Alert archive / Arizona / Severe Thunderstorm Warnings in 1999

Severe Thunderstorm Warning 39, NWS Phoenix, AZ

August 10, 1999Maricopa County, Arizona

NWS Phoenix, AZ issued this severe thunderstorm warning at Aug 10, 1999, 9:28 PM MST for Maricopa County, Arizona. It was in force for 62 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Aug 10, 1999, 9:28 PM MST (04:28 UTC)
Expired: Aug 10, 1999, 10:30 PM MST
In force: 62 min
Issued by: NWS Phoenix, AZ
Area: Whole counties

County Maricopa County, AZ

The radar

The Phoenix radar (KIWA), 77 km from the middle of the area, began a volume at 04:30 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.

The nearest sounding before it

Tuscon, AZ (KTUS), launched 00:00Z, 4.5 hours before the alert went out and 198 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: 210 J/kg
Mixed-layer CIN: -12 J/kg
Mixed-layer LCL: 2377 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 23 m²/s²
0-3 km storm-relative helicity: 22 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 
TTAA00 KPHX 110429 RRA
SVRPHX
AZC013-110530-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE PHOENIX AZ
928 PM MST TUE AUG 10 1999

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  CENTRAL AND NORTHEASTERN MARICOPA COUNTY IN CENTRAL ARIZONA

* UNTIL 1030 PM MST

* AT 925 PM MST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM NEAR FOUNTAIN HILLS... MOVING NORTH AT2 15 TO 20
  MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  RIO VERDE AT 945 PM

DAMAGING WINDS...HEAVY RAIN...AND LARGE HAIL ARE LIKELY. GO INSIDE A
STURDY BUILDING AND STAY AWAY FROM WINDOWS!

CJB

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 10, 9:10 PM MST, 18 minutes earlier.

Area forecast discussion, Aug 10, 9:10 PM MST, 18 minutes before

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
910 PM MST TUE AUG 10 1999

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM OVER NORTHERN CALIFORNIA WILL MOVE
TO THE NORTHEAST WEDNESDAY.  A LARGE AREA OF HIGH PRESSURE OVER TEXAS
PUSHES TO THE SOUTHWEST...TO BE LOCATED OVER AND TO THE SOUTH OF
ARIZONA.  A DRY SOUTHWEST FLOW PREVAILS OVER THE REGION THROUGH THE
END OF THE WEEK...AND INTO THE WEEKEND.

.DISCUSSION...
THIS AFTERNOON SOUTH CENTRAL AZ EXPERIENCED A STRONG LOW LEVEL
MOISTURE SURGE...WITH SFC DEWPOINTS CLIMBING QUICKLY INTO THE UPPER
60S.  PSR UA 00Z SOUNDING HAD PW 1.76 AND 850 MB DPT OF 13.  THAT WAS
AN INCREASE FROM THE PREVIOUS 12Z SOUNDING.  AS OF 900 PM TONIGHT...
THIS SURGE HAS ENDED ABRUPTLY...WITH SFC DPTS FALLING 10 DEG...INTO
THE 50S IN JUST ONE HOUR.  AT THE SURGE MAXIMUM LT THIS AFTN...WE HAD
AN ISOLATED SEVERE THUNDERSTORM WITH MICROBURST WINDS ON THE WESTERN
EDGE OF THE MOISTURE BOUNDARY IN SOUTH CENTRAL AZ. BECAUSE OF THE
VICINITY OF THE DRIER AIR TO THE WEST...AND THE STORMS WIND
ENVIRONMENT...THIS COMPACT STORM HAD A DRYLINE TSTM TYPE
CHARACTERISTIC.

LATE THIS EVENING...THE TREND IS DOWN.  THE ISOLATED WEAK TSTMS ON
OUTFLOW BOUNDARIES ARE DMNSHG.  EXPECT DRYING TO CONTINUE FM W TO E
OVERNIGHT...AS MOISTURE AT NEARLY ALL LEVELS IS SHUNTED TO THE EAST
OF OUR CWA.  NEW ETA CONTS THE DRYING TREND INTO THE END OF THE WEEK.
RUNYAN

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 10, 5:08 PM MST	Severe Thunderstorm Warning	PSR	Maricopa	47 min

Nearby

Severe Thunderstorm Warnings in Arizona, 1999 Every severe thunderstorm warning in 1999

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.