Archive for the 'Weather & Sky' Category

Oct 05 2014

Graupeling

Published by under Weather & Sky

Garupel in Elko, NV (photo from Wikimedia Commons)

Yesterday afternoon I was caught in a graupel storm.

I was standing on Bellefield Avenue looking at the Cathedral of Learning through binoculars when the clouds darkened, the wind increased and it started to rain.  I was trying to find the peregrines.

The rain turn white and then, between the Cathedral of Learning and Heinz Chapel, it didn’t come down.  It floated up.  What was this?

A woman ran past me talking on her cellphone, “I’ve got to hang up. It’s hailing out here.”

Why was it hailing in 46 degree weather without a thunderstorm?

When I got home I looked up the NOAA weather forecast discussion which said, “Shortwaves combined with cold air aloft will bring scattered showers to the region today.  Some isolated graupel is also possible.”

Graupel is a German word for “precipitation that forms when supercooled droplets of water collect and freeze on a falling snowflake, forming a 2–5 mm ball of rime.”(*)

The balls look like hail but they’re fluffier.  No wonder they were floating on the updraft at the Cathedral of Learning.

It wasn’t hailing. It was graupeling.

 

(photo of graupel in Elko, Nevada via Wikimedia Commons.  Click on the image to see the original.)

(*) definition from Google.  By the way, “graupel” fails all my spell-checkers so I’m guessing that “graupeling” is spelled with one L as is normal when adding ‘-ing’ to ‘el’ in American English.

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Sep 16 2014

Mirage On Cold Water

Published by under Weather & Sky

September mirage of distant islands near Great Wass, Maine (photo by Kate St. John)

It was brilliantly sunny with a chilly east wind when I hiked at Schoodic Peninsula on the coast of Maine last Wednesday.  Little did I know the conditions were perfect for a superior mirage.

Schoodic is one of the endless procession of peninsulas and islands that reach into the Gulf of Maine east of Acadia National Park‘s Cadillac Mountain.  Though Schoodic is part of the park it takes an hour and a half to drive there around Frenchman Bay.

That day from the top of Schoodic Head the nearby islands and peninsulas were undistorted but on the horizon the land looked really odd.  One pink granite island was shaped like an hourglass and a peninsula looked sparsely tree-covered with a flat top.

This was a “superior mirage,” so called because the upside down images are above the real objects.  They are typical in cold water zones where the inversion of warm air above cold air distorts the light.  When very complex they’re called Fata Morgana, an Italian reference to the sorceress Morgan le Fay, because reality is distorted as if by magic.

Mirages are so common in the Arctic that explorers learned to be very careful before they labeled what they saw as solid land.  In 1818 Sir John Ross gave up pursuing the Northwest Passage when he saw mountains blocking Lancaster Sound.  He named them the Croker Mountains and headed back for England despite the protests of several of his officers including Edward Sabine (for whom the Sabine’s gull is named).  The mistake ruined Ross’ career. Eighty-eight years later Robert Peary thought he saw a distant land mass and named it Crocker Land.  It too was a mirage. Beware of naming anything in the Arctic with the letters C, R, O, K, E, R. It doesn’t turn out well.

Even spookier:  A re-examination of testimony surrounding the sinking of the Titanic indicates a mirage may have hidden the iceberg from the Titanic’s lookout and hidden the Titanic from the nearest rescue ship.  Click here for illustrations that show how this could happen.

Mirages change quickly so I was able to snap only one good image before it became less interesting. I was fascinated but not fooled.

 

(photo by Kate St. John)

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Sep 13 2014

Isabella Scoffs At Winter

Isabella tiger moth caterpillar (photo by Kate St. John)

Yesterday I found this Isabella Tiger moth caterpillar in Schenley Park.  Does she have a prediction for the coming winter?

Legend has it that wide brown stripes on woolly bear caterpillars predict a mild winter; narrow brown stripes mean a harsh one.

In the 1950′s the former curator of insects at the American Museum of Natural History surveyed a very small sample of woolly bears and found that the caterpillars had an 80% accuracy rate.  However, no one’s been able to replicate Dr. C. H. Curran’s findings.  Instead a whole host of factors influence the stripes including species, diet and age.  Especially age.  The older instars are browner.

