Archive for the 'Weather & Sky' Category

Oct 01 2016

A Shiny Thing in the Sky

Published by under Weather & Sky

International Space Station as seen from Space Shuttle Atlantis, 19 Jul 2011 (photo from NASA via Wikimedia Commons)

International Space Station as seen from Space Shuttle Atlantis, 19 July 2011 (photo from NASA via Wikimedia Commons)

If it’s clear tonight in Pittsburgh (1 Oct 2016) you’ll be able to see the International Space Station (ISS) traverse the sky for six minutes.

At 7:41pm the ISS will appear in the southwest and pass directly overhead on its way northeast at 17,150 miles per hour.  At five miles per second it doesn’t take long to disappear.  Read more here in the Post-Gazette on what and where to look for it.

You don’t have to be in southwestern Pennsylvania to see it.  NASA’s Spot The Space Station website predicts ISS’s appearances around the world.

Armed with this information you can impress your friends.  Casually looking at the night sky you can say, “Look over there.  In half a minute the International Space Station will appear on the horizon and pass directly overhead.”

A fast-moving shiny thing in the sky.


(photo of the International Space Station as seen from the Space Shuttle Atlantis, 19 July 2011.  Click on the image to see the original)

p.s. Unless they’ve already fixed it,I believe there’s a typo in the Post-Gazette’s 2nd paragraph which says “Monday” but probably means Saturday.

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Sep 30 2016

Black Moon Today

Published by under Weather & Sky

New moon symbol (image from Wikimedia Commons)

THE BLACK MOON MADE ME FORGET SOMETHING I ALREADY KNEW.  BIG CORRECTION AT 10:45AM!  We never see the dark side of the moon except from outer space. Thank you, Tom Hoffman, for reminding me. (Shaking fist at Black Moon!)

30 September 2016:  Today the media is peppered with the ominous words “Black Moon.”  Here’s what that’s all about.

By the time you read this the moon has already risen in Pittsburgh at 6:46am. It came up half an hour before sunrise, will reach its zenith at 1:00pm, and will set at 7:07pm four minutes after sunset.  It’s in lock step with the sun.

But we won’t see it.

It’s a new moon traveling so close to the sun that the sun’s glare hides it.  And it’s not illuminated.  It is back lit by the sun.

This is the second new moon this month, the so-called “Black Moon.” Like its bright twin, the Blue Moon, two of these in a month are a relatively rare occurrence.  The last Black one was 32 months ago.

What about the dark side of the moon.  Is it always black?

No. Today’s Black Moon is sunlit on the other side.  But if we could see it, it would look unfamiliar.

During the new moon last July, the dark side of the moon was facing the DSCOVER satellite when NASA’s EPIC camera recorded time lapse photos.  Watch as the dark side flies by the southern hemisphere.  Doesn’t it look odd!

NASA's EPIC camera captures the dark side of the moon as it travels between Earth and the DSCOVR satellite (animation from NASA)

NASA’s EPIC camera captures the dark side of the moon as it travels between Earth and the DSCOVR satellite, 5 Jul 2016 (animation from NASA)

For starters, it’s darker than we expect.  Even when fully illuminated the moon is darker than Earth from outer space because it reflects less light.  Our planet is bright blue and white because it has lots of water.  The moon is dry and dark.  It matches the color of Australia.

Here’s the dark side in a still photo from August 2015.

NASA's EPIC camera captures the dark side of the moon as it travels between Earth and the DSCOVR satellite, Aug 2015 (animation from NASA)

NASA’s EPIC camera captures the dark side of the moon as it travels between Earth and the DSCOVR satellite, Aug 2015 (animation from NASA)

Look closely and you’ll see that it’s missing the craters we always see.

Of course we shouldn’t expect the dark side to match the bright side.  But the fact that it looks so different makes this Black Moon unsettling.  😉


(New moon symbol from Wikimedia Commons. Moon and earth animation from NASA.  Click on the images to see the originals.)

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Aug 13 2016

Why It Feels SO HOT Outside

Published by under Weather & Sky

It’s not the heat, it’s the humidity.  But its not the relative humidity.(*)

As a raw number, relative humidity doesn’t tell you anything.  The video above shows how the same amount of water produces different relative humidities depending on air temperature.

For example, early yesterday morning in my backyard it was 80 degrees with relative humidity 79%.  Last Tuesday it was 66 degrees with relative humidity 83%.

