
Misinterpreting hurricane forecasts - tysone
https://www.nytimes.com/interactive/2019/08/29/opinion/hurricane-dorian-forecast-map.html
======
jsight
This article is a little bit misleading, unless I am misinterpreting his
pictures. But that would be horrible for an article trying to explain
pictures.

Here is the graphical archive for all 5 day forecasts of Irma:
[https://www.nhc.noaa.gov/archive/2017/IRMA_graphics.php?prod...](https://www.nhc.noaa.gov/archive/2017/IRMA_graphics.php?product=5day_cone_with_line)

Now note the image that the article depicts for Hurricane Irma with this text:
"These misunderstandings have real-world consequences. As Hurricane Irma
approached Florida’s east coast in 2017, people near the cone’s center began
preparing and even evacuating."

The image and the graphical archive do not correlate. Where did the author get
this image from? The actual NHC cone covers the entire width of Florida (apart
from maybe the smallest western tip of the keys) for days before the storm
arrives. Its actually pretty accurate.

IMO, this article and its poor visualizations is part of the problem.

~~~
albertocairo
Hi Jsight, Alberto Cairo here. I wrote the piece, but didn't design the maps,
so I'll ask.

In any case, even if there's an inconsistency between the maps in the
piece—which are intended to be illustrative, I guess—and the NHC ones, it
doesn't undermine, I think, the overall message, which is that, regardless of
whether you are inside of the cone or outside and close to it, it's safer to
prepare just in case.

People should pay less attention to the center dots or line of the cone (many
do that) and focus more on facts such as that (a) the cone is essentially tons
of possible positions of the center of the storm in the next few days, (b) the
storm may end up going outside of the cone 1/3 of the time (so I'd say it
doesn't matter much that, say, Naples is outside of the cone, but very close
to it on the map.)

I've been in Miami since 2012 and lived through Irma, so I remember what I
wrote in the piece well. When the central line of the cone was running over
Miami, people over here got crazy, and people on the West coast of Florida
were watchful, but a bit less concerned (there's a link to an LATimes article
in the piece that describes that), again likely because some folks tend to
focus too much on the center line and dots inside the cone. There's tons of
evidence for this kind of misinterpretation (one academic paper is linked from
the piece).

The piece was reviewed by scientists at UM's School of Marine and Atmospheric
Sciences; I won't say it's 100% correct, but I'm relatively confident the
description, albeit simplified (I didn't explain what that "uncertainty" is
for, instance!), is sound.

~~~
Retric
Risks _are_ higher at the center of the cone. A hypothetical 100 mile wide
storm that’s 40 miles west of the centerline still covers the centerline, but
likely misses the eastern edge.

Also, staggered evacuation is a good thing, you don’t want everyone in a city
to decide to leave at the same time.

~~~
albertocairo
That might be true mathematically but talking to forecasters who work on this,
they greatly de-emphasize the center line. Instead, they do emphasize that the
forecast is the cone, not the center line alone. They direct your attention
away from the center line (readers tend to stick too much to it), and say
something similar to what is in the article: areas outside will be likely
affected, everyone should take precautions and prepare regardless of where we
are — and we should read other graphics and messages that can tell us, for
instance, whether there may be storm surge, flooding, or whether we need to
evacuate or not; the cone tells us nothing about any of that.

~~~
albertocairo
One last thing: risks aren't necessarily higher on the center line. Just to
give you an example: if you live in a low-level region far from the center
line but that is prone to flooding, risks may be higher than if you are by the
line but your house is on high ground (again, the cone says nothing about
hazards, as pointed out).

Thanks for the comment!

------
acchow
"The National Hurricane Center says cones will contain the path of the storm
center only 60 to 70 percent of the time"

Sounds like the communications fix is easy. Increase the uncertainty to 90-95%
which also increases the cone size. And make it blood red and tell anyone
inside the red that they need to be prepared.

