Alert archive / California / Flash Flood Warnings in 2012

Flash Flood Warning 4, NWS Los Angeles, CA

September 10, 2012Los Angeles County, California

NWS Los Angeles, CA issued this flash flood warning at Sep 10, 2012, 3:40 PM PDT for Los Angeles County, California. It was in force for 3 hr. 1 report came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued
Sep 10, 2012, 3:40 PM PDT (22:40 UTC)
Expired
Sep 10, 2012, 6:30 PM PDT
In force
3 hr
Issued by
NWS Los Angeles, CA
Area
Storm-based polygon
Flood severity
None

County Los Angeles County, CA

The radar

The Santa Ana Mts radar (KSOX), 65 km from the middle of the area, began a volume at 22:43 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

TimeReportWhereRemark
Sep 10, 4:35 PM PDTFLASH FLOOD6 Ese Lake Los Angeles, CAFLASH FLOODING AT INTERSECTION OF 220TH STREET EAST AND PALMDALE BLVD.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Edwards AFB, CA (KEDW), launched 12:00Z, 10.7 hours before the alert went out and 56 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Edwards AFB, CA at 12:00Z on 2012-09-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Edwards AFB, CA at 12:00Z on 2012-09-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 61 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
2666 m above ground
0-6 km bulk shear
13 kt
0-1 km storm-relative helicity
61 m²/s²
0-3 km storm-relative helicity
75 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

227 
WGUS56 KLOX 102240
FFWLOX
CAC037-110130-
/O.NEW.KLOX.FF.W.0004.120910T2240Z-120911T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE OXNARD CA
340 PM PDT MON SEP 10 2012

THE NATIONAL WEATHER SERVICE IN OXNARD HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  EAST CENTRAL LOS ANGELES COUNTY IN SOUTHWEST CALIFORNIA...

* UNTIL 630 PM PDT

* AT 330 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A 
  STORM CAPABLE OF PRODUCING FLASH FLOODING OVER THE WARNED AREA     
  NEAR LAKE LOS ANGELES AND PEARBLOSSOM IN THE SOUTHEAST CORNER OF   
  THE ANTELOPE VALLEY AND ADJACENT FOOTHILLS. THIS STORM IS MOVING   
  AT LESS THAN 5 MPH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO
AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY
DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL
ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED
ROADS MAKE THE SMART CHOICE...TURN AROUND...DONT DROWN.

&&

LAT...LON 3418 11767 3425 11805 3478 11792 3475 11766
      3446 11766 3432 11764 3427 11764

$$

RK
1 follow-up statement
438 
WGUS76 KLOX 110129
FFSLOX

FLASH FLOOD STATEMENT
NATIONAL WEATHER SERVICE OXNARD CA
629 PM PDT MON SEP 10 2012

CAC037-110135-
/O.EXP.KLOX.FF.W.0004.000000T0000Z-120911T0130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
LOS ANGELES CA-
629 PM PDT MON SEP 10 2012

...THE FLASH FLOOD WARNING WILL EXPIRE AT 630 PM PDT FOR EAST CENTRAL
LOS ANGELES COUNTY...

HEAVY RAINFALL THAT OCCURRED OVER THE AREA EARLIER HAS SUBSIDED. 
TRAINED WEATHER SPOTTERS HAVE REPORTED WATER AND MUD ACROSS ROADWAYS 
IN THE EASTERN ANTELOPE VALLEY...AND SOME ROADWAYS AND DRAINAGES MAY 
STILL BE FLOWING THIS EVENING. WHEN ENCOUNTERING FLOODED ROADS MAKE 
THE SMART CHOICE...TURN AROUND...DONT DROWN.

LAT...LON 3418 11767 3425 11805 3478 11792 3475 11766
      3446 11766 3432 11764 3427 11764

$$

HALL

The office that day

Everything else NWS Los Angeles, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 9, 5:22 PM PDTFlash Flood WarningLOXLos Angeles3 hr
Sep 9, 6:40 PM PDTAreal Flood AdvisoryLOX93 min
Sep 10, 3:23 AM PDTFlash Flood WatchLOX16 hr
Sep 10, 2:15 PM PDTAreal Flood AdvisoryLOX3 hr
Sep 10, 2:38 PM PDTFlash Flood WarningLOXVentura3 hr
Sep 10, 3:49 PM PDTSevere Thunderstorm WarningLOXLos Angeles26 min
Sep 10, 4:11 PM PDTSevere Thunderstorm WarningLOXLos Angeles64 min

Nearby

Flash Flood Warnings in California, 2012Every flash flood warning in 2012

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.