Apple #661: Blizzards

So about a week ago, I was out & about in the woods, as I am wont to do.  It started snowing, which I of course enjoyed.  Then the wind picked up and the snow got thicker.  It didn't take long before my coat was coated with snow, my gloves, the front of my pants, and later when I took off my hat which is brown, it was white with thick snow.  The trees were creaking and cracking in the wind, and the snow was coming down diagonally, stinging my cheeks.

But since I was wearing my super sweater, plus sweater tights under my pants, and various other warm and cozy garments, I was snug as a bug and digging the heck out of the crazy weather.  Some guy and I crossed paths--one of the few people I saw out & about too--and he grinned and said, through the wind and snow, "Awesome, isn't it?"    I grinned back and said, "Yeah, it is."



This squirrel and I were both digging the snowstorm.
Photo by the Apple Lady


I did wonder, though, was I out in a blizzard?  When does a regular old snowstorm cross the line into blizzard-land?

Crossing the bridge to blizzard land?
(Photo by the Apple Lady)

• For a snowstorm to be classified as a Blizzard, the following criteria must be true:

• The wind must reach speeds over 35 mph for 3 hours or longer
• Visibility must be less than 1/4 mile due to falling or blowing snow

Would you say this is visibility less than 1/4 mile? I really don't know.
Photo by the Apple Lady

• It's important to note that a storm could reach blizzard status without any falling snow.  The wind could pick up loose snow from the ground and blow it around, to the point that visibility is reduced to less than 1/4 mile.  That doesn't happen very often, but it is possible.  Technically, that's called a Ground Blizzard.

• In my particular snowstorm, even if the winds were as high as 35 mph (I did not have my anemometer on me so I don't know how fast the wind was blowing), and even if the visibility was that poor, I would have had to wait for 3 hours before calling it a blizzard.

• I wasn't out in that weather for 3 hours, but for the amount of time I was in it, I'd say that storm at least qualified as a Snow Squall:

• Heavy snow shower combined with gusty winds.
• May be short in duration, but can still bring a significant amount of snowfall
• Snow squalls are typical in the Great Lakes region. 

At the very least, a snow squall.
Photo by the Apple Lady

• On the other extreme, a blizzard becomes a Severe Blizzard when

• Winds are over 45 mph
• Visibility is near 0
• Temperatures drop to 10F or lower

• Unlike in regular blizzards, duration is not a factor.  I guess they figure, if things get that bad, it doesn't matter how long it lasts, it's just plain bad. 

If you want to see what the effects of a severe blizzard look like, check out what recently happened in Slovenia, plus other parts of Europe:




Sources
CBS Chicago, Blizzard vs. Snowstorm: What's the Difference?
National Geographic Daily News, What's the Difference Between a Snowstorm and a Blizzard?
Weather.com glossary, snow squall; blizzard & severe blizzard
Encyclopedia Britannica, severe blizzard
About.com, 9 Types of Snow Storms

Apple #621: Naming Winter Storms

Questions about why winter storms are getting named first came up in November.  I found an article about it and posted it to the Daily Apple news feed on facebook.  It seemed like that article covered all the bases and a full Daily Apple would only be redundant, so I left it at that.

But I see that some people are still asking questions, and it seems that the controversy about this practice is continuing.  So I thought a full Daily Apple entry was in order after all.



The Weather Channel's list of names they plan to use for winter storms.  Won't winter storm Ukko be fun?
(Image from weather.com)

• The Weather Channel is the only weather service that is naming winter storms.  They came up with this idea in November 2012, and they're the ones deciding which winter storms get names and what to name them.

• NOAA's National Weather Service (NWS), which is essentially the official weather service for this country, and the American Meteorological Society (AMS), which is the leading society of licensed meteorologists, are not participating in the TV channel's practice of naming winter storms.

• The National Weather Service is the official meteorological body that names hurricanes and tropical storms.  Unlike hurricanes and tropical storms, the NWS has not named winter storms for several reasons:

• winter storms can weaken and redevelop across a wide area, making it difficult to determine where one storm starts and another begins

• a winter storm can be very erratic, with several centers that may not be well-defined, so it's difficult to determine who will be affected, and how, by a "single storm."

• since the weather within a winter storm area can vary significantly (e.g., fog and rain in one area, heavy snowfall in another, wintry mix of ice and snow in still another), it may be confusing to call such a range of weather by a single name.

The radar maps below show what can happen with winter storms. In this system, there was a southern branch of this storm that was mainly freezing rain, though the northern swath also included freezing rain.  After a while, the southern branch broke away.  So was that 1 storm that became 2?  Would you then keep talking about the 2 branches with the same name?  Or were they really 2 storms that happened to be next to each other?

