Alert archive / Iowa / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 95, NWS Des Moines, IA

August 24, 2021Black Hawk County, Bremer County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 24, 2021, 1:53 PM CDT for Black Hawk County, Bremer County, Iowa. It was in force for 67 min. 7 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Aug 24, 2021, 1:53 PM CDT (18:53 UTC)
Expired: Aug 24, 2021, 3:00 PM CDT
In force: 67 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

Counties Black Hawk County, IA, Bremer County, IA

The radar

The Des Moines radar (KDMX), 155 km from the middle of the area, began a volume at 18:53 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.

What was reported inside it

Time	Report	Where	Remark
Aug 24, 2:19 PM CDT	TSTM WND GST 61	Waterloo Regional Airpo, IA
Aug 24, 2:22 PM CDT	TSTM WND GST 60	2 Sw Cedar Falls, IA
Aug 24, 2:30 PM CDT	TSTM WND DMG	4 Nnw Readlyn, IA	SEMI TRAILER TURNED OVER, BIN BLOWN IN TO FIELD, BIN ROOF BLOWN OFF, CORN DAMAGE, BRANCHES ON HOUSES, ROOF DAMAGE, UPROOTED TREES. TIME ESTIMATED BY RADAR.
Aug 24, 2:30 PM CDT	TSTM WND DMG	Waterloo, IA	TREE LIMBS & A FEW POWER LINES DOWNED. PONDING OBSERVED ON AREA ROADWAYS.
Aug 24, 2:30 PM CDT	TSTM WND GST 60	Readlyn, IA	CROPS FLATTENED AND TREES DOWN ABOUT 1 MILE W OF READLYN.
Aug 24, 2:38 PM CDT	TSTM WND DMG	5 E Plainfield, IA	TREES DOWN ALONG HIGHWAY 188. TIME ESTIMATED FROM RADAR.
Aug 24, 2:40 PM CDT	TSTM WND DMG	Tripoli, IA	REPORTS OF TREES DOWNED AND SEMI OVER-TURNED IN THE TRIPOLI AREA.

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Aug 24, 1:52 PM CDT	Severe Thunderstorm Watch	SPC	5 hr

The nearest sounding before it

Davenport, (KDVN), launched 12:00Z, 6.9 hours before the alert went out and 176 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: 1809 J/kg
Mixed-layer CIN: -127 J/kg
Mixed-layer LCL: 1284 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 35 m²/s²
0-3 km storm-relative helicity: 9 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

271 
WUUS53 KDMX 241853
SVRDMX
IAC013-017-242000-
/O.NEW.KDMX.SV.W.0095.210824T1853Z-210824T2000Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines IA
153 PM CDT Tue Aug 24 2021

The National Weather Service in Des Moines  has issued a

* Severe Thunderstorm Warning for...
  Black Hawk County in northeastern Iowa...
  Bremer County in northeastern Iowa...

* Until 300 PM CDT.

* At 153 PM CDT, a severe thunderstorm was located over Shell Rock,
  or 7 miles west of Waverly, moving southeast at 45 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Hail damage to vehicles is expected. Expect wind damage 
           to roofs, siding, and trees.

* This severe thunderstorm will be near...
  Waverly around 200 PM CDT.
  Cedar Falls and Denver around 210 PM CDT.

Other locations in the path of this severe thunderstorm include
Waterloo Municipal Airport, Waterloo, Evansdale, Elk Run Heights and
Jesup.

This includes Interstate 380 between mile markers 58 and 73.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4236 9207 4247 9255 4291 9255 4291 9208
      4247 9208 4247 9206
TIME...MOT...LOC 1853Z 296DEG 40KT 4272 9262 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Krull

2 follow-up statements

651 
WWUS53 KDMX 241928
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
228 PM CDT Tue Aug 24 2021

IAC013-017-242000-
/O.CON.KDMX.SV.W.0095.000000T0000Z-210824T2000Z/
Black Hawk IA-Bremer IA-
228 PM CDT Tue Aug 24 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 300 PM CDT
FOR BLACK HAWK AND BREMER COUNTIES...

At 227 PM CDT, a severe thunderstorm was located near Elk Run
Heights, or 8 miles northeast of Waterloo, moving east at 65 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Waterloo ASOS reported a 61 MPH gust.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

This severe thunderstorm will remain over mainly rural areas of Black
Hawk and Bremer Counties, including the following locations...
Janesville, Raymond, Plainfield, Dunkerton, Washburn, George Wyth
State Park, Waverly Municipal Airport, Readlyn, Frederika and
Gilbertville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4236 9207 4247 9255 4291 9255 4291 9208
      4247 9208 4247 9206
TIME...MOT...LOC 1927Z 277DEG 54KT 4256 9221 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...OBSERVED
MAX WIND GUST...60 MPH

$$

Krull

067 
WWUS53 KDMX 241949
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
249 PM CDT Tue Aug 24 2021

IAC013-017-242000-
/O.CON.KDMX.SV.W.0095.000000T0000Z-210824T2000Z/
Black Hawk IA-Bremer IA-
249 PM CDT Tue Aug 24 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 300 PM CDT
FOR NORTHEASTERN BLACK HAWK AND BREMER COUNTIES...

At 248 PM CDT, a severe thunderstorm was located over Independence,
moving southeast at 45 mph.

HAZARD...60 mph wind gusts and quarter size hail.

SOURCE...Radar indicated. This storm has a history of producing 60 
         MPH near Waterloo, and causing tree damage near Tripoli. 

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

Locations impacted include...
Waterloo, Evansdale, Jesup, Sumner, Denver, Tripoli, Elk Run Heights,
Crossroads Mall, Washburn, Dunkerton, Readlyn, Raymond, Gilbertville
and Frederika.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4243 9238 4291 9237 4291 9208 4247 9208
      4247 9206 4236 9207
TIME...MOT...LOC 1948Z 296DEG 40KT 4246 9192 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.00 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

Krull

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 24, 11:06 AM CDT	Special Weather Statement	DMX	Emmet	24 min
Aug 24, 11:30 AM CDT	Special Weather Statement	DMX	Kossuth, Winnebago	45 min
Aug 24, 12:07 PM CDT	Special Weather Statement	DMX	Cerro Gordo, Hancock, Worth	68 min
Aug 24, 12:26 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Hancock	49 min
Aug 24, 12:51 PM CDT	Severe Thunderstorm Warning	DMX	Cerro Gordo, Franklin, Hancock, Wright	54 min
Aug 24, 1:18 PM CDT	Severe Thunderstorm Warning Considerable damage threat	DMX	Butler	57 min
Aug 24, 1:44 PM CDT	Severe Thunderstorm Warning	DMX	Butler	31 min
Aug 24, 2:17 PM CDT	Special Weather Statement	DMX	Butler	28 min
Aug 24, 3:00 PM CDT	Special Weather Statement	DMX	Black Hawk, Bremer	30 min
Aug 24, 3:28 PM CDT	Severe Thunderstorm Warning	DMX	Hamilton, Hardin, Marshall, Story	47 min
Aug 24, 4:03 PM CDT	Severe Thunderstorm Warning	DMX	Black Hawk, Grundy, Hardin, Marshall, Poweshiek, Tama	57 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.