"Hurricanes are also hundreds of miles wide, and the cone shows only the
possible path of the storm’s center"

Add an additional yellow area around it. This makes it extra clear visually
that the red zone is quite bad.

~~~
matwood
I've been living with hurricanes my entire life, and have been through many
(the largest was Hugo in '89). The problem with all these cones is when they
extend them beyond 72 hours. At that point, if we used your suggestion, the
entire east coast could be in the cone. That means either no one pays
attention, or everyone evacuates and _next_ time ignores the warnings.

What officials (and the news) need to do is tell everyone to hold tight until
3 days out, and then start making decisions.

People also need to understand their personal situation. If an area floods
during a summer rain storm or simply when the tide is high, then they need to
be extra cautious.

The other problem is that many people simply have no idea what it's like to go
through a hurricane. The mass migration to the coast means large parts of the
population do not have the experience to make informed decisions. This goes
back that officials and the news need to do a better job at informing.

My personal rule to consider evacuating is a cat 4+ predicted direct hit or
just south and it is less than 48 hours out.

~~~
jnbiche
> My personal rule to consider evacuating is a cat 4+

As you know well having lived through Hugo, the S/S category pertains to the
wind speed. However, it's the flooding and storm surge, not the wind, that are
by far the most deadly features of a hurricane.

I'd be much more wary of a big, slow moving cat 2 arriving right at high tide
and full moon than I would be a small, fast moving cat 4 arriving at low tide
and a new moon, unless I have some particular reason to fear the wind and not
the water (eg I'm in a mobile home on high ground).

Source: lived through or evacuated for multiple hurricanes.

~~~
mnw21cam
Note for the record that large tides (spring tides) are associated with full
moon _and_ new moon. Smaller tides (neap tides) are associated with half
moons.

~~~
jnbiche
You're absolutely right. I've been living away from the coast for too long now
(~15 years).

------
haubey
I grew up in South Florida, and I'm surprised to hear people think the storm
is getting bigger over time. I guess that's just something you grow up with
knowing down there. People on the west coast tell me they're terrified of
hurricanes, and I'm terrified of earthquakes. You can generally get out of the
way of a hurricane if you feel you need to...

There are of course common sense things to do to be prepared: get bottled
water, food, fill your bathtubs with water and a drop of bleach, make sure the
car has a full tank of gas. We personally brought my grandparents down from
Boca to stay with us. You can do those maybe a week, 4 days out before stores
start to get really empty (grandparents can be moved earlier or later). If you
have any coconuts palm trees, chop down your coconuts. These are common sense
things to do if there's a remote possibility of a tropical storm or hurricane
coming your way.

But I do think it's a little disingenuous to say that people didn't do enough
to prepare if they lived on the west coast, given how quickly the path
shifted. Partly because the NHC is generally so good at their predictions. If
you saw the earlier map that had Irma going up east coast, and you were in
Naples, you wouldn't think about moving, or at least I wouldn't. Our
buildings, especially the newer ones, are built to withstand at least some
level of wind. My house built in the 90s has held up through multiple Category
3s (Charlie and Wilma). It's of course all luck, and I know plenty of other
houses that have had damage, parts of the roof torn off, shattered windows,
though nothing catastrophic, built around the same time. I've driven through
the outer bands of a tropical storm (not that you should, but I was in high
school and we had a back to school party the night before, and I wanted the
car to be home).

That's not to disparage the work of the NHC. They're great at what they do,
and I read pretty much every advisory for every hurricane that's in the
Atlantic. When you've got no place to go, a hurricane bearing down on you is a
very scary thing. But if I'm in Naples, and 4 days out it looks like it's
heading towards Ft. Lauderdale? I'm not making plans to move.

~~~
cowboy69
This is a great comment that accurately (and nonsensationally) depicts what
it’s like to live/grow up in a hurricane area.

~~~
haubey
Thank you. I will say that we are relatively lucky in that we live inland, so
we didn't have to worry about storm surge, in a newer suburb that had its
power lines underground. We maybe lost 20 minutes of power during Wilma. I
have family that lives in East Ft. Lauderdale, they were out of power for two
weeks.

~~~
js2
I was in Miami, Coral Gables specifically, for this guy:

[https://www.nhc.noaa.gov/gifs/1992andy1.gif](https://www.nhc.noaa.gov/gifs/1992andy1.gif)

I hope you never have to live through one of those. Not fun. Good luck with
Dorian.

