State Climatologist Dr. Justin Glisan

Iowa Press | Episode
Jun 28, 2024 | 27 min

On this edition of Iowa Press, Dr. Justin Glisan, state climatologist of Iowa, discusses recent flooding and major weather events, drought relief and other climate issues impacting Iowa.

Joining moderator Kay Henderson at the Iowa Press table will be Dave Price, Iowa political director for Gray Television, and Linh Ta, reporter for Axios Des Moines.

Program support provided by: Associated General Contractors of Iowa and Iowa Bankers Association.



A wet spring and summer finally brought drought relief, but now devastating flooding. We'll talk about this year's severe weather with state climatologist Dr. Justin Glisan on this edition of Iowa Press.


Funding for Iowa Press was provided by Friends, the Iowa PBS Foundation.

The Associated General Contractors of Iowa, the public's partner in building Iowa's highway, bridge and municipal utility infrastructure.

Elite Casino Resorts is rooted in Iowa. Elite's 1,600 employees are our company's greatest asset. A family run business, Elite supports volunteerism, encourages promotions from within, and shares profits with our employees.

Across Iowa, hundreds of neighborhood banks strive to serve their communities, provide jobs and help local businesses. Iowa Banks are proud to back the life you build. Learn more at


For decades, Iowa Press has brought you political leaders and newsmakers from across Iowa and beyond. Celebrating 50 years of broadcast excellence on statewide Iowa PBS, this is the Friday, June 28th edition of Iowa Press. Here is Kay Henderson.


Henderson: What is that old saying? Water, water everywhere and none of it to drink? Some of our fellow Iowans are living that reality right now. Our guest today is able to talk about the weather phenomenon that they are living through and what we lived through I guess for the past six months. Our guest is state climatologist Justin Glisan. He started the role in 2018 and this is his fifth appearance on the program to talk weather, which Iowans love to do. Welcome back to Iowa Press.

Glisan: Always great to be here. Thanks, Kay.

Henderson: Also joining the conversation are Dave Price of the Gray Television stations in Iowa and Linh Ta of Axios Des Moines.

Ta: It felt like a roller coaster of a year for Iowans in terms of severe weather. Can you just take us back to what all has happened starting in January?

Glisan: Yes. So, great question. My middle name is average as a climatologist and we have been above and below average. You look at the severe weather season that we've had, 116 tornados, and we average about 44 per year. You think of Greenfield with the high end EF4 that we saw. DOW, Doppler on Wheels sampled over 300 mile per hour winds in that tornado. You think of the hail and high wind events also. The setup that we've been in has been a drought buster though. With all these thunderstorms, we've seen record amount of rainfall, particularly in spring, but also in May, the sixth wettest May on record, eighth wettest spring on record. You look year to date, we're about halfway through the year, very wet conditions, some of the wettest starts that we've seen in 152 years of records.

Henderson: Was that snow event that we had in January sort of a harbinger?

Glisan: That's a great question. I haven't thought about it. That was the only snow event that we had, the second warmest winter on record. Again, 152 years of records. Around the Caucuses we had that epic amount of snow pack, actually insulated the surface, didn't allow that Arctic air to get down very deep so the frost level really wasn't there. Why that's important is all the snow melt that we got infiltrated into the profile and then the rainfall that started to come into play early spring was able to soak in, hence we start to see drought conditions being removed across the state after 204 weeks of consecutive drought.

Price: A couple of weeks ago we had gone through a stretch, it seemed like every day we had some severe weather. And I was telling the kids about, oh it may get a little funky tonight. And my daughter is eight and a half and she said, does that mean we're going to sleep in the basement again? As you look more broadly at this, is this a funky blip we're in? Or is this some kind of extended thing that we need to realize is more semipermanent?

