Weather Forecasting: What It’s All About

As a meteorologist, it is difficult for me to turn that part of myself off wherever I go.  When people try to make small talk about the weather with me, they usually regret it, because to me weather isn’t just to pass the time, but it’s interesting.  However, for most people it is small talk.  Invariably whenever I go out in public I overhear conversations about the weather, whether in restaurants, museums, the locker room at the gym, etc.  There is a common theme I hear which is that forecasters don’t know what’s going on.  I hear and read things like prediction is not even possible.  I have had people come up to me and jokingly say, “Meteorology must be a great profession because you can be wrong 50% of the time and still have a job.”  Though they clearly are telling one of those jokes that they actually believe to be true, the chuckle I give in return is not nearly as sincere.  To explain would require more time than I often have, so I thought maybe I should write a post explaining some of the basics, and explain some of the most common things people misunderstand about the weather.

Why Forecast?

There is a lot to the history of forecasting, but I think it’s fairly clear why people want to have some knowledge about what sort of weather was coming their way.  Whether you wanted to know when to plant crops, went to harvest, or where and when to sail your ship, having knowledge of the atmosphere, knowing what weather is coming your way has huge advantages.  The beginnings of forecasting as a science were driven by WWI when aviation was added to warfare and they quickly realized that having weather observations and an ability to know what weather was coming was a huge tactical advantage.  The weather forecast is something almost everyone utilizes today, whether you think it means something or not, people will still look to try to make the best guess about what to wear, whether to bring an umbrella, or whether travel or not will be hazardous.

How Accurate are Forecasts and Why Do People Think They Are Not Accurate?

First things first.  Currently the National Whether Service is accurate for 1 and 2 day  temperature forecasts to within 2.5 – 4 F, and has an 82% accuracy rate when it comes to precipitation.  I am not going to spend a lot of time proving accuracy here, you can check out these links as they have already done the work.

What I will say is that it is important to understand how our cognitive biases shape our perception.  The one at work here is that what sticks in memory are the misses, and not the hits.  When the forecast is right, you don’t think about the forecast.  When it’s wrong you do.  This creates a data point in your brain only when there is a missed forecast, but it’s poor way to draw meaningful statistical conclusions.  I think it’s also important to note that I see a lot of click bait type headlines for upcoming weather and this may be what’s drawing our attention.  Extreme gets clicks, but may not be what’s being endorsed by the National Weather Service.  It’s also not clear whether people are staying current with the latest forecast.

Finally I think it’s important to remember that in extreme weather situations forecasters will err on the side of caution.  It is a difficult line to walk.  When extreme predictions don’t happen, the public loses trust in your forecast, and this can cost you lives in the future.  If on the other hand you don’t communicate the possibility of an extreme situation, that can also lose you lives.  So in erring on the side of caution, more often than not people will find that it might not have been quite as bad as predicted.  Erring on the side of caution is the right thing to do, because there is an inherent error to the forecast.  Sometimes in the margin of error, the extreme end of that error can be the difference between life and death.

Hard Rain

Precipitation is the hardest variable to forecast for and some of the reasons for that are given in the next section, but a few points are worth talking about here.  First, many people don’t understand the precipitation forecast.  This has been a criticism of the National Weather Service to change their way of forecasting precipitation, but for now, there seems to be no better way of doing it.  When the probability of precipitation (PoP) is reported, it is reported as a percent.  But what does that percent mean?  This probability is actually the product of two other numbers.  One is the actually chance of precipitation but the other is the percentage of the forecast area that will be impacted by precipitation.  Each National Weather Service office has a specific region in which they are suppose to forecast for and they usually break those down into smaller regions for the purpose of precipitation forecast, but the fact remains that incorporated into that PoP is areal coverage.  So 50% chance of precipitation is not the coin toss that some make it out to be, but it could mean that there is a 100% chance of rain over half the forecast area.  Of course it could also mean that there is a 50% chance over all the forecast area.  But it’s also important to remember that even in the latter case it’s not a coin toss, but rather based on evidence that pegs precipitation as more likely. The difference between rain and no rain can often be very small and requires knowledge of atmospheric properties at high resolution.  A far higher resolution than we have.

