Alert archive / California / Severe Thunderstorm Warnings in 2003

Severe Thunderstorm Warning 46, NWS Phoenix, AZ

August 20, 2003Riverside County, California

NWS Phoenix, AZ issued this severe thunderstorm warning at Aug 20, 2003, 4:24 PM PDT for Riverside County, California. It was in force for 51 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 20, 2003, 4:24 PM PDT (23:24 UTC)
Expired: Aug 20, 2003, 5:15 PM PDT
In force: 51 min
Issued by: NWS Phoenix, AZ
Area: Counties, with a storm outline in the text

County Riverside County, CA

The radar

The Yuma radar (KYUX), 153 km from the middle of the area, began a volume at 23:26 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The nearest sounding before it

Yuma Intl Airpor, AZ (KYUM), launched 12:00Z, 11.4 hours before the alert went out and 143 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 4 J/kg
Mixed-layer CIN: -263 J/kg
Mixed-layer LCL: 1937 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 44 m²/s²
0-3 km storm-relative helicity: 33 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.

000 
WUUS55 KPSR 202324
SVRPSR
CAC065-210015-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHOENIX AZ
424 PM PDT WED AUG 20 2003

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CENTRAL RIVERSIDE COUNTY IN SOUTHEAST CALIFORNIA

* UNTIL 515 PM PDT

* AT 424 PM PDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A 
SEVERE THUNDERSTORM NEAR DESERT CENTER...OR ABOUT 30 MILES EAST OF 
INDIO...AND MOVING NORTH AT 10 MPH.

THIS STORM WILL AFFECT DESERT CENTER...EAGLE MOUNTAIN...AND 
INTERSTATE 10 BETWEEN INDIO AND DESERT CENTER. 

DAMAGING MICROBURST WINDS ARE LIKELY WITH THIS STORM. VERY HEAVY RAIN
IS ALSO POSSIBLE. TAKE COVER IN A SUBSTANTIAL SHELTER UNTIL THE STORM
PASSES.

REPORT SEVERE WEATHER TO THE NEAREST LAW ENFORCEMENT AGENCY. THEY
WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE FORECAST
OFFICE IN PHOENIX.

LAT...LON 3377 11519 3371 11599 3357 11603 3346 11606
          3347 11513

$$

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Phoenix, AZ wrote its last area forecast discussion before this severe thunderstorm warning went out at Aug 20, 3:15 PM PDT, 1 hour 9 minutes earlier.

Area forecast discussion, Aug 20, 3:15 PM PDT, 1 hour 9 minutes before

AZZ020>028-CAZ030>033-210545-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
WEATHER SERVICE PHOENIX AZ
315 PM MST WED AUG 20 2003

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL MOVE NORTH ACROSS SOUTHERN CALIFORNIA
AND SOUTHWEST ARIZONA THIS EVENING. THIS MEANS SCATTERED SHOWERS AND
THUNDERSTORMS MAINLY OVER SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA
WITH LOCALLY HEAVY RAIN THERE THIS AFTERNOON THROUGH THIS EVENING.
HIGH PRESSURE ALOFT OVER NEW MEXICO WILL MOVE NORTH TO COLORADO BY
THURSDAY...AND STAY TO THE NORTH THROUGH MONDAY. THIS MEANS A MOIST
FLOW OF AIR FROM THE EAST WITH A CHANCE OF AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS THROUGH EARLY NEXT WEEK.

.DISCUSSION...
A FLASH FLOOD WATCH IS IN EFFECT FOR SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA UNTIL 9 PM MST OR 9 PM PDT THIS EVENING. A MOIST AND
UNSTABLE AIRMASS...AND A WEAK LOW PRESSURE SYSTEM MOVING NORTH OVER
SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA ARE RESPONSIBLE FOR THE
FLASH FLOOD PRODUCING STORMS. AS A RESULT...TEMPERATURES WERE MUCH
COOLER BY MID AFTERNOON IN PORTIONS OF THOSE AREAS. MEANWHILE...IT
WAS MUCH WARMER IN THE GREATER PHOENIX AREA TODAY DUE TO SUNNY SKIES
COMPARED WITH MOSTLY CLOUDY SKIES YESTERDAY. THERE IS STILL A CHANCE
OF SHOWERS AND THUNDERSTORMS DEVELOPING IN WESTERN MARICOPA COUNTY
WITH A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS DEVELOPING FROM
THE SOUTH IN THE REST OF THE SOUTH-CENTRAL ARIZONA DESERT AREAS
INCLUDING PHOENIX THIS EVENING. HIGH PRESSURE ALOFT CENTERED OVER
NEW MEXICO WILL MOVE NORTH TO COLORADO BY THURSDAY...AND STAY TO THE
NORTH THROUGH MONDAY. THIS MEANS A MOIST FLOW OF AIR FROM THE EAST
WITH A CHANCE OF AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
THROUGH EARLY NEXT WEEK. WEAK LOW PRESSURE SYSTEMS IN THIS FLOW ARE
EXPECTED TO ENHANCE THE CHANCE OF SHOWERS AND THUNDERSTORMS AT TIMES
MAINLY IN THE ARIZONA PORTION WHICH IS EXPECTED TO BE THE CASE
THURSDAY NIGHT INTO FRIDAY MORNING.

ELLIS

.PSR...FLASH FLOOD WATCH FOR SOUTHWEST ARIZONA AND SOUTHEAST
       CALIFORNIA UNTIL 9 PM MST OR 9 PM PDT...INCLUDING AZ ZONES
       20...21...25...AND 26...AND CA ZONES 30...31...32...AND 33.

Hazardous weather outlook, Aug 20, 12:40 PM PDT, 3 hours 44 minutes before

AZZ020>028-CAZ030>033-210100-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1240 PM MST WED AUG 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST AND
SOUTH-CENTRAL ARIZONA...AND SOUTHEAST CALIFORNIA.

.DAY ONE...TODAY

A FLASH FLOOD WATCH IS IN EFFECT FOR SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA UNTIL 9 PM THIS EVENING. PLEASE SEE THE FLASH FLOOD WATCH
PRODUCT PHXHWOPSR OR WMO HEADER WGUS65 KPSR FFAPSR.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.INSTRUCTIONS TO SPOTTERS...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

ELLIS

In the hours before

Local storm report, Aug 20, 4:10 PM PDT, 14 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX, AZ
410 PM MST WED AUG 20 2003

TIME(MST)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0200 PM    JOSHUA TREE NATIONAL PARK CA   1.75 INCH HAIL
08/20/03   RIVERSIDE                      GOLFBALL SIZED HAIL AT
                                          BLACK ROCK CANYON
                                          CAMPGROUND. REPORTED BY LAW
                                          ENFORCEMENT

0315 PM    5 E YUMA                  AZ   FLASH FLOODS
08/20/03   YUMA                           SEVERAL ROADS CLOSED DUE
                                          TO FLASH FLOODING IN THE
                                          YUMA FOOTHILLS AREA.
                                          REPORTED BY SPOTTERS

FOWLE

The office that day

Everything else NWS Phoenix, AZ issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 20, 3:21 PM PDT	Severe Thunderstorm Warning	PSR	Riverside	54 min

Nearby

Severe Thunderstorm Warnings in California, 2003 Every severe thunderstorm warning in 2003

Sources

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