Alert archive / Arizona / Mesoscale Discussions in 2021

Mesoscale Discussion 1328

July 22, 20214 counties in Arizona

The Storm Prediction Center issued this mesoscale discussion at Jul 22, 2021, 3:35 PM MST for 4 counties in Arizona. It was in force for 85 min.

The area

The outline as issued.

The facts

Issued
Jul 22, 2021, 3:35 PM MST (22:35 UTC)
Expired
Jul 22, 2021, 5:00 PM MST
In force
85 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
20%

Counties Graham County, AZ, Pima County, AZ, Pinal County, AZ, Santa Cruz County, AZ

The radar

The Tucson radar (KEMX), 55 km from the middle of the area, began a volume at 22:37 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 12:00Z, 10.6 hours before the alert went out and 18 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, Tuscon, AZ at 12:00Z on 2021-07-22Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 970 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, Tuscon, AZ at 12:00Z on 2021-07-22The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -25 square meters per square second.193958Sfc1 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
970 J/kg
Mixed-layer CIN
-227 J/kg
Mixed-layer LCL
1720 m above ground
0-6 km bulk shear
12 kt
0-1 km storm-relative helicity
-25 m²/s²
0-3 km storm-relative helicity
-68 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

621 
ACUS11 KWNS 222235
SWOMCD
SPC MCD 222235 
AZZ000-230000-

Mesoscale Discussion 1328
NWS Storm Prediction Center Norman OK
0535 PM CDT Thu Jul 22 2021

Areas affected...Portions of southern Arizona

Concerning...Severe potential...Watch unlikely 

Valid 222235Z - 230000Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated to widely scattered strong to severe storms are
expected through the evening across portions of southern Arizona.

DISCUSSION...Thunderstorms have developed in southern Arizona where
temperatures are in the 90s with dewpoints in the low to mid 60s
yielding MLCAPE around 1500 to 2000 J/kg. The KEMX VWP shows very
weak flow in the lowest 6 km with stronger flow above 6km. These
storms are quite tall, with forecast EL around 12 to 13 km and IR
satellite measurements around -65C confirming this depth. Therefore,
this stronger flow above 6 km is likely contributing to the
effective shear and is likely responsible for the somewhat organized
nature of several of the cells in the past 2 hours. In fact, the
storm in north-central Pima county has shown some supercell
characteristics with anti-cyclonic rotation despite right (poleward)
movement. Expect this activity and additional development over the
next few hours with mainly a threat for severe winds.

..Bentley/Edwards.. 07/22/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...TWC...PSR...

LAT...LON   31611204 32521209 33061143 33341060 33370988 32990965
            32200987 31321040 31301104 31611204

Nearby

Mesoscale Discussions in Arizona, 2021Every mesoscale discussion in 2021

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.