Glisan: I'm a basement dweller as a kid because I was scared to death of severe weather. Hence why I'm here. And we've talked about this on previous episodes. But this looks like a blip. You have to go back to 2011 to see severe weather of this magnitude and that was another wet start to a year, then we get back into the 2012 drought. So, it's always difficult to forecast what kind of severe weather we're going to have in a given season. But the initial outlooks that we saw seasonally for spring in winter were showing a higher probability of warmer and wetter conditions. When you're getting into the growing season and the warmer time of year, those are the two signals for thunderstorms. And hence what those thunderstorms a pretty anomalous severe weather season so far. June is our top tornado month. We've only had seven. But 116 tornados is distressing, but it looks like it could be a blip. Now, if we look at the climate model getting out several decades, in that April, May, June timeframe, we are seeing the ingredients come together more often to support severe weather, at least in the spring, kind of ebbing off in summertime. So, those are the types of trends that we monitor across the state.

Price: So, are we at the end of the blip for now?

Glisan: I won't say no. You look at the outlooks getting into the middle of July, still an elevated warm and wet signal, so more thunderstorms, seven day forecast for precipitation one to three inches across the state, changes of severe weather later today and maybe next week as well.

Henderson: For the benefit of our viewers, we are having this conversation at about one o'clock on Friday afternoon. So, things may change.

Glisan: Absolutely.

Ta: Back in 2019, towns along the Missouri River in Western Iowa dealt with flooding. There were repairs and improvements made to the levees along there. But this year we're seeing issues again in places like Rock Valley with the levees. What do you say to people who are living in these towns who are dealing with this over and over again?

Glisan: Right. So, first, our hearts go out to the people that are impacted. We've had fatalities with this flooding, fatalities in Greenfield, terrible loss of life. What we like to tell people is the infrastructure that we have built is not built for what we're seeing precipitation wise. You look at 2019 with the bomb cyclone and epic flooding along the Missouri Basin, all of the corps’ levees south of Council Bluffs were damaged or destroyed. Those have since been rebuilt. But we're squeezing water down the system. And the infrastructure, you look at urban infrastructure, can't keep up with these higher intensity rainfall events. Warmer atmosphere holds more water vapor, but it also takes more water vapor loading to produce a meteorological event. But when you do, instead of getting these historic quarter inch, half an inch over 24 to 48 hours, you're getting an inch, two, three inches. Our systems can't keep up with that type of behavior. And we're only seeing that behavior increase into the future.

Price: Many of us have friends and family on the coast, California, Florida. In those states in particular they are starting to deal with, sometimes they can be tough to get insurance anymore because of these severe situations here. Do we have to be concerned enough -- maybe to piggyback off her question about the levees -- I remember I grew up in the St. Louis area and in the floods of '93 we had a town that essentially just shut down. And there have been pockets in our state that have largely done that as well. Do we have to prepare for that for some of these river towns?

Glisan: I think so. I'm also from St. Louis, St. Charles. I remember vividly watching on the news as a bulldozer went through a levee to release water from farmland. With these higher amounts of precipitation at a faster rate on top of saturated soils from a record wet start to the year, flooding is forecasted, that's what we see. And then you're adding more rainfall on top of it. But you take all of these, what we're seeing universally, and you project those out into the future, we're only going to see increases in the amount of precipitation that we're going to see across the Upper Midwest. Why that's important is Iowa has the distinction of having two of the most, largest rivers in the northern hemisphere as our borders. 10% to 15%, 20% increase in precipitation over the next several decades, flooding.

Henderson: So, let's talk about predicting. How difficult is it for, in this case the National Weather Service, to issue predictions about when those two rivers are going to crest and all of the rivers that are in between the Missouri and the Mississippi?

Glisan: So, we have United States Geological Survey stream gauges within the basins that collect the water that falls meteorologically. We have National Weather Service hydrologists that do an excellent job with their water models to see how fast or slow this water is going to move through the system. Then you couple that with the quantitative precipitation forecast or the amount of rainfall that we're expecting over the next seven days, plug that into the modeling, it gives us a very good idea. Now, it's not written in stone, but the hydrological forecast that we do, similar to the forecast you see for weather on the news, are pretty good. And we get daily updates on those river levels and how the crest is occurring.

Henderson: I've heard it's easier though to predict the snow melt as opposed to rainfall.

Glisan: Well, I don't want to teach grad school but --

Henderson: Okay, this is not a credit course.

