Alert archive / Arizona / Mesoscale Discussions in 2012

Mesoscale Discussion 1944

September 10, 20125 counties in Arizona; Riverside County, San Bernardino County, San Diego County, California; Clark County, Nevada

The Storm Prediction Center issued this mesoscale discussion at Sep 10, 2012, 12:47 PM MST for 5 counties in Arizona; Riverside County, San Bernardino County, San Diego County, California; Clark County, Nevada. It was in force for 118 min.

The area

The outline as issued.

The facts

Issued
Sep 10, 2012, 12:47 PM MST (19:47 UTC)
Expired
Sep 10, 2012, 2:45 PM MST
In force
118 min
Issued by
the Storm Prediction Center
Chance of a watch
5%

Counties La Paz County, AZ, Maricopa County, AZ, Pima County, AZ, Pinal County, AZ, Yuma County, AZ, Riverside County, CA, San Bernardino County, CA, San Diego County, CA, Clark County, NV

The radar

The Yuma radar (KYUX), 114 km from the middle of the area, began a volume at 19:49 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

Yuma Intl Airpor, AZ (KYUM), launched 12:00Z, 7.8 hours before the alert went out and 101 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, Yuma Intl Airpor, AZ at 12:00Z on 2012-09-10Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 102 joules per kilogram.LCLLFCEL10008507005003002001001 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, Yuma Intl Airpor, AZ at 12:00Z on 2012-09-10The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 35 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
102 J/kg
Mixed-layer CIN
-219 J/kg
Mixed-layer LCL
1370 m above ground
0-6 km bulk shear
10 kt
0-1 km storm-relative helicity
35 m²/s²
0-3 km storm-relative helicity
89 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.

869 
ACUS11 KWNS 101947
SWOMCD
SPC MCD 101947 
AZZ000-NVZ000-CAZ000-102145-

MESOSCALE DISCUSSION 1944
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT MON SEP 10 2012

AREAS AFFECTED...SRN INTERIOR CA...SRN NV...WRN/SRN AZ

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 101947Z - 102145Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...A FEW STORMS MAY PRODUCE SVR WIND GUSTS ON AN ISOLATED
BASIS INTO EARLY EVENING...AND WW ISSUANCE IS NOT NEEDED.

DISCUSSION...VISIBLE SATELLITE IMAGES SUGGEST CONVECTION INCREASING
OVER THE COASTAL RANGES FROM ERN LOS ANGELES COUNTY SWD INTO SAN
DIEGO COUNTY...AIDED BY UPSLOPE FLOW WITHIN THE NRN SEMICIRCLE OF A
MID-LEVEL LOW JUST WEST OF THE NRN COAST OF BAJA CA. SCATTERED
THUNDERSTORMS WILL LIKELY EVOLVE FROM THIS ACTIVITY THROUGH THE
AFTERNOON POTENTIALLY IMPACTING ADJACENT SECTIONS OF THE COASTAL
PLAIN...WHILE TERRAIN-DRIVEN CIRCULATIONS AND DIFFERENTIAL HEATING
ZONES SUPPORT ADDITIONAL STORMS FARTHER EAST TOWARD THE LOWER CO
RIVER VALLEY INTO S-CNTRL AZ. PW VALUES OF GENERALLY 1.5-2.1 INCHES
WILL BOLSTER WATER-LOADING PROCESSES TO SUPPORT THE POTENTIAL FOR
STRONG/LOCALLY SVR WIND GUSTS...AIDED IN SERN CA AND SWRN AZ BY
20-25 KT OF LOW-TO-MID-LEVEL SSELY FLOW -- REF. YUMA VWP DATA. THE
THREAT WILL BE GREATEST WHERE SFC HEATING HAS BEEN MAXIMIZED IN
PERSISTENTLY CLOUD-FREE AREAS. HOWEVER...WEAK HIGH-LEVEL FLOW
YIELDING WEAK EFFECTIVE-LAYER SHEAR...AND WEAK MID-LEVEL LAPSE
RATES...SHOULD KEEP ANY INSTANCES OF SVR STORMS ISOLATED.

..COHEN/THOMPSON.. 09/10/2012

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

ATTN...WFO...TWC...FGZ...PSR...VEF...SGX...LOX...

LAT...LON   32541623 32501649 32591690 32971701 33321713 33761745
            34041775 34371793 34671753 35161679 36251572 36241409
            34901354 33961208 33271130 32071098 31491141 31811271
            32051344 32561428 33261464 33361505 33321544 33091586
            32541623

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Sep 10, 12:46 PM MSTMesoscale DiscussionSPCWhite Pine119 min

Nearby

Mesoscale Discussions in Arizona, 2012Mesoscale Discussions in California, 2012Mesoscale Discussions in Nevada, 2012Every mesoscale discussion 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.