Snow forecasts are often worse, and this is largely due to two factors.  One, is that it depends on temperature whether you get rain or snow.  It takes a very slight error in the forecasted temperature for rain to suddenly become snow or vice-versa.  So being 2 F off in our forecasted temperature may make no difference in what you wear for the day, but it can have huge impacts on what driving conditions are like.  The second important factor here is that water expands when it freezes such that the ratio of snow to liquid precipitation is 10:1.  Forecast models only determine the precipitable water for a particular area.  If that prediction is off by 0.2 inches this could be the difference between 1 and 3 inches of snow, which is a rather big deal when it comes to driving.  But it’s not always a matter of the forecast model being wrong in terms of precipitable water.  Across any storm system there is going to be variation in the amount of precipitable water and thus getting the storm track exactly right also matters.  Mix this in with a possible slight error in forecast temperature can lead to a vast difference the amount of snow accumulation for a particular location.  On top of that the 10:1 ratio is more like 7:1 if the snow is really wet, so this adds error into the forecast as well.

Weather is a matter of Scale

Image result for synoptic scale mesoscaleA lot get’s said about the difference between weather and climate, but very little is said about differences among various types of weather systems.  Typically, the average meteorologist separates scale into 3 categories.  Turbulent eddies near the surface to convection currents in clouds make up the microscale (< a few km) A thunderstorm or a system of thunderstorms or series of cloud bands for lake effect snow would be part of the mesoscale (about 10-100 km, several hours), and then things like low pressure systems would be on the synoptic scale (about 1000 km, several days).  Our ability to forecast events along these scales depends largely on our ability to make observations smaller than the scale we are trying to predict in both space and time.  For instance if I am at a station 100 km away from the nearest station, even if I make continuous observation a thunderstorm that happens somewhere in between will not be observed by me.  When you look at the number of tornadoes in the U.S. over a 100 year period, you will see a dramatic rise in the number from a few hundred to over a 1000.  This is no climate change phenomena, but a matter of our ability to observe tornadoes, and the advent of a national radar network that dramatically increased our ability to determine where tornado producing storms were.  Similarly if I make observations only two times a day, I’m unlikely to be able to resolve well the changes that occur between those observation times.

Computer models that forecast weather have similar problems.  Computer models operate by breaking up the atmosphere into a 3-D  grid that then processes the physical equations that describe the atmosphere at equal time intervals.  The size of these grids and the spacing of the measurement network that gives the initial data for these models to work lends itself best to the forecasting on the synoptic scale.  What this means is that we are likely to best forecast the development and movement of low pressure systems and high pressure systems, and forecast widespread rain.  The timing and movement of individual thunderstorms represent processes that occur at the sub-grid level.  In essence, noise.  Obviously a potential hail or tornado producing thunderstorm is not really noise, but this is why your forecaster is pretty good at telling you when that cold front is coming through the next day, but not so good at pinpointing where thunderstorms will be the strongest.  That type of accuracy is usually only made several hours in advance.  Although we’re pretty good at assessing a day or two in advance which day will have a high potential for thunderstorms.

Practical vs. Theoretical

When it comes to the theory about how weather works we are, in general, ahead of the game, but practical considerations take precedent.  For instance we could do an excellent job of forecasting if we had weather data every 10 km over the surface of the earth and sent up weather balloons once every hours.  The cost however of such an enterprise would be enormous.  Especially considering it’s very difficult to get this information over the ocean.  Remote sensing devices like satellite and radar are making strides in provide better spatial coverage, but even those have limitations.  We are never going to have perfect data over as wide a range and as often as we need it, and this is always going to lead to some error.  Computer power is also a practical limitation although it has accelerated greatly since the first model.  Previously, with all the theory we knew, trying to create a model that matched our data network would have taken the computer so long to produce an output that the time we were trying to forecast for would have been past.  This is no longer a terribly relevant problem, but it is if we really want to be able to break into models that compute both synoptic and mesoscale features.  It’s a bit hard to explain but you can think of a computer model as potentially like a nesting doll.  We could run a model at the smaller scale within in each grid of the synoptic scale model.  So a model within a model.  That becomes computationally laborious and can take intense amount of computer processing power.

Image result for sounding stations north america weather
It might look like a lot, but these are all the weather balloon stations in North America. Typically one or two per state and at minimum more than a 100 miles apart, and in some cases more than 500. Canada is worse. Not near enough for getting good data for thunderstorm formation.