 
 

By the way, I deeply apologize for the use of Comic Sans in these images.  But they're from 2008, so hopefully the image creator knows better now.
(Weather radar maps from Chicago Area Weather Blog)

• In spite of such scientifically-based reasons for not naming winter storms, the Weather Channel, a TV station, decided to start naming winter storms anyway.  They say they decided to do so because:

• "Naming a storm raises awareness.
• Attaching a name makes it much easier to follow a weather system’s progress.
• A storm with a name takes on a personality all its own, which adds to awareness.
• In today’s social media world, a name makes it much easier to reference in communication.
• A named storm is easier to remember and refer to in the future."

• I find it interesting that when they say "raises awareness," they do not add "about the storm." I think they're hoping to raise awareness about The Weather Channel. 

• I think I'm guessing accurately because they also list this as their final (and I think real) reason: "Finally, it might even be fun and entertaining and that in itself should breed interest from our viewing public and our digital users."

• In other words, they're doing it for the ratings!  For the money!  They want to make it rain for TWC! 

• I imagine somebody at TWC pitching the idea something like this:

• Picture this: snow is forecast across several states a few days from now.  Everyone is waiting on tenterhooks to see what TWC will name the storm.  Everyone tunes in, and then when the storm is named, everyone uses TWC's storm-name and mentions The Weather Channel when they talk about how much snow is falling.  Think of the free publicity!  It'll be practically snowing mentions of TWC!   

• Well, that's my fanciful idea.  But in practice, things haven't worked out like that for TWC at all.

Behind the scenes at The Weather Channel.  I see a lot of TV-related stuff.  Not much weather-related stuff.
(Photo from Inc.)

• After TWC named the first winter storm Athena, the National Weather Service issued an internal memo, which said: "The NWS does not use named winter storms in our products. Please refrain from using the term Athena in any of our products."

• Publicly, the NWS said they didn't care if any private businesses wanted to go around naming winter storms, but the NWS wouldn't be doing that. 

• (Except they do name winter storms after the fact when they can tell exactly what happened where, and they can quantify the data.)

The NWS. Not afraid to zap bad ideas.
(Logo sourced from The Houston Chronicle)

• Shortly after this, meteorologists, weather forecasters & broadcasters, and just plain weather buffs from around the country started to weigh in.  Pretty much universally, they hated it.  In a nutshell, here are the reasons they gave:

• The TWC is doing this completely unilaterally.  They're not communicating with anyone else before they name the storms. Instead of fostering communication and awareness, by acting so independently from the rest of the weather community, they're actually creating disunity and fostering confusion. ("The Weather Channel has essentially tossed effective risk communication out the window"; "Who died and made them King?!")

• By deciding on their own and in secret when and how to name the storms, they are closing the process to scientific input.  Maybe it really would be a good idea to name winter storms, but by not allowing any peer review to take place, they're keeping their decisions at the level of gimmick, rather than a meteorologically sound practice.

• That said, naming winter storms as if they're one unified event really isn't accurate, and it is confusing, so they shouldn't be doing it. (“In unilaterally deciding to name winter storms, The Weather Channel has confused media spin with science and public safety. We have explored this issue for 20 years and have found that this is not good science and will mislead the public.")

• The criteria that TWC are using are very closely tied to ratings.  One of their determining factors is the amount of "impact" it will have, and they're defining "impact" in terms of the number of viewers--er, people affected.  Time of day (e.g. prime time-- er, rush hour) and day of the week (e.g., Monday vs. Saturday) are also factors.  Thus, in the eyes of TWC, not all winter storms are created equal. ("A bad winter storm here in CNY could miss out on getting named. Big lake effect events wouldn't count.")

• Compared to hurricanes whose effects are widespread, devastating, and deadly, while some winter storms can be severe, winter storms often do not approach the same level of threat.  Especially since winter storm "Athena" happened shortly on the heels of Hurricane Sandy, it was kind of laughable by comparison. ("TWC gimmick named it Athena today. Most mets [NYers] laughing at them.")

"Winter Storm Athena"
(Weather map from Heavy.com)


Hurricane Sandy
(Weather GIF from Hurricane Season 2012)

• So the upshot is, pretty much no weather service is joining in TWC's storm-naming games.  Instead of all kinds of happy bandwagon publicity, the real result seems to be that they've only created a vehicle that makes it all too obvious that very few people in the weather community take them seriously.  Call it Meteorology Freeze-Out Freddy. 

• See also #RejectedTWCNames

• By the way, guess who are part-owners of The Weather Channel?  NBC and Bain Capital. Talk about strange bedfellows.

