# Iowa tornado outbreak of July 2018

On July 19 and 20, 2018, an unexpected strong tornado outbreak affected Iowa and nearby areas. The event was triggered mostly by three supercells that produced several tornadoes across southeastern Iowa east and southeast of Des Moines. Two of the tornadoes reached EF3 intensity, affecting Pella and Marshalltown. These were the strongest tornadoes to hit Iowa since June 22, 2015, when another EF3 tornado struck near Lovilia. Of the 37 injuries, 13 occurred in Pella, and 23 in Marshalltown, and one the following day in Indiana. The event was also notable due to the Table Rock Lake duck boat accident that killed 17 people and injured 7 others at Table Rock Lake, Missouri.

## Meteorological history

The tornado outbreak as well as the other the severe weather that day was either poorly forecasted or essentially unforecasted; the outlook from the Storm Prediction Center that day had much of eastern Iowa under a 2% risk area for tornadoes. This was due to an inaccurate analysis of a closed low over the northern part of the state . At the time, the low was analyzed as being closed at the 500 mb level. However, reanalysis of the event revealed that the low was closed at only 700 mb. As the event began, several weak supercells formed over central Iowa and moved eastward, producing multiple weak tornadoes. However, one supercell produced two simultaneous EF2 tornadoes in Bondurant. Shortly afterwards, a tornado watch was issued for the region from 3:10–10 pm CDT. However, a significant tornado outbreak was still not expected as the threat for tornadoes was only increased to 5% at the 20:00 UTC outlook, indicating the threat of only a couple of tornadoes. At 21:00 UTC on July 19 (4 pm CDT), a large Storm-Relative Helicity (SRH) and low level wind shear was reported across the region. The dewpoints were also in the 70s°F (20s°C), which is moist for this type of event. Around this time, the southern-most storm evolved into a large tornadic supercell and moved southeastward, producing several tornadoes, including an EF3 tornado that passed near Pella. The Bondurant supercell, then weakened, but another strong supercell developed to its north and absorbed it as it moved eastward. Fueled by an interaction with an outflow boundary from the southern supercell, the storm produced a large, wedge EF3 tornado that directly struck the town of Marshalltown. Afterwards, the northern supercell and the storms north of it weakened, but the southern supercell continued southeastward and eventually transitioned into a small squall line.
As the system trekked eastwards into July 20, damaging winds and hail became the main threat, with a 30% chance of strong wind across much of Arkansas, Tennessee and Kentucky, and a 45% chance of damaging hail across central Tennessee and Kentucky. However, a 10% tornado risk was also issued for western Tennessee and eastern Kentucky, with the threat of tornadoes stretching from western Arkansas to southern Michigan. An EF1 tornado in Indiana caused an injury to a camper, who was flipped over. However, that was the only casualty, as no tornadoes that day were stronger than EF1 intensity.

## Confirmed tornadoes

Confirmed tornadoes by Enhanced Fujita rating :
| EFU | EF0 | EF1 | EF2 | EF3 | EF4 | EF5 | Total |
| 1 | 16 | 6 | 2 | 2 | 0 | 0 | 32 |

