September 20, 2021

Library Series - "Tornadoes and Derechoes"

Library Series - "Tornadoes and Derechoes"

Some of you may already be aware, but for those who are not, one of my hobbies is collecting rare meteorological texts and manuscripts. I generally focus on original or rare publications in the severe convective storms space, but occasionally collect things in the space of general meteorology antiquities. Over the last year and a half I've taken this collection more seriously, finding signed first edition prints, rare out-of-print originals, and even off-prints and publishers copies of some important works. I thought it might be fun to have a space to share these fine additions to my collection, discuss the history and context in which they were written, and maybe even provide an opportunity to discuss how it shaped our current knowledge or even how our current knowledge has improved. I'm not sure with what frequency these will be conducted, but it's something different that will help carry me on through the long and dark winter months with no thunder.

So, without further adue, let's discuss this publication I found from world-renowned, multi-disciplinary scientist Dr. Gustavus Hinrichs.

Dr. Gustavus Hinrichs

Dr. Gustavus Hinrichs completed his education at the University of Denmark and later emigrated to Davenport, Iowa in 1860. He became a professor of natural philosophy, chemistry, and modern languages at the University of Iowa, and is remembered as one of the first people to discover the presence of periodic laws, the basis for the periodic table of elements. He presented his ideas as early as 1855, but it would be later scientists like Mendelev that would take the ideas to full fruition. Hinrichs's larger contributions, though arguably not as well known, were in the meteorological community. Dr. Hinrichs was the founder of the first ever state weather service in 1875, the Iowa Weather Service, and lead its operations until 1886. This act on its own is already hugely influential, as the Iowa Weather Service is considered one of the direct predecessors to the current U.S. National Weather Service that the U.S. Weather Bureau would eventually transition to. However, this isn't even his greatest contribution to the severe storms community; Dr. Hinrichs is responsible for identifying and coining the term we use for long-lived severe convective wind events: Derechoes.

Dr. Hinrichs was an enigmatic, abrasive, and controversial figure in his time, though undisputedly had a major impact on the field of meteorology. If you'd like to have a deeper understanding of his biography and contributions outside of the publication to be discussed below, the NOAA Storm Prediction Center has a rather comprehensive page about his life and contributions.

For now, we move on to discussing one of my favorite pieces of my collection: Tornadoes and Derechoes. This publication is incredibly hard to come by. In fact, I've only ever seen the one I have acquired. So if you are interested in reading it for yourself, there is a nice PDF scan of it available here.

Publication Context

The context in which Hinrichs published his research on Derechoes is actually rather fascinating, because it was written as a rebuke to the research of another defining scientist for our field: John Park Finley. We are going to spare a lengthy discussion of John Park Finley, as he's worth a post or two of his own (and don't worry - there will be more posts about works of his I've acquired), but if you aren't aware for some reason, John Park Finley is regarded as the very first scientist to properly study tornadoes and compile a climatology of their occurrence in the United States. Of particular relevance to this discussion is one of Finley's Signal Corp publications: "The Tornadoes of Iowa for 51 Years", in which Finley compiled a climatology of tornado events for the state. The opening paragraph of "Tornadoes and Derechoes" makes the feelings of Dr. Hinrichs on Finley's publication quite clear:

... according to the Signal Service authority, Iowa is credited with over a hundred tornadoes for this period of time [the 13 years of the Iowa Weather Service's activity]; but fortunately for our peoeple, a goodly number of these tornadoes have never existed outside of the archives and publications of the Signal Service, and a great many others were simulations. The real difficulty of writing on this subject consists in the fact that two radically different phenomena are described and officially catalogued under the name of tornado.

While the criticism of Finley errs on the side of harsh, it isn't entirely without merit, as the paper shows that a great many of Iowa's "tornadoes" were in fact long-lived straight-line wind events. Criticism of Finley was also the norm; he was widely criticized for "creating hysteria" because people believed he was inflating the number of actual tornado occurences, as they were believed to be quite rare. We now know that if anything, Finley was under-counting the number of tornado occurences given our improvements in observations and reporting of these events, but it does not change the fact that in this case, Hinrichs had rightfully identified an error in how the Signal Service was identifying tornadoes. So, it is with this background chaining of events that Hinrichs decided it was time to classify a new type of storm, giving us the term we use now, Derecho.

Derecho Observations

A comparison of the tornado track maps of John Park Finley (top) and Dr. Gustavus Hinrichs (bottom) from "Tornadoes and Derechoes" - 1888

The formal definition of a derecho given in this paper is a "straight blow of the paries", drawing from the root origin of the Spanish word "tornado" meaning "twister of the praries". Hinrichs made some remarkable observations about derechoes with relatively little data, describing them as downward rushes of cold air coming from the North-West. He also accurately observed that tornadoes were primarily a Springtime phenomena, with derechoes being more likely during the Summer. This is a trend we still see today and know to be true.

Dr. Hinrichs analyzed and cross-referenced many of the events Finley considered to be tornadic, and identified which ones were legitimate and which were actually Derecho events. As you can see from the compared analyses, many of the "tornado"tracks that were corrected have an East or South-East orientation, or were in general much longer than the tracks that turned out to be tornadoes. The tornado tracks follow a rather predictable Southwest-Northeast orientation, and are shorter in length.

We know nowaways that there can be an average of 1,400 tornadoes across the whole U.S. over the course of a year, and that Dr. Hinrichs's postulation that there couldn't be anywhere near as many tornadoes as Finley suggested is flat out wrong. However, Hinrichs did correctly identify a lack of thoroughness in Finley's method for identifying tornado events, casting doubt on the early tornado record he was compiling. Lets just say he spared no words in making sure his opinions of Finley were well known in the paper though.


So this has been the first entry into my collection of historical meteorological documents! I wanted to start with this one not only because of its uniqueness, but also because of the underlying scientific conversation and drama in which this publication was birthed. Its also fun to talk about because I'm not entirely sure how aware the community is on the origin of the term "derecho". At the very least, I was not aware of the history until I came across the opporunity to acquire this document! If you've enjoyed this at all and want me to continue to share more things like this, feedback here or on Twitter lets me know. Cheers.