Sources
Tom Niziol, weather.com, Why The Weather Channel is Naming Winter Storms, November 11, 2012
examiner.com, Weather Channel naming system backfires when NWS rejects Athena, November 7, 2012
Rob Manker, Winter Storm Athena? National Weather Service tells its forecasters not to use The Weather Channel's name for storm, The Chicago Tribune, November 7, 2012
Jason Samenow, TV weathercasters criticize unilateral action by The Weather Channel on storm naming, Washington Post blog, October 3, 2012
American Geophysical Union Blogosphere, Weather Channel Plan To Name Winter Storms Gets Frosty Reception, October 3, 2012
Weather Underground, MAweatherboy's blog, Why TWC Is Wrong To Name Winter Storms, November 9, 2012
Matthew Kemeny, 'Khan' shows its wrath on midstate highways; Weather Channel names winter storms to 'raise awareness, The Patriot News, January 25, 2013
Michael de la Merced, Weather Channel Is Sold to NBC and Equity Firms, The New York Times, July 7, 2008

Apple #593: Derechos

So I've been away on vacation, and I read about those derechos that hit several states.  They didn't hit where I was, and I had zero access to the internet or TV.  Those of you at home may have heard all sorts of explanations and definitions of a derecho already, but I had only a smallish daily newspaper, so I did not.  Now that I'm back among the swirl of telecommunications, I want to find out about these derechos.


The June 2012 derecho on the southeast side of Chicago.
(Photo from Twitter, sourced from The Original Weather Blog)


Mainly I want to know, what the heck are they, and is this some new term the meteorologists have cooked up?  Is this a sign that global warming is getting crazy?

Definition

• NOAA's Storm Prediction Center says that a derecho is a
• widespread
• long-lived
• wind storm,
• accompanied by rapidly moving rain or thunderstorms

• I'll take each of those attributes in turn.

• Widespread: extends in a swath of more than 240 miles or greater along most of its length.  In other words, the storm encompasses a huge amount of territory all at once.

 
Radar image of the derecho on June 29, 2012 (my birthday, by the way, and this is the second one to happen on my birthday).  This derecho was especially widespread, sweeping across 700 miles.
(Image from the National Weather Service, sourced from Wikipedia)

• Long-lived: this one seems to be inaccurate, since your experience of a derecho might seem relatively brief, only about ten or fifteen minutes.  But the key is that the derecho spans the entire 240+ miles, and the entire storm continues along that span for several tens of minutes. What's more, the system may take as long as 24 hours to develop and its entire lifespan can last 2 days.

• Wind storm: wind gusts have to reach at least 58 mph for the storm to get called a derecho. Why 58, I don't know.  Seems pretty random, but that's what NOAA says.  Sometimes winds can exceed 100 mph.

• The wind storm attribute has another important aspect, which is that while tornadoes spin and hop about, dropping down to inflict damage in a few places and hopping up to move someplace else, the derecho moves in a straight line across an area.  So a derecho is sometimes described as inflicting "straight-line wind damage."

• In fact the word derecho is Spanish for "straight ahead" or "direct." (More on the word origin in a bit.)

This field of corn in Indiana has been all smashed down by the high winds of the 2012 derecho. Gives a pretty good sense of a derecho's straight-line, strong winds.
(Photo from the DuBois County Free Press)

• Accompanied by fast-moving thunderstorms: usually there are several thunderstorms happening within the band, or bow, of the derecho.  There can be all sorts of downbursts, sometimes occurring a fair distance apart, or clustered together, or ganged in one big swath.  The downbursts themselves can individually last a brief time, but as the entire bow of the derecho moves across the landscape, more downbursts can get whipped up and release their rain.

You've probably seen this image of the 2012 derecho all over the place.  This was taken in La Porte, Indiana.  The front line is clearly visible here.  That's typical of thunderstorms, but this is like a line drawn in the sky with a ruler. And you can just tell by those roiling clouds that they are not messing around, this is going to be a big-ass storm.
(Photo by NASA Goddard Photo and Video)

• The damage caused by a swath of downbursts can be similar to the damage caused by a tornado.  What's more, a tornado or tornadoes can occur within a derecho.  During a May 2009 derecho, 45 tornadoes were reported.

• The damage a derecho can cause typically includes uprooted and fallen trees or utility poles; overturned boats, SUVs, or even cars; collapsed barns and small buildings; and flying debris including tree limbs, roofing material, broken glass, etc. Power lines are also very vulnerable, and power outages that last for extended periods of time across large areas are very likely.

• In the June 29, 2012 derecho, 3 million homes were without power, 12 people were killed, and 20 people were injured.

This is in the DC area, after the 2012 derecho. The root mesh is sticking up 10 feet in the air, which gives you an idea of how large this tree is. Note the power lines pulled down by the tree.  This sort of thing happened all over the place, which is one of the reasons it took so long for the power to get turned back on for so many people.
(Photo by woodleywonderworks on Flickr)

How, When, & Where Derechos Form

• Meteorologists have a tough time predicting derechos for several reasons:

• because derechos encompass so much territory, and it's hard to amass all the data in time to put together that big a picture. 

• because sometimes a derecho can form very rapidly when several thunderstorms suddenly gang together to form one great big storm

• because meteorologists still don't understand enough about how and why they form

• But some things about how derechos form meteorologists do feel fairly sure of:

• They happen most often in May, June, and July. These months are when thunderstorms are more likely to occur.