### July 19 event

List of confirmed tornadoes – Thursday, July 19, 2018 :
| EF# | Location | County / Parish | State | Start Coord. | Time (UTC) | Path length | Max width | Summary |
| EF0 | WNW of Ceylon | Martin | MN | 43°32′N 94°40′W﻿ / ﻿43.54°N 94.67°W﻿ / 43.54; -94.67﻿ (Ceylon (Jul. 19, EF0)) | 17:45–17:56 | 0.21 mi (0.34 km) | 10 yd (9.1 m) | A tornado was reported in the area with trees downed. |
| EF0 | S of Clarion (1st tornado) | Wright | IA | 42°38′45″N 93°47′47″W﻿ / ﻿42.6457°N 93.7965°W﻿ / 42.6457; -93.7965﻿ (Clarion (Jul. 19, EF0)) | 19:30–19:37 | 3.5 mi (5.6 km) | 80 yd (73 m) | A tornado damaged crops. |
| EF0 | S of Clarion (2nd tornado) | Wright | IA | 42°34′45″N 93°46′44″W﻿ / ﻿42.5791°N 93.7789°W﻿ / 42.5791; -93.7789﻿ (Clarion (Jul. 19, EF0)) | 19:35–19:47 | 4.43 mi (7.13 km) | 80 yd (73 m) | A tornado was photographed to the south of Clarion. Only crop damage occurred. |
| EF0 | NE of Woolstock | Wright | IA | 42°34′50″N 93°42′46″W﻿ / ﻿42.5806°N 93.7128°W﻿ / 42.5806; -93.7128﻿ (Woolstock (Jul. 19, EF0)) | 19:42–19:45 | 1.28 mi (2.06 km) | 60 yd (55 m) | High-resolution satellite imagery confirmed a tornado over agricultural areas. |
| EF0 | Northeastern Ankeny | Polk | IA | 41°44′22″N 93°34′24″W﻿ / ﻿41.7394°N 93.5732°W﻿ / 41.7394; -93.5732﻿ (Ankeny (Jul. 19, EF0)) | 19:48–19:49 | 0.88 mi (1.42 km) | 50 yd (46 m) | Several trees, fencing, and pieces of playground equipment were damaged by this weak tornado. |
| EF2 | N of Bondurant | Polk | IA | 41°43′29″N 93°29′42″W﻿ / ﻿41.7246°N 93.4951°W﻿ / 41.7246; -93.4951﻿ (Bondurant (Jul. 19, EF2)) | 19:50–20:02 | 3.68 mi (5.92 km) | 130 yd (120 m) | This low-end EF2 tornado occurred simultaneously with the tornado below. A well-built metal outbuilding had most of its roof removed and sustained collapse of two walls. Numerous trees were snapped or uprooted, and severe crop damage occurred along the path. |
| EF2 | Bondurant | Polk | IA | 41°42′03″N 93°30′13″W﻿ / ﻿41.7008°N 93.5037°W﻿ / 41.7008; -93.5037﻿ (Bondurant (Jul. 19, EF2)) | 19:51–20:00 | 2.95 mi (4.75 km) | 100 yd (91 m) | A low-end EF2 tornado moved through residential areas in Bondurant. One home had its second story blown off, a few homes had major roof damage, and other homes sustained less severe damage. An unanchored detached garage was swept away, and vehicles were overturned as well. |
| EF0 | W of Story City | Story | IA | 42°10′22″N 93°39′33″W﻿ / ﻿42.1727°N 93.6592°W﻿ / 42.1727; -93.6592﻿ (Story City (Jul. 19, EF0)) | 19:52–19:57 | 2.07 mi (3.33 km) | 40 yd (37 m) | This rope tornado remained over open country, causing only crop damage. |
| EF0 | N of Blairsburg | Hamilton | IA | 42°29′19″N 93°39′22″W﻿ / ﻿42.4887°N 93.656°W﻿ / 42.4887; -93.656﻿ (Blairsburg (Jul. 19, EF0)) | 19:56–20:05 | 2.67 mi (4.30 km) | 60 yd (55 m) | A weak tornado north of Blairsburg damaged crops. |