Then we have the reality of cost-benefit analysis.  Decisions about weather research and preparedness have a lot to do with what the costs are.  This is hardly surprising.  If snow is rare in your city you might find that it’s easier for the city to just close down for a day than spend a lot of money on snow plows.  As mentioned above, to take ideal amount of measurements would be of great cost and despite the scientist’s love of data, the question must be asked do the gains in forecast accuracy outweigh the costs.  Improved technology can help reduce cost and make instruments more maintenance free, but instruments still need to be recalibrated, replaced and maintained.  These instruments are outdoors and can get pelted by hail, get dirty, or get spiderwebs or hornets nests, etc.  You will find the densest network of measurements in areas where lots of people live.  Sparsely populated areas, areas with complex terrain, will have less measurements and this means they will experience greater errors in forecasting.  In addition to the complex wind flow that occurs in mountainous areas leading to a large variability in conditions, there are far few weather observing stations.  If you live in such a region you are likely less than impressed by your local forecaster.

The Answer is Blowing in the Wind

The prevailing wind direction in mid-latitudes (where most of the U.S. resides) is from west to east.  Thus even being downstream of areas that have sparse observing stations also are more poorly forecasted.  The best way to know what weather you are about to get is to have good measurements upstream of your location.

Communication Breakdown

Finally, there are also communication issues.  The National Weather Service has put a lot of effort into this area, to think how to better communicate and disseminate weather information.  For instance if we have a particular graphic showing probabilities for where the eyewall for a hurricane is going to hit, is that graphic communicating what it needs to the person who needs to see it, whether that’s an emergency response worker or the average person?

Image result for hurricane eyewall probability map
                          How well do you understand what this graphic is showing you?

In this day and age of instant media and social media, it should in some ways make communication easier, but what I’ve noticed that it’s not always clear whether people are paying attention to the most current information, if they’re getting their information from a good source, and even if it seems whether or not they are aware what location a particular forecast is for and may think a forecast was bad even if it wasn’t for where they live.  As I mentioned at the beginning there is also a lot of clickbait and alarmist language being used.  Things like “bomb cyclone” and other colorful adjectives.  At the same time there has been criticism that the normal scientific tendency to temper their language in communicating important information may make people pay less attention to situations they should pay attention to.  Undoubtedly there are going to be consequences of both extremes.  Overuse of strong language, especially when conditions end up not being that extreme can numb the public to more dire warnings. Trying to find the best way to get people to understand, and pay attention is difficult, but this is a challenge the weather community takes seriously.  In the end, there probably is no perfect way to communicate, and it is up to the consumer of the information to educate themselves as well as to what this weather stuff is all about.

Hopefully this little piece helped explain a few things.  If you have any other questions, let me know.  I’ll add to this so this remains a fixed guide to helping people understanding the challenges in forecasting and why we might have misconceptions about forecasting accuracy.

 

 

Technological Literacy

I’ve been thinking a lot about technology lately. There are times when I feel I have made it too big a part of my life.  While I tend to be positive about this new age we live in, as I’ve written before, there are times when I feel like I might not be made for it because it can get very draining.  I see too much of the compassionless banter in comments sections or Facebook threads; story after story of tragedy, injustice, or prejudice.  Then there are times when I miss it.  There are people I have good conversations with over the internet.  There are moments where I laugh, and there are plenty of moments when I learn something valuable, something important, and something that will make me a better person.  I think about my many friends, some who I have known in person and live far away from, and I can still keep in touch and follow their lives to a certain extent.  I care and wonder about them often and the internet gives me ways of staying in touch that would be harder without it.  Some friends, I have never even met in real life, yet all of who I enjoy learning from, getting to know better, and some who have become as close as any other friend in my life, always provide me with an enriching experience.  In some ways I feel like my life would be less for not having met them and am thankful I have this thing called the internet that has such long arms that I can reach across the world and hold on to people that seem amazing to me and when they reach back I know it’s the beginning of a wonderful relationship.

I’ve been listening to a podcast on NPR called Invisibilia and one episode on there is looking at how computers have changed our lives and how they might change our lives in the future. What’s interesting is that you find many people who have zero problem with the way computers and related technology (smart phones, tablets, Google glasses) have become a regular part of our lives and have made us better humans.  They are ready for the future and all the wonders it will bring.  One gentleman named Thad Sturner believes that in time humans will have interfaced with computers so completely that eventually we will all become essentially cybernetic.  Those that have lived more “integrated” lives claim that the technology has made them better in every way, from how well they do their job to more meaningful face to face interactions with other humans.

