On November 11, 1918, at 11 a.m., the armies of the First World War laid down their weapons on the western front. This moment has been symbolized in memory as "Armistice Day" in the Western world. After World War II, the name was broadened to "Remembrance Day" in countries outside the US, and "Veterans Day" in the United States. It is a day of remembrance and reflection for those who fought for the countries of the West.
In early November, Veterans Day can coincide with nasty weather events. One of the most famous events was in 1940 with the Armistice Day Blizzard that impacted parts of the Midwest. Tornadoes are uncommon to occur on Veterans Day, but they happened in Iowa. In 2015, Iowa experienced the largest November tornado outbreak on record as over a dozen tornadoes impacted the state's southern half.
THE SET-UP
For severe weather to occur, you need four ingredients: moisture, instability (energy), wind shear, and lift. In the cool season, moisture struggles to get as far north as Nebraska and Iowa, hence our lack of severe weather. Rarely do we get enough moisture and warmth this far north, combined with the other ingredients to see severe weather. This is best exemplified on December 15, 2021, when a major tornado outbreak and windstorm occurred.
As for Veterans Day 2015, all four ingredients were present in southern Iowa. Temperatures by the afternoon rose into the 60s and even a few 70s near the Missouri border. Dew points, the measure of moisture in the air, reached the mid to upper 50s. In Spring, any dew point over 60 is adequate for severe weather. In the cool season, dew points above 50 suffice. Therefore, moisture was present. As the air above the air turned sharply colder, it added a lot of instability or energy to the atmosphere.
In terms of wind shear, there was an abundance of that. A powerful low-pressure system was lifting northeast from Colorado into Iowa. This storm system packed a punch with a big snowstorm in the Rocky Mountains, and strong winds up to 45 mph for much of the Midwest. In the "warm sector" thunderstorms erupted in eastern Nebraska and expanded into Iowa and northern Missouri. These storms brought widespread damaging winds and several tornadoes.
THE TORNADOES
November 11, 2015, was the epitome of "if you don't like the weather, wait a few minutes". Around mid-morning in the Omaha metro, a strong thunderstorm brought heavy rain and small hail. It stormed through the rest of the morning, but the afternoon was just windy. By the evening, temperatures crashed from the 50s in Omaha to the 30s. It got cold enough for the rain to change to snow, coating grassy surfaces and vehicles.
As the mid-morning storms moved into western Iowa, hail was still a concern. One storm in Cass County, NE produced 1.75" hail near Plattsmouth. Then the tornadoes began. The first one began in northern Pottawattamie County, west of Avoca. Minor damage was done to a grain bin before the tornado crossed I-80. As it did so, it picked up a tractor-trailer heading eastbound and hurled it across the median, setting it down on the westbound lanes. Thankfully, the driver was not injured. The tornado continued into Shelby County where farmsteads, outbuildings, and trees suffered damage. The final act of the tornado was crossing over the Harlan Municipal Airport, where a 76 mph wind gust was recorded on the weather station, the tornado lifted just north of the airport doing no major damage to the facility. The Avoca-Harlan tornado was rated an EF-1 with wind speeds up to 110 mph.
Tornadic activity increased as the storms approached the US-71 corridor. Storm chasers documented a brief tornado in Page County east of Shenandoah, but it did no damage. In Carroll County, an EF-0 tornado created scar marks in a field between Manning and Templeton. In Cass County, a potential tornado snapped trees northwest of Cumberland. Down in eastern Taylor County, an EF-1 tornado clipped the northwest side of Clearfield, then continued another 15 miles before lifting south of Creston.
As the storms neared Des Moines, tornadoes became more frequent. Tornadoes impacted the areas around Mount Ayr near the Missouri border, Winterset southwest of Des Moines, and Adel west of Des Moines. An EF-0 tornado hit the Des Moines International Airport, causing minor damage. Southeast of Des Moines, an EF-1 hit Knoxville where one person was injured. The strongest tornado of the day, an EF-2, crossed over Rathbun Lake and severely damaged multiple homes north of the lake. Another EF-2 occurred between Des Moines and Iowa City.
Into eastern Iowa, the storms produced more damaging winds than tornadoes. A few more tornadoes did come, however. One of which impacted the northeast suburbs of the Quad Cities. As the storms crossed into Illinois, they began to weaken and dissipate.
In total, 19 tornadoes occurred in Iowa, with many more likely but not rated. Damage estimates range in the 3-5 million dollar range, mainly to homes and businesses. Thankfully, no one was killed in the tornadoes, which is the best statistic of all.