| EF0 | NW of Prairie City | Jasper | IA | 41°37′45″N 93°20′02″W﻿ / ﻿41.6293°N 93.334°W﻿ / 41.6293; -93.334﻿ (Prairie City (Jul. 19, EF0)) | 20:18–20:24 | 2.35 mi (3.78 km) | 60 yd (55 m) | This was the first tornado produced by the Pella supercell. It remained over open farm fields, causing no damage. |
| EF0 | NE of Roland | Story | IA | 42°10′44″N 93°29′08″W﻿ / ﻿42.1789°N 93.4856°W﻿ / 42.1789; -93.4856﻿ (Roland (Jul. 19, EF0)) | 20:22–20:30 | 2.79 mi (4.49 km) | 60 yd (55 m) | High-resolution satellite imagery confirmed a tornado with damage to crops. |
| EF0 | SE of Prairie City | Jasper | IA | 41°34′23″N 93°13′07″W﻿ / ﻿41.573°N 93.2186°W﻿ / 41.573; -93.2186﻿ (Prairie City (Jul. 19, EF0)) | 20:28–20:34 | 2.62 mi (4.22 km) | 80 yd (73 m) | This was the second tornado produced by the Pella supercell. Crops and trees were damaged along the path. |
| EF0 | NE of Collins | Story | IA | 41°55′13″N 93°18′01″W﻿ / ﻿41.9202°N 93.3002°W﻿ / 41.9202; -93.3002﻿ (Collins (Jul. 19, EF0)) | 20:35–20:40 | 2.48 mi (3.99 km) | 40 yd (37 m) | High-resolution satellite imagery confirmed a tornado with damage to crops. |
| EF1 | E of Monroe | Jasper, Marion | IA | 41°31′43″N 93°03′51″W﻿ / ﻿41.5286°N 93.0643°W﻿ / 41.5286; -93.0643﻿ (Monroe (Jul. 19, EF1)) | 20:45–20:52 | 3.96 mi (6.37 km) | 500 yd (460 m) | This was the third tornado produced by the Pella supercell. A machine shed lost a small part of its roof, and trees and crops were damaged. |
| EF0 | E of Otley | Marion | IA | 41°28′31″N 92°58′48″W﻿ / ﻿41.4752°N 92.9801°W﻿ / 41.4752; -92.9801﻿ (Otley (Jul. 19, EF0)) | 20:56–20:58 | 0.99 mi (1.59 km) | 40 yd (37 m) | A brief tornado caused little to no damage. |
| EF3 | Eastern Pella | Marion | IA | 41°27′37″N 92°56′14″W﻿ / ﻿41.4602°N 92.9371°W﻿ / 41.4602; -92.9371﻿ (Pella (Jul. 19, EF3)) | 21:01–21:24 | 9.17 mi (14.76 km) | 800 yd (730 m) | The fourth produced by the Pella supercell, this large cone tornado clipped the eastern edge of Pella, causing major structural damage to large factory buildings at the Vermeer plant complex. Reinforced masonry exterior walls were bowed in and collapsed at this location, metal support beams were severely bent, and large amounts of roofing was peeled from the buildings and scattered. Numerous vehicles, semi-trailers, and pieces of machinery were thrown and mangled at the plant, some of which were found piled atop each other and wrapped in sheet metal. Outside of town, barns were destroyed and a wide swath of corn was flattened in farm fields. A two-story farm home was shifted off of its foundation, and an addition to the south side of the house was destroyed. A few other homes sustained less severe damage. Thirteen people were injured. |