So didn’t yesterday’s 79% humidity feel better than 83% last Tuesday?  No!  Yesterday’s 80 degrees held a lot more water.

Dewpoint (the temperature at which the air is so saturated that it rains or produces dew) is the helpful number that tells us that.  If you know the temperature and relative humidity you can calculate the dewpoint here.

The National Weather Service in Chicago made a chart to describe how we feel at various dewpoints.  I’ve marked it in red to show my own heat-averse opinion.  (Click on the screenshot to see their dewpoint video that includes this chart.)

How dewpoints feel (chart from NWS Chicago video, altered to show how it feels to me)

How dewpoints feel (chart from NWS Chicago video, altered to show how it feels to me)

So here’s what was really going on this week and why it felt so hot yesterday even though the temperature never reached 90 degrees.  Notice that the relative humidity was at its lowest yesterday afternoon.

Date/Time Temperature Relative Humidity Dewpoint Comfort Range
Tuesday Aug 9, 7am 66oF


61oF Rather humid, almost comfortable
Friday Aug 12, 7am 80oF



Friday Aug 12 afternoon, 2pm 88oF





Find out the dewpoint before you go outdoors and you’ll know whether you want to brave it!


(*) p.s. See the comments!

(video from Richard Clements on YouTube. screenshot from NWS Chicago video. Click on the screenshot to see the video)

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Jun 20 2016

Today Is Astronomical

Published by under Weather & Sky

Sunrise at the summer solstice, Stonehenge 2005 (photo from Wikimedia Commons)

Summer solstice sunrise at Stonehenge, 2005 (photo from Wikimedia Commons)

Today is astronomical.  It’s been 68 years since we’ve seen one like it.

Full moon at the sea (photo from Wikimedia Commons)

Full moon over the sea (photo from Wikimedia Commons)

The last time the summer solstice occurred on the same day as the full moon was in 1948.

By the time you read this the moon will have done its job, having reached maximum fullness at 7:05am in Pittsburgh.  It had already set by then (6:13am) so we didn’t see it.

The summer solstice is yet to come — 11.5 hours after the moon’s event — at 6:34pm.

The moment when the sun stands still is such a big deal that they’re celebrating it with a four-day solstice festival at Stonehenge, pictured above.  But they won’t be able to see the sun during its special moment.  It’ll be almost midnight at Stonehenge, 11:34 pm.

Read more about this astronomical event at the Old Farmer’s Almanac.


(photo from Wikimedia Commons. Click on the image to see the original)

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May 25 2016

Pigeons and Bicycles Test The Air

Screenshot from Pigeon Air Patrol website:

Screenshot from Pigeon Air Patrol website:

The air’s going to be bad in Pittsburgh today — Unhealthy for Sensitive Groups orange flag — so don’t take baby out for a stroll this afternoon. How can we know exactly where it’s safe to breathe?  Birds and bicycles test the air.


Birds: London, England, March 2016:

Pigeons have been used for breeding, racing and message-carrying.  This spring in London the Pigeon Air Patrol tested the air — quite literally.

In March three members of a flock of racing pigeons were outfitted with air quality monitors and GPS.  Then the flock was released from various points in the city to record — and tweet — air quality data on their way.  People could see what they were breathing in real time.

This is of interest in London because they have a history of bad air with darkness at noon and killer smog (1952).  But the air’s OK now, right?  Well, that’s not what the pigeons found.

Typical air monitors sample fixed locations but the pigeons flew through hotspots of bad air.  Who knew that a particular street corner was a bad place to breathe?  The pigeons did.

Check the Plume Labs website to see what’s happening in the air in London and around the world right now.  (Scroll down to see the map.) If you have breathing problems there are quite a few places you should never visit.


Bicycles: Pittsburgh, PA, ongoing:

Two thirds of the year Pittsburgh’s air quality is in the “moderately polluted” range which doesn’t sound like much but constitutes a health risk in the long term.  Today our air will be worse –> Unhealthy for Sensitive Groups.

Air Now forecast for Pittsburgh, PA, 25 May 2016 (screenshot from

Air Now forecast for Pittsburgh, PA, 25 May 2016 (screenshot from

The regional map doesn’t tell the whole story.  Some places have better air than others so the Group Against Smog and Pollution enlisted bicycles to help.  In this ongoing project, volunteers carry monitors on their bicycles and collect air quality data as they ride.  GASP then maps the data on a street by street basis.

