How to reduce artificial boundaries in severe weather warnings

If you’ve been around here a while, you’ve seen me have opinions about the shapes of so-called “storm-based warnings”. Years ago, the National Weather Service changed the shape of tornado and severe thunderstorm warnings. Instead of issuing warnings based on the county, warnings are arbitrary polygons fitted to the threatened area. The idea is that by shaping warnings to the actual threat, the public gets a more accurate warning.

The reality is a little messier. Warnings are still frequently communicated to the public on a county basis. Worse, the warnings themselves are sometimes shaped to a county line. This is sometimes done to prevent a tiny sliver of a county to be included in a warning. Other times, it’s the result of a boundary between the responsibility areas of different NWS Forecast Offices.

Last week gave a great example close to home. The NWS office in Northern Indiana issued a tornado warning on the edge of their forecast area. Because the adjacent office didn’t issue a warning for that storm, the resulting shape was comically bad.

A tornado warning (red) shaped by the boundary (blue) between the IWX and IND forecast areas.

To be clear: I don’t blame the forecasters here. It was a judgment call to issue or not issue a warning. The real problem is that the artificial boundary does the public a disservice. Most of the general public probably does not know which NWS office serves them. Bureaucratic boundaries here only add confusion.

One solution is for the offices to coordinate when issuing warnings near the edge of their area. That doesn’t hold up well in the short time frame of severe weather, especially if an office is understaffed or over-weathered. Coordination takes time and minutes matter in these situations.

My solution is simpler: allow (and encourage) offices to extend warnings beyond their area. Pick a time frame (30 minutes seems reasonable) and allow the warning to extend as far into another office’s area as it needs to in order to contain the threat at that time. Once the threat is entirely into the new area, allow that office to update the warning as they see fit.

This allows offices to draw warnings based on the actual threat. It buys some time for additional coordination if needed, or at least gives a cleaner end to the warning. It does mean that some local officials will need to have a relationship with two NWS offices, but if they’re on the edge they should be doing that anyway.

The downside is that it increases the effort in verifying warnings because you can no longer assume which office issued the warning. And it could lead to some territorial issues between offices. But the status quo provides easier bureaucracy by putting the burden on the public. That’s not right.

Sidebar: what about issuing warnings at the national level?

Another solution would be for a national center to issue warnings. This is already the case for severe weather watches, after all. While it would solve the responsibility area problems, it would also reduce the overall quality of warnings. Local offices develop relationships with local officials, spotters, etc. These relationships help them evaluate incoming storm reports, tailor warnings to local conditions and events, etc. While a national-level warning operation would clearly provide some benefit, warning response is ultimately a very personal action that benefits from putting the warning issuance as close to the public as possible.

Measuring hurricanes and tornadoes

Today marks the beginning of the 2017 Atlantic hurricane season, which runs through the end of November. As you may be aware, we measure hurricane intensity by measuring the wind speed. We categorize hurricanes into one of five levels on the Saffir-Simpson scale. In use since 1971, the scale is widely known, but does it serve the public well?

The United States has not seen a landfall from a “major” (category 3 or above) hurricane since Hurricane Wilma in 2005. But that doesn’t tell the whole story. The original Saffir-Simpson scale included effects from storm surge and flooding. However, the Saffir-Simpson Hurricane Wind Scale in use today excludes those; it is solely a measure of wind speed. So even though the U.S. has avoided major hurricanes, it has not avoided major damage. Consider that two of the three costliest hurricanes in U.S. history were not major hurricanes. Sandy wasn’t even technically a hurricane.

More recently, Hurricane Matthew caused a great deal of devastation in the Carolinas and Virginia. Matthew could have caused massive damage along the Florida Atlantic coast, but remained just far enough out to sea. And the damage further north was primarily due to inland flooding, not the near-shore wind and surge. By the time Matthew reached the Carolinas, it was “just” a Category 1 storm. As a result, many in the public did not recognize the serious threat it posed.

The National Hurricane Center in particular, and the weather industry in general, are working to improve hazard communication. The public, after all, doesn’t really care about the wind speed per se, but the effects of that wind (and rain). Last fall, several meterologists on discussed this on Twitter:

The discussion turned to the idea of real-time rating of tornadoes. NOAA researchers found that weather radar velocity data can be used to estimate the ultimate Enhanced Fujita Scale rating of a tornado. While not operational yet, it will be a big benefit to the public if it is further developed.

The ideal situation would combine the impact focus of the EF scale with the real-time rating used for hurricanes. Hurricanes are much easier to evaluate in real time for a variety of reasons, so they have a head start. Now if we can just start measuring hurricanes correctly.

