Category Archives: Weather & Sky

Back Into the Deep Freeze

Bald eagle with ice on his forehead and belly, Crooked Creek, Jan 2018 (photo by Steve Gosser)
Bald eagle with ice on his forehead and belly, Crooked Creek, Jan 2018 (photo by Steve Gosser)

After a balmy Thursday and Friday the temperature is plummeting tonight to 5oF.

During the last deep freeze, Steve Gosser photographed a bald eagle at Crooked Creek with iced feathers on his belly and head. Notice how his head feathers are standing up as if he used hair gel!

The eagle's ice shows the great insulation power of feathers and how extreme cold can form ice very quickly when the eagle lifts his head out of the water.

He'll be getting another chance to wear icicles this weekend.  Brrrrr!

 

(photo by Steve Gosser)

Why Is It Warming So Fast?

  • Friday, 5 Jan 2018

Egads, it was cold last weekend!  Here in Pittsburgh it was -6 to 11 degrees F, but yesterday things turned around.  Sunday (7 Jan.) started at -6oF but warmed to a high of 30.  Today will be above freezing and by Thursday the high will be 64oF.  That's a swing of 70 degrees in only four days!

The slideshow above shows this in color for January 5, 8, 11 and 12.

I'm not complaining that we're out of the deep freeze but ... this weather is really odd.  Why did it get so cold and why is it warming so fast?  Why don't we have a moderate winter like we used to?

Crazy as it sounds, it's because the arctic is warming faster than the rest of us.  When there's not a big temperature difference between the North Pole and the mid-latitudes (us) the jetstream slows down.  When it's sluggish, it wobbles in high amplitude loops that dip as far south as Florida(*).

The video below explains why.  I recommend watching it twice; you see more the second time.  (My end notes have info on millibars, etc.)

So when a cold loop settles over us, we're really cold and when it moves on we're really hot.  It happens quickly in both directions.

Don't put away your winter clothes on Thursday.  The forecast says it'll be 5 degrees on Saturday night.

 

(temperature forecast maps from NOAA; Jet stream explanation by Jennifer Francis on YouTube)

Definitions and notes:

  • A millibar (or mb) is a unit of air pressure.
  • The average air pressure at sea level is 1013.25 millibars = 14.7 pounds.
  • What's the significance of 500 millibars?   The 500 millibar pressure zone is where air pressure is half what it was at sea level, halfway up in the atmosphere. Since air pressure varies as weather systems move above us, the 500mb map is a great diagram of what the weather systems are doing.    Here's the air pressure map for Friday 5 Jan 2018 at 1200z (8am).  Notice that the pressure lines echo Friday's temperature map above.
  • (*) I wrote above that the jetstream dips as far south as Florida.  Well, it dips even further than that.  In June 2016 the northern jetstream crossed the equator and joined the southern one!

At Cape Cod: Before and During the Storm

Before the storm: Icy blue ocean at West Dennis Beach, Mass. 3 Jan 2018 (photo by Barb Lambdin)
Before the storm: Icy blue ocean at West Dennis Beach, Mass. 3 Jan 2018 (photo by Barb Lambdin)

On the day before the "bomb cyclone" hit Massachusetts my sister-in-law, Barb Lambdin, sent me two photos of the frozen ocean at West Dennis Beach, Cape Cod.   Intrigued by the coming storm, I asked her to take more photos when it hit.

The photo locations are part of the story:

  1. Before the storm: West Dennis Beach on the ocean side.
  2. During the storm: Corporation Beach in the protected middle of the bay shore.

Map of Massachusetts showing 1: oceanside photos at West Dennis Beach, 2: bayside photos at Corporation Beach (from Wikimedia Commons, annotated)
Map of Massachusetts. 1: oceanside photos at West Dennis Beach, 2: bayside photos at Corporation Beach

 

BEFORE THE STORM:

Above, the ocean was so calm on 3 January 2018 that ice had formed in flat sheets and blue-green water ponded on top.

The waves were small and slushy (below).  Barb calls them Frozen Margarita waves.