See Pittsburgh’s air quality here on GASP’s street-by-street map, or here at Plume Labs.

When it comes to breathing, we need all the help we can get.


p.s. Do you ride a bike in Pittsburgh? Do you want to help map air quality? Click here.

(screenshots from Pigeon Air Patrol website and from Air Now)

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May 18 2016

More Robins, Fewer White-throated Sparrows

American robin, white-throated sparrow (photos by Marcy Cunkelman)

American robin, white-throated sparrow (photos by Marcy Cunkelman)

We humans are starting to respond to climate change. The birds already have.

In a study on two continents — North America and Europe — data from 1980 to 2010 shows that populations of our common birds have been affected by climate change and the gap is growing.  Bird species expected to do well due to climate change have substantially outperformed those expected to do badly over the 30 year period.  It’s the first real demonstration that climate is having a similar, large-scale influence on the abundance of common birds in widely separated parts of the world.(*)

Here are two examples from North America:

American robins are an adaptable species whose range has expanded as the climate warms.  Robins don’t have to go as far south in the winter and now they breed in Alaska!

White-throated sparrows are a common winter species in the Lower 48 but when it comes time to breed they’ll be in trouble.  As they move north the forest they require for breeding gives way to treeless landscapes.  It takes decades to grow a forest and climate is changing faster than the plants can catch up.  White-throated sparrows are losing ground.  Click here to see their changing map.

More robins, fewer white-throated sparrows.  The populations of common birds are affected by climate change.

Read more about the study here in Science Daily(*).  See Audubon’s climate website for details on North American birds.


(photos by Marcy Cunkelman)

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Mar 10 2016

Will We Have An Early Spring?

Dutchman's breeches, 25 March 2012 (photo by Kate St. John)

Dutchman’s breeches, 25 March 2012 (photo by Kate St. John)

Climate change is giving us some weird weather extremes.  From 9oF below normal a week ago we’ve now had two hot days 24 degrees above normal.

On Monday (March 7) I saw coltsfoot blooming in Schenley Park. It usually blooms in late March so this may be an indication that Spring is two weeks ahead of schedule.

In March 2012 we had an unprecedented heat wave in North America.  Pittsburgh had highs in the 80’s and all of our woodland wildflowers, which normally bloom from late March to late April, opened at the same time.  Dutchman’s breeches and trillium bloomed four weeks ahead of schedule.  Some plants were six weeks early.

In this trip down memory lane, read about the extreme spring of March 2012 in this post: The New Normal.

Do you think we’ll have an early Spring this year?


p.s.  We all like warm weather but be careful what you wish for.  Summer temperatures in March 2012 gave way to extreme heat in July 2012 with drought and highs of 100 degrees!   🙁

(photo by Kate St.John)

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Feb 29 2016

The Gift Of Time

Published by under Weather & Sky

Today we get the gift of time.  Leap Day, February 29, gives us 24 hours that are usually missing from our calendars.

You probably know we have to insert this day every four years because the earth revolves around the sun in approximately 365.25 days.  To make the calendar match the stars and seasons we add an extra day every fourth year with a complicated century exception.  The 4-year-old video above explains the details of this astronomical problem and how Julius Caesar and Pope Gregory XIII figure into it.

Last June 30 we received the gift of an extra second.  You probably missed it because it happened just before midnight.

Leap Second on June 30, 2015 (image from Wikimedia Commons)

Leap Second on June 30, 2015 (image from Wikimedia Commons)

Leap Years and Leap Seconds are unrelated but caused by a similar problem. Just as calendars must adjust for Earth’s rotation, so too must atomic clocks. The clocks are extremely accurate but Earth’s rotation is slowing down and not even at a consistent rate.  An extra second is added whenever the difference between mean solar time (UT1) and Coordinated Universal Time (UTC) reaches 0.9 seconds.  The need for this second is so unpredictable that it’s announced only six months in advance.  Computers hate this but there are workarounds.

In the past eight months we’ve gained 24 hours (on February 29, 2016) + 1 second (on June 30, 2015) + 1 hour (changed to Standard Time on November 1, 2015).  This nets us 25 hours + 1 second.

Do something fun with the gift of time.  Happy Leap Day!


p.s. We’ll lose an hour in two weeks on Sunday March 13 when we switch to Daylight Savings Time.  Yikes!

