June 30, 2014 Severe Weather Event Summary

Tornadoes:

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Tornado #1 - 4.0 mi SE of Casey Adair County Date June 30, 2014 Time (CDT) 12:24pm - 12:50pm EF Rating EF-1 Est. Peak Winds 100 mph Path Length 7.68 miles Max Path Width 200 yards Injuries/Fatalities 0/0 Summary: This tornado had an intermittent beginning track, but strengthened and produced EF-1 damage to a house and outbuildings towards the end of its life southwest of Stuart. Track Map Downloadable KMZ File

A classic hook echo develops on reflectivity as the tornado forms at 12:42pm SE of Casey. Note the large hail core over Casey. A tightening velocity couplet is also observed near the surface at 12:46pm. The house near the farm outbuilding lost a large portion of its roof. Damage was also rated EF-1. (NWS Storm Survey) A farm outbuilding was completely destroyed SW of Stuart towards the end of the tornado's path. Damage here was rated at EF-1. (NWS Storm Survey)

Tornado #2 - 1.7 mi E of Zearing Story, Marshall & Hardin Counties Date June 30, 2014 Time (Local) 1:02pm - 1:25pm EF Rating EF-1 Est. Peak Winds 110 mph Path Length 12.86 miles Max Path Width 460 yards Injuries/Fatalities 0/0 Summary: This tornado tracked across NE Story, NW Marshall, and southern Hardin counties. The worst damage occurred in far west Marshall County, where a grove of trees sustained severe damage and an outbuilding was demolished. Other damage was to trees on farmsteads and a hog confinement building. The tornado dissipated about 1.5 miles SE of Union. Track Map Downloadable KMZ File

Radar loop of the tornado with the path overlaid. Base reflectivity is on the left and storm relative velocity on the right. A 300-400 yard wide swath of trees along a stream were demolished. (NWS Storm Survey) A barn was destroyed, with the debris blown into the trees to the north and east. (NWS Storm Survey) Convergent tree damage as the tornado narrowed at the end of the track. (NWS Storm Survey)

Tornado #3 - 5.7 mi NE of Winterset Madison County Date June 30, 2014 Time (Local) 1:13pm - 1:14pm EF Rating EF-1 Est. Peak Winds 90 mph Path Length 1.34 miles Max Path Width 75 yards Injuries/Fatalities 0/0 Summary: This short-lived tornado tracked southeastward for slightly over a mile and briefly reached EF-1 strength early in its life. Track Map Downloadable KMZ File

Another hook echo develops north of Winterset 6 minutes before the tornado touchdown. While not as strong of a couplet as seen with the previous tornado, there is still evidence of at least broad rotation at the location of touchdown at 1:13pm. Siding was removed from the east side of this house early in the tornado's path. (NWS Storm Survey) A healthy tree was stripped of many of its large branches. (NWS Storm Survey)

Tornado #4 - 3.9 mi NW of Patterson Madison County Date June 30, 2014 Time (Local) 1:15pm - 1:23pm EF Rating EF-1 Est. Peak Winds 100 mph Path Length 6.50 miles Max Path Width 400 yards Injuries/Fatalities 0/0 Summary: This EF1 tornado snapped or uprooted several hundred trees. The worst damage occurred to a home 2.5 miles NW of Bevington, which had the attached garage roof fail and take out part of the house roof as well. Roof and siding damage was noted to 7 homes. Track Map Downloadable KMZ File

Radar loop of the tornado with the path overlaid. Base reflectivity is on the left and storm relative velocity on the right. Convergent and narrow area of tree damage in the middle of the track. (NWS Storm Survey) A house lost the roof from its garage and part of the main roof. (NWS Storm Survey) Trees downed early in the tornado path. (NWS Storm Survey)

Tornado #5 - 2.6 mi W of Bangor Marshall & Hardin Counties Date June 30, 2014 Time (Local) 1:15pm - 1:26pm EF Rating EF-0 Est. Peak Winds 85 mph Path Length 6.57 miles Max Path Width 150 yards Injuries/Fatalities 0/0 Summary: As the first tornado from this supercell began to occlude and pull NE, a second tornado formed a mile to the south and east. Damage was mostly to trees, with occasional outbuilding damage. The tornado dissipated just before reaching the Iowa River. Track Map Downloadable KMZ File

Radar loop of the tornado with the path overlaid. Base reflectivity is on the left and storm relative velocity on the right. The circulation of the tornado oddly never appeared on radar (beam height 2500 ft), thus it is believed that this was a very shallow vortex, or possibly even a strong gustnado. Many softwood trees were snapped around this house early in the track. (NWS Storm Survey) A narrow corridor of damage through the trees on the right side of the photo. (NWS Storm Survey) The weakening tornado came through this grove of trees. (NWS Storm Survey)

Tornado #6 - 1.0 mi N of Matensdale Warren County Date June 30, 2014 Time (Local) 1:27pm - 1:29pm EF Rating EF-1 Est. Peak Winds 90 mph Path Length 2.06 miles Max Path Width 190 yards Injuries/Fatalities 0/0 Summary: This tornado formed north of Martensdale and quickly tracked to the SE, reaching its widest and strongest point just east of the city where it damaged dozens of trees. The surface circulation weakened as it ascended a 100 foot high ridge south of the Middle River and then dissipated about a half mile south of the ridge crest. Track Map Downloadable KMZ File