Before the storm, slushy waves at W Dennis Beach, MA 3 Jan 2018 (photo by Barb Lambdin)
Before the storm, slushy waves at W Dennis Beach, MA 3 Jan 2018 (photo by Barb Lambdin)

 

DURING THE STORM:

On 4 January it was too windy and dangerous on the ocean side so Barb went to the bay side at Corporation Beach.  The two photos below were taken at high tide.

Keep in mind that this is the calm side of Cape Cod yet the waves are high and about to flood the parking lot.  I have never seen waves break at Corporation Beach!

During the storm: Corporation Beach at high tide, Dennis,Mass. 4 Jan 2018 (photo by Barb Lambdin)
During the storm: Corporation Beach at high tide. Dennis, MA 4 Jan 2018 (photo by Barb Lambdin)

This high tide set a record at Boston, 60 miles north across the bay.

During the storm: Corporation Beach at high tide, Dennis,Mass. 4 Jan 2018 (photo by Barb Lambdin)
During the storm: Corporation Beach at high tide. Dennis, MA 4 Jan 2018 (photo by Barb Lambdin)

For more information and cool graphics see The 10 best images of this week's historic bomb cyclone in the Washington Post.

Is this the worst nor'easter we'll see this winter? Who knows.

p.s. Why is it so cold?

Actually it's extremely cold in the eastern U.S. but very warm in the West (click here for Departure From Normal Temperature graphic).

Four years ago we experienced the Polar Vortex of 2014 when the jet stream wobbled southward. It's happening again. And it's a feature of climate change.

Learn more at CBCnews: Why has it been so cold? Here's what science says.

 

(photos by Barb Lambdin. Massachusetts map from Wikimedia Commons. Temperature map from the National Weather Service; click on the images to see the originals)

Black And Blue Ice

Transparent ice coating the street in Sapporo, Japan (photo from Wikimedia Commons)
Transparent ice coating the street in Sapporo, Japan (photo from Wikimedia Commons)

28 December 2017:

This morning it's 3o F in Pittsburgh with a forecast high of 15o F.  Yesterday was just as cold.  It's 20 degrees below normal here.

Less than a week ago, on 22 December, the low was 40o with a high of 57o F.  It was 19 degrees above normal.  To accomplish this temperature swing it rained half an inch on December 23 and froze solid on Christmas Eve night.  We had black ice on Christmas Day.

Black ice isn't really black.  It just looks that way because it's such a thin, smooth coating of clear ice that the dark pavement shows through.

Technically speaking "black ice" forms when pavement looks dry but its porous surface contains water.  When that water freezes it's invisible.  So the photo at the top isn't really "black ice" (it was probably laid down by freezing rain) but who can find a photo of something invisible?

Pittsburgh has black ice but we don't have blue ice.

Blue ice is very old ice from the lowest layers of a glacier.  It's blue because the weight of the glacier above compressed all the air bubbles out of it.  The lack of air makes the ice look blue like sea water.

Blue ice at a glacier in Iceland (photo from Wikimedia Commons)
Blue ice at a glacier in Iceland (photo from Wikimedia Commons)

I learned about blue ice in the description of this photo taken in Iceland.

So... black ice occurs where temperatures move above and below freezing (Pittsburgh).  Blue ice occurs where it's so cold that the glaciers are old (Iceland).

Pittsburgh or Iceland?  Where would you rather be on this cold day?

 

p.s. Be careful out there!  If you fall on the ice you'll be black and blue.

(photos from Wikimedia Commons. Click on the images to see the originals.)

Crazy Warm

Barrow, Alaska as seen from the air, Aug 2007 (photo from Wikimedia Commons)
Barrow, Alaska as seen from the air, Aug 2007 (photo from Wikimedia Commons)

The computer said, "Those numbers are too high. They must be in error. Throw them out."  And so Barrow, Alaska disappeared from the climate analysis database.

Fortunately a lot of people missed Barrow when it was gone. In fact they suspected it  might disappear some day because it's so unusual.  The error was found quickly and the raw data will be restored.