~~~
haubey
Wasn't alive for this one, but this was one that my parents got out of the way
for. With the forecast shifting south every day, I have a sneaking feeling
this could be another one they get out of the way for. The problem with Dorian
is it looks like it's going to hit south, and then move up the state. Nowhere
really to go.

------
marksomnian
For this exact reason, the image of the cone on the NHC website [0] has the
following disclaimer on the top:

"Note: The cone contains the probable path of the storm center but does not
show the size of the storm. Hazardous conditions can occur outside of the
cone."

But apparently media organisations repost that image without the added
disclaimer.

[0]:
[https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/144746.s...](https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/144746.shtml?cone#contents)

~~~
mehrdadn
Even reading that, I wouldn't expect the implications to fully sink in for
everyone immediately. It's really unintuitive.

------
Clubber
I live in a hurricane area. We don't use the news for any information other
than watching the weatherman stand in the storm and film, and satellite
imagery while it's going on. We use noaa.gov, it has all those prediction
maps. It's very good.

Here's Dorian's maps:

[https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/144923.s...](https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/144923.shtml?cone)

For those that haven't been through these, the predictions do shift up to the
last minute, so we'll check the maps every few hours just to see where it's
headed. They update more frequently the closer it gets. Dorian's path seems to
have moved a little south since this morning. Also, most areas aren't what you
see on the news; they like to show the exception areas as the norm (shocker).

~~~
tsumnia
I "still" live in a hurricane area, but less so than when I lived at the
beach. As OP mentions, I only use NOAA's page. Anything else is flair or
outright deception [1]. Florence was bad, but the video clearly shows the
reporter hamming it up.

There are people that simply cannot afford to evacuate or otherwise choose not
to. When I first moved to Wilmington, I was scared of Category 1's. After
living there for a decade, I didn't even prepare for anything less than a Cat
4 - unless you count grabbing beer for the inevitable "hurricane party".

While I will accept the articles premise that people can't understand graphs,
my major issue is in the study [2] they refer to. The surveys are all
retrospectives on assessing uncertainty after the fact. It would be like
asking people why they thought a stock would go up when it ended up going
down. In the end, who's to blame? Where do we direct the pitchforks? Or is it
simply a call to learning how the charts work? If it is the 3rd option, then
Times is fearmongering a little hard in my option.

[1]
[https://www.youtube.com/watch?v=ZyrRCx8-fZk](https://www.youtube.com/watch?v=ZyrRCx8-fZk)

[2]
[https://pdfs.semanticscholar.org/f7c0/4b6eb883cf7d7fdee007cd...](https://pdfs.semanticscholar.org/f7c0/4b6eb883cf7d7fdee007cda056ed18182829.pdf)

------
mattfm
"Graphics like these need to be read closely and carefully. Only then can we
grasp what they're really saying."

A cone showing the likely paths of the storm's eye seems like the incorrect
graphic to communicate to the public. The public cares about how much rain and
wind they are going to get. The take-away to me is that maybe we should just
emphasize maps of expected cumulative rainfall and wind speed, and not present
something that is uninformative (or prone to misinterpretation) to begin with.

~~~
dmurray
"expected" is perhaps the wrong metric here. There's a difference between
being certain of getting 10mm of rain and 20 km/h winds, and a 10% chance of
100mm rain and 200 km/h winds, and you want people to prepare accordingly.

The thrust of the article - although it can't state it directly and frames it
as a graphics/communications issue - is that more people should prepare for
hurricanes, that the cost of more false positives outweighs the downsides of
increased false negatives.

------
savagedata
When Irma was making landfall two years ago, I did an animation demonstrating
this for r/DataIsBeautiful. [1] The real hurricane path is in red with the
forecast at each timestamp in black. If you look at the forecasts through
time, you can see that they're frequently off by a distance the width of
Florida.

(This final graphic is an amalgamation of all the useful comments I got on the
original thread. It was a really cool experience getting so much feedback so
fast, like a giant collaboration with all of Reddit. You can see the original
not-so-beautiful here. [2])

[1] [https://github.com/savagedata/hurricane-
animation](https://github.com/savagedata/hurricane-animation)

[2]
[https://www.reddit.com/r/dataisbeautiful/comments/6z0w20/tim...](https://www.reddit.com/r/dataisbeautiful/comments/6z0w20/timelapse_of_hurricane_irma_predictions_vs_actual/)

~~~
jsight
It would be great if this also had the cone overlaid on top of it. It is often
interesting to read the forecaster's notes along with each of these graphics,
as it is fairly common for the "line" to basically just be an average of
several models without much expectation for it to be accurate in itself.