The Local Storm Report product still has value

Several tornadoes hit central Indiana last month. During the event, a tornado warning was issued for Indianapolis. I saw several local media people tweeting that police had reported a tornado but no Local Storm Report (LSR) had been issued by the National Weather Service. I thought that was rather odd, and mentioned this incongruity in a tweet. It didn’t seem right to me that a tornado could be reported in the 14th-largest city in the United States but have no LSR issued.

Several people replied to tell me that the police report was included in the text of the warning. I did not take kindly to that. While including such information in a warning is great, that’s not what I was after. I specifically wanted an LSR. I was asked if it’s still a relevant product,  so here’s this post.

The Local Storm Report is still a distinctly useful product because it has a defined format. While most people do not consume LSRs directly, the rigid format allows it to be used in a variety of useful ways. For example, a media outlet can parse the incoming LSRs and use the coordinates and type to make a map for TV or web viewing. This can help the audience better understand the type and location of a threat.

Additionally, they’re helpful for downstream experts (other forecast offices, emergency managers, etc.) to know what a storm has produced. I often watch the LSRs issued by the Lincoln, IL or Chicago offices when severe weather is approaching my area to see the ground truth to go along with the warning. Knowing that a storm has (or hasn’t)  produced what the warning advertised can be very helpful in formulating a response to an approaching weather threat.

Apart from the warnings, timely and frequent LSR issuance is one of the most valuable functions of a National Weather Service office during a severe weather event.

But what about social media?

I’m glad you asked. Someone suggested that social media is a better avenue for communicating storm reports, in part because a picture is worth a thousand words. I agree to a point. Seeing a picture of the tornado heading for you is more powerful than words or a radar image. In that sense, social media is better.

But Facebook is awful for real-time information. Twitter is limited in the amount of detail you can include and has a relatively small audience. Plus, social media is hard to automatically parse to reuse the data, unless every forecaster tweets in a prescribed format.

The ideal scenario would be to tie social media into the process of issuing LSRs. As an LSR is generated, the forecaster would have the option of posting the information to the office’s social media accounts (perhaps with a link to the LSR) . If we’re granting wishes, the posting process would also allow for the inclusion of external images.

Until that day comes, I’m going to keep looking to LSRs for verification during severe weather events. And I’ll keep being disappointed when they’re not issued. 

To warn or not to warn?

The decision to issue a tornado warning is a difficult one for meteorologists. A timely and accurate warning can save lives, but a false alarm contributes to an already-too-high indifference among the public.

On March 31, thunderstorms moved through Indiana in the mid-afternoon. The Storm Prediction Center had a slight risk for the area, so I had been keeping an eye on them. One cell had shown rotation since it had been in east-central Illinois. After a while, it started to fall apart. Then around 4:40 PM, I happened to glance back over at the radar, and I saw this:

KIND reflectivity and velocity at 4:42 PM Eastern on March 31, 2016.

KIND reflectivity and velocity at 4:40 PM Eastern on March 31, 2016.

Oh yeah, there’s something going on there. I was talking to my friend Kevin and we were wondering why there was no warning. Even if the forecaster didn’t think a tornado warning was justified, a severe thunderstorm warning would have been a good hedge. As it turns out, the storm produced a brief EF1 tornado about a mile east of my house.

I don’t know why no warning was issued. But here’s a different take: should a warning have been issued? No one was injured and the damage that was done couldn’t have been prevented with a 10-15 minute lead time. Should this count as a false negative?

Yeah, probably. Although no one was injured, a small difference in the location could have easily changed that. But it makes me wonder if warning for every tornado is a reasonable goal.

Reporting severe weather via social media

It feels weird writing a post about sever weather in mid-December, but here we are. Over the weekend, storm chaser Dick McGowan tried to report a tornado to the NWS office in Amarillo, Texas. His report was dismissed with “There is no storm where you are located. This is NOT a valid report.” The only problem was that there was a tornado.

Weather Twitter was awash in discussion of the exchange on Saturday night. A lot of it was critical, but some was cautionary. The latter is where I want to focus. If you follow me on Twitter, it will not surprise you to hear that I’m a big fan of social media. And I think it’s been beneficial to severe weather operations. Not only does it make public reporting easier, but it allows forecasters to directly reach the public with visually-rich information in a way not previously possible.

But social media has limitations, too. Facebook’s algorithms make it nearly useless for disseminating time-sensitive information (e.g. warnings), and the selective filtering means that a large portion of the audience won’t get the message anyway. Twitter is much better for real-time posting, but is severely constrained by the 140 character limit.  In both cases, NWS meteorologists are experts on weather, not social media (though there are efforts to improve social media training for forecasters), and there’s not necessarily going to be someone keeping a close eye on incoming social media.

I don’t know all of the details of Saturday night’s event. From one picture I saw, it looked like the storm in question looked pretty weak on radar. There were also several possible places Dick could have been looking and it didn’t look he made which direction he was looking clear. At the root, this is a failure to communicate.

