Beware weather forecast snake oil

Snake oil salesman are found in every industry and weather forecasting is no different. So how do you identify weather forecast snake oil? One major sign is that the forecaster doesn’t talk about it until after the fact. Another is that you only hear about the successful forecasts. And of course, if it seems to good to be true, there’s a good chance it is.

I recently saw someone talking about severe weather forecasts months out. The man behind these forecasts isn’t just some rando with a website. He has a PhD in meteorology from the University of Oklahoma and is a forecaster at the Storm Prediction Center. So it’s entirely possible that he’s on to something here. But I’m suspicious.

He recently posted about his forecast for March tornadoes. The forecast is ostensibly from three months before the outbreak. I looked through the archives and there was no indication prior to the fact. His website contains no forward-looking forecasts. There’s no methodology. There’s no discussion of busted forecasts.

I don’t know Dr. Cook. I don’t want to say anything about him as a person or a forecaster. But until he shows more transparency on his forecasts, I’m inclined to call it weather forecast snake oil.

Where is spring?

I look at my calendar and it says that we’re well into April. But the weather hasn’t received the memo. I’m a warm weather person anyway, and by April I expect to have more good days than bad. But it’s still cold. It snowed yesterday and snow remains in the forecast.

How not-spring is it? Here are some “fun” facts:

  • Zero days in March 2018 had a temperature above 60 degrees Fahrenheit. The last time Lafayette did not reach 60 in March was in 2001. Since then, we’ve hit the 80’s twice (80 in 2007 and 86 in 2012).
  • We briefly reached the 60’s on Tuesday. That was the first time we hit the 60’s since February 28.
  • We haven’t had three consecutive days above 60 since October 23.
  • The highest temperature in March was 2.5 degrees colder than the highest temperature in January.
  • The average temperature in March was only 3.4 degrees warmer than February. The normal increase is 9 degrees.
  • As measured by the monthly heating degree days, March 2018 was colder than six of the last 10 Marches.
  • Yesterday’s high temperature (which happened just after midnight) is only two degrees above the normal low for the day.

Now March 2018 hasn’t been historically cold for the Lafayette area. It’s just obnoxiously cold. And the cold pattern looks like it will stick around through at least the middle of the month. So I’ll keep my shorts put away and my window closed a little longer. Spring has to happen eventually.

Describing areas affected by weather

My local National Weather Service office recently issued a Special Weather Statement with an unhelpful headline: “Wintry mix likely Friday night and early Saturday along and northeast of a Clinton to Greensburg line.” I have at least a passing familiarity with many small towns in Indiana, but I had no idea where this line is.

Greensburg, I remembered after looking at a map, is in southeastern Indiana. It has a population of less than 12,000. Clinton turns out to not be terribly far from my home town of Lafayette. It’s a tiny little hamlet of fewer than 5,000 residents.

It seems pretty unreasonable to expect members of the general public to know where either of these towns are unless they happen to live near them. This means the headline of the product told the audience absolutely nothing.

In this particular case “the Interstate 74 corridor” would be an improvement. There’s still no guarantee that someone will know where that is, but if nothing else, it’s easier to find on a map. Of course, sometimes there’s not even a major highway or river to use as a reference.

But wait! It’s 2018. What if it just said “central Indiana” and directed people to the NWS website for more information? Then there could be a map that clearly shows the area affected. That’s tough for immediate impact events like tornado warnings, but it works for longer-fused products. And not everyone has an Internet connection, but it can still be shown on TV. And later in the body, a description can be given. But it doesn’t need to be the headline.

For a variety of reasons, NWS text products are stuck in a paradigm that no longer applies. Hopefully this changes as the agency continues to embrace modern methods of communication.

Changes to weather radar rolling out this spring

Since this week is Severe Weather Preparedness Week in Indiana, I figured it’s a good time to have a weather post. The National Weather Service is rolling out some changes to the 159 NEXRAD weather radars sites across the country. These changes affect the Volume Coverage Patterns (VCPs) – how the radars scan the sky.

How weather radar works

To put it in the simplest terms, radars work by sending out pulses of energy and listening for the echos. The radar antenna rotates in a circle in order to get a view all around. But it doesn’t just move in a circle. The antenna also tilts upward. By moving up through increasing tilts, the radar eventually gets a 3D image of precipitation.