------
satokema_work
I've worked with this data on a daily basis.

It's a cone of probability, which is about as reliable as you think it is.
There are gridded wind speed forecasts (still probability) and NWS watches and
warnings if you want something more specific.

It helps with general preparedness at best. If you're in hurricane alley it
serves as a good reminder to be prepared, but not as a notice to pack your
car.

------
2bitencryption
Fun fact about Dorian right now: the tried-and-true European system predicts
the hurricane will head up the opposite Florida coast as the new-hotness of
the updated GFS[0]. Who will be right (or will both be wrong?). Will be
interesting to see.

[0]
[https://twitter.com/GregDeeWeather/status/116668585469538304...](https://twitter.com/GregDeeWeather/status/1166685854695383040)

------
choward
There are two problems here. People don't know what the cone means. But even
if they did, how are they supposed to act on it?

It's hard to know what the cone means because it's way too over-simplified and
they really shouldn't have that line there. Of course people are going to be
confused. Why can't it just be a color coated overlay where different colors
mean different probabilities of the hurricanes path?

Even if you do know what the cone means, how are you supposed to act on it?
What if I live 10 miles from the cone, should I prepare? How about 20 miles?
100 miles? 500 miles? 1,000 miles? And the idea I had doesn't really solve
this problem either. How are you supposed to act on the probabilities? If
there's a 50% chance, do I prepare? What about 20%? 10%? 5%? 1%? 0.1%?

~~~
flukus
> If there's a 50% chance, do I prepare? What about 20%? 10%? 5%? 1%? 0.1%?

Prepared/unprepared isn't a binary state either and your level of preparation
can match the certainty. At 10% check your supplies of water, candles, gas,
canned food. At 20% decide if you'll evacuate. At 50% tape/board up the
windows.

------
timerol
The bottom line of the article is that we should use better and more
understandable metrics about a hurricanes path, like
[https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/174008.s...](https://www.nhc.noaa.gov/refresh/graphics_at5+shtml/174008.shtml?tswind120#contents),
which was referenced in the article

~~~
thermonot
Now go to the NYT main hurricane article and what do you see? The same
misleading map that this article says people don't understand instead of the
better wind speed probability alternative:

[https://www.nytimes.com/2019/08/29/us/hurricane-dorian-
flori...](https://www.nytimes.com/2019/08/29/us/hurricane-dorian-florida-
updates.html)

~~~
dandelany
This one?
[https://www.nytimes.com/interactive/2019/08/27/us/hurricane-...](https://www.nytimes.com/interactive/2019/08/27/us/hurricane-
dorian-map.html)

This is _not_ the same cone map, the shaded area represents "50 percent or
higher chance of experiencing wind speeds of at least 39 miles per hour" \-
ie. a simplified version of the map you recommend.

------
mehrdadn
If we want to show people a probability map, why not just show maps for
"probability of necessary evacuation" or "probability of serious structural
damage" or similar? Instead of probability of hurricane center path or
whatever that nobody cares about?

------
40acres
I think the issue is that most people don't understand probability very well,
myself included. After reading the explanations I prefer the layout with
possible paths color coded by probability -- in this instance it shows that
both the West and East coast of Florida should've prepared.

------
sambe
Three main misinterpretations:

1) Getting bigger over time.

2) Safe outside the cone.

3) Further from centre implies less preparation required.

1) Is maybe true anyway? I have no idea. Is it an important error?

2) Is more of a problem with the chart than the people. There's a hard border.
It implies 95/99.7% confidence instead of 68%. Were the graph more intuitively
designed, the interpretation would not be wrong, really, insofar as one maps
probability to a binary choice.

3) Seems completely logical - the expected threat is lower further from the
centre. People are still underestimating the risk, but for the same reason as
2).

------
irrational
I think I prefer the image that showed all of the possible paths predicted by
different computer models, rather a summarizing cone of probability.

------
MarkMc
"People who are inside the cone, but far from the center, tend to prepare less
than those closer to the central line. All of these interpretations of the map
are incorrect"

I'd assume people closer to the central line have a greater chance of being
hit. Is the auther saying people with a greater chance of being hit shouldn't
prepare more?