And frankly, this caterpillar doesn’t care how harsh the winter.  It can survive to -90 degrees F, hibernating as a caterpillar (not in a cocoon!) curled up in a ball under a rock or bark.  It freezes completely except for the innermost portions of its cells which are protected by naturally produced glycerol.  In the spring the caterpillar thaws and resumes eating before making a cocoon and becoming a moth.

Theoretically this particular caterpillar is saying “mild winter” but we know it ain’t so.

Isabella scoffs at winter.

Read more here about the woolly bear legend and amazing winter feats.

 

(photo by Kate St. John)

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Sep 10 2014

Waves In The Sky

Published by under Weather & Sky

Cloud ripples 12 hours before the cold front (photo by Kate St. John)

What does it mean when there are waves in the sky?

These altocumulus undulatus clouds form at mid height at the spot where moisture meets wind shear.  Straight above my camera the wind abruptly changed direction and speed.  The long lines are perpendicular to the strongest wind, just like waves on a lake.

Altocumulus undulatus are typically only 300 feet wide so the wind shear here is a narrow zone.  If you flew through these clouds you’d probably feel a bump.

The waves might mean something big is about to happen … or not.  If they thicken over time, they indicate that moisture is building ahead of an approaching front 100 to 200 miles away.  If they cover only a small part of the sky, they merely mean that something’s going on right there.

Keep looking up.

 

(photo by Kate St. John)

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Sep 05 2014

In Fog

Published by under Weather & Sky

On chilly autumn mornings, the fog rises from Pittsburgh’s rivers and envelops the town.

Our fog is nothing to the thick fogs on northern coasts.

In San Francisco, Simon Christen took time lapse photos of moving fog and wove them into his beautiful video:  Adrift.

Play it above in small format or click here for the full screen version on Vimeo.

 

See more of his fascinating photos and videos at Simon Christen’s website.

(video by Simon Christen on Vimeo)

p.s. If the video plays haltingly on your computer, click on the HD letters at bottom right of the video window to turn off High Definition which requires lots of bandwidth.

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Aug 25 2014

Why Does Thunder Rumble?

Published by under Weather & Sky

Lightning over Schaffhausen and Kohlfirst (photo by Hansueli Krapf via Wikimedia Commons)

After a week of daily thunder and heavy rain we’re finally getting a spate of clear weather.  Today’s interesting thunder facts can’t be applied immediately but we’ll get another chance before long.

We’re all familiar with the crack of lightning and thunder’s low rumbles.  Sometimes we hear another loud bang in the middle of the series.  Why does thunder rumble and what are those mid-bangs about?  I found an explanation at the UK’s Weatheronline website.

First, let’s review the basics about light and sound.  Lightning travels at the speed of light, thunder at the speed of sound.  There’s such a time lag between them that we can figure out how far away the lightning is by counting the seconds between the flash and the sound, 5 seconds per mile.

The initial thunderclap is the closest part of the lightning but (amazingly!) the bolt itself is several miles long. We see it flash in twists and turns, branches and offshoots.  Every piece makes a thunderclap but many of the parts are so distant they sound like rumbles instead of booms.

What’s the bang in the middle?  It might be a new lightning bolt but … it could be the same bolt zigzagging closer as it travels through the sky.  The closest part is that middle bang.  Click here for an illustration showing how sound lags within a single lightning bolt.

Thunder rumbles because lightning is not a short, contained flash.  If it was we would hear a single loud boom, like the boom of an electrical transformer blowing up on the pole outside your house.  (I know something about this!)

And here’s a cool note about the photo:
Do you see the birds flying below the cloud?  It’s actually only one bird!  The lightning flashed four times while the shutter was open so the bird appears four times as it flies through the storm.  Brave bird!

 

p.s. It’s hard to see four birds in this small reproduction. Click on the image to see the original including annotations.

(photo of lightning in Switzerland by Hansueli Krapf via Wikimedia Commons)

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May 18 2014

Weather’s Wardrobe Challenge

Published by under Weather & Sky

What to wear. Weather's wardrobe challenge, May 2014 (photo by Kate St. John)

The weather has been so up-and-down lately that it’s hard to dress for birding. At home my winter clothes are piled in stacks, waiting to be washed after I pulled out summer shirts for last week’s 87 degrees.