As I said above, I’m a big fan of social media. If I need to get in touch with someone, social media is my first choice. I frequently make low-priority weather reports to the NWS via Twitter. For high-priority reports (basically anything that meets severe criteria or that presents an immediate threat to life), I still prefer to make a phone call. Phone calls are less parallelizable, but they’re lower-latency and higher-bandwidth than Tweets. The ability for a forecaster to ask for a clarification and get an answer quickly is critical.

If you do make a severe weather report via Twitter, I strongly encourage enabling location on the Tweet. An accurate location can make a big difference. As with all miscommunications, we must strive to be clear in how we talk to others, particularly in textual form.

Tornado warning false alarm rates

Five Thirty Eight recently ran a post about the false alarm rate of tornado warnings. Tornado warnings fail to verify (i.e. have no tornado) approximately 75% of the time, a number that has held steady for years. This comes as no surprise to meteorologists, and probably not to the general public. What’s disappointing about the article is that it doesn’t address the reason that the false alarm rate hasn’t improved: because it’s not a priority.

The ideal case, of course, is a false alarm rate of zero. While the article quotes the reasoning (“you would rather have a warning out there and have it miss than have an event and not have one out there”), it doesn’t explain why that reasoning leads to a high false alarm rate.

The first reason is that an emphasis on maximizing detection means that in questionable scenarios, forecasters will lean toward issuing a warning instead of not. I’ve been in an office when an unwarned tornado has been reported. The forecasters are not happy about that. They take the National Weather Service mission of protecting life and property seriously. The impact of a false alarm (inconvenience and lost productivity) outweighs the potential loss of life from a missed event.

After inadvertently posting this when I meant to save the draft, a friend commented that the “ideal FAR is actually non-zero if you want lead time.” This leads to the second reason an emphasis on detection increases the false alarm rate. Issuing a tornado warning seconds before the tornado hits is of limited utility. People in the warned area need time to move to safety. The article does point out that lead time has increased steadily for the past few decades. But the more lead time you have, the more likely it is that a warned storm won’t produce a tornado. Tornadoes are exceptional events.

There’s a balance between detection rate and lead time on one side and false alarm rate on the other. Like a seesaw, lowering one side raises the other (if you play with the signs on the numbers, that is). Prudent policy focuses first on detection and then on lead time, so the false alarm rate has to suffer. Improvements in technology and science will hopefully move the fulcrum such that we can lower the false alarm rate without reducing the lead time or probability of detection too much.

Communicating weather safety information

Weather is complicated and hyper-local. The general public often lacks a basic understanding of weather evolution and people are generally bad at risk assessment. These facts combined make it really hard to provide general safety advice. It’s made even harder by the fact that if you give bad advice, you may be responsible for injury or death.

What to do when you’re in a car and a tornado is coming is perhaps the epitome of this issue. The National Weather Service office in Kansas City recently posted a scenario to its Facebook page. I saw some dismay expressed about how many people said they’d keep driving in that scenario. But here’s the kicker, I think that’s (conditionally) the right answer.

In the scenario you’re smack in the middle of a six mile stretch of interstate highway that’s expected to be impacted by a tornado in 15 minutes and you’re at an exit. The overpass is clearly the wrong answer. A very good answer would be to go to one of the gas stations or restaurants in the picture and seek shelter there. A car is about the worst place to be in a tornado, so why did I say “keep driving” is the right answer?

Let’s assume you’re traveling at 60 miles per hour. In three minutes, you’ve reached the edge of the warned area. The tornado won’t reach that area for another 12 minutes. Of course, there’s likely some error in the projection, but even if the forward motion is twice what was stated, you still have a cushion of over three minutes. If, in addition, the danger area is twice as large as stated, you still have 30 seconds. That’s cutting it too close, but we’re being really conservative here.

Now let’s look at all of the underlying assumptions that I made. First, I assume that you can safely travel at normal speed the necessary distance. This means no traffic, accidents, construction zones, or debris from earlier storms. In some places, you’d probably have sufficient visibility to make that determination, but certainly not in all places, and not in the picture shown. Second, I assume that you are just passing through. If you’re 10 minutes from home, it might be tempting to try to get there, but that eats into a lot of your safety buffer. Third, I assume you’re traveling south or that the main part of the supercell (another assumption) does not contain heavy rain or large hail that would slow you down or cause damage/injury on its own.

What would I do in that situation? It would depend on my familiarity with the area, my awareness of the storm type and evolution, and (most importantly), my ability to process it all quickly enough.

What should you do in that situation? See above. The best default answer is to seek shelter in one of the buildings off the exit, but that’s not always the best answer.

