
.VI...SCA AMZ750-770-773. HSA VIZ001-002-AMZ750-773.

WRITTEN TEXT FORECASTS (IN ENGLISH OR SPANISH)...SATELLITE IMAGERY
...DOPPLER RADAR DATA...AND A VIRTUAL LIBRARY OF WEATHER INFORMATION
CAN BE FOUND AT THE NWS SAN JUAN WEB SITES AT:

HTTP://WWW.SRH.NOAA.GOV/SJU (ALL LOWER CASE).

    OR

HTTP://WWW.UPR.CLU.EDU/NWS (ALL LOWER CASE).

Event by event

2 flash flood. Local standard time, as filed.

Flash Flood, Mayaguez and Vicinity

When: May 10, 3:00 PM AST to 6:00 PM AST
Where: Mayaguez and Vicinity County, Countywide
Property damage: $40,000
Reported by: EMERGENCY MANAGER

Flash Flood, Northwest

When: May 10, 3:00 PM AST to 6:00 PM AST
Where: Northwest County, Countywide
Property damage: $10,000
Reported by: EMERGENCY MANAGER

What these are

Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.

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

The same day elsewhere

More

Every storm in Puerto Rico in 2001 Every state in 2001 This day in weather history Warnings in Puerto Rico, May 2001

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: 5250249, 5250250.