Now the summer clothes are in stacks and I’ve yanked sweaters out of the winter pile.  It’s 42 degrees this morning and will be 37 at dawn tomorrow.

What to wear for outdoor activities this month?  It’s a wardrobe challenge.

 

p.s.  It’s more than a wardrobe challenge for swallows, purple martins, chimney swifts and nighthawks.  It can be life-threatening.  These species eat flying insects which don’t fly when it’s cold.  Fortunately the next two days will be sunny with highs of 62 and 71 so the insects will be flying later in the day.  If you missed it, read here about purple martin landlords providing supplemental feedings in cold weather.

(photo by Kate St. John)

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May 17 2014

Rain, Rain, Here To Stay

Published by under Weather & Sky

Rain in Ukraine (photo by Pridatko Oleksandr via Creative Commons license Wikimedia Commons)

Thursday afternoon it rained like this for about an hour.  Additional rain fell all day giving us 1.10 inches, a new record for May 15 in Pittsburgh.

The rain messed up rush hour and now the Ohio River is close to flood stage, but this is minor compared to the April 29-30 rain event in Pensacola, Florida when they received an amazing 10-15 inches in 9 hours, a total of 22 to 26 inches for the period.

Precipitation in Pittsburgh feels abnormal this spring.  Aren’t we wetter than usual this year?  No.  The rain gauge is less than 1/2 inch above normal since January 1.  The real difference is that the rain falls all at once.

We’ll have to get used to frequent heavy downpours, a hallmark of climate change in the northeastern U.S.  Click here to read more.

 

(photo of rain in Ukraine by Pridatko Oleksandr via Creative Commons license Wikimedia Commons)

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Apr 15 2014

It Was Fun While It Lasted

Published by under Plants,Weather & Sky

Bloodroot blooming at Cedar Creek Park, 12 April 2014 (photo by Kate St. John)

During the past three days we had a burst of blooms in Pittsburgh.  Between Saturday morning’s foggy low and Sunday’s high of 82F the landscape transformed from incipient buds to gorgeous flowers.  (Today will be different, but more on that later.)

On Saturday I found bloodroot at its peak at Cedar Creek Park in Westmoreland County (above) as well as spring beauties…
Spring beauties (photo by Kate St. John)

trout lilies…
Trout Lily at Cedar Creek Park, 12 April 2014 (photo by Kate St. John)

and hepatica.
Hepatica blooming at Cedar Creek Park, 12 April 2014 (photo by Kate St. John)

 

This morning the temperature is dropping fast.  It was 65oF at 5:00am and has already fallen to 47oF as I write.

Tomorrow’s prediction: 21oF at dawn. This will surely ruin the flowers.

It was fun while it lasted.

 

(photos by Kate St. John)

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Mar 19 2014

Frequent Heavy Downpours

Published by under Weather & Sky

Map predicting change in downpour frequency, 2040-2070 (map from NOAA Climate.gov).
Here’s something to look forward to … or not!

If you’ve been keeping track of intense downpour events for the past 50 years as NOAA has, you’ve noticed that they are more frequent in Pittsburgh than they used to be.  This will only get worse.

According to NOAA’s National Climate Assessment, by mid-century the frequency and intensity of heavy rain events will increase dramatically in some parts of the country, especially in Washington, Idaho and western Montana.  The bluest locations on the map will experience two or more additional days per year of record rainfall.

Pittsburgh is not exempt. We’ll see an increase in downpours and there will be an even higher frequency north and south of us.  Watch out, Cleveland and West Virginia!

For Allegheny County this map is particularly scary because of our old combined sewer infrastructure (sewage + storm water) that overflows into the rivers after as little as 1/10″ of rainfall.  If you visit our rivers you’ve seen the toilet paper.  The situation is so bad that Allegheny County is under a 2007 EPA consent decree to fix it.  We are not the only city with this problem!

Obviously, the time to fix our sewers is now and the solution has to handle more rain that we get today.

Click here to read more about downpours on NOAA’s website and here for information on Allegheny County’s wet weather problem.

 

(map from Climate.gov. Click on the image to see the original map and accompanying article)

p.s. 24 March 2014: Oh no! Rain is the culprit in the deadly mudslide in Washington State last weekend: http://m.motherjones.com/blue-marble/2014/03/climate-change-mudslide-washington-weather

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