Radar loop of the tornado with the path overlaid. Base reflectivity is on the left and storm relative velocity on the right. A 100 yard wide region of snapped trees. (NWS Storm Survey) Uprooted trees in the middle of the path. (NWS Storm Survey) Large branches and whole trees downed along the Middle River. (NWS Storm Survey)

Tornado #7 - 3.3 mi W of Traer Tama County Date June 30, 2014 Time (Local) 2:02pm - 2:10pm EF Rating EF-2 Est. Peak Winds 115 mph Path Length 3.99 miles Max Path Width 150 yards Injuries/Fatalities 0/0 Summary: This tornado formed northwest of Traer where it heavily damaged outbuildings on a farmstead. It then turned southeastward and clipped the southwest and southcentral parts of Traer. EF-2 damage was sustained to one home on the edge of town with the roof completely removed and destroyed. The tornado quickly weakened as it moved further into town and dissipated over the southeast side of town. Track Map Downloadable KMZ File

The Traer tornado never really stood out on reflectivity imagery, mostly due to the ongoing cell merger with the squall line to the south. However, a faint hook is visible as an area of higher reflectivity values NW of Traer. However, storm-relative velocity imagery clearly shows a violently rotating couplet bearing down on Traer from the NW. A farmstead was damaged early in the track of the tornado. (NWS Storm Survey) Low EF-2 damage occurred to this house on the SW side of Traer where portions of the roof failed. (NWS Storm Survey)

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Wind & Hail:

Wind

Damaging straight-line winds affected much of the southern half of Iowa at some point during the day. The first wave of damaging winds originated from a squall line tracking out of northeastern Nebraska into Woodbury and Monona counties around 10:30am. However, the strongest winds were not realized at the surface due to the storm being somewhat elevated and the bow echo weakened as it crossed Crawford County as a new complex of cells took shape to the south over Shelby and Audubon counties just before noon.

Multiple cells out ahead of this main squall line contained damaging winds. One storm in particular tracked through Ida and Sac counties fast on the heels of the 4 inch hailstorm and continued on a due east course to Tama County before being absorbed by the main squall line. WSR-88D velocity data indicated winds of 55 to 60 kts with the line as it pushed towards I-35. The aforementioned second, southern supercell merged with this line in northern Boone County, and this merger generated a small but intense region of damaging winds from NE Boone County eastward to Tama County.

Once the hail core collapsed on the newly developed southwest complex before 1:00pm, it quickly transitioned into a wind threat in eastern Guthrie and Adair counties. Meanwhile, the first squall line caught up with this developing southern line and began to strengthen as well. It was here that the complex rolled through the Des Moines metro, with the strongest winds over Madison and Warren counties but there were sufficient winds to cause some tree damage throughout the metro. Once the line cleared the metro, it rapidly grew upscale into a powerful windstorm as it merged with the northern cell in Tama County. A potent bow echo developed at the merger point by the time the storms reached eastern Tama County and only continued to intensify as it rolled towards Cedar Rapids. Widespread winds of 70-80 kts were measured by the Des Moines WSR-88D radar over eastern Tama County, with similar winds extending southwestward along the line to northern Marion County. This line would accelerate and press eastward across the Mississippi River and reach Chicago by the late afternoon, leaving a trail of widespread wind damage in its wake.

Base reflectivity (left) and base velocity (right) radar imagery at 11:20am as the first squall line moves into western Crawford County. Note the bow echo signature with winds of 90+ kts measured at 9500 ft punch through to the front of the line. A rear inflow notch is also visible on the reflectivity image.	Base reflectivity (left) and base velocity (right) radar imagery at 11:33am of a discrete cell producing damaging winds over NW Greene and SE Calhoun counties. Winds on velocity are measured at 55-65 kts at 3000 ft. This cell would eventually track into Tama County, where it would merge with the main squall line and produce the Traer tornado.	Base reflectivity (left) and base velocity (right) radar imagery at 12:52pm as the squall line approaches Des Moines. Note that the northern and southern lines have merged and the northern line is starting to re-intensify on velocity over Perry. The wind threat is just starting to get organized in NE Adair and SE Guthrie counties as Tornado #1 dissipates.	Base reflectivity (left) and base velocity (right) radar imagery at 1:26pm as the squall line leaves Des Moines. The line is now catching up with the supercell in SE Hardin County while the strongest winds are from SE Des Moines to east central Madison County. Note that the wind direction is normal to the radar beam, so the winds are poorly sampled by the radar in Des Moines.

Base reflectivity (left) and base velocity (right) radar imagery at 2:11pm showing the squall line rapidly intensifying over Tama, Poweshiek, Jasper, and Marion counties. A robust line on reflectivity has replaced the previously fragmented structure and widespread velocities of 60 to 80 kts are being sampled by the radar only a few thousand feet off the ground.	Base reflectivity (left) and base velocity (right) radar imagery at 2:42pm. The line has rapidly developed into a classic bow echo as it accelerates towards Cedar Rapids. A bookend vortex also has developed on the north end of the line in the remnants of the old supercell. A rear inflow jet is also starting to show up punching in through Tama County. Wind velocity values of 70-95 kts are being measured at this point at the apex of the bow.	Tree damage in Newton. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	A large section of tree on a shed in Roland. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.