~~~
brians
Right. People near the center line are all guaranteed to get hit, and should
prepare appropriately

------
allday
Wow, this story is annoying me a lot more than I expected. There's a whole lot
of shaming of the layperson in here, with a wink wink nudge nudge that if
people would just _think a little_, they could save themselves a lot of
trouble.

> Graphics like these need to be read closely and carefully. Only then can we
> grasp what they're really saying.

Well, that's ridiculous. If these graphics were in an app, we'd tear them
apart for the poor user experience. Look at this:
[https://imgur.com/a/Ko2Z4uM](https://imgur.com/a/Ko2Z4uM)

There is nothing there to indicate that what you're looking at is the
probability distribution of the center of the storm. The very obvious
interpretation of this graphic, without additional context, is that this cone
is the area that could be affected by the hurricane. This is reinforced by:

1\. The size of the start of the cone is the same as the size of the hurricane
2\. There is a well defined border to the path 3\. There is no additional
shading outside the cone that indicates "could also face danger"

Furthermore, "probable path of the storm center" is not something the general
public cares about! That is not the question that needs answered! What people
want to know is, "will I be in the path of the hurricane?"

Even the official NHC product has its faults:
[https://www.nhc.noaa.gov/storm_graphics/AT05/refresh/AL05201...](https://www.nhc.noaa.gov/storm_graphics/AT05/refresh/AL052019_5day_cone_no_line_and_wind+png/144746_5day_cone_no_line_and_wind.png)

There is a big box with a bunch of text at the top of the graphic saying that
it is showing the probable path of the storm's center, but does not show the
size of the storm. This is different than saying "the storm may extend beyond
the edges of the cone". And the next line is "hazardous conditions may occur
outside the cone." Okay, every time there's a thunderstorm or 50mph wind
gusts, there's an alert in my weather app about hazardous conditions. That
information is too vague to be actionable. This doesn't even touch on the
design aspects of this graphic, such as how the massive amount of text, size,
color, spacing, etc, seems to draw the eye away from that message at the top.

But getting back to a point from a previous paragraph, why is this even
disseminated widely at all, when this graphic is so misleading and also not
what people need to know? Is it the NHS pushing it out to the public? Is it
the media? It seems wildly irresponsible. The tropical storm force wind speeds
graphic mentioned in TFA would be a much better product to deliver. Or, just
create a graphic that is what the article has already identified as the
natural interpretation - a cone of the possible area that could be affected by
the hurricane!

Sorry, but excuses for poor design are a real pet peeve of mine.

~~~
mehrdadn
Seriously. I already _know_ everything in the aricle (because I've read
similar before) and yet I still have trouble remembering it when reading a map
and trying to visualize the area I actually care about. I can't imagine how
the heck purple are supposed to just deal with this and wrap their head around
it, especially regarding an emergency.

I'm wondering if the people who didn't prepare due to a misleading map despite
a technically accurate prediction can sue for damage? Not that I would enjoy
seeing NOAA et al. in a lawsuit, but if nothing else has gotten them to fix
these, maybe a lawsuit will?

------
75dvtwin
Relying on modern day 'journalists' to interpret weather (or anything else
requiring domain expertise, for that matter) -- is very questionable.

Why not use windy.com pick a model (the exceptionally well designed UI, makes
it easy), and let it play out the tracks.

[https://www.windy.com/22.837/-67.544?27.897,-66.753,5](https://www.windy.com/22.837/-67.544?27.897,-66.753,5)

They have 4 models, and it just as easy to use as posting stuff on Instagram
or something..

Meteorologists covering those events, are not journalists, which is good. I
trust their coverage more.

------
gdubs
I’ve always thought the term “Cone of Uncertainty” sounded like something out
of a kitschy TV show from the 1960s.

The “spaghetti models” are what I tend to look at. A blend between those and
the cone might alleviate some of the confusion about what the cone represents.

But a serious question: is this about the general public becoming more
distracted? Did people not understand these graphics two decades ago?

------
bluetidepro
Wow, this is fascinating. I had no idea, either. I def always thought what
they showed people thought wrongly. Granted, I don't live anywhere near these
areas so it's never anything I have had to worry about in real life, but still
fascinating and interesting to learn about it more. Very useful to know.

------
ridaj
I personally feel like the "spaghetti bundle" representation of the data
(where a random sample of potential paths are drawn) was the most
straightforward image of the uncertainty embedded in the forecast. Has it been
considered as a means of public communication?