The key word here is “eventually”. The slowest VCP takes about 10 minutes to complete a full scan. This is generally used with clear skies or light wintry precipitation. The slow speed allows for more sensitivity and saves wear on the radar’s mechanical parts. But even the fastest scan modes take 4.5-5 minutes. During rapidly-evolving severe weather events, that can be a long time.

The changes

This spring, the weather service is rolling out changes that will introduce two new VCPs. Critically, the new software build will also remove four existing VCPs. By reduce the total number of options, forecasters will have to spend less time thinking about which radar mode to select so they can spend more time interpreting the radar data.

One of the new VCPs is focused on general precipitation and is designed to include the best parts of the patterns it replaces. The other is a new clear air pattern that shares common scan elevations with the precipitation modes and can be used for non-convective precipitation. The NWS has a paper describing the new VCPs in greater detail.

The changes will happen via software updates planned to begin later this month or in early April. It may take some time to know what the daily impact of the new patterns is. Still, it’s good to see that over 25 years after the first operational NEXRAD was deployed, the system is continuing to evolve.

Please don’t argue with the warning system

“Please don’t argue with the warning system”, Indiana University told a lecturer from its meteorology department as he rightly criticized their communications on Sunday.

Despite being wrong, the university continued to insist that they were making the right choice. Now as a Boilermaker, I’m normally in favor of Indiana University embarrassing itself. But this time, it’s just bad. Warning fatigue can kill people. The false alarm rate is already too high; telling people about warnings that don’t exist only makes it worse.

The “warnings affect the entire county until notified otherwise” statement is only a decade out of date. But I get it, our warning dissemination technology hasn’t caught up with how warnings are issued. You may recall I’ve written a few words on the subject.

The fact that dissemination technology is still (mostly) stuck in a county-based paradigm 10 years after the nationwide implementation of polygon-based warnings is an embarrassment. Emergency management is more than just weather, so I don’t expect emergency managers to know as much as meteorologists. I do expect them to not act silly when they’re corrected by experts. But most of all, I expect things to get better.

I don’t know why I expect things to get better. It’s hard to imagine the large public- and private-sector investments that are necessary to fix the issue. Storm deaths are relatively low, so there’s not even mass tragedy to spur action. It’s much easier to just work around the edges and pretend the glaring issues don’t exist. But if we’re serious about being a Weather-Ready Nation, we need to fix it at some point. Otherwise public institutions will continue making themselves look bad and misinforming the public.

Two months with the Davis Vantage Vue weather station

I’ve always wanted a weather station in my yard. Not one of those cheap “here’s the outdoor temperature” deals, but something I could really play around with. I finally decided I could treat myself a few months ago and I bought myself a Davis Vantage Vue.

Picture of a Davis Vantage Vue weather station mounted on a pole.

My Vantage Vue weather station mounted on a pole in my yard.

The Vantage Vue isn’t the top of the Davis line. To be honest, I’d have rather gone for a Vantage Pro, which has more sensors. But it’s also more expensive and I don’t have anywhere in my yard that’s a good site for a weather station. And it turns out that siting was the hard part of the whole setup.

The initial assembly and configuration was easy. The instructions were very well-written. Since I don’t have a Windows machine, I couldn’t use the Davis software for data logging. However, several open source projects fill that gap for Linux. I tried WeeWx first and it worked so well that I didn’t bother trying anything else. WeeWx pulls data, generates web sites, and provides a control interface for the console.

I left the station on my patio table overnight to make sure the radio signal was going to work well. It looked good, so I began the process of putting it on a pole. I attached the mounting pole to a fence post. The mounting brackets in the pole kit (sold separately) probably would have held it just fine. In the interests of over-engineering, I added a small ledge to the fence post for the pole to sit on.

With one pole kit, the station ended up about 7 feet above ground level. This seemed too low for both science and resistance to errant toys. I added a second pole and that raised it up a few more feet. It’s still a sub-optimal siting, but it’s the least-bad option I have.

In an ideal world, I’d set up the station two meters above an open field. That’s not an option in my yard, so I did what I could. The station is in the sun much of the day (at least this time of year). It’s as far away from trees as I can get it. It’s probably fine for rainfall, but I anticipate the wind readings will be not great. The direction seems to be pretty noisy, no doubt because of nearby obstructions. And I suspect the speed will tend to read low for the same reason.

