Subj : MESO: Mesoscale Discussion 0789
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat May 13 2023 20:32:45

ACUS11 KWNS 132032
SWOMCD
SPC MCD 132031=20
IAZ000-MOZ000-132230-

Mesoscale Discussion 0789
NWS Storm Prediction Center Norman OK
0331 PM CDT Sat May 13 2023

Areas affected...Central to southeast Iowa

Concerning...Tornado Watch 223...

Valid 132031Z - 132230Z

The severe weather threat for Tornado Watch 223 continues.

SUMMARY...The tornado threat continues across parts of WW 223.
Confidence in the severe threat is highest across parts of
central/northwest IA as well as south-central/southeast IA for the
next few hours.

DISCUSSION...Regional radar imagery over the past couple of hours
has shown a broken band of discrete convection across northwest IA
as well as more discrete convection across central/southeast IA.
Despite a favorable thermodynamic and kinematic environment for
supercells (MLCAPE over 1000 J/kg and 40-50 knots of effective bulk
shear per latest RAP analyses), convection thus far appears to not
be fully realizing the available environment based on the relatively
short lifespan of individual cells and rather anemic appearance of
most convection in IR imagery. This is likely due to fairly weak
low-level forcing for ascent with a notable diminishment of cumulus
depth and westward retrograde of the warm front noted in surface obs
across central IA. Despite this limitation, a few brief tornadoes
have been reported since 18 UTC, and the KDMX VWP continues to
sample 0-1 km SHR on the order of 100-150 m2/s2. Given the
aforementioned environmental characteristics, a conditional tornado
threat continues across the entire watch area.=20

Over the next couple of hours, a relatively higher severe threat
will likely be focused within two corridors to the northwest and
southeast of the Des Moines area. Within these corridors, visible
satellite imagery has shown persistent agitated cumulus and multiple
attempts at more robust convection. This supports recent RAP
analyses that depict locally enhanced low-level convergence and
ambient vorticity along the frontal boundary that may be conducive
for tornadogenesis with any stronger updraft. Recent hi-res guidance
continues to hint that the greatest potential for long-lived
tornadic supercells resides across south-central IA, which matches
environmental trends (higher buoyancy and stronger baroclinicity
along the warm front) and recent radar/satellite observations.

...Moore.. 05/13/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!9E2ucEEtgU44rKwakTeWP048DxG7AYLDqvm5cL0tiZgOK6Rv_EDucyGiuPAbJH4Ygh5zKY4OS=
sHRw8F7FS6j2IqTNg4$  for graphic product...

ATTN...WFO...DVN...DMX...EAX...FSD...

LAT...LON   41489446 41689472 42009506 42309534 42639551 42809541
            42899506 42779454 42389404 41949339 41739279 41559216
            41369180 41089158 40679172 40589204 40599254 40769304
            40979355 41079378 41489446=20


=3D =3D =3D
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