 
Months when derechos are most likely to happen in the United States
(Graph from NOAA)

• They often happen in the midst of a heat wave. When a large upper-level high pressure system just sits over the Midwest, something called an elevated mixed layer (EML) of air forms.   This means that above the place where the hot air is just sitting, as you move higher into the atmosphere, the temperature drops rapidly with each incremental climb. There's no breeze mixing up or even moving the hot air down below, so it gets all concentrated there, and the cool air up above doesn't move around either.  Big differences in air temperature is the main thing that results in big storms.

• They may also happen in early spring or early fall.  This is less common, but it can happen. Derechos that spring up during these times are a little different, since they're associated with very strong low pressure systems, as opposed to those long-lasting high pressure systems.

• They tend to occur east of the Rockies.  The Rocky Mountains are tall enough that that big fat layer of hot air can't sit in one place low to the ground, so the EML doesn't develop above it.  This is why derechos usually happen in the Plains states or in the Midwest, or occasionally along the Atlantic.

 
Map showing how likely derechos are to occur in various parts of the United States. From this map, it looks like derechos never occur west of the Rockies.  That isn't exactly true; they have happened in the West, but extremely rarely.
(Map from NOAA)


I wonder if the stratifications visible in this cloud -- which is the 2012 derecho -- are the stratifications that occur in the elevated mixed layer.
(Photo from WordlessTech)

Derechos and Global Warming?

• By now you've probably gathered that derechos have been known to meteorologists for a while. The term was first coined by a physics professor, Dr. Gustavus Hinrichs, at the University of Iowa, in 1888.  One of the storms he used as a basis for his term occurred in 1877.

 
Hinrich's figure depicting a storm he was the first to call a derecho sweeping across Iowa in 1877.
(Image from NOAA)

• So they're nothing new.  It's apparently only that the term hasn't entered common (that is, non-meteorological) parlance until recently.

• Since derechos are often linked with heat waves, it is tempting to think that if global temperatures rise, we may see more derechos in the future. But meteorologists hesitate to make such a leap.  For one thing, they say they don't have enough data to 

• make a definite link between greenhouse gas emissions and heat waves, or indeed any weather pattern associated with derechos

• come up with any consistently reliable weather pattern for derechos in general.  They simply don't have enough records or enough data about derechos to make these kinds of sweeping generalizations about them.

• In fact, while they have a list of derechos that have occurred in the past, they say right up front that they know the list isn't complete.  All the sites I checked on this refer to NOAA's list of "noteworthy" derechos, which is to say, it's nowhere near all of them.

I don't have anything insightful to say about this photo other than holy crap, look at that thing. This is Minnesota, June 29, 2012.
(Photo by Brittney Misialek for the Minnesota Star Tribune)

• So there's no way to be certain of all sorts of things; for example, how many derechos happened in the late 1800s when the term was first coined, or even before that.  Which means scientists can't compare the frequency now with the frequency then and therefore can't draw any real conclusions.

• The list of noteworthy derechos, in chronological order, goes like this:

• July 4, 1969: Ohio Fireworks Derecho
• July 4, 1977: Independence Day Derecho
• July 4-5, 1980: More Trees Down Derecho
• June 7, 1982: Kansas City Derecho of 1982
• July 19, 1983: I-94 Derecho
• May 17, 1986: Texas Boaters' Derecho
• July 28-29, 1986: Supercell Transition Derecho
• May 4-5, 1989: Texas Derecho of 1989
• April 9, 1991: West Virginia Derecho of 1991
• July 7-8 1991: Southern Great Lakes Derecho of 1991
• March 12-13, 1993: Storm of the Century Derecho
• July 12-13, 1995: Right Turn Derecho
• July 14-15, 1995: Ontario-Adirondacks Derecho
• May 30-31, 1998: Southern Great Lakes Derecho of 1998
• June 29, 1998: Corn Belt Derecho of 1998
• Sept 7, 1998: Syracuse Derecho of Labor Day; NYC Derecho of Labor Day
• July 4-5, 1999: Boundary Waters-Canadian Derecho
• May 27-28, 2001: People Chaser Derecho
• July 22, 2003: Mid-South Derecho of 2003
• May 8, 2009: Super-Derecho of May 2009
• June 28, 2012: (not yet named as far as I know)

• Now here's what they look like put on a timeline:

 (Data from NOAA; chart by the Apple Lady)

• According to this very incomplete data, it's tempting to conclude that there was a spike in activity in the mid-to late 1990s and that it's declined again.  But you can't make that conclusion because this isn't all the derechos that have occurred, only the noteworthy ones.  So it's impossible to say whether they're increasing in frequency or not.

• Many meteorologists say that you can expect about one derecho every year or two somewhere in the US.  Usually they're not as huge as the one we had this year, though.

Derecho from May 27-28, 2001 near Fort Supply, Oklahoma.
(Photo from NOAA, by Douglas Berry)

• Some evidence suggests that derechos seem to be more damaging because shade trees planted in the postwar years in urban and suburban areas are now matured, so many more trees have fallen in recent years.

• So the final answer on the relationship between derechos and global warming is maybe. 