A large tree crushed a porch in Pella. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	A large tree crushed a porch in Pella. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	A large tree split in southeast Des Moines. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	Large tree branches downed southwest of Story City. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.

Hail

Multiple supercell thunderstorms formed during the early to middle stages of the event and unleashed dangerously large hail over parts of western Iowa. One northern cell tracked across Sac, Calhoun, and Webster counties between 9:00am and 11:00am, dropping hail close to the size of baseballs on Rockwell City and tennis ball size hail on Fort Dodge. This hail smashed car windshields and damaged roofs in both towns. A second supercell ongoing at the same time to the south plotted a course from Harrison County to northern Boone County before merging with another cell and transitioning into a wind/tornado threat, with hail as large a golf balls falling from this storm. Finally, a third massive supercell developed over Audubon, Cass, Adair, and Guthrie counties shortly after 12:00pm and proceeded to drop wind-driven golf ball size hail over a wide swath of prime farm land.

All three storms exhibited impressive structure and characteristics normally seen with storms over Texas, Oklahoma and Kansas. The northern supercell extended up to 52,000 ft in the atmosphere (with a sustained core of 50+ dBZ to 46,000 ft) with a ZDR column that reached up to 25,000 ft high (freezing level was 13,000 ft). A ZDR column is an area of higher differential reflectivity values well above the freezing level that denote the presence of liquid water drops being lofted by the storm's updraft. The higher the ZDR column, the stronger the updraft and the higher the hail producing potential. Meanwhile, the second cell to the south sported a very classic supercell structure with a persistent RFD (which generates the telltale "hook echo") that lasted for much of its life. Both the first and third supercells developed features known as bounded weak echo regions (BWERs) in their mid levels, a key tip off that the storm's updraft is quite strong and capable of producing massive hail. The latter supercell in particular was well sampled by the WSR-88D radar in Des Moines, with radar cross sections easily resolving a large BWER juxtaposed on a tall ZDR column just below a large hail core. The radar images below highlight some of the defining characteristics of these storms, followed by several public photos of the resultant hail.

Radar cross sections of the first supercell in northwest Iowa when it was by Sac City. It clearly shows the highly sheared updraft and ZDR column.	Four panel radar image showing the vertical reflectivity structure of the first supercell over Sac and Calhoun counties, extending above 46,000 ft. Also note the BWER on the bottom left image.	Base reflectivity and ZDR imagery of the first supercell over Rockwell City as it was producing 4 inch hail in the city. Note the depressed (grey) ZDR values on the right image, indicative of large hail falling out.	Base reflectivity and ZDR of the second, classic supercell that moved through central Iowa. The white arrow denotes the RFD and the orange arrow highlights the small but still potent hail core on the southern flank of the storm next to the updraft.

Cross sections of the third supercell in southwestern Iowa, showing the huge vaulted updraft and ZDR column. Also note the large hail core just above the ZDR column and on the left side of each cross section.	Mid-level view of the third supercell at about 15,000 ft, showing the BWER on reflectivity, a ZDR column in the middle of the BWER, a large hail spike down radial of the core on CC, and a large rotating mesocyclone on SRM.	Multi-layered hail in Rockwell City. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	Baseball sized hail that fell in Rockwell City. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.

Golf ball to tennis ball sized hail that fell south of Stratford from the southern-most of the first two supercells. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	A house damaged by wind-driven hail in Adair County. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	House windows destroyed by wind-driven hail in Casey. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	Car windshield broken out in Rockwell City. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.

Flooding

On top of the damaging winds, large hail, and tornadoes, these storms produced copious amounts of rain in a very short time span that simply could not be handled by the already saturated ground. Rainfall easily exceeded 2-3 inches per hour and many locations picked up 1-2 inches of rain in the first half hour of the event. The first round of excessive rainfall occurred as multiple rounds of storms tracked across Sac and Calhoun counties. The flash flood threat then shifted southward to two main swaths--one from northern Boone county to Black Hawk county, and another from Adair County eastward, through Des Moines, and through east central Iowa. A widespread 2-3 inches of rain fell in central Iowa with 3-5 inches common further east. A few spots even eclipsed the 6 inch mark for the day in east central Iowa (e.g. Iowa City). The resultant flash flooding washed out many roads and tragically led to one death in Cedar Rapids.

Radar/Photos

A washed out road in Adair County. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	Backyards flooding in Ankeny. Photo Courtesy of the KCCI uLocal page. Uploaded by the public.	KDP, or specific differential phase, measures the attenuation difference between the horizontal and vertical channels of the radar beam through precipitation. The higher the difference, the larger the raindrops. KDP can thus help locate areas of high rainfall rates. In this image, multiple waves of very efficient rainfall producing storms were moving through NW Des Moines.	KDP (right image) helped locate the areas of higher rainfall rates that might not have been as obvious on conventional reflectivity imagery.