Still of course there are those who have a not so favorable view of it. It can be addictive like anything else, and often not in a healthy way.  The validation we often get when we post things on-line through likes and comments can often give us a dopamine release but doesn’t necessarily help us really solve problems we might have or understand issues that make us upset.  A study of Chinese tweets found that anger was the most common emotion expressed over social media, and the anonymity of the internet can cause many people to let out cruelty that they would never let out in a face to face situation.  However that anonymity can also allow people to participate in discussions and express themselves in positive ways, that they may be too shy to do face to face, or because of societal pressures that prevent them from expressing themselves in ways that they would wish.

Rather than spend a lot of time posting all the research about how social media and the internet has or can change us, what’s clear is that academically a lot of people are studying it. People find adverse effects and positive effects.  It seems to me that most of what gets posted are negative impacts of technology or that our choices are between using technology and dealing with the consequences or backing away from it because it is seen as an unhealthy source of stress, shame, or anger.  But perhaps the time has come where we shouldn’t be trying to fight technology.  Our children are going to be immersed in this world, and while there is no doubt that developmentally children need time away from the screen, they are still going to be using smart phones, and tablets, and computers regularly in their lives.  So what they really need from parents, teachers, and society is the simple acceptance of this fact and need to be taught what are the harmful and beneficial behaviors in this new world of the internet and social media.  They need to learn about better ways to communicate through this medium.  They need to be reminded that technology is always a tool to be used as a means to end, and not the end itself.  As a tool, the internet, computers, social media have a vast variety of uses some good and some bad; some enhancing our functions, some suppressing or adversely shaping our functions.   As parents of this next generation we must help our keeps be effective navigators in this digital world, not just literate in finding information and surfing the web, but navigating the emotions, the attitudes, the pitfalls, and the advantages of this world.  Just like being aware of cognitive biases helps us perceive the world in a better way.  Being more aware of the impacts of computers in our lives will help us utilize the technology better.  I would support modern research about the interaction between humans, computers, and social media being used to design a curricula to be taught to school children. Perhaps around middle school.  I think it’s become that important.

I had recently reblogged a couple of good ethics posts about robots and artificial intelligence and what challenges our future holds. This era is coming sooner or later and so it’s time we gave up the fight against these technologies and start using them in a more moral and impactful way.  I say this not in any kind of judgment either, but rather as one who struggles with this myself.  We need to gain the literacy and positive ethics with this technology so that as new technology develops with the potential to be more world changing, that we can don’t find ourselves behind the curve as we seem to be today on the more negative aspects.

I for one am making a vow that I am going to work to use technology in a way that enhances me  and my world instead of diminishing me and my world.

Parinternetiatrician

The internet gets a lot of flack these days.  And why shouldn’t it?  It’s destroying the fabric of modern society.  I know it to be true, because some very important people have blogged about it and I have watched some of their news reports on YouTube.  It’s always tough to stay current with these issues when you have a social media addiction.  I’m trying to not let it stress me out though. 🙂

Seriously internet and social media haters.  You’d be at least half as popular as you are now if it wasn’t for that massive exposure the internet gives your un-researched and unsubstantiated nonsense.   You can be addicted to a lot of things, some are far worse than others.  And “Experts” are always worried about addiction in kids.  Music, video games, drugs, sex, violence, texting, etc.  Right now my kid is pretty addicted to breast milk.  It’s ALL he eats.  I’m a bit worried.  I figure with enough things out there to get addicted to, at least there is choice.  At least theirs diversification in the things they are addicted to. 😉

Of course, I don’t think the internet is a bad thing, and to be quite honest it has been the greatest companion through this whole baby thing.  I want to of course make it clear before I say anymore that I am not suggesting the internet is any kind of substitute for a doctor in any way, shape or form, but let’s face it, there is a lot of stress to this process, and as a whole the information that is available on-line helps.  A lot.

In an effort to confuse you I’ll start of negating my previous statement, by saying that I was a bit annoyed at the internet at the beginning of the

From see7aa.blogspot.com

pregnancy.  A lot of information out there seems focused on worst-case-scenario things without giving you any sense for what type of probabilities we are talking about.  For instance when my wife was feeling incredibly thirsty in her first trimester, several sites said “this is normal” (good), “not getting enough water can cause deformation in your babies limbs” (scary).  I mean what the hell people? How often does this happen?  How little water was the person getting?  I’m yelling at my wife “Drink water woman…limbs are deforming!!”.