Glisan: Okay. The modeling that we use, a couple of models, meteorological, land surface model, we have snow models, we have sea ice models, we have oceanographic models. All of these plug into an interface that kind of solves the equations, the primitive equations that we use to produce forecasts. You think about the severe weather that we've had over the season, the storm prediction center has done a particularly good job on getting these outbreaks four to five days out. So, this shows you the power of the modeling that we have. And when the models are keyed in on specific meteorological variables, they do an excellent job.

Price: I went to Greenfield for a couple of days after that tornado hit and I talked -- it's kind of a thing for people to always rip on the weather person, right, oh they never get it right and whatever. It was remarkable how many people brought up the early warning of the tornado there and how folks there were warned so early they dismissed school early so they brought these kids home on the buses and they were already back home when they would have been on the buses when this awful storm hit. Can you talk about that process, maybe the post after a tornado hits, what you learned from that and then how that then helps the next storm by forecasting early, predicting early?

Glisan: Yeah, we talk about lead time. Can you imagine that Greenfield tornado going through without those schools being dismissed? It sends shivers down my spine. 30-to-40-minute lead time on that tornado. I was watching storm chasers following the tornado. The National Weather Service pinned it down in Omaha and Des Moines and got those lead times out. We've been increasing lead time for tornados and severe weather events over the last 20, 30 years after the Twister generation started to go to college. These models are very good when they are keyed in. We also had those Doppler on Wheels in Greenfield that were sampling the tornado couplet. So, with the five people that we lost in Greenfield, it's always hard to lose people, but the science that we're going to get out of it I really think is going to move us forward in terms of enhanced lead times and even predicting these types of tornados further out.

Price: Can you explain how, how when you look at the aftermath does that help you predict it sooner the next time?

Glisan: Well, we -- so the sampling of the data, you can parameterize the scale models, the smaller scale models that can predict thunderstorms that produce tornados, particularly super cells. So, if you're sampling these super cells and getting pressure, temperature, moisture, all of those different parameters that go into building a super cell, then you're more knowledgeable about the mechanisms in physics and thermodynamics that caused them, then you're able to build a better model to mimic those types of events. And that is where we've really been leaps and bounds in terms of the computing power that we have with all the data that we're getting. Now introduce artificial intelligence, we might see a leap in that as well.

Price: That's why he was a professor at Iowa State obviously.

Henderson: Exactly. You mentioned 300 miles an hour. How would that rank the Greenfield tornado?

Glisan: That would be above EF5. Now, the sampling of 318 miles per hour right now preliminarily the second strongest tornado on record. That 318 mile per hour wind was about 160 feet up. So, surface drag, things at the surface, tamped down wind speed and that's why you see higher end EF4 damage. But definitely with 300 mile per hour plus winds that's hard to fathom.

Henderson: In the continental United States or in the world?

Glisan: The world.

Henderson: Wow.

Ta: We dealt with 204 consecutive weeks of drought and then finally at the end of May we got out of it. But at this point, how easy could it be to go back into drought in the state?

Glisan: So, you look at that southeastern corner of the state currently still in D0, which is abnormal dryness, more a reflection of 30-to-60-day dryness. I will say if this forecast verifies over the next seven days, we could see some removal of that D0. But you look at the longer-term implications of almost four years of drought, our aquifers have been somewhat depleted where we pull water from for drinking. Agricultural soil moisture profiles are near where they should be for this time of year. As we increase vegetative demand though, as we get into warmer temperatures, we're starting to see more atmospheric thirst. If we go get into a dry stretch in July or August, that's where we could back slide into drought again. But right now, with the amount of water that we have on our landscape I don't foresee that right now.

Price: Can I ask an old man question? Back in my day I don't remember it being windy like this every day and it feels like every stinking day it is windy. Is this real or are we remembering this wrong?

Glisan: That's a great question, Dave, I get it a lot. There is a psychological component to that. We've had five to six derechos across the state. April is the windiest month climatologically. But with all these thunderstorms we've also seen more wind because of the pressure gradient and temperature gradient. You look at the amount of CO2 in the atmosphere. More CO2, that is fuel for plant life. So, I read an interesting study in nature in which with more CO2, more green up faster, we're actually decreasing the amount of surface wind that we're seeing. But where we are seeing an increase in wind is aloft, basically let's say hub height for our turbine farms. So, meteorology is the study of equilibrium. If you slow down winds at the surface, they have to speed up somewhere else and that's what we're seeing. That's one study. But there is some science behind that we're seeing less windy days but they're becoming higher up.