Storm Reports

...TIME...  ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
...DATE...  ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0645 AM     HEAVY RAIN       ROCKWELL CITY           42.40N 94.63W
06/30/2014  M2.20 INCH       CALHOUN            IA   MESONET

            ESTIMATED TO HAVE FALLEN IN 1.5 HOURS BASED 
            ON RADAR. 


0700 AM     HEAVY RAIN       SAC CITY                42.42N 95.00W
06/30/2014  M2.20 INCH       SAC                IA   CO-OP OBSERVER

            ESTIMATED TO HAVE FALLEN MOSTLY BETWEEN 4 AM 
            AND 7 AM. 


0700 AM     HEAVY RAIN       1 N ROCKWELL CITY       42.41N 94.63W
06/30/2014  M2.65 INCH       CALHOUN            IA   CO-OP OBSERVER

            ESTIMATED TO HAVE FALLEN MOSTLY IN THE LAST 
            TWO TO THREE HOURS. 


1003 AM     HAIL             ROCKWELL CITY           42.40N 94.63W
06/30/2014  E3.00 INCH       CALHOUN            IA   TRAINED SPOTTER



1005 AM     HAIL             5 SW LOHRVILLE          42.21N 94.61W
06/30/2014  E1.00 INCH       CALHOUN            IA   TRAINED SPOTTER



1006 AM     HAIL             ROCKWELL CITY           42.40N 94.63W
06/30/2014  E2.00 INCH       CALHOUN            IA   TRAINED SPOTTER

            SPOTTER CH119 


1007 AM     HAIL             ROCKWELL CITY           42.39N 94.64W
06/30/2014  E2.00 INCH       CALHOUN            IA   TRAINED SPOTTER

            SPOTTER CH210 


1010 AM     HAIL             ROCKWELL CITY           42.40N 94.63W
06/30/2014  E1.75 INCH       CALHOUN            IA   LAW ENFORCEMENT

            CALHOUN CO. SHERIFF 


1011 AM     HAIL             ROCKWELL CITY           42.40N 94.63W
06/30/2014  E4.00 INCH       CALHOUN            IA   TRAINED SPOTTER

            SPOTTER CH119 


1043 AM     HAIL             FORT DODGE              42.51N 94.18W
06/30/2014  E1.50 INCH       WEBSTER            IA   AMATEUR RADIO



1044 AM     HAIL             FORT DODGE              42.51N 94.17W
06/30/2014  E1.50 INCH       WEBSTER            IA   TRAINED SPOTTER

            SPOTTER WE118 


1045 AM     HAIL             FORT DODGE              42.51N 94.18W
06/30/2014  M1.75 INCH       WEBSTER            IA   TRAINED SPOTTER

            GOLF BALL HAIL IN FORT DODGE. 


1046 AM     HAIL             FORT DODGE              42.51N 94.18W
06/30/2014  E1.00 INCH       WEBSTER            IA   LAW ENFORCEMENT

            CEDAR FALLS STATE PATROL 


1048 AM     HAIL             FORT DODGE              42.51N 94.18W
06/30/2014  E2.50 INCH       WEBSTER            IA   TRAINED SPOTTER

            SPOTTER WE239 


1050 AM     HAIL             2 S FORT DODGE          42.48N 94.18W
06/30/2014  E2.00 INCH       WEBSTER            IA   BROADCAST MEDIA

            WHO-TV REPORTED. 


1052 AM     HAIL             1 WNW FORT DODGE        42.51N 94.19W
06/30/2014  E2.00 INCH       WEBSTER            IA   TRAINED SPOTTER

            SPOTTER WE211 


1125 AM     TSTM WND DMG     DENISON                 42.02N 95.35W
06/30/2014                   CRAWFORD           IA   EMERGENCY MNGR

            MULTIPLE TREE-LIMBS DOWN AND WINDS ESTIMATED 
            AT 60 TO 70 MPH. 


1136 AM     HAIL             GRAND JUNCTION          42.03N 94.24W
06/30/2014  E1.00 INCH       GREENE             IA   AMATEUR RADIO



1141 AM     HAIL             2 W OGDEN               42.04N 94.07W
06/30/2014  E1.50 INCH       BOONE              IA   EMERGENCY MNGR



1146 AM     HAIL             2 NW OGDEN              42.06N 94.05W
06/30/2014  E1.00 INCH       BOONE              IA   TRAINED SPOTTER

            BN109 SPOTTER REPORT VIA WEB LSR FORM. 


1147 AM     HAIL             3 S ODEBOLT             42.27N 95.25W
06/30/2014  M1.75 INCH       SAC                IA   FIRE DEPT/RESCUE

            ODEBOLDT FIRE REPORTED GOLF BALL HAIL SOUTH 
            OF TOWN AND 60 TO 70 MPH WIND GUSTS IN TOWN. 