Man, the wind pulled up that tree and the grass like it was sitting in carpet. This is in Vineland, NJ, and that's Grace.
(Photo from MyFoxPhilly, taken by Margaret Hartman)

Related entries: Thunderstorms; Where Does the Debris Go?

Sources
NOAA Storm Prediction Center, About Derechos
Kristina Pydynowski, Intense Storms Called a "Derecho" Slam 700 Miles of US, AccuWeather.com, July 2, 2012
ABCNews Good Morning America, "Derecho" Storm Ravaged Washington Area, July 2, 2012
Jason Samenow, Did global warming intensify the derecho in Washington, D.C.? Washington Post Local, July 5, 2012

Apple #538: Thunder

We had a pretty hefty thunderstorm here today. I was listening to the thunder for quite a while before the storm actually arrived. I like the sound of faraway thunder. It reminds me of stomach grumbling sounds. I find it almost soothing.

The more I listened, though, the more it occurred to me how mysterious a phenomenon it is. So I thought, time to remind myself how thunder works.


When you type the word "thunder" into a Google image search, you get all kinds of pictures like this, of lightning. That's because thunder is the sound that lightning makes, and it's really hard to take a picture of sound.
(Wallpaper photo from layoutsparks.com)

• Very simply, thunder is the sound that lightning makes.

• There is no thunder without lightning, and no lightning without thunder.

• Lightning gets really hot, many times hotter than the surface of the sun. The air around the lightning strike gets heated up and compressed by that flash of electricity. Very quickly the compressed air explodes outward in waves, and that's what we hear as thunder.

• Now I'll slow it down and explain the process in more detail.

How Thunder Happens

• When thunderclouds or cumulonimbus clouds form, they take that shape because the hot air in the cloud is rising away from the cooler air at the bottom of the cloud.

• Positively-charged electrons cluster in the hot air at the top, and negatively-charged electrons gather in the cooler air at the bottom.

Distribution of charged particles in a thundercloud. Negatively charged particles are at the bottom of the cloud.
(Diagram from Museum of Science)

• Eventually the division between the two types of electrons becomes so great that the electrons simply must meet up with each other. Sometimes the electrons find each other from one cloud to another. Sometimes the negatively charged electrons at the base of the cloud link up with the positively charged electrons on the ground.

Negatively charged particles at the bottom of the thundercloud are seeking the positively charged particles on the ground. This is the first part of a lightning strike, a cloud-to-ground flash.
(Diagram from Museum of Science)


The second part of a lightning strike is the ground-to-cloud flash.
(Diagram from Museum of Science)

• In either scenario, intra-cloud or cloud-to-ground, a huge charge of millions of volts of electricity is created. We see that exchange of electrons, that huge burst of electricity, as a flash of lightning.

• When the lightning flashes, the air gets heated to incredibly hot temperatures that can be anywhere from 18,000 degrees F to 60,000 degrees F. That's up to 6 times hotter than the surface of the sun.

• Normally, when things get hot, they expand. Spread out. But when the lightning flashes that hot and that fast, the air doesn't have enough time to expand.

• So all that super-hot air is bunched up together, or compressed. The pressure is so great that, blammo, the hot air explodes outward. That explosion of hot, compressed air is thunder.

• When you blow air into a bag and smack your hand against the bag to make the bag burst, you hear a loud POP. The air breaking the bag and escaping out through the hole in a rush is what makes that sound. That's pretty much what happens when you hear thunder.

Why Thunder Sounds the Way it Does


This is one reason why thunder rumbles. Lightning bolts strike in jagged lines. Each bend in the bolt sends out waves in a different direction. So the sound waves start out traveling in ripples in all sorts of directions.
(Image from the Weather Doctor)

• We hear the thunder as a rumbling sound essentially because that explosion of air travels in waves.

• When you hear far-off thunder, a lot of things have happened to the sound waves before they've reached you. The waves will have bounced off other clouds, buildings, the surface of the earth, all kinds of things first. So the sound waves are actually arriving in bits and pieces.
  

• Also, some of the sound waves also will not have managed to travel the entire distance to you. So it won't be as loud and distinct, but will sound long, drawn-out, and soft.

• The higher frequency sound waves don't travel as far as the lower frequencies. By the time far-off thunder reaches you, only the lower frequencies will have made it that far. Think of how, as a car approaches playing music, you can hear the thump of the bass long before you hear any of the melody.
  

• All of these things taken together plus the effects of wind and variations in air temperature are why, when a thunderstorm is still far away, the thunder sounds like long, low, soft rumblings.

Boy, that's a really beautiful picture of lightning at sunset. isn't it? But look for a moment at all the branches of lightning, and notice all clouds that are nearby. You can almost imagine how the thunder will start shooting off in all directions, and how it will bounce off those clouds and maybe those hills and the trees before it gets to you.
(Photo from crystalinks)

• As lightning gets closer, the sound of its thunder changes. It sounds less like rumbling and becomes quicker, sharper, until it's so close it sounds like a single, loud CLAP. When the lightning is that close, the sound waves haven't bounced off anywhere near as many things before getting to you, you're hearing the higher frequencies as well as the lower frequencies, and you're hearing a lot more of the sound waves.

