APRIL 12, 2022 IOWA: CLOSE RANGE TORNADO CHASE NEAR GILMORE CITY
Severe warned storm to the south of Fonda, Iowa. Already getting that look to it with a broad, rotating wall cloud at this point.
Storm still looking good and intensifying as it approaches us.
Here it comes! Had to bail shortly after this photo was taken due to the proximity of the wall cloud moving overhead and hail starting to fall.
Mothership structure to this storm as it became tornado warned and soon dropped a tornado. Big blocky lowering in there on the left that was rotating hard.
TORNADO!! No condensation funnel making contact yet but the tornado is definitely down as it began churning up dirt over the field ahead of us. This is looking to the northwest near Palmer, Iowa.
Tornado starting to fully condensate to the ground. Nice and clear mesocyclone rotating above the tornado.
Tornado taking on the shape of a thick elephant trunk at this point.
After the initial touchdown in the previous photos, we drove up at it and got closer as the tornado planted once again and became stronger. Now between Palmer and Gilmore City.
Damage to a farmstead. Lots of tree and grain bin damage but appeared to be fairly minor damage to the house.
Grain bin destroyed with corn spilling out. Sheet metal from the grain bin was strewn downwind throughout the field for miles.
Tornado occluding and starting to weaken near Gilmore City, Iowa. This storm went on later to product another tornado that we could not get a view of.
Got back ahead of the tornado warned storm Kanawha, Iowa. Very dark at this point but could make out what appeared to be a base embedded in there.
The path of the tornado in yellow and the path we took with our vehicle in red, coming up at it from the south.
WATCHES AND MESOSCALE DISCUSSIONS:
SUMMARY...Convective initiation is expected by around 21-23z. A
tornado watch will likely be needed in the next hour or so. Severe
thunderstorms capable of large hail, damaging gusts and a few
tornadoes are possible.
DISCUSSION...A surface low is located near the central NE/SD border
as of 19z. A warm front was noted in surface analysis arcing from
the low across northeast NE into southern IA. Meanwhile, the surface
cold front was located across central NE and rapidly approaching the
surface dryline just a few counties to the east. Increasing cumulus
has been noted in visible satellite imagery along the dryline and
across the warm sector to the east across northeast NE. The cumulus
along the dryline has shown modest vertical development where
capping is likely less than further east. As the warm front
continues to lift northward and better quality boundary-layer
moisture works northward in conjunction with strong large-scale
ascent, convection is expected to develop near the triple point by
21-23z.
Initial convection across southeast SD into southwest MN to near the
NE/IA border may be elevated near/just to the cold side of the warm
front, with a better-quality warm sector remaining quite narrow from
near the MO River into northwest IA. Fast storm motion toward the
northeast could result in these storms rapidly moving away from the
better warm sector as they mature. Nevertheless, strong vertical
shear, steepening midlevel lapse rates and sufficient instability
should support organized supercells capable of large hail and
perhaps strong gusts. Any storm that develops in the better warm
sector or that can anchor to the warm front will access better
low-level shear and see an increased risk for tornado development.
Furthermore, any storm that develops further south along the cold
front/dryline in NE may be higher-based, posing a threat for large
hail and damaging gusts. If any dryline convection persists eastward
into better moisture, these cells also could become surface-based
within the better-quality warm sector with a corresponding increase
in tornado potential. With time into the evening, more linear
convective development is expected near/east of the MO River as the
cold front surges east.
SUMMARY...Supercell development will be possible in the next couple
of hours, near and east of a surface cyclone along the
Nebraska/South Dakota border. The storm environment will continue
to become more favorable for a few tornadoes (a couple of which
could be strong) and very large hail, if storms can mature quickly
enough in the relatively narrow, unstable warm sector near the warm
front. Damaging winds will also be possible, especially late this
evening when storms could grow upscale into a squall line along the
cold front approaching from the west.
The tornado watch area is approximately along and 60 statute miles
east and west of a line from 50 miles northeast of Yankton SD to 45
miles south of Sioux City IA. For a complete depiction of the watch
see the associated watch outline update (WOUS64 KWNS WOU1).
SUMMARY...Sustained strong supercells appear increasingly likely
through early evening. Some probably will pose a risk for producing
tornadoes, particularly around the Storm Lake and Fort Dodge IA
areas by 7-9 PM CDT, where a strong tornado or two is possible.
Additional, a severe thunderstorm watch will probably be issued soon
to the north of the current watch, where severe hail may become an
increasing concern this evening.
DISCUSSION...Thunderstorms are now initiating along the warm frontal
zone, north through east of a deep surface cyclone slowly migrating
east-northeast of the Sioux City area. This is being supported by
lift driven by low-level warm advection, and perhaps a subtle
mid-level perturbation forecast to migrate north-northeastward
across the mid Missouri Valley around Sioux City through early
evening.
The strongest thunderstorms probably will tend to evolve along the
front to the east-southeast of the warm front/dryline intersection,
now generally east of the Missouri River, where a narrow tongue of
modest boundary-layer moistening wrapping toward the surface low
center may be contributing to mixed-layer CAPE as high as 3000 J/kg
to the southwest of Fort Dodge. Into the the 00-02Z time frame,
southerly 850 mb flow across the narrow warm sector, into and across
the warm frontal zone is forecast to strengthen to 50-60+ kt,
contributing to very large, clockwise curved low-level hodographs.
As this occurs, the warm frontal zone is expected to become the
focus for intensifying supercells, including the evolution of strong
low-level mesocyclones, potentially capable of producing tornadoes.
The warm front is rather sharp, and the air to the north of the
front rather cool and stable. However, the front is slowly
advancing northward, and model forecast soundings indicate low-level
thermodynamic profiles will destabilize across much of northwestern
through north central Iowa into early evening. It appears possible
that this will become sufficient for tornado development, with
highest probabilities for sustained/longer track tornadic supercell
development around the Storm Lake/Fort Dodge Iowa vicinities.
As storms progress north of the warm frontal zone, into the colder
air, stronger cells could continue to pose a risk for severe hail
while the tornado threat diminishes.
SUMMARY...The evolution of an increasingly organized cluster of
storms seems probable this evening, before overspreading the region
through 10 PM-Midnight, accompanied by a risk for damaging wind
gusts and tornadoes.
DISCUSSION...Strong thunderstorm development continues to increase
in coverage in association with large-scale ascent downstream of a
deep northeastward migrating surface cyclone. This is being aided
by forcing associated with a subtle lead short wave perturbation,
and includes an evolving cluster of supercells near the Fort Dodge
IA area.
As the mid-level perturbation migrates northeast of the mid Missouri
Valley toward the Upper Midwest through mid to late evening,
considerable further upscale convective growth will continue to
ensue. The evolution of an increasingly organized mesoscale
convective system seems probable as the environment destabilizes
coincident with increasing forcing for ascent overspreading the
region.
Embedded within strengthening deep-layer ambient mean flow (in
excess of 50 kt), increasingly widespread damaging wind gusts are
possible. A coinciding larger-scale bow structure may evolve in
radar reflectivities, with embedded supercell structures posing a
risk for tornadoes, mainly where the apex of the bow intersects a
northeastward advancing warm front ahead of the surface cyclone.
