Archive for the 'Weather & Sky' Category

Dec 14 2014

Ice Sculptures

Published by under Weather & Sky

Needle ice on a cold morning at Moraine State Park (photo by Kate St.John)

Have you ever seen these ice structures?

Needle ice forms when the soil is still warm and the air is freezing.  As ice forms on the soil’s surface, it draws up subsurface water by capillary action and builds new ice from the bottom.  The result is a structure that looks like needles or tiny barricades. Since there is very little soil above the ice it pokes into the air.

Later in the season when the soil freezes, needle ice forms underground as part of a frost heave.  Click here to see a cut-away frost heave in Vermont.

This patch of needle ice formed above a seep at Moraine State Park last weekend.  Downstream the ground was squishy but here it was forming ice that looked like tiny walls.

Needle ice at Moraine State Park (photo by Kate St. John)

Watch for these ice sculptures on moist soil.

 

(photos by Kate St. John)

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Dec 07 2014

Chicken In The Sky

Stellar nursery IC 2944 as seen by ESO's Very Large Telescope (photo by ESO)

If our eyes could look deep into space we’d see the clouds in this stellar nursery in the Centaurus constellation, 6,500 light years away.

This pink glowing nebula and clouds of dust were photographed by the European Southern Observatory (ESO) at Cerro Paranal, Chile.  The nebula’s formal name is IC 2944.  Because it’s visible to the naked eye it has a nickname too: The Running Chicken Nebula.

According to ESO’s description, the clouds are Thackeray globules “under fierce bombardment from the ultraviolet radiation from nearby hot young stars.”

Click here or on the image to find out what will happen to the clouds.

If you know where to look on a clear night, you can see a running chicken in the sky.

 

 

(photo of stellar nursery IC 2944 by ESO, the European Southern Observatory at Cerro Paranal, Chile. Click on the image to see the original)

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Nov 24 2014

Avoiding The Storm

Red-breasted mergansers (photo by Shawn Collins)

While seven feet of snow fell on parts Buffalo, New York last week, the birds on Lake Erie did their best to avoid the storm.  Because they can fly, it wasn’t hard to do.

The lake effect storm was so localized that it hammered communities south of Buffalo but barely snowed Downtown.  On November 18 Alfonzo Cutaia recorded the amazing wall of white picking up moisture from the lake and carrying it away from Downtown Buffalo.

 

That night it snowed three inches at Presque Isle State Park in Erie, PA but conditions had improved by the next morning.  Jerry McWilliams described the scene at Sunset Point: “The severe winter storm that was hitting the Buffalo area continued out over the lake until at least 0800 hours [with] heavy storm clouds and whiteout conditions about a mile out on the lake. This may have been the reason for a massive movement of waterfowl this morning, especially Red-breasted Merganser.  Except for Redheads which were mainly moving east, most ducks were moving west.”

Jerry counted 11,400 red-breasted mergansers flying away from the storm.

The ducks escaped but I can only wonder what happened to the songbirds.  I hope they left on Tuesday during the first break in the three-day storm.

And now, as if the snow wasn’t enough, Buffalo has rain, snowmelt, floods and high winds today.

Fly away!

 

(photo of red-breasted mergansers by Shawn Collins)

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Nov 23 2014

Hot, Cold, or Lukewarm?

Published by under Weather & Sky

Winter temperature outlook 2014-2015 (map from climate.gov)

What’s the weather going to be like this winter?  NOAA’s Climate.gov has a prediction.

If you live in the U.S. West, Alaska, or northern New England, chances are you’ll be warmer than normal.  In the south-central and southeastern U.S. you’ll probably be colder.

But as the map text explains, the white zones aren’t necessarily going to be “normal.”  There’s an equal chance of being hot, cold or lukewarm in Pennsylvania.  We’ll just have to live through it to find out.

Click on the image to read this winter’s prediction at climate.gov.

 

(Winter temperature outlook 2014-2015 from climate.gov.  Click on the image to see the original)

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Nov 18 2014

Winter Is A Great Pest Control System

Published by under Weather & Sky

Frozen lake in Poland (photo from Wikimedia Commons)

While we brace for 150F this morning and moan that it’s 300F below normal in Pittsburgh, it’s important to look at the bright side.

Last winter’s “polar vortex” put a real dent in invasive insect populations.  It reduced the hemlock woolly adelgid population in the eastern U.S. and completely wiped out adelgids in some of the infected stands in Cook Forest.  It also killed emerald ash borers and stink bugs.

This one-to-two day cold snap won’t seriously reduce invasive insects but it may zap a few bugs caught unexpectedly outside their lairs.  Every little bit helps.

And one more thought in case you aren’t convinced.  There are no poisonous snakes in Alaska and very few in Canada and northern-border U.S. states.

Winter is a great pest control system.   :)

 

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

p.s.  It also reduces human pests.  No one’s “partying” at the park across the street from my house.

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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 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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