1150 AM     TSTM WND GST     5 W GOWRIE              42.27N 94.38W
06/30/2014  E70 MPH          WEBSTER            IA   TRAINED SPOTTER

            SPOTTER WE421 


1150 AM     TSTM WND GST     5 W GOWRIE              42.28N 94.39W
06/30/2014  E60 MPH          WEBSTER            IA   TRAINED SPOTTER

            WE421 


1152 AM     HAIL             1 S BOXHOLM             42.16N 94.11W
06/30/2014  E1.75 INCH       BOONE              IA   EMERGENCY MNGR



1202 PM     TSTM WND GST     OTTOSEN                 42.90N 94.38W
06/30/2014  E50 MPH          HUMBOLDT           IA   TRAINED SPOTTER



1205 PM     TSTM WND DMG     5 ESE EXIRA             41.56N 94.78W
06/30/2014                   AUDUBON            IA   PUBLIC

            SECOND HAND REPORT OF WIND DAMAGE AT 
            LITTLEFIELD RECREATION AREA. TIME ESTIMATED 
            VIA RADAR. 


1213 PM     HAIL             STRATFORD               42.27N 93.93W
06/30/2014  E1.25 INCH       HAMILTON           IA   TRAINED SPOTTER



1214 PM     HAIL             BOXHOLM                 42.17N 94.11W
06/30/2014  E1.75 INCH       BOONE              IA   EMERGENCY MNGR

            BOONE EM REPORTS GOLFBALL SIZE HAIL AND 
            STRONG WINDS IN BOXHOLM. TREE BRANCHES 
            COMING DOWN. 


1230 PM     HAIL             ADAIR                   41.50N 94.64W
06/30/2014  E2.50 INCH       ADAIR              IA   EMERGENCY MNGR

            EMERGENCY MANAGER REPORTED AROUND 300 HOMES 
            DAMAGED FROM LARGE WIND DRIVEN HAIL. 
            NUMEROUS TREES DAMAGED. NUMEROUS CARS ON I80 
            HAD THEIR WINDOWS BROKEN 


1231 PM     HAIL             ADAIR                   41.50N 94.64W
06/30/2014  E1.50 INCH       ADAIR              IA   EMERGENCY MNGR

            ALSO 40 TO 50 MPH WINDS IN TOWN OF ADAIR. 


1234 PM     HAIL             3 S STRATFORD           42.23N 93.93W
06/30/2014  E1.75 INCH       HAMILTON           IA   LAW ENFORCEMENT



1236 PM     HEAVY RAIN       5 W GOWRIE              42.27N 94.38W
06/30/2014  E1.13 INCH       WEBSTER            IA   TRAINED SPOTTER

            1.13 INCHES OF RAIN IN 45 MINUTES. 


1241 PM     HAIL             1 SE ADAIR              41.49N 94.63W
06/30/2014  E1.75 INCH       ADAIR              IA   LAW ENFORCEMENT

            GOLF BALL ON I80 MILE MARKER 77 DAMAGE TO 
            CARS AND WINDOWS 


1244 PM     TSTM WND GST     2 SW STORY CITY         42.17N 93.62W
06/30/2014  E70 MPH          STORY              IA   STORM CHASER

            65 TO 75 MPH ESTIMATED GUST FROM THE 
            SPOTTERNETWORK.ORG 


1245 PM     TSTM WND GST     3 S STUART              41.46N 94.32W
06/30/2014  E60 MPH          ADAIR              IA   TRAINED SPOTTER

            REPORT VIA THE LSR WEB REPORT FORM. 


1245 PM     TSTM WND DMG     RANDALL                 42.24N 93.60W
06/30/2014                   HAMILTON           IA   STORM CHASER

            AT LEAST 2 TREES, 1 POWER POLE, AND 
            WIDESPREAD LARGE TREE LIMBS DOWN ACROSS 
            RANDALL. 


1247 PM     TORNADO          5 S STUART              41.43N 94.32W
06/30/2014                   ADAIR              IA   BROADCAST MEDIA

            APPARENT TORNADO DAMAGE TO HOME FROM WHO-TV. 


1250 PM     HAIL             1 SE ELLSWORTH          42.30N 93.57W
06/30/2014  E0.88 INCH       HAMILTON           IA   TRAINED SPOTTER



1254 PM     TSTM WND DMG     2 SSW RANDALL           42.21N 93.62W
06/30/2014                   HAMILTON           IA   STORM CHASER

            TREES SNAPPED OFF AT BASES AND LARGE LIMBS 
            ACROSS US 69 HIGHWAY. SPOTTERNETWORK.ORG VIA 
            NWSCHAT. 


1254 PM     TSTM WND DMG     ZEARING                 42.16N 93.30W
06/30/2014                   STORY              IA   EMERGENCY MNGR

            NUMEROUS 40 TO 50 FEET TALL TREES DOWN IN 
            ZEARING. LARGE TREE BRANCH ACROSS HIGHWAY 69 
            1 MILE SOUTH OF STATE ROAD E29. REPORT FROM 
            EM VIA NWSCHAT. 


0107 PM     HAIL             ESE HUBBARD             42.30N 93.29W
06/30/2014  E1.00 INCH       HARDIN             IA   TRAINED SPOTTER

            TRAINED SPOTTER REPORTS DIME TO QUARTER 
            SIZED HAIL...CONSIDERABLE WIND AND HEAVY 
            RAIN. 


0110 PM     TSTM WND GST     1 S HUBBARD             42.28N 93.30W
06/30/2014  M81 MPH          HARDIN             IA   MESONET

            MEASURED BY HOME WEATHER STATION. TWO LARGE 
            ASH TREES SNAPPED. PINE TREE SNAPPED. CORN 
            AND BEAN CROPS FLATTENED. 


