A fast moving cold front crossed western Pennsylvania yesterday. The wind roared and temperatures fell from 61 degrees F Sunday morning to 19 degrees yesterday afternoon. The weather news called it a clipper.
Technically it’s an “Alberta clipper,” described by Wikipedia as a fast moving low pressure area that typically affects the central provinces of Canada and parts of the Upper Midwest and Great Lakes.
Clippers start as warm moist wind from the Pacific that crosses the Rockies into Alberta. When the wind hits cold air on the Canadian prairies it becomes a storm that rides the jet stream on a fast track east. By the time clippers get to Pennsylvania, Alberta is rarely mentioned.
Though clippers sweep across the continent, they’re regional so if you live outside their zone — say in California, Colorado, or Florida — the word brings to mind the fast-moving sailing ships of the mid 19th century, famous for sailing through dangerous storms at Cape Horn (above). The weather system is named for the ship.
Yesterday’s clipper left Pennsylvania but now we’re in for real winter — a low of 1 degree F Thursday morning.
Fill your bird feeders! Birds need food to survive this cold.
(Clipper Ship at Cape Horn, painting by James E. Butterworth, public domain via Wikimedia Commons. Click on the image to see the original)
Because the earth’s orbit is slightly elliptical, we’re always closest in early January and furthest in July (aphelion), a difference of about 3 million miles. This sounds like a lot but it’s tiny compared to the size of our orbit. The distance has no practical effect on our temperature.
… but …
When the earth gets close to the sun, the gravitational pull makes us speed up as you can see in the animation. Right now we’re moving about 1 km/second faster (2,237 mph) than we do in July and this does affect our seasons. The season surrounding early January (our winter) is 5 days shorter than the season surrounding early July. This is nice for us but too bad for Australia where their summer is short.
This animation shows our fast and slow progress but its real purpose is to illustrate earth’s orbital precession (in an exaggerated way).
Earth’s orbit is not a closed ellipse. Instead it tracks out a little further each time as if drawing a huge daisy in outer space without lifting its pencil. In 21,000 years we come back to where we started and trace the same daisy again.
(animation posted by WillowW on Wikimiedia Commons. Click on the image to see the original with documentation)
Today’s going to be a dark day in Pudasjärvi, Finland, where this photo was taken. Within the next 12 hours, the sun will reach its southern solstice(*).
Pudasjärvi is so far north (at 65° 22′ 39″ N, 26° 55′ 04″ E) that during the winter solstice the sun is up only 3 hours and 30 minutes, rising at 10:27am and setting at 1:58pm. At high noon it will be only 1.5 degrees above the horizon — barely risen — and to make matters worse the moon is New so it won’t provide any light at all.
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, including the places I named above.
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 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!
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.
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.
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.
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.