Category Archives: Weather & Sky

Have You Ever Seen…

Weather & Sky
Fallstreak hole over Big Island Wildlife Area Ohio, March 2019 (photo by Monica Miller)

9 August 2019

Have you ever seen a fallstreak hole?

Fallstreak holes or cavum (the formal name) are circular or elliptical holes in a blanket of cirrocumulus or altocumulus clouds. They occur when super-cooled moisture in the cloud starts to form ice crystals. In rare instances this sets off a chain reaction that causes nearby water droplets to evaporate while the ice crystals fall out of the hole. As they fall the crystals melt and evaporate.

Monica Miller and Don Weiss were at Big Island Wildlife Area, Ohio in March when this one appeared above their heads. Monica wrote, “We kept expecting the hand of God or the mothership to come down.”

Fallstreak holes are always amazing, some more stunning than others. Here are a few photos from Wikimedia Commons.

Fallstreak, Italy, Borso del Grappa, March 2019 (photo from Wikimedia Commons)

Airplanes can create elongated fallstreaks when they pass through the cloud layer. This cavum has an added bonus. There’s a sundog inside it.

Cavum are particularly dramatic near sunset.

Fallstreak hole, August 2008, Linz, Austria

Click here to see an amazing fallstreak hole over Niederlenz, Switzerland. There are birds in the photo! Probably common swifts or alpine swifts.

I don’t remember ever seeing a fallstreak hole. I can hardly wait!

(top photo by Monica Miller, remaining photos from Wikimedia Commons; click on the captions to see the originals)

Lightning Indoors

Weather & Sky
Lightning strike (photo from Wikimedia Commons)

We all know it’s unsafe outdoors in a thunderstorm but did you know that lightning can be dangerous indoors, too? It depends on what you’re doing.

When lightning strikes a building it follows the quickest path to the ground. If the building has ample lightning rods it follows their lead. Otherwise it travels through the plumbing, wiring, metal door jambs, even the metal rebar inside concrete. If a building doesn’t have plumbing or electricity it’s not safe during lightning.

Here are some indoor lightning safety tips, paraphrased from weather.gov.

  • Don’t touch any electrical equipment unless it’s completely cordless. Anything that’s plugged in is bad.
    • A cellphone or cordless phone is OK, but not a landline that’s got a cord.
    • A laptop is OK if it’s not plugged into any wires, not even the charger.
    • Don’t run around unplugging everything while the storm’s in progress. Lightning could strike while your hand is on the cord.
  • Avoid the plumbing. Lightning can travel in water. Don’t take a shower, wash your hands, etc.
  • Stay away from the windows, not because lightning will come through the window (it won’t), but because it will explode the glass if it hits, creating lots of flying glass.
  • This one is the hardest: Avoid metal structural components including metal window frames, door jambs, and concrete rebar. If you’re in a concrete building good luck!

Of course it goes without saying that carports, porches and balconies are not safe because they’re outdoors. Cars are safe, but only if the windows are closed.

Read some hair raising lightning stories (pun intended) in this vintage article: Looking Forward to a Little Less Lightning.

p.s. Check out the Real Time Lightning Map to see where lightning is striking right now!

(photo from Wikimedia Commons; click on the caption to see the original)

High Tide On The Allegheny

Climate Change, Weather & Sky
High water at Highland Park Dam, 11 July 2019, 4pm (photo by Kate St. John)

12 July 2019

Yesterday morning heavy rain caused flash floods, road closures, landslides, basement and first floor flooding, and car accidents in Pittsburgh.

The rain gauge at the airport measured 2.32″ for the day. All but .01″ of it fell in just four hours.

Precipitation at Pittsburgh International Airport, 11 July 2019 (graph from National Weather Service)

There were three huge rain events so thick that you couldn’t see to drive.

  • Half an inch (0.53″) in 50 minutes, 7:05a-7:50a
  • More than a third of an inch (0.38″) in 25 minutes, 7:55-8:17a
  • 1.4 inches in an hour, 10:05a-11:05a

If you want to see what it was like, click here for great footage from WPXI.

Hours later, at 3:30pm, a friend and I made our way from Indiana Township (between Fox Chapel and Cheswick) to Churchill. It took over an hour to get there. The traffic was horrendous and the roads that were open were littered with debris. Nadine, Sandy Creek, and Washington Boulevard were all closed.

But I got two photos of the river in flood.

High water on the Allegheny River at Sharpsburg, 11 July 2019 (photo by Kate St. John)

High tide on the Allegheny!

p.s. This rain didn’t even set a record at the airport though there may have been localized records. My friend Julie had 4″ in her rain gauge in her Squirrel Hill backyard. Sue Vrabel commented below that she had 4.5″ in Churchill.

(photos by Kate St. John, rain graph from the National Weather Service)

Beat The Heat With Trees

Climate Change, Trees, Weather & Sky
Schenley Park Upper Trail, July 2017 (photo by Kate St. John)

3 July 2019

It’s been hot in Pittsburgh lately but nothing like the heat wave that’s sweeping Europe with highs above 100 degrees F. @JeremyDBarrell tweeted a long term solution with a compelling image by Meg Caffin.

Meg Caffin is an urban forest consultant from Australia who provides guidance for cities looking to beat the heat. Her image at top used an infrared camera to show the temperature difference between a paved churchyard and the trees behind it. I’ve made a Fahrenheit translation below. Yes, it’s 113oF on the pavement and only 77oF under the trees.

Tree shade is cooler than building shade because buildings merely block the sun while the trees actually lower the temperature.