0115 PM     HAIL             2 W ADEL                41.61N 94.07W
06/30/2014  E1.00 INCH       DALLAS             IA   EMERGENCY MNGR



0116 PM     TSTM WND DMG     URBANDALE               41.64N 93.74W
06/30/2014                   POLK               IA   PUBLIC

            MEDIUM SIZE TREE LIMB DAMAGE 


0118 PM     HAIL             1 W NEW PROVIDENCE      42.28N 93.19W
06/30/2014  E1.00 INCH       HARDIN             IA   EMERGENCY MNGR

            ALSO A LARGE TREE ACROSS A ROAD AT THIS 
            LOCATION DUE TO STRONG (UNKNOWN SPEED) WIND. 


0120 PM     TSTM WND DMG     LISCOMB                 42.19N 93.01W
06/30/2014                   MARSHALL           IA   EMERGENCY MNGR

            LARGE MACHINE SHED DOWN. NUMEROUS REPORTS OF 
            TREES DOWN ACROSS NORTHERN MARSHALL COUNTY 
            INCLUDING IN CLEMONS AND ALBION. TIME FOR 
            THE LISCOMB REPORT ESTIMATED BY RADAR 


0120 PM     TSTM WND DMG     1 SE BEVINGTON          41.35N 93.78W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            SEMI-TRUCK BLOWN OVER ON I-35 AT THIS 
            LOCATION. 


0122 PM     FUNNEL CLOUD     MARTENSDALE             41.37N 93.74W
06/30/2014                   WARREN             IA   PUBLIC

            FUNNEL LASTED LESS THAN 1 MINUTE AND RECEDED 
            INTO CLOUDS 


0125 PM     TSTM WND DMG     2 S MARTENSDALE         41.34N 93.73W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            3195 KIRKWOOD ST., PROLE, IA... LARGE GRAIN 
            BIN DESTROYED ALONG WITH TWO HOOP BUILDINGS. 
            TIME EST. FROM RADAR FROM NWSCHAT POSTING 
            FROM WARREN CO. EMA. 


0125 PM     TSTM WND DMG     1 ESE MARTENSDALE       41.37N 93.71W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            BUILDING AND HOUSE PARTIALLY DESTROYED 50TH 
            AVENUE AND HIGHWAY 92, VIA NWSCHAT. 


0127 PM     TSTM WND GST     1 W CUMMING             41.48N 93.78W
06/30/2014  E70 MPH          WARREN             IA   STORM CHASER

            SPOTTERNETWORK.ORG VIA NWSCHAT. 


0128 PM     TSTM WND DMG     1 N MARTENSDALE         41.39N 93.74W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            BARN DESTROYED BY WIND. 


0128 PM     TSTM WND DMG     MARTENSDALE             41.37N 93.74W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            ALL WINDOWS BROKEN OUT OF HOUSE AT THIS 
            LOCATION. EM VIA NWSCHAT. 


0130 PM     TORNADO          TRAER                   42.19N 92.46W
06/30/2014                   TAMA               IA   FIRE DEPT/RESCUE

            TRAER FIRE DEPT. REPORTS SEVERAL HOMES 
            DAMAGED OR DESTROYED IN TRAER. 


0130 PM     TSTM WND GST     MARTENSDALE             41.37N 93.74W
06/30/2014  E70 MPH          WARREN             IA   PUBLIC



0135 PM     TSTM WND DMG     2 NNW GRIMES            41.69N 93.80W
06/30/2014                   POLK               IA   TRAINED SPOTTER

            SMALL TREES REPORTED UPROOTED. DITCH 
            FLOODING AROUND BRIARCREEK HOUSING 
            DEVELOPMENT 


0140 PM     HAIL             GRUNDY CENTER           42.36N 92.77W
06/30/2014  E0.88 INCH       GRUNDY             IA   TRAINED SPOTTER

            SPOTTER ESTIMATES WIND GUST 40 MPH 


0140 PM     TSTM WND DMG     MARTENSDALE             41.37N 93.74W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            POWERLINES DOWN ON HIGHWAY 28 JUST NORTH OF 
            MARTENSDALE AND TREE LIMBS DOWN ON HOUSE IN 
            MARTENSDALE. EM REPORT VIA NWSCHAT. 


0141 PM     HAIL             NORWALK                 41.50N 93.68W
06/30/2014  M1.00 INCH       WARREN             IA   TRAINED SPOTTER

            HEAVY RAINFALL ALSO OCCURING AT THIS TIME 
            CAUSING PONDING OF WATER. 


0141 PM     TSTM WND GST     1 WSW INDIANOLA         41.36N 93.58W
06/30/2014  E60 MPH          WARREN             IA   FIRE DEPT/RESCUE

            ESTIMATED 60 MPH WIND, HEAVY RAIN AND SMALL 
            LIMBS DOWN. INDIANOLA FD VIA MICRN. 


0147 PM     FLASH FLOOD      ANKENY                  41.72N 93.61W
06/30/2014                   POLK               IA   TRAINED SPOTTER

            WATER OVER CURBS AND FLOWING. 9TH ST AND 
            DELAWARE IN ANKENY. 