Thunder Without Lightning, or Lightning Without Thunder?

• Q: Everybody always says light travels faster than sound, and this is why, when a storm is close, we see the flash of lightning before we hear the sound of thunder. But as a storm approaches, we usually hear the thunder long before we see lightning. Shouldn't it be the other way around? Shouldn't we see lightning long before we hear thunder?

• A: We hear the thunder as a storm approaches because those lightning flashes are happening several miles away. In between that lightning flash and us are all sorts of clouds and rain. The lightning is actually getting obscured by the storm itself, but we can still hear the thunder because those big, low frequencies slowly bounce their way to us in spite of -- or maybe even courtesy of -- the rain and the clouds.

• Also, 85% of lightning happens from one cloud to another, never touches the ground. So we may be hearing thunder from lightning that's happened inside clouds, where we can't see it.

On a dark, rainy day like this, it might be too cloudy to see lightning.
(Free photo from Google Chrome web store)

• Q: You say there's no lightning without thunder, but how come I sometimes see heat lightning flashing in the sky like mad, and I never hear any thunder?

• Heat lightning is essentially the opposite of what I've just described. In this case, the thunderstorm is so far away, the lightning reaches us but the sound of the thunder does not. In this situation, the sky around us is clear enough that clouds don't obscure the sight of the lightning that's happening many miles away.
  

• We call it heat lightning because it usually happens to be hot and hazy where we are when we can see the far-away storm, and people assume that it's the heat that's creating the lightning. But in fact the heat where we are has nothing to do with the lightning that's happening in the storm a great distance away.

You might think this is heat lightning. But really it's lightning that is happening very far away, and it happens to be hot where you're standing when you see it.
(Photo from Wikipedia)

• When conditions are right, you can hear thunder as far as 12 or 15 miles away. By contrast, if there aren't clouds in the way, you can see lightning happening as far as 100 miles off.

• If you hear thunder, somewhere there was lightning. If you see lightning, somewhere there was thunder.

What's that thing about counting the seconds between lightning and thunder again?

• When you can both see lightning and hear thunder, count the seconds that pass between the lightning flash and the thunder.
  

• Each second represents about 350 meters, or about 4 football fields.
  

• That gives you a rough idea of how far away the lightning is.

Related entries: Lighting, Lightning Striking Airplanes, Thunderstorms


Sources
Science Made Simple, What Is Thunder?
Library of Congress, Everyday Mysteries, What causes the sound of thunder?
Weather Wiz Kids, Experiments, Make thunder, Lightning
Weather Imagery, Facts About Thunder
Amber Wozniak, Northern Michigan University, When Does Lightning Occur and Why?
Meteorologist Jeff Haby, theweatherprediction.com, What is Heat Lightning?
Howstuffworks, Can you calculate how far away lightning struck by how long it takes for the thunder to arrive?

Apple #505: Record Snowfalls

With the incredible amounts of snow that have blanketed all sorts of places across the country in the past couple of days, I got curious about snowfall records.  What are some of the records for snowfall, and how do those compare to the current situation?

So what location would you expect to be the snowiest place in the country?  Maybe Alaska, or maybe in the mountains?  You'd be correct.

According to NOAA's National Climatic Data Center, the location that had the greatest amount of snowfall in one day was Georgetown, Colorado, on December 4, 1913.  They got 63 inches in one day.  That's 5.25 feet of snow.


Where Georgetown, CO is.  It's an old mining town outside of Denver, elevation 8,520 ft.  So, yeah, you'd expect this place to get some snow.
(Map from ePodunk)

The place that got the greatest daily snow depth -- that would be snow that's accumulated over some unspecified number of days, but it's continued to pile up -- was recorded by the Rainier Paradise Ranger Station in Washington. This is in the Mount Rainier National Park. They managed to get an accumulated 293 inches of snow.  Or nearly 25 feet.
 

The star marks the location of Mount Rainier National Park.  It's about a 3-hour drive from Mount St. Helens.
(Map from National Parked)


Mount Rainier, which is actually a volcano, is in the pretty much in the center of the park.  The Paradise Ranger Station is on the south side of the mountain.
(Map from Gorp)

Mount Rainier's elevation, as you can see, is over 14,000 feet.  The ranger station, quite a ways down from the top of the volcano, is at 5,550 feet.  The ranger station's average snowfall for December and January is between 105 and 175 inches (those are monthly totals). So yeah, another pretty snowy place.

The place that got the most amount of snow to fall over the course of a month is Tamarack, California, which got 313 inches of snow in the month of March in 1907.  That's more than 26 feet of snow.


Tamarack is a tiny place, so tiny I couldn't find a map that indicates it.  It's south of South Lake Tahoe and east of Sacramento.  It's in the Sierra mountains.
(Map from Always on Vacation)

The Central Sierra Snow Lab has an even bigger monthly record: 390 inches in Tamarack in January 1911.  I don't know why NOAA doesn't have that 1911 amount.  But Tamarack, high in the mountains, is another regularly snowy place.


