Alert archive / Arizona / Mesoscale Discussions in 2011

Mesoscale Discussion 2158

September 11, 20114 counties in Arizona

The Storm Prediction Center issued this mesoscale discussion at Sep 11, 2011, 2:47 PM MST for 4 counties in Arizona. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Sep 11, 2011, 2:47 PM MST (21:47 UTC)
Expired: Sep 11, 2011, 5:15 PM MST
In force: 2 hr
Issued by: the Storm Prediction Center

Counties Gila County, AZ, Maricopa County, AZ, Pinal County, AZ, Yavapai County, AZ

The radar

The Phoenix radar (KIWA), 74 km from the middle of the area, began a volume at 21:48 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

Phoenix, AZ (KPSR), launched 12:00Z, 9.8 hours before the alert went out and 43 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: 97 J/kg
Mixed-layer CIN: -384 J/kg
Mixed-layer LCL: 1826 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 111 m²/s²
0-3 km storm-relative helicity: 189 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

Open this sounding in Storm Lab

The text

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

235 
ACUS11 KWNS 112147
SWOMCD
SPC MCD 112147 
AZZ000-120015-

MESOSCALE DISCUSSION 2158
NWS STORM PREDICTION CENTER NORMAN OK
0447 PM CDT SUN SEP 11 2011

AREAS AFFECTED...AZ

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 112147Z - 120015Z

THE DIURNAL TSTM SCENARIO ACROSS SRN AZ APPEARS SIMILAR TO SATURDAY
WITH STORM DEVELOPMENT AND PERSISTENCE ZONE SHIFTED WEST TO THE PHX
METRO AREA. STORMS SHOULD INCREASE IN THIS ZONE THROUGH THE REST OF
THE AFTERNOON. WHILE A COUPLE OF THESE STORMS COULD PRODUCE HAIL AND
HIGH WINDS...A WATCH IS NOT CURRENTLY PLANNED FOR THE AREA.

MODEST 20-30KT DEEP-LAYER SSWLY FLOW EXISTS ATOP A HOT AND
WELL-MIXED BOUNDARY LAYER OVER SRN AZ THIS AFTERNOON.
MEANWHILE...SUBTLE DISTURBANCES CONTINUE TO ROTATE AROUND THE LARGE
AND NEARLY STATIONARY UPPER LOW OFF THE SRN CA COAST AND LEND
SUPPORT IN THE FORM OF POCKETS OF STRONGER BACKGROUND ASCENT/DPVA
OVER THE LOWER CO RIVER VALLEY AND POINTS EAST. TSTM
DEVELOPMENT...AIDED BY WEAK SYNOPTIC FORCING AND DIURNAL REMOVAL OF
CONVECTIVE INHIBITION...SHOULD BE FURTHER ENHANCED BY FAVORABLE
UPSLOPE FLOW THROUGH THE LOWER LEVELS. THUS...EXPECT A STEADY
INCREASE IN TSTMS...ESPECIALLY OVER AND ACROSS THE HIGHER
TERRAIN...TO CONTINUE FOR THE NEXT COUPLE OF HOURS. THERMODYNAMIC
AND KINEMATIC PROFILES ARE GENERALLY SUPPORTIVE OF BOTH HAIL AND
LOCALLY STRONG DOWNDRAFTS. GIVEN ONLY WEAK TO MODEST LARGER SCALE
FORCING...AND GENERALLY HIGHER UNCERTAINTY REGARDING SEVERE STORM
COVERAGE...A WATCH IS NOT ANTICIPATED AT THIS TIME. HOWEVER...THE
AREA WILL CONTINUE TO BE MONITORED CLOSELY FOR ANY INCREASING TREND
IN SEVERE WEATHER POTENTIAL.

..CARBIN.. 09/11/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...TWC...FGZ...PSR...VEF...

LAT...LON   33411349 34131385 34821320 34681180 34041052 33411065
            32321128 32101271 32371335 33411349

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 11, 3:30 PM MST	Mesoscale Discussion	SPC	Coconino	3 hr

Nearby

Mesoscale Discussions in Arizona, 2011 Every mesoscale discussion in 2011

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.