(Leap year video by Epipheo on YouTube. Leap second illustration from Wikimedia Commons; click on the image to see the original)

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Feb 08 2016

Winds On Water

Published by under Weather & Sky

Screenshot of animated Earth Wind Map from Click on the image to see the animation. (To help orient you, red dots were added to the map for Seattle, San Francisco and Los Angeles)

Screenshot of animated earth wind map from “earth: a global map of wind, weather and ocean conditions.”  Click on the image to see the animation. (I added 3 red dots to the map to help orient you: Seattle, San Francisco and Los Angeles)

Science Fun on Monday:

John English told me about this cool website that animates global weather, especially wind on water.  The website is called earth, “a visualization of global weather conditions forecast by supercomputers updated every three hours.”

Click on the screenshot above to see conditions in the eastern North Pacific. Before you do, here are some tips:

  • In the animation, slow winds are blue to green, intense winds are orange to red.
  • Everywhere on earth, the most exciting winds are those surrounding low pressure systems.  In the northern hemisphere, they circle counter-clockwise. (How to remember this? See below.)
  • Notice the blank zones where there’s no wind. The largest are often in the center of high pressure zones.  Some of these line up with the warm water “Blobs” that are killing seabirds by starvation.
  • If you watch for 60 seconds more winds on the continent will start to show up. They aren’t as intense.
  • Click and drag to change the location of the map.
  • Click on the word [earth] at bottom left to change the parameters.  Select a new Mode to see pollution (“chem”) or dust/smoke (“particulate”).

Follow this quick link to see the North Atlantic and Great Lakes map.  There’s usually less excitement here but look north toward Greenland and you’ll see why the North Atlantic is a dangerous place to cross in winter.

And for a really tangled mess of wind click here to see the air flow between South America and Antarctica!

Visit “earth” on Facebook for more screenshots and videos of amazing storms.  You don’t need a Facebook login; just click on the link.


BONUS: Here’s how to identify low and high pressure systems in the northern hemisphere based on the direction the winds are circling. Use the right-hand rule. Curl your fingers in the direction of the winds (B) and point your thumb. The air column (I) is moving in the direction of your thumb. Low pressure sucks the air column up; high pressure pushes it down. The orientation of this diagram would be a low pressure system in the northern hemisphere.

Right-hand rule, illustration linked from Wikipedia

(screenshot of the earth wind map from, right-hand rule illustration from Wikipedia)

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Jan 26 2016

Death By Warm Water

Common Murres, Peruvian Boobies (photos from Wikimedia Commons)

Common Murres, Peruvian Boobies (photos from Wikimedia Commons)

These two species — common murres and Peruvian boobies — have something in common. Both have starved in record numbers in the Pacific Ocean recently.

Common murres (Uria aalge) have a circumpolar range in the North Atlantic and North Pacific while Peruvian boobies (Sula variegata) are native to the west coast of South America yet both seabirds are affected by the same problem: warm seawater.

In the southern Pacific, the failed trade winds of El Niño have ceased the upwelling of cool undercurrents and raised the sea surface temperature near South America.  A similar lack of wind has caused three warm Blobs to persist in the Northern Pacific.  Sea surface temperatures in these regions are running 2oF to 7oF warmer.  That small rise doesn’t sound like much but it’s enough to scare off cold water fish and even generate toxic algae blooms.  There’s a drop in nutrients, a drop in fish life, and that means starvation for seabirds.

Three "blobs" of warm surface water in the Northern Pacific, 1 Sept 2014 (image from NOAA via Wikimedia Commons)

Three “blobs” of warm surface water in the Northern Pacific, 1 Sept 2014 (image from NOAA via Wikimedia Commons)

In June 2014 Peruvian boobies were the first wildlife indication of a strong El Niño when thousands of dead and starving boobies washed ashore on the coasts of Peru and Chile.  Their cold water fishery had failed.  Some were so desperate they flew way out of range to the Galápagos and Panama.

That winter, November 2014 to January 2015, Cassin’s auklets (Ptychoramphus aleuticus) became a warm water casualty on the U.S. West Coast.  In their case the original Blob was to blame.

And now 100,000 dead common murres have washed ashore on the coast of Alaska, victims of warm water in the Gulf of Alaska.

Where will it end?  The El Niño may weaken this spring but who knows when The Blobs will change?

For cold-water sea life, it’s death by warm water.


(photos from Wikimedia Commons. Click on these links to see the original photos of common murres and Peruvian boobies)

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