| EF0 | E of Clemons | Marshall | IA | 42°06′16″N 93°08′00″W﻿ / ﻿42.1045°N 93.1332°W﻿ / 42.1045; -93.1332﻿ (Clemons (Jul. 19, EF0)) | 21:11–21:13 | 0.85 mi (1.37 km) | 40 yd (37 m) | High-resolution satellite imagery confirmed a tornado with damage to crops. The same storm produced the EF3 Marshalltown tornado. |
| EF0 | NE of Pella | Mahaska | IA | 41°25′08″N 92°51′26″W﻿ / ﻿41.4188°N 92.8571°W﻿ / 41.4188; -92.8571﻿ (Pella (Jul. 19, EF0)) | 21:15–21:18 | 1.16 mi (1.87 km) | 60 yd (55 m) | A satellite tornado to the Pella EF3 tornado damaged crops. This was the fifth tornado produced by the Pella supercell. |
| EF3 | Marshalltown | Marshall | IA | 42°04′58″N 93°01′39″W﻿ / ﻿42.0829°N 93.0275°W﻿ / 42.0829; -93.0275﻿ (Marshalltown (Jul. 19, EF3)) | 21:24–21:47 | 8.41 mi (13.53 km) | 1,200 yd (1,100 m) | A large and intense multiple-vortex wedge tornado moved directly through downtown Marshalltown, prompting the issuance of a tornado emergency and causing widespread major damage. Numerous brick businesses in the downtown area were severely damaged, some of which sustained total destruction of their upper floors. Streets in this area were littered with bricks and structural debris, and the Marshall County Courthouse had the top portion of its clock tower ripped off. A large office building had much of its facade ripped off, and sustained loss of exterior walls on multiple floors. Homes in residential areas of town were heavily damaged and a few were destroyed, along with numerous vehicles and detached garages. A Lennox International plant had significant roof loss and collapse of multiple reinforced exterior walls, with many cars tossed and damaged in the parking lot. Numerous trees, light poles, signs, and power poles were downed throughout the town as well. Twenty-three people were injured. |
| EF0 | S of Oskaloosa | Mahaska | IA | 41°13′43″N 92°36′37″W﻿ / ﻿41.2285°N 92.6102°W﻿ / 41.2285; -92.6102﻿ (Oskaloosa (Jul. 19, EF0)) | 21:50–21:53 | 1.24 mi (2.00 km) | 60 yd (55 m) | High-resolution satellite imagery confirmed a tornado with damage to crops. This was the sixth tornado produced by the Pella supercell. |
| EF1 | NNE of Keosauqua (1st tornado) | Van Buren | IA | 40°48′11″N 91°58′12″W﻿ / ﻿40.803°N 91.9699°W﻿ / 40.803; -91.9699﻿ (Keosauqua (Jul. 19, EF1)) | 23:07–23:15 | 2.14 mi (3.44 km) | 50 yd (46 m) | A large historic stone barn was destroyed. Trees, a corn field, and a small farm outbuilding were damaged. This was the seventh tornado produced by the Pella supercell. |
| EF1 | NNE of Keosauqua (2nd tornado) | Van Buren | IA | 40°44′54″N 91°57′24″W﻿ / ﻿40.7482°N 91.9567°W﻿ / 40.7482; -91.9567﻿ (Keosauqua (Jul. 19, EF1)) | 23:09–23:11 | 0.19 mi (0.31 km) | 75 yd (69 m) | Several large farm outbuildings and equipment were destroyed. Corn crops were damaged. This was the final tornado produced by the Pella supercell. |