The place that's racked up a ton of records is Thompson Pass, Alaska.


Here's Alaska.  The place we're interested in is on the peninsula that sticks out into the Prince William Sound, near Valdez.
(Map from Sarah Palin Truth Squad)


Thompson Pass is at the top of that peninsula, just northeast of Valdez.
(Map from Moon Travel Guides)

Their big records came in 1953 and 1955. They win for the following:

• Greatest 2-day snowfall: 120.6 inches, December 30, 1955
• Greatest 3-day snowfall: 147 inches, also December 30, 1955
• Greatest 4-day snowfall: 163 inches, also December 30, 1955
• Greatest 5-day snowfall: 175.4 inches, the next day, December 31, 1955
• Greatest 6-day snowfall: 172.6 inches, February 24, 1953 (1953 beat 1955)
• Greatest 7-day snowfall: 186.9 inches, February 25, 1953
• Greatest snowfall August through July: 974.1 inches, 1953

So Thompson Pass, Alaska is another always-snowy place.

Let's put these numbers into perspective.  170 inches of snow is about 14 feet.  Some of those other records were for 25 and 26 feet.  But what does that much snow look like?


This is Jim. He's standing in front of a snow drift about 15 to 20 feet high.  This is at Crater Lake, Oregon.
(Photo from Fred and Hank Mark America)


This is the gift shop at Crater Lake, surrounded by snow, probably also somewhere between 15 and 20 feet.  As Jim from the above picture says, "Does this gift shop/cafe remind you of the Overlook Hotel or what?"
(Photo from Fred and Hank Mark America)


This photo along with a couple others showing construction equipment shoveling out snow have been getting passed around the internet for several years now. This is probably from Newfoundland or Labrador, in Canada. How much snow would you say is here, 12 feet? 15 feet?
(Photo from Snopes)


No idea where this is or how much snow is here. 20 feet or more?
(Photo from Gallary Photo)


Here's Chicago in 1967.  4 inches of snow were predicted, but they got 23 inches total instead.  It started snowing on a Thursday in January, kept it up all day, and continued until early Friday morning.  Two days before, the temperature had hit a record 65 degrees.

(I think these are Chicago Tribune photos, but I found them at PlanetBarberella)


(Photo from PlanetBarberella. She has tons more good ones at her site)


Now here's Chicago on February 2, 2011.  I can't seem to find any definitive snowfall amounts, but apparently various locations around the city are reporting anywhere from 20 to 24 inches.  The winds got up to 60 or 70 miles per hour at night, which made for lots of snow drifts.


This is roughly near Logan Square
(Photo from Avoision)


Liz is standing in thigh-deep in the snow.  There's an undefined amount of snow between the bottom of her feet and the ground, but probably if she'd been able to tunnel down that far, the snow would be to her waist.
(Photo from Avoision)


This is Milwaukee Avenue, normally super-busy.  Normally, there's no way people would be able to walk any distance in the middle of that street.  But today, because of all the snow, it's a completely different story.
(Photo from Avoision)


Now here's what two feet of snow looks like:


Har har.
(Snow sculpture by G. Lynas, photo sourced from Lorna Sass At Large)


Okay, so my whole point was, all those places that got record-holding amounts of snow were in places where you'd expect a ton of snow.  High in the mountains, or in Alaska.  Those places get 20+ feet of snow, while Chicago got 20+ inches. But I still find the amount that Chicago got to be impressive because Chicago is nowhere near any mountains.

That's what being close to the Great Lakes will do for you.


Sources
NOAA National Climatic Data Center, National Snowfall and Snow Depth Extremes Table
ePodunk Georgetown Community Profile
USA Today, Climate of Mount Rainier National Park, Wash.
National Park Service, Mount Rainier FAQs
The Storm King, Sierra Snowfall
Chicago Tribune, The Chicago Blizzard of 1967
National Examiner, Punxsutawney Phil and the Blizzard of 2011: Record snowfall in Chicago, Midwest, February 2, 2011

Apple #503: Lightning Striking Airplanes

So I was watching a really bad and therefore entertaining disaster movie this weekend.  It was one of those global-warming-is-causing-crazy-weather-and-destroying-the-planet situations.  


The movie in question, Category 7: The End of the World. A storm with multiple tornados is on the path to colliding with a hurricane. Starring such luminaries as Randy Quaid, Shannen Doherty, Robert Wagner, Swoosie Kurtz, James Brolin, Tom Skerrit, and more. Superb 3-star entertainment.
(Photo from Amazon)


At one point in this movie, Tom Skerrit had to fly his airplane into one of these really bad storm clouds to collect weather data, and his plane got struck by lightning.  It wasn't just a simple lightning strike, of course, but one that enveloped the plane in blue zappy light.  This caused me and my movie-watching companion to wonder, what happens in real life when a plane gets struck by lightning?