Book review: “Tornado Warning”

Three years ago this month, the city of Joplin, Missouri was devastated by an EF-5 tornado. Not only were numerous buildings destroyed, but 159 people lost their lives. This was the first 100-fatality tornado since 116 people died in a 1953 tornado in Flint, Michigan. As word of the impact spread, I can recall being thankful that my chasing range was limited to northern Illinois that day. Author Tamara Hart Heiner drove through the Joplin area in the days after the tornado and was struck by the extent of the devastation. After speaking with survivors, she decided to write her first non-fiction book. Tornado Warning, released earlier this month, tells the story of the tornado through the eyes of seven women who survived it.

The women of Tornado Warning led varied-but-normal lives before the storm. Normalcy would not survive the day. I found the early part of the book a little dull, which is to be expected. The women and their families were going through their usual Sunday routine. When the tornado hits, the book becomes positively riveting. One woman rides it out in a bathtub, covering her children with her body and a mattress. Another was in her van. That she and her son survived is nothing short of miraculous.

Heiner does not dwell on the tornado itself. Indeed, the narrative moves the tornado along quickly; like its real-life counterpart, it is here and gone within moments. Much of the book focuses on the hours immediately following the tornado when Joplin residents frantically search for loved ones, rescue their neighbors, and try to come to grips with the stark new reality.

Although scenes shift quickly from one protagonist to another, the reader gets a definite sense of each woman’s personality. The narration seems to take on some of the character of the woman being followed. The rapid shifts made it difficult to keep track of the characters initially, but it proved to be the appropriate style during and after the tornado.

In all, this is an excellent read. It showcases the human side of tornadoes that never seems to make it into IMAX films. The tornado preparedness and safety advice is invaluable and I encourage all readers to not skip it. Some of the meteorological discussion at the beginning of the book is painful (particularly “the jet stream is typically 300 millibars strong”), but this is not a story about meteorology. Heiner does an excellent job of capturing the humanity of the Joplin tornado, so I can forgive meteorological errors.

The net proceeds from Tornado Warning are being donated to Joplin recovery charities.

Reflectivity tags

Sometimes you don’t notice something until it is pointed out to you, then you see it everywhere. That was the case for me when the near-ubiquity of clear slots near tornadoes was pointed out a few years ago. Suddenly, I began to (legitimately) see them everywhere. The feature was there, just completely overlooked. I expect a similar effect after learning about reflectivity tags at the Central Indiana Severe Weather Symposium in March.

Reflectivity tags are hardly new. The concept appears to have been introduced in a 2006 paper by Llyle Barker. The basic idea is that a small blob of reflectivity overtaking an area of rotation is often an indicator of tornado formation or intensification. Ed Shimon’s presentation at the Symposium pointed out how the Washington, IL tornado of November 17 grew from a small tornado into a neighborhood-leveling monster when the reflectivity tag passed.

There’s a danger in over-relying on the new shiny you’ve just picked up of course. The vast majority of storms still don’t produce tornadoes. I suspect that the majority of storms that feature reflectivity tags also don’t produce tornadoes. The presence of a fast-moving tag shouldn’t mean immediate panic. At the same time, it’s another piece of information to consider when watching storms.

Ten years since Jamestown

Ten years ago, I was sitting in my apartment on a rainy Tuesday afternoon. My last class of the day ended around 1:30 and I was settled in to get some work done on the forecast game that I ran for the University. WFO Lincoln had issued a few tornado warnings and there were reports of cold air funnels, so my friend Mike Kruze and I decided to spend the afternoon driving around getting rained on. Instead, we saw one of the most photogenic tornadoes ever recorded in Indiana. And then another one. And then a third (though this one is unofficial, since we could not see the ground from our position and no damage was observed in the empty field).

This was only two days after Mike and I had returned from a marathon drive to northern Iowa, where the most we saw was vivid lightning and large hail after sunset. By this point, I had been chasing for a year and a half. Chase attempts evolved from some undergrad doofuses piling in the car and driving around to a fairly mature venture with thoughtful forecasts, data stops, and real efforts to be in position. Of course, as luck would have it, April 20 ended up being somewhat of a doofus day. Mike had a data plan on his Sprint PCS phone, and it was just enough for us to pull up the occasional radar image. Without that, we’d never have found ourselves standing in rural Boone County with a tornado directly to our west.

At the time of the Jamestown tornado, wasn’t even a gleam in my eye. I was planning on making a career in the National Weather Service. I figured chasing would be a thing I did with regularity. Ten years on, I’ve earned my meteorology degree, but I’ve never worked as a professional in the field. I have one chase day in the last five years, and I’m less than a year from a decade-long tornado drought. I’ve still only chased west of the Mississippi twice. With a toddler and home and another baby due early summer, I’m not likely to get out this year. But I still feel the gentle tug of the storm, pulling me to go out and seek it. I know I will at some point. I just don’t know when.