0148 PM     TSTM WND GST     3 S GRUNDY CENTER       42.32N 92.77W
06/30/2014  E70 MPH          GRUNDY             IA   LAW ENFORCEMENT

            SHERIFF DEPUTY ESTIMATED AT LEAST 70 MPH 
            WINDS AND PEA SIZE HAIL AT 229TH AND 260TH 


0153 PM     TSTM WND DMG     SANDYVILLE              41.37N 93.39W
06/30/2014                   WARREN             IA   EMERGENCY MNGR

            ALL WINDOWS ON NORTH SIDE OF HOUSE 
            DESTROYED. LIKELY WIND AND HAIL DAMAGE BOTH. 
            TIME ESTIMATED FROM RADAR. NWSCHAT REPORT 
            FROM EMA. 


0153 PM     HAIL             SANDYVILLE              41.37N 93.39W
06/30/2014  E2.75 INCH       WARREN             IA   EMERGENCY MNGR

            DELAYED REPORT FROM EM VIA NWSCHAT. GOLFBALL 
            TO BASEBALL SIZED HAIL. 


0156 PM     TSTM WND DMG     TRAER                   42.19N 92.46W
06/30/2014                   TAMA               IA   CO-OP OBSERVER

            HALF OF ROOF BLOWN OFF. 


0157 PM     FLASH FLOOD      2 NNW GRIMES            41.69N 93.80W
06/30/2014                   POLK               IA   AMATEUR RADIO

            6 INCHES OR MORE OF WATER, RAPIDLY MOVING, 
            IN AREAS IT TYPICALLY DOES NOT OCCUR. 2.5 
            INCHES OF RAIN IN 45 MINUTES. LITTLE BEAVER 
            CREEK OUT OF BANKS 


0202 PM     TSTM WND GST     PLEASANTVILLE           41.39N 93.27W
06/30/2014  E60 MPH          MARION             IA   TRAINED SPOTTER

            SPOTTER MN402 ALSO NICKEL HAIL IN THIS 
            GENERAL LOCATION VIA THE PHONE. 


0210 PM     TSTM WND DMG     TRAER                   42.19N 92.46W
06/30/2014                   TAMA               IA   BROADCAST MEDIA

            KCVM...KCNZ... KCFI REPORT VIA NWSCHAT WITH 
            TIME ESTIMATED FROM RADAR REPORTING DAMAGE 
            IN TRAER...TREES OVER POWER LINES, SEMI 
            TRAILER TIPPED OVER AND DAMAGE TO HOUSES. 
            REPORT VIA NWSCHAT. 


0210 PM     TSTM WND GST     8 WNW LA PORTE CITY     42.34N 92.34W
06/30/2014  E60 MPH          BLACK HAWK         IA   TRAINED SPOTTER

            SPOTTER BH410 VIA PHONE. ALSO 1.25 INCHES OF 
            RAIN FROM AROUND 2:10 PM TO 2:35 PM. 


0217 PM     TSTM WND DMG     CHELSEA                 41.92N 92.40W
06/30/2014                   TAMA               IA   FIRE DEPT/RESCUE

            CORN CRIB DESTROYED BY HIGH WINDS. DELAYED 
            REPORT FROM CHELSEA F.D. 


0217 PM     TSTM WND GST     1 S GRUNDY CENTER       42.35N 92.77W
06/30/2014  E70 MPH          GRUNDY             IA   FIRE DEPT/RESCUE

            ESTIMATED 70 MPH WINDS IN AND JUST SOUTH OF 
            CHELSEA ALONG WITH TORRENTIAL RAIN. POWER 
            LINES DOWN, A LOT OF TREE DAMAGE IN CHELSEA. 


0225 PM     TSTM WND DMG     LA PORTE CITY           42.31N 92.19W
06/30/2014                   BLACK HAWK         IA   EMERGENCY MNGR

            BLACK HAWK COUNTY EMERGENCY MANAGER REPORTS 
            TREE AND CROP DAMAGE. TIME ESTIMATED BY 
            RADAR. 


0230 PM     HEAVY RAIN       1 E HARTFORD            41.46N 93.39W
06/30/2014  M1.60 INCH       WARREN             IA   TRAINED SPOTTER

            HEAVY RAIN DURATION 1 HOUR OBSERVER LOCATION 
            HARTFORD 


0230 PM     TSTM WND DMG     DUNKERTON               42.57N 92.16W
06/30/2014                   BLACK HAWK         IA   PUBLIC

            TREES AND POWERLINES DOWN IN TOWN. IMAGES 
            RELAYED BY KWWL. TIME ESTIMATED FROM RADAR 


0259 PM     HEAVY RAIN       4 SW DUNKERTON          42.53N 92.22W
06/30/2014  M2.00 INCH       BLACK HAWK         IA   TRAINED SPOTTER

            BH206 SPOTTER REPORT OF 2.0 INCHES OF RAIN 
            IN 20 MINUTES. 