Graph of temperature and dew point showing noisy data when the unit is in direct sunlight.

Daily temperature and dew point plot generated by WeeWx. The unit began receiving direct sunlight around noon.

One thing I did notice was that the temperature and dew point data got very noisy. The lines had been relatively smooth until about noon on August 30th. After a few days of keeping an eye on it and comparing to the official observations from the Purdue airport, I had a satisfactory answer. It seems that the noise happens when the unit is in direct sunlight and there is little or no wind. The solar shield that houses the sensors does not have a fan, unlike higher-end models. So in still air with direct sunlight, it may develop hot spots. I could build my own aspirator, but I’m not sure I care that much.

After two months, the Vantage Vue seems like a pretty solid weather station. Of course, the weather has been pretty uneventful the last two months, so I still have some unanswered questions.

  • How will it perform as the sun angle decreases? It will still get some direct sunshine in the winter, but less that it’s getting right now. This may test the limits of the built-in battery.
  • What will happen during a thunderstorm? We haven’t had any severe weather yet. I’m interested to see how the wind speed works. Of course, I don’t have a good way to verify it. I’m also curious to see if the unit gets lifted off the pole and flung into the back yard. I don’t think that will happen, but it’s a possibility.
  • How will it handle freezing/frozen precipitation? There’s no warmer on the tipping bucket as far as I can tell, so how well will snow melt to run into the tipping bucket?

I have a couple of projects I want to undertake now, too. I’d like to get a couple of small displays so I can have the basic conditions displayed by the door. I also want to modify a WeeWx template so I can make a web page that I can share that doesn’t have my lat/long prominently displayed.

Communicating uncertainty to the public

Forecasting weather is a very imprecise endeavor. This is due in part to the fact that forecasts matter on very local scales. If I cancel a cookout due to a thunderstorm forecast, I won’t care that it rained everywhere else if it didn’t rain in my back yard. Given that the forecast will never be certain, how can forecasters communicate uncertainty to the public?

As the Washington Post‘s Capital Weather Gang wrote:

As much as we communicated the uncertainty, the forecast cannot be considered a success if the message we were trying to send … did not reach some people.

So what do they suggest? The high-level suggestion is to use a “traffic light” metaphor to indicate how people should proceed with their day. This benefits from being simple, but it has some key failings. As Jason Samenow noted, it needs to be broken into at least two dayparts. As many as five dayparts may be necessary: morning commute, day, afternoon commute, evening, and overnight.

Time-of-day isn’t the only issue. Thunderstorm forecasts are particularly sensitive to geography as well. Even if you’re only forecasting for a metro area, you may not end up with the same observed weather. So the system would need to account for multiple areas. If you divide the area into quadrants, that gives you 20 time/area combinations.

At some point, the simplified system becomes almost as complicated as the status quo. This means that the public will miss the nuance in the same way they do now. It’s a hard problem. An ideal balance between simplicity and nuance exists somewhere. But who can say where?

Potential Tropical Cyclone Nine Forecast Contest

Hear ye! Hear ye! I’ve opened up the Tropical Forecast Game for Potential Tropical Cycle Nine. Forecasts are due by 8 PM EDT Friday.

Chances are very good that this storm will be named later today. I’ll keep the “nine” appellation until after the contest closes to avoid any confusion. (Yes, the code is old and crusty so the name matters).

Investigating weather data with xmACIS2

Single points of weather data are often not very interesting. You can look at see what the high temperature was on a given day, but so what? Trends and streaks are much more interesting. How many consecutive days above 60°F has your city had in January? When’s the last snowfall greater than 2″?

If you’re looking to answer those kinds of questions, the NOAA Regional Climate Centers (RCCs) has a tool for you. xmACIS2, part of the Applied Climate Imitation System, provides a free web interface to get that data. xmACIS2 provides a variety of configurable queries to provide data in tabular or graphical form.

xmACIS2 interactive temperature graph for Lafayette, IN.

xmACIS2 interactive temperature graph for Lafayette, IN.

This is an interesting tool to explore, especially when you’re in the throes of exceptional weather.

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.