### July 20 event

List of confirmed tornadoes – Friday, July 20, 2018 :
| EF# | Location | County / Parish | State | Start Coord. | Time (UTC) | Path length | Max width | Summary |
| EF0 | NW of Camdenton | Camden | MO | 38°04′N 92°52′W﻿ / ﻿38.07°N 92.87°W﻿ / 38.07; -92.87﻿ (Camdenton (Jul. 20, EF0)) | 09:32–09:33 | 0.12 mi (0.19 km) | 75 yd (69 m) | Numerous trees were uprooted and tree limbs were snapped. Power lines were downed as well. |
| EF0 | SW of Bremen | Marshall | IN | 41°22′56″N 86°13′11″W﻿ / ﻿41.3823°N 86.2197°W﻿ / 41.3823; -86.2197﻿ (Bremen (Jul. 20, EF0)) | 17:53–17:55 | 0.5 mi (0.80 km) | 50 yd (46 m) | A barn sustained damage to its cinder block exterior wall, corn was flattened, and some tree branches were broken. |
| EF0 | WNW of Wautoma | Waushara | WI | 44°03′45″N 89°15′06″W﻿ / ﻿44.0624°N 89.2517°W﻿ / 44.0624; -89.2517﻿ (Wautoma (Jul. 20, EF0)) | 17:55–17:56 | 0.08 mi (0.13 km) | 10 yd (9.1 m) | A small tornado snapped branches off of several pine trees and tossed them into the air. |
| EF0 | N of Salem | Washington | IN | 38°38′01″N 86°06′34″W﻿ / ﻿38.6336°N 86.1095°W﻿ / 38.6336; -86.1095﻿ (Salem (Jul. 20, EF0)) | 18:03–18:05 | 1.1 mi (1.8 km) | 75 yd (69 m) | A weak and intermittent tornado downed a few tree limbs and small fences. Multiple metal roof panels were ripped from a barn, while its overhead garage doors were blown in and the entrance door was ripped off. A house sustained considerable damage to its siding and roof, a small play shed was destroyed, and corn was flattened in a field. |
| EF1 | S of Corydon | Harrison | IN | 38°09′10″N 86°09′00″W﻿ / ﻿38.1527°N 86.1501°W﻿ / 38.1527; -86.1501﻿ (Corydon (Jul. 20, EF1)) | 18:04–18:20 | 6 mi (9.7 km) | 250 yd (230 m) | A multiple-vortex tornado impaled a wooden two-by-eight plank into a concrete grain silo, extensively damaged four large barns, and caused significant tree damage. One tree fell on a garage, several homes sustained substantial roof damage, a pole barn was completely destroyed, and a truck and horse trailer was twisted and moved 50 ft (15 m). Corn crops were flattened, a camper was tossed and flipped over, and single-wide trailers were flipped over as well. |
| EF0 | N of La Fontaine | Wabash | IN | 40°43′41″N 85°43′05″W﻿ / ﻿40.7281°N 85.7180°W﻿ / 40.7281; -85.7180﻿ (La Fontaine (Jul. 20, EF0)) | 19:14–19:15 | 0.8 mi (1.3 km) | 25 yd (23 m) | A brief tornado ripped the roof from an outbuilding and snapped or uprooted trees. |
| EF1 | Moonville | Madison | IN | 40°11′43″N 85°36′41″W﻿ / ﻿40.1954°N 85.6115°W﻿ / 40.1954; -85.6115﻿ (Moonville (Jul. 20, EF1)) | 19:50–19:52 | 0.6 mi (0.97 km) | 30 yd (27 m) | A barn was destroyed, a storage shed was flipped onto its side, and trees in town were damaged. |
| EF0 | ESE of Sweetwater | Miami-Dade | FL | 25°45′39″N 80°21′44″W﻿ / ﻿25.7608°N 80.3623°W﻿ / 25.7608; -80.3623﻿ (Sweetwater (Jul. 20, EF0)) | 20:22–20:24 | 0.19 mi (0.31 km) | 20 yd (18 m) | Trees, mailboxes, street signs, canopies, and basketball hoops all sustained minor damage from a brief tornado that eventually became a waterspout over a large retention pond before lifting. |
| EF0 | SE of Edmonton | Metcalfe | KY | 36°57′41″N 85°35′35″W﻿ / ﻿36.9614°N 85.5931°W﻿ / 36.9614; -85.5931﻿ (Edmonton (Jul. 20, EF0)) | 23:03–23:05 | 2.1 mi (3.4 km) | 60 yd (55 m) | A carport was overturned and two metal outbuildings lost roofing material. A double-wide mobile home was shifted off its foundation, with its windows broken and shingles ripped from the roof. Numerous trees were snapped. |
| EF1 | NE of Priceville | Hart | KY | 37°23′24″N 85°56′39″W﻿ / ﻿37.39°N 85.9443°W﻿ / 37.39; -85.9443﻿ (Priceville (Jul. 20, EF1)) | 02:56–02:59 | 1.2 mi (1.9 km) | 60 yd (55 m) | A large barn and several large hay bales were destroyed. Numerous trees were snapped along the path. |

## Non-tornadic effects

As part of the storm system as a whole, a duck boat tour sank in Table Rock Lake, Missouri, at approximately 7 pm CDT. Of the 31 people on board, 17 of them died and 7 were injured. Nine of them were in a single family. Wind gusts were reportedly in excess of 60 miles per hour (97 km/h). A wind gust in Branson, Missouri reached 74 miles per hour (119 km/h).

## Impact and aftermath

Pella had 14,000 power outages while Bondurant, which got hit by an EF2 tornado, had 1,800 outages. Despite the damage and injuries, though, no one died due to tornadoes, which is likely credited to timely warnings once the tornadoes actually did touch down. Following these tornadoes, several counties in Iowa were declared disaster zones by Kim Reynolds. Marsalltown would suffer even more destruction just over two years later when a powerful derecho produced widespread destruction across the city. Several buildings in downtown Marshalltown were condemned and demolished in the following years as a result of both storms.