0349 PM     FLASH FLOOD      CONRAD                  42.22N 92.87W
06/30/2014                   GRUNDY             IA   LAW ENFORCEMENT

            GRUNDY COUNTY LAW ENFORCEMENT REPORTS 
            NUMEROUS CREEKS HAVE RISEN OUT OF THEIR 
            BANKS AND SEVERAL ROADS ARE UNDERWATER 
            AROUND THE COUNTY. 


0603 PM     HAIL             3 SW TAMA               41.93N 92.62W
06/30/2014  E0.88 INCH       TAMA               IA   LAW ENFORCEMENT



0614 PM     FLASH FLOOD      MARSHALLTOWN            42.04N 92.91W
06/30/2014                   MARSHALL           IA   TRAINED SPOTTER

            FAST MOVING WATER OF UNKNOWN DEPTH MOVING 
            DOWN AN ENTIRE CITY STREET 


0620 PM     HEAVY RAIN       W MANSON                42.53N 94.54W
06/30/2014  E2.80 INCH       CALHOUN            IA   TRAINED SPOTTER

            RAINFALL TOTAL FOR TODAY 

Environment

The overall environment was primed for a major severe weather event on the morning of June 30. A sharp upper-level shortwave trough was diving south as it rotated around its parent low in south central Canada. A 60-80 kt zonal jet stream existed upstream of this trough over South Dakota and Minnesota, with a 100 kt jet streak located over Minnesota (Fig. 1). Iowa was situated under the right-rear quadrant of this jet, an ideal location to maximize the synoptic, broad-scale lift provided by this jet streak. Ample low-level moisture was available for ingesting into the storms (850mb Fig. 2) while the 12Z Omaha sounding on June 30 (Fig. 3) revealed a deep elevated mixed layer (EML) from 800 to 600 mb. This pocket of dry air increased the surface-based CAPE (SBCAPE) of the sounding to over 4000 J/kg, more than ample instability to fuel thunderstorm development.

Figure 1: 300 mb Heights, Winds, and Divergence	Figure 2: 850 mb Heights, Temp, and Dewpoint	Figure 3: Omaha Sounding at 7:00am CDT on 6/30

The near-storm environment was just as potent as the synoptic environment. Wind shear throughout the lower to mid troposphere was quite strong, often times in the 50 to 60 kt range (Fig. 4). This change in wind speed/direction enabled the storms to maintain their organization over long periods of time, increasing their severity. The shear also led to updraft rotation in many of the storms which accelerated the growth of hailstones and can aid in tornado formation. Initially the storms were elevated, that is that the updrafts were ingesting instability based not at the surface, but potentially thousands of feet in the atmosphere. Many storms during the overnight and morning hours are elevated due to the presence of a nocturnal inversion. While the threat for damaging winds and tornadoes lessens with elevated storms, these cells can still be prolific hail producers. This was the case with the initial supercells that impacted the state (Fig. 5). Despite 2000-4000 J/kg of CAPE, the inversion was still in place (measured by convective inhibition, or CIN). However, as daytime heating commenced, the inversion at the surface was wiped out and the storms became rooted at the surface (Fig. 6), allowing for the onset of widespread damaging winds and tornadoes.

Figure 4: Effective Shear (kts) at 1:00pm CDT 6/30	Figure 5: Surface-Based CAPE at 11:00am CDT 6/30	Figure 6: Mixed-Layer CAPE at 1:00pm CDT 6/30

The tornadic environment also became more favorable as the late morning and early afternoon wore on. In addition to the storms becoming surface-based, the low-level helicity, a measure of the potential for updraft rotation (using sounding hodographs), increased from about 50 m2/s2 to 200 m2/s2 by 1:00pm CDT, around the time of the first tornado touchdown (Fig. 7). The lifted condensation level, or LCL, also fell to around 750 m in central Iowa by 1:00pm CDT (Fig. 8). Generally any values less than 1000 m are conducive for tornado development. At the time of the first tornado touchdown around 12:45pm CDT, the significant tornado parameter, which takes all of these aforementioned variables and more to determine the potential for a tornado, was pegged over southwest Iowa, almost precisely where the first tornado touched down (Fig. 9).

Figure 7: 0-1 km Helicity (m2/s2) at 1:00pm CDT 6/30	Figure 8: LCL Height (m) at 1:00pm CDT 6/30	Figure 9: Sig Tor Parameter (Eff) at 1:00pm CDT 6/30

By the mid afternoon, conditions had also become conducive for a widespread, damaging wind event. Values of Downdraft CAPE (DCAPE), which measures the potential negative buoyancy of a parcel, had exceeded 1000 J/kg out ahead of the developing bow echo (Fig. 10). The derecho composite parameter, which uses several variables to predict the likelihood of a widespread, damaging wind event, had risen quite high in the same locations out ahead of the storm (Fig. 11).

Figure 10: Downdraft CAPE (J/kg) at 1:00pm CDT 6/30	Figure 11: Downdraft CAPE (J/kg) at 1:00pm CDT 6/30

Additional Information

The Forecast

SPC Day 3 Categorical Outlook	SPC Day 3 Probabilistic Outlook	SPC Day 2 Categorical Outlook	SPC Day 2 Probabilistic Outlook
SPC Day 1 Categorical Outlook	SPC Day 1 Tornado Outlook	SPC Day 1 Hail Outlook	SPC Day 1 Wind Outlook