Okay so it takes a little time to get used to the tone of information on the internet.  Once you get used to it, you realize that it is really just trying to help you.  “Here’s what you should do take care of yourself, and here is what CAN happen if you don’t”.  When it comes to having a baby, erring on the side of

From thetvchick.com

caution isn’t a bad thing, and I had to remind myself how inaccessible such nutritional and pre-natal care information would have been 30 years ago compared to now.  Of course back then they would have given you a pamphlet.  Does anybody seriously read pamphlets though?  They are small, recyclable, and look so much better folded then unfolded.  Unfolding something is messy.  Nobody wants that.  What people want is a search engine where you can just type in “I’m pregnant.  Why am I so thirsty?”  Web pages don’t fold.  They have links.  “Yes Mr. Internet (or Ms. Internet) I would like to know more about the importance of water to the build up of blood, amniotic fluid, and nutrient flow to the baby”.  Click.  Brilliant.

Baby merchandise.  You need to get stuff for your baby.  But what stuff?  What’s really important?  In a consumer driven society there is no question companies prey on our fear of ruining our babies lives and thus convince us to buy the most ridiculous things and pay a lot of money for them.  The internet can save you money.  It’s a huge marketplace, and thus competition drives prices down.  It also allows you to read a large quantity of customer reviews.  It appears that a lot of people have babies.  It tells you if you really need something, or if you don’t.  If you want to go green, organic or whatever you can find it on the internet.  If you suddenly become concerned because you never took a baby CPR training class, you can find a YouTube video on it.  How do I swaddle my baby?  How do I burp it?  What are some good songs that I can sing to it?  Can I hire someone to sing them for me, because I can’t sing?  The answers are on the internet.  All of these things can be easily ordered on the internet with a click of the mouse as you quickly vomit into the pail next to you because of your morning sickness.  Wandering around department stores, or Wal-mart can make you nauseous enough, and they typically don’t put reviews next to the items you are looking at on the shelf.  Only the price.  Thank you consumer friendly internet!

The internet is also your friend in other ways.  Let’s say you are just walking along, you’re pregnant, and all of a sudden your wrist hurts like a bitch.  So you think to yourself well I’ve known a lot of pregnant people in my time and their wrists seemed fine.  I must be defective and I’m going to bring doom to my baby somehow.  You get a bit anxious.  So you go on-line and you find a forum where it’s a whole bunch of women talking about their hurt wrists being pregnant.  Bam!  Instant group therapy session.  You are not alone.  Others have had the problem.  This is what they did.  This is something you can try.  This is something to talk to your doctor about.  Again, the internet doesn’t replace your doctor, but there can be a big delay between you experience something or having a question, and calling your doctor and waiting for someone to get back to you.  It can be stressful wondering if something is really wrong?  Should my baby be sneezing?  Why is his eye crusting up?  Is this normal?  Is it the plague?  OMG please don’t let it be the plague?  I thought the plague was over.  But there was that rat yesterday…it’s the plague.  It’s got to be the plague.  Tell me internet is it the plague?  It’s not the plague?  This is common?  Happens in 20% of newborns?  Clogged tear duct?  Oh that doesn’t sound so bad.  Panic attack quelled.  It can be easy to think that any little thing is not common or that it’s a sign of something serious.  You will be hard pressed as a parent to find a question that hasn’t already been asked.  A baby3million times.  And you will be comforted just because at the very least you will know how much you should actually worry. or how aggressively you need to try and contact your doctor, or whether you should go to the emergency room.  I would say that if the question you have hasn’t been asked before you probably need to go to the ER, or run a spell check on your question., or check your internet connection.  Most people out there are just like you.  They get a bit worried over small things, and even that you are not alone. And they are responded to by well meaning, experienced parents who politely share their experience with you.  Sure a few people on their blame your baby’s problems on Obama, but those people are few and far between.  If you are still confused at the end of the deluge of internet information, the doctor is still there to call.  But just knowing other people are experiencing what you are is such a great help.

So we can criticize this culture of instant gratification, but you know what, some things can’t be instant.  Just don’t fool yourself into thinking that everything can be instant and you’ll be fine.  For instance babies still take about 9 months.  So thank you internet!  I appreciate you.  You’re not all pornography after all.  Who knows what else might be contained within your four walls…hmmm…that doesn’t sound right.  Actually what is the internet contained in? Hmmm…question for another blog. 🙂