Archive for the 'Weather & Sky' Category

Dec 19 2014

Here’s How It Melts

Published by under Weather & Sky

Moulin in Greenland (screenshot from National Geographic video online).

The news was bad this week for the Marshall Islands, South Florida, the Netherlands and Lower Manhattan.

Contrary to earlier predictions, satellite data from Greenland’s ice sheet shows that climate change is melting it a lot faster than we thought.  When all that land-based water melts into the sea, the ocean will rise and permanently flood low-lying land around the world.

Why is it melting so fast?  A big reason is the action of numerous superglacial lakes (i.e. lakes on top of the glacier) that form in the summer. The lakes collect ice melt but they also speed up melting because they empty all at once — downward! — and flow under the ice sheet, lubricating it and sending it much faster to the sea.

If you find this hard to imagine — or even if you don’t — click on the screenshot above (or here) to see a great video showing how this happens.

In the video National Geographic follows a group of scientists camped near a superglacial lake as they studied its development.  One day the lake disappeared, but the weather was so foggy so they couldn’t see what happened. All around them the ice they were standing on cracked and heaved and boomed.  Scary!

When the weather finally cleared they retrieved the measuring devices they’d left on the lake bottom (now no more) and pulled the data.

The lake they’d camped next to — two miles wide and 40 feet deep — had emptied to the ground 3,000 feet below in only 40 minutes!

Yow!

 

(screenshot from National Geographic online video.  Click on the image to watch the show)

 

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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 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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