What happened?

This month more than a year's worth of temperature data for the northernmost point in the U.S. -- Barrow, or Utqiávik, Alaska (see arrow) -- automatically disappeared from the National Centers for Environmental Information temperature analysis system because it looked so out of whack.

Barrow, Alaska locator map (image from Wikimedia Commons; arrow added)
Barrow, Alaska locator map (image from Wikimedia Commons; arrow added)

Why would a computer throw away real data?

Computers that collect automated weather data have algorithms that test for wild abnormalities so that instrument errors are isolated (rejected) from the clean data calculations.  For instance, when a weather thermometer breaks or goes offline, the temperature is recorded as "zero."  When this happens in July in Pittsburgh it's so obviously incorrect that the software rejects it. Algorithms for climate analysis are even more stringent because a change to an instrument's location can look like a trend even though it isn't.

Here's why Barrow looks crazy to a computer.  This graph by Derek Arndt at climate.gov shows circles for Barrow's 1979-1999 average monthly temperatures, triangles for 2000-2017.  Notice that for most of the year those 20-year averages are pretty close but for October, November and December they're widely different.  Computers don't like that!

Average Monthly Temperature at Barrow in two eras 1979-1999 vs 2000-2017 (graph from NOAA)
Average Monthly Temperature at Barrow in two eras 1979-1999 vs 2000-2017 (graph from NOAA)

Barrow is experiencing rapid warming because there's a lot less sea ice than there used to be.  When ice crowds the shore in the fall, Barrow gets cold, but now the ice recedes so far in the summer that it takes months longer to reach the town.

It's crazy warm in Barrow.

 

A tip of the hat to Angela Fritz at the Washington Post for her 12 December article that brought this to my attention.  Read all about it at NOAA's Beyond the Data blog: Alaskan North Slope climate change just outran one of our tools to measure it.

(photo and map of Barrow, Alaska from Wikimedia Commons. Graph from climate.gov. Click on the images to see the originals)

p.s. Barrow is now called by its native Alaskan name, Utqiávik.

Winter Solstice

Winter sunset (photo by Paul Aniszewski from Shutterstock)
Winter sunset (photo by Paul Aniszewski from Shutterstock)

Today is the shortest day in the northern hemisphere, the official start of Winter.  But don't worry.  Spring comes faster than any other season.

Because the Earth doesn't move at a constant speed in its elliptical orbit, the seasons are different lengths.  From a warmth perspective, the northern hemisphere is lucky.  Our winter is the shortest season.

  • Winter, December-to-March: 89.0 days from winter solstice to vernal equinox
  • Spring, March-to-June: 92.8 days from vernal equinox to northern summer solstice
  • Summer, June-to-September: 93.6 days from the summer solstice to the autumnal equinox
  • Autumn, September-to-December: 89.8 days from the autumnal equinox to the winter solstice

So after the sun stands still at 4:28pm UTC (Universal Time) -- 11:28am in Pittsburgh -- it'll start its journey northward.

Spring will be here soon.

 

p.s.  Groundhog Day is halfway between the winter solstice and vernal equinox.  It's something to look forward to.

(photo by Paul Aniszewski from Shutterstock)

Overcast

Overcast sky above a bare tree, Pittsburgh, PA, 11 Dec 2017 (photo by Kate St. John)
Overcast sky above a bare tree, Pittsburgh, PA, 11 Dec 2017 (photo by Kate St. John)

We've had a long run of overcast days that began on Sunday, December 10.

On Monday morning Pittsburgh looked gray outside my window.

Overcast sky in Pittsburgh, 11 Dec 2017, 8:15am (photo by Kate St. John)
Overcast sky in Pittsburgh, 11 Dec 2017, 8:15am (photo by Kate St. John)

 

On Tuesday it was so gloomy that a few street lights came on in Schenley Park at 11:30am.