Henderson: You mentioned 1993. We're sitting in a metropolitan area that lost its drinking water because all of the water sort of came downstream. What should other communities in the state be doing? Because there's still torrential rain happening all over the state.

Glisan: The forecast from the National Weather Service in terms of meteorological forecast but also the hydrological forecast that you brought up earlier, those are an excellent indicator of the potential of river cresting because that water slowly moves down the system. But if you get rainfall on top of that, of course it's going to impact the crest. You can have a double crest. You look at the Little Sioux, the Big Sioux, the West Fork of the Des Moines River, above 1993 levels, that water is moving south. Luckily you think about Saylorville Dam, Lake Red Rock, those are reservoirs built to help protect urban areas and rural parts of the state. So, we're not seeing a broad scale red flag in terms of this. But if we stay in a wet pattern, and this is going to sound counterintuitive, the Iowa Drought Plan, we have trigger tables in there that discuss when we get into various levels of drought. We also can use those to look at the levels of wetness, particularly soil moisture. If we have infiltration of the soil moisture and it gets saturated, we're much more prone to runoff and flooding.

Henderson: You mentioned aquifers. The legislature set aside a quarter of a million dollars to start the process of mapping the aquifers. I don't believe you’re directly involved in that. But what value would a map of the underground aquifers be?

Glisan: So, I'm a data nerd, so a map of anything is right down my alley. Having an idea of the amount of water in an aquifer, if you go through an extended period of drought, the longest drought since 1954 to 1959, we need to know how much moisture is down deep and how much we've taken out of those aquifers. That also gives us an idea of if we develop a water plan moving forward as a companion to the drought plan. What we can do if we foresee a drought of longevity coming up across the state or across the Upper Midwest, we're interconnected with water systems from our states, the political boundaries mean nothing. So, having a better idea of our resources and the availability of those resources helps us in times of flood and in times of dryness and those extremes seem to be becoming more extreme.

Price: You talked about water plans. If we look outside of Iowa, you go look at California, Arizona in particular, water plans out there you have farmers and producers changing crops, maybe they don't have to rely on irrigation so much. In the southeast we're already seeing some people are growing peaches and blueberries, they didn't used to be able to do that. And others are thinking about as a homeowner, do I have the right kind of roof to withstand these crazy storms? Just looking at infrastructure, do we have to change some stuff in our state based on these weather patterns?

Glisan: Yes. Easy question. I talk with city managers, city engineers a lot and you think of Ankeny and Altoona, some of the fastest growing metropolitan areas in the United States, that infrastructure is starting to keep up with the precipitation regimes that we're seeing. But you think of the Spencer Dam in Nebraska being destroyed during the bomb cyclone and the dam up in Minnesota. Those infrastructure features are not meant for the precipitation that we're seeing. That's 40 or 50 years ago. So, this is an infrastructure question and it must be addressed because we're only going to see more rainfall, we're only going to see more precipitation events and it will really test infrastructure moving forward.

Price: So, what if we don't live in a newer house.

Glisan: Well, it depends on your, the style and build of these new houses, as you know I live in a very old house, 100 years old, problems crop up but those foundations were built to withstand. So again, it depends on your construction style.

Ta: I went to school at the University of Northern Iowa where we always liked to joke that we felt like it was the windiest place in the whole state of Iowa. Can you just talk a little bit about how diverse is the different climate or weather across the state? Is one area more likely to experience some type of weather than another area?

Glisan: We're uniquely situated in the United States in that we're right in the middle of everything. We've got the Gulf of Mexico moisture gate moving north, Canadian cold air coming south. The Rocky Mountains, you have low pressure systems that go over the Rocky Mountains and they stretch out, like a figure skater spin faster. All of those ingredients come together in the Midwest to Tornado Alley and that is where we get those severe thunderstorms. Looking across the state, we're basically topographically flat, so we don't see a lot of variation. Now of course, the southern part of the state is wetter than the northern part of the state. The northern part of the state is cooler than the southern part of the state on average. But overall, we don't see a lot of variation across the state. My colleagues in Nebraska, east and west of Nebraska, and my friends state climatologists of Texas and California have a much more difficult job than I do.