~~~
duanem
I've just implemented this in Flowx[1], the Android weather app I develop.

I have the "spaghetti bundle" but it was a major improvement when I added dots
indicating the location of the hurricane center with time, as shown in this
YouTube video[2]

[1]
[https://play.google.com/store/apps/details?id=com.enzuredigi...](https://play.google.com/store/apps/details?id=com.enzuredigital.weatherbomb)

[2]
[https://www.youtube.com/watch?v=I46IJcnf_bY](https://www.youtube.com/watch?v=I46IJcnf_bY)

~~~
duanem
BTW, these are ensemble models for the NOAA GFS (FV3) and CMC GDPS models.
Ensemble models are where the starting conditions of weather simulation is
perturbed slightly and the simulations re-solved. They do this 20-odd times
and you end up with 20-odd tracks. So for both GFS and GDPS there will give
40-odd paths.

Sometimes, it can be interesting how the cluster of GFS tracks may differ from
the GDPS tracks.

------
jobigoud
It's the first time I see this kind of graphic, but that cone looks very
suspiciously narrow and smooth, especially in the later days.

Are they really properly compounding the probabilities here? Like to create
the boundary for the second day you have to sample a number of possible
positions from the first day, recompute a possible path from these samples,
and then expand the area out of these forwarded samples, based on uncertainty.
The boundary at day 2 should be related to the samples that went the most off
course.

It looks like they just restart from the best-guess predicted position for day
2 which is already based on a _prediction_ for day 1, and multiply it with the
uncertainty, with a factor to account for one passing day. If that's the case
this is _really_ misleading. I imagine if they did it the way I'm thinking the
cone could get very large very fast, but most importantly it wouldn't be
smooth and symmetrical like this.

------
OrgNet
Forecasts from multiple sources gathered here:
[https://www.spaghettimodels.com/](https://www.spaghettimodels.com/)

------
bogwog
Unrelated, but I was SO happy when I finished reading and clicked the back
button on my browser and it actually took me back to HN instead of showing me
the previous slide.

------
RandomBacon
On mobile, the "subscribe" bar at the bottom covers up the text.

I had to use a "remove cookie notification" bookmark to be able to read the
text.

    
    
        javascript:(function(){(function () {var i, elements = document.querySelectorAll('body *');for (i = 0; i < elements.length; i++) {if (getComputedStyle(elements[i]).position === 'fixed') {elements[i].parentNode.removeChild(elements[i]);}}})();document.querySelector('body').style.setProperty('overflow','auto','important'); document.querySelector('html').style.setProperty('overflow','auto','important');})()

~~~
Wowfunhappy
Oh cool, how frequently does this bookmarklet actually work?

~~~
penagwin
It appears to just set anything positioned as fixed to being normal instead.

Which should be most popups/cookie notifications. Might break certain websites
that try to be clever or "artsy" but as a bookmarklet it shouldn't cause any
issues.

------
Ancalagon
Looks like the scientific illiteracy sponsored by this country's education
system is really starting to pay off!

~~~
amluto
What kind of scientific literacy would make this obvious? They need a better
presentation.

~~~
Ancalagon
confidence intervals...

~~~
choward
Ok, so what if I live just outside the cone? What does that mean? The map is
the same color for 1 mile from the cone and 1,000 miles from the cone. The map
is flawed not the people looking at it.

~~~
Ancalagon
I mean take a look at this bell curve chart with a 0.95 confidence interval
(what I assumed the confidence interval of the hurricane path was):
[https://www.statisticshowto.datasciencecentral.com/wp-
conten...](https://www.statisticshowto.datasciencecentral.com/wp-
content/uploads/2014/12/ci95.png)

Its all one color...