Overcast sky in Pittsburgh, 12 Dec 2017, 11:30am (photo by Kate St. John)
Overcast sky in Pittsburgh, 12 Dec 2017, 11:30am (photo by Kate St. John)

 

On Wednesday we had a splash of sun in the morning, then overcast skies and snow.  Here's the sky above PPG Place downtown on Wednesday at 4:15pm.  The rest of the week was partly overcast, too.

The sky above PPG Place on Fourth Avenue, 13 Dec 2017, 4:15pm (photo by Kate St. John)
The sky above PPG Place on Fourth Avenue, 13 Dec 2017, 4:15pm (photo by Kate St. John)

This is not just one layer of clouds. It's often one or two low layers of broken clouds overtopped by an overcast layer.

Cloud cover is reported for aviation purposes in Weather Observations and TAF/METAR(*) at Pittsburgh International Airport (KPIT).  Here's the cloud cover for this morning and the three times photographed above:

  • 11 Dec 8:15 am ... OVC030 = Overcast at 3,000 feet
  • 12 Dec 11:35am ... BKN008 OVC039 = Broken clouds at 800 feet, Overcast at 3,900
  • 13 Dec 4:16 pm ... FEW014 OVC024 = Few clouds at 1,400 feet, Overcast at 2,400
  • 16 Dec 7:00am ...  OVC041 = Overcast at 4,100

My husband tries to see the good in everything.  He sees value in a rainy day (we need rain on a regular basis) so he wondered, "What's the value of an overcast day? What good is it?"

Ummm... perhaps... You can't get a sunburn when the clouds are this thick.

That's a poor excuse for so much gloom.

 

(photos by Kate St. John)

p.s. (*) TAF = Terminal Aerodrome Forecast. METAR = Meteorological Terminal Aviation Routine Weather Report. "Terminal" = airport terminal.

Which Glaciers Will Flood Your City?

Map of glacial contribution to sea level rise in Miami (screenshot from NASA JPL)
Map of glacial contribution to sea level rise in Miami (screenshot from NASA JPL, pink circle added to highlight Miami)

Though the ocean will never flood Pittsburgh, I'm still fascinated by the rising sea. (*)

Back in October I wrote about sea level fingerprints, the pattern of tiny elevation changes in sea level caused by uneven gravitational forces around the globe.  The highest ocean peaks are in the tropics, the deepest valleys are near melting glaciers.  As the land loses mass (ice) its gravitational pull decreases and it stops hugging the ocean to its shore.  The water has to go somewhere so it goes to the tropics.

This means that glacial melt affects sea level rise in two ways:  (1) It adds water to the ocean that used to be sequestered on land and (2) it alters the sea level fingerprint, lowering the ocean nearby and raising it far away.

If you do the complicated math, you can find out how individual melting glaciers will affect sea level at specific locations.

Last month, scientists at NASA Jet Propulsion Lab did just that when they published a paper in Science Advances and an online tool that illustrates how glaciers will affect 293 coastal cities.  Let's take a look at Miami.

Almost half the sea level rise in Miami will be caused by glaciers (47.4% of total sea level rise) and almost half of that will be Greenland's fault (20% of total sea level rise). That's why Greenland is so red in the screenshot above.

The next highest glacial contributor in Miami will be Antarctica (12% of total sea level rise).  In the screenshot below you can see that South American glaciers help, too.

Map of Antarctic and South American glacial contribution to sea level rise in Miami (screenshot from NASA JPL)
Map of Antarctic and South American glacial contribution to sea level rise in Miami (screenshot from NASA JPL)

In fact, the entire northern hemisphere is endangered by Antarctica's melting ice because it's so far away.  Ironically the safest place to be is right next to a melting glacier.  Sea level will go down at those sites.

See the maps for yourself and try the online tool at NASA JPL.  Read more about it at These are the melting glaciers that might someday drown your city, according to NASA in the Washington Post.

 

(*) Pittsburgh's Point is 711 feet above sea level. My immediate family lives 10 to 25 feet above sea level in Virginia and Florida.

(screenshots of glacial contribution to sea level rise in Miami from the online tool at NASA Jet Propulsion Lab.  On the first screenshot I added a pink circle to highlight Miami. Click on the images to use the online tool.)