Schenley Park near Bartlett entrance (photo by Kate St. John)

Trees cool the air by transpiring. They take up water from the ground and release it from the stomata in their leaves. The release doesn’t usually drip from the leaves as shown below. Instead it evaporates and that’s what cools the air.

Transpiration droplets from a leaf (photo from Wikimedia Commons)

Evaporation — changing a liquid to a gas — uses energy. According to the Transpiration blog, “Energy is absorbed into liquid water. This reduces the temperature of the surrounding plant tissue and nearby atmosphere. To evaporate 1 gram of water 590 calories of energy is required.”

So more trees mean less heat.

If that isn’t enough reason to like trees, here’s another benefit. Trees increase your property value as shown in the EPA cost-benefit analysis below.

Trees increase property value far beyond cost of maintenance (EPA)

Plan to plant a tree this fall or plan to keep one. It’s cheaper to keep an existing tree than to plant a new one and mature trees increase property value even more.

Meanwhile if you’re feeling hot right now, visit a local park. Beat the heat among the trees.

(embedded Tweet from Jeremy Barrell; infrared heat image by Meg Caffin for the City of Geelong, Australia (Fahrenheit added); transpiring leaf from Wikimedia Commons; photos of Schenley Park by Kate St. John)

In Nome On The Longest Day

Alaska, Travel, Weather & Sky
Sunrise in Nome on the summer solstice (photo from Wikimedia Commons)

Alaska Birding with PIB: Nome Alaska 21 June 2019

Today we’re in Nome, Alaska on the summer solstice. If we were north of the Arctic Circle the sun would never set today but Nome is 143 miles south. The sun does set here, but barely. It never gets completely dark. Instead, twilight lasts for 2.5 hours and then the sun is up again.

The photos above and below were taken at sunrise during the 2013 summer solstice from the Bering Land Bridge Preserve office in Nome. The photo caption says, “Up here in Bering Land Bridge, summer solstice means almost 24 hour days. Sunrise at our office here in Nome on the solstice is around 04:18 am, and the sun won’t set until 01:47 am the next day.”

Summer solstice sunrise over Anvil Mountain, Nome, Alaska (photo from Bering Land Bridge National Preserve on Flickr)

The sun just skims below the horizon, then circles the town.

Indeed it is the longest day.

(photos from Bering Land Bridge National Preserve on Flickr, Creative Commons license; click on the captions to see the originals)

Pennsylvania Fire Season

Phenology, Weather & Sky
Fire in the Wayne National Forest, March 2009 (photo from Wikimedia Commons)

4 April 2019

Spring is fire season in Pennsylvania. 85% of our wildfires occur in March, April and May.

There’s no drought in Pennsylvania right now, nor in most of the U.S. — as shown on the map below.

US Drought Monitor for 28 March 2019

But you don’t need drought to have a fire. All you need are dry conditions, fuel, and a spark. In Pennsylvania we have all three in the spring: low humidity, gusty winds, and lots of old leaf litter drying out in the sun. The spark comes from people.

98% of Pennsylvania’s wildfires are caused by people and most of those are caused by people burning debris. On a sunny windy day those fires blow onto dry grass and escape to the wild. In April 2016 more than 10,000 acres burned in Pennsylvania.

Yesterday the fire danger was high in our state because the weather was so nice — warm and sunny with gusty winds. Across Pennsylvania people were out doing yard work. Some were probably burning piles of debris. I haven’t heard if there were any fires. (The fire danger is lower today, 4 April 2019, because the weather changed.)

U.S. Forest Service Wildfire Danger Forecast

If you live in a place that allows outdoor trash burning be careful out there! Spring is Pennsylvania fire season.

(photo of fire from Wikimedia Commons (actually a prescribed burn). Maps from US Drought Monitor and U.S. Forest Service Wildfire Danger Forecast; Click on the captions to see the originals)

Note: Allegheny County does not allow outdoor trash burning.

Is It Spring Yet?

Climate Change, Weather & Sky
Honeysuckle leaves in the City of Pittsburgh, 16 March 2019 (photo by Kate St. John)

20 March 2019

Today is the astronomical First Day of Spring when the sun crosses the celestial equator at 5:58pm EDT. But is it Spring yet? It depends on where you live.

The USA National Phenology Network tracks spring across the continental U.S. based on first leaf out conditions for honeysuckle (Lonerica) and first bloom conditions for lilacs (Syringa vulgaris). The plants are non-native, and honeysuckle is invasive, but they make good indicators because they’re early responders to springtime warmth.

Monday’s animated Spring Leaf Index (18 March 2019) shows that leaf out was ahead of schedule through late February but fell behind in northern Virginia, the southern Great Plains, and the Pacific Northwest when cold weather hit in early March.

Spring Leaf Index as of 18 March 2019 (animation from USA NPN)

According to the model, spring hasn’t reached Pittsburgh yet but I’m conducting my own Leaf Out Survey in my neighborhood. I took the honeysuckle photos below on 11 March and 16 March 2019. Both were cold days after a spurt of exceptionally warm weather. The tiny leaves on the right show the effect of 77 degrees F on March 14!

Honeysuckle leaf out, City of Pittsburgh, 11 March and 16 March 2019 (photos by Kate St. John)

Do you have leaves in your neighborhood yet? Is spring on time?

Follow spring’s progress at the USA National Phenology Network. For blooming times click here for the latest Spring Bloom map.

(animated map from the USA National Phenology Network. photos by Kate St. John)