Ta: You mentioned Tornado Alley. Can you talk a little bit about how has that changed over the years? What does it cover now? And why is it shifting?

Glisan: Yeah, two things there. We're seeing less one-off tornadic events. Since 1950, the trendline has been down for one, two, three tornados occurring just here or there. You think of the July event with Pella and Oskaloosa, Marshalltown, we're seeing more outbreak events, 30 or more tornados. Dixie Alley is where we're seeing a shift of tornadic activity, Alabama, Mississippi. We're not really sure why we're seeing a decrease in tornados in Tornado Alley. It could be that the jetstream has become more variable in terms of the temperature gradient between where we live in the mid-latitudes and the high latitudes. A relaxed temperature gradient because of warming in the atmosphere produces a relaxed temperature gradient. That slows down the jet Now, when you slow down the jet, you get into persistent features as we're seeing across northern Iowa with record amounts of precipitation but also less variability where thunderstorms form. So, I think the key there is that we've seen tornadic activity shift further east and further south.

Henderson: Kind of a weather geek question for you.

Glisan: I'm here for it.

Henderson: Iowans have learned some new weather terms recently. Graupel. Haboob. And derecho. What is the next term we need to learn?

Glisan: So, I anticipated this question because of my last time here I was tasked with coming up with a word. And we did have one during the drought and derecho of August 2020, a deroucho, derecho and drought together. We were watching that line come across West Central Iowa becoming a derecho and we were hopeful that we could get a lot of rain out of it to quash the drought. Didn't happen, but we came up with that word to describe the possibility.

Henderson: Final question. I saw online a couple of people say, I'm only in my 30s and I've lived through a couple of hundred-year floods. Do you need to redefine those terms?

Glisan: Yes. So, we're looking more at a probabilistic stance for 100-year, 500-year flood, 0.02% for example. So, we call those return periods. I've spoken with a lot of municipal engineers that have talked about cutting off one of those zeros from a hundred year or 500-year flood, making it a 50 or a 10-year flood because we've seen these events more often. And this is tied in with the climate system. More water vapor, as I mentioned, we're getting higher intensity rainfall events, but also much more rainfall across the Upper Midwest. All of that drains down through Iowa and we are seeing a paradigm shift I think in how we address flooding and even drought. Should we take 100 years of drought as a record? Or should we look at the last 30 to 40 years to give us an idea if we're seeing a different type of drought or a different type of flood.

Henderson: We have less than a minute left. Very good warnings about tornados. How do you get better warnings about flash flooding?

Glisan: That's a great question. We have in the modeling a precipital water variable in the atmosphere that tells us how much water vapor is available to produce rain. So, the Weather Service issues a technical forecast several times a day. I read that, like the nerd I am as a meteorologist. But we've been getting better on when flash flooding is possible. We take soil moisture, we take stream flows, all of those hydrological variables that can kind of give us an indicator that if we get this amount of rainfall over this period of time definitely look for flash flooding.

Henderson: Well, thank you for all of the information that you have shared with our viewers on this edition of Iowa Press. Thanks for being here.

Glisan: Thanks, Kay.

Henderson: On behalf of everyone here at Iowa PBS, we extend our wishes to those who are living through the aftermath of floods and tornados. You can watch every episode of Iowa Press and if you didn't catch all of this one you can catch it online at Thanks for watching.


Funding for Iowa Press was provided by Friends, the Iowa PBS Foundation.

The Associated General Contractors of Iowa, the public's partner in building Iowa's highway, bridge and municipal utility infrastructure.

Elite Casino Resorts is a family-run business rooted in Iowa. We believe our employees are part of our family and we strive to improve their quality of life and the quality of lives within the communities we serve.


Across Iowa, hundreds of neighborhood banks strive to serve their communities, provide jobs and help local businesses. Iowa Banks are proud to back the life you build. Learn more at