• The short answer: not much.

• In 2001, an engineer for a company called Lightning Technologies Inc (LTI) wrote an article for Scientific American about lightning strikes and airplanes. His company makes equipment to protect airplanes from lightning strikes, so apparently he knows a lot about the topic. Anyway, everybody has been quoting his data ever since.

• According to this LTI guy, somebody (the FAA?) estimated that, on average, each US commercial airplane gets struck by lightning at least once a year, if not more often.

• But even though lightning strikes are rather common, they don't do a whole lot of damage. 

• The National Lightning Safety Institute says that since 1959, there have been 7 airplanes in the world that have gone down due to lightning strikes.  The last US plane to have gone down due to lightning was a Pan Am Boeing in 1963.  Given that each commercial airplane gets struck by lightning once or twice a year, the fact that none have crashed due to lightning in 48 years is a pretty good safety record. 

• Most of the time, passengers are completely unaware of it if lightning strikes an airplane in flight. Sometimes they may notice a bright flash or hear a loud noise, or the lights in the cabin may flicker.  But usually everybody flies onward, blissfully ignorant.

• After a plane has landed, the ground crews and pilots walk around the outside of the plane to check for any damage. They do this for every plane, at every landing.  Damage from lightning strikes is one of the things they look for. Such damage is usually very small, burned-looking hole about the size of a quarter, and most often at the tip of the wing or the tail.

Small burned patches where lightning entered and exited the nose of this private plane. This type of lightning damage is even smaller and less common on commercial aircraft.
(Photo from Learn to Fly)

• But most of the time if a plane does get struck by lightning, there isn't even this much damage. Usually, the plane is pretty much unaffected. This is because airplanes have been engineered, since the 1930s and more recently, to withstand lightning strikes.

• First of all, the outer "skin" of an airplane is made almost entirely of aluminum.  Aluminum conducts electricity very well, which means that if lightning strikes the plane, the bolt won't zap through the frame but instead the electricity will travel along the skin and exit at one of those pointy places, usually the tail or the end of the wing.

• If the "skin" has other metals in it that are less conductive, the manufacturers will add composites which are more conductive.  They'll line the outside of the plane with these composites in such a way that they'll act as a kind of channel or pathway for the electricity to follow along the body of the plane toward the pointy places at the extremities. 

• The nose cone (radome) contains the radar and electronic equipment associated with the flight instruments, and those can't be covered with conductive material or they won't work.  So the nose cone also gets additional strips of conductive material applied along it.  Sometimes instead of strips, the conductive metal is in the form of buttons that are spaced close together.  Closely spaced dots are visible on the photo of the radome above.

• Another lightning precaution is pointy metal things called static wicks. You've probably noticed them sticking off the wing of the airplane you're flying on.  They're connected to the pointy parts of the aircraft, and they're encased in fiberglass so that whatever charge they collect won't be transferred to the frame.  Any static electricity that builds up in the air around the plane gets dissipated through the static wicks. If lightning does strike the plane, the electricity often will travel to and along the wicks, away from the plane.  They're not supposed to be considered as lightning protection, but some people describe them as doing that.  Missing static wicks is another thing the crew look for when they're doing a visual check of the plane.

One kind of static discharge wicks mounted along the wing of an airplane.
(Photo from the 737 Technical Site)

• Additionally, all the parts that are anywhere close to the fuel supply have to be built to withstand any lightning currents and so that no sparks will enter the fuel system. The tanks have to be made to a required thickness, the joints and fasteners must be kept to a specified tightness to prevent sparks, and caps, doors, vents, and fuel lines all have to be tested to make sure they're thick enough and can withstand lightning. Fuel tanks also contain their own static discharge equipment.

• The electronics within the plane are also built -- "hardened" -- to withstand lightning and to protect against static buildup.

• Finally, pilots are trained to avoid flying through or even close to thunderstorms.  They're actually trying to avoid wind shear and turbulence, which are far more problematic for an airplane than lightning, but reducing the possibility of lightning strikes is of course helpful, too.

• Because of all these precautions, lightning strikes, though common, are considered to be a pretty low threat in air travel.

Here's a Boeing 747 taking off in a rainstorm. As it ascends, a bolt of lightning hits it. The video shows this once, then loops back to show the same lightning strike in super-slow-motion again. You'll be able to see how the bolt enters near the front of the plane and exits at the tail. The plane keeps right on flying, undisturbed.



You may also be interested in my entry on Lightning or another one on Thunderstorms.


Sources
Edward J. Rupke, What happens when lightning strikes an airplane? Scientific American, 2001 (reprinted August 14, 2006)
A. Pawlowski, Can lightning bring down a plane? CNN, August 17, 2010
National Lightning Safety Institute, Aviation Losses from Lightning Strikes 
Physlink.com, How is a plane protected from Lightning strikes?
The 737 Technical Site, Wingtips, Static Dischargers
Jack Williams, USAToday Weather, Answers: Does lightning hit airplanes, June 1, 2004