Tornadoes in November

Damage in Williamsfield, Ohio from 5 Nov 2017 tornado (photo from National Weather Service, Cleveland)
Damage from 5 Nov 2017 tornado in Williamsfield, Ohio (photo from National Weather Service, Cleveland)

You know things are strange when there's an outbreak of 15 tornadoes in Ohio and western Pennsylvania in November.

Just over a week ago, on Sunday November 5, 2017, a cold front passed over the southern Great Lakes and Ohio River Valley.  Before the front arrived it was humid and around 70 degrees -- as much as 17 degrees above normal -- so the front's leading edge spawned 15 tornadoes.

The National Weather Service in Cleveland mapped 14 of them in their region.  I've added the EF-1 tornado in Calcutta, Ohio just west of Beaver County, PA reported by the National Weather Service in Pittsburgh.  Yes, 15 tornadoes!

Map of Nov 5, 2017 Tornado Outbreak in Ohio and northwestern PA (map from National Weather Service Cleveland. Added 1 tornado reported in NWS Pittsburgh region in Columbiana County, Ohio)
Map of Nov 5, 2017 Tornado Outbreak in Ohio and northwestern PA (map from National Weather Service Cleveland. I added 1 tornado reported by NWS Pittsburgh region in Columbiana County, Ohio)

The tornado in Williamsfield, Ashtabula County, Ohio was one of the strongest, an EF-2 with winds of 127 miles per hour.  It cut a swath 7 miles long ending at the western shore of Pymatuning Lake.  The damaged house shown above makes me glad I wasn't there!

Calcutta, Ohio's EF-1 tornado in the Pittsburgh Forecast Area blew down some trees and damaged the local YMCA.  And an EF-1 tornado blew through the city of Erie, PA for 2.4 miles, downing trees and crossing I-79 on its way.  Here's its path through a very populated area.

Map of tornado path in Erie, PA on 5 Nov 2017 (map from National Weather Service, Cleveland)
Map of tornado path in Erie, PA on 5 Nov 2017 (map from National Weather Service, Cleveland)

Pittsburgh's National Weather Service office points out how rare even one tornado is for our forecast area in November:

This [Calcutta, Ohio tornado] is the 14th confirmed tornado so far this year in our county warning area. On average, we see five tornadoes a year. This is the first November tornado since 2003 /14 years/ in New Philadelphia, Ohio. This is the 5th tornado in November for Columbiana county since 1950.

Experts say that climate change increases the frequency of severe weather.  I'd say that 15 tornadoes in November look like a good example.

 

(photo and maps from the National Weather Service in Cleveland. 14-tornado map altered to include the EF-1 tornado in Calcutta, Ohio reported by the National Weather Service in Pittsburgh. Click on the images to see the originals)

p.s. From Nov 5 to Nov 10, 2017 the temperature in New Philadelphia, Ohio went from 17 degrees above normal to 15 degrees below normal.  Yo-yo weather.

The Sky Last Week

Sunset as seen from the Roberto Clemente Bridge,Pittsburgh, 21 October 2017 (photo by Kate St.John)
Sunset at the Roberto Clemente Bridge, Pittsburgh, 21 October 2017 (photo by Kate St.John)

Last week the sky put on a show in Pittsburgh.  Here are just a few of its moods, October 21 to 24, 2017.

A clear blue sky with one colorful tree, Youghiogeny Bike Trail, 22 October 2017 (photo by Kate St. John)
A clear blue sky with one colorful tree, Youghiogeny Bike Trail, 22 October 2017 (photo by Kate St. John)

A double rainbow over Pittsburgh, 23 October 2017, 7:40am (photo by Kate St. John)
A double rainbow over Pittsburgh, 23 October 2017, 7:40am (photo by Kate St. John)

Beautiful clouds over Schenley Park, 24 October 2017 (photo by Kate St. John)
Beautiful clouds over Schenley Park, 24 October 2017 (photo by Kate St. John)