Strange as it looks, this fluffy white object is not a UFO (Unidentified Flying Object), it’s a special cloud.
Lenticular clouds form when the wind blows horizontally toward a fixed object that forces the air to rise and fall in a wave. If the air is moist it condenses at the crest of the wave and forms lenticular clouds at the top. The diagram below shows the wind flowing over a mountain, forming two mountain-shaped waves and lenticular clouds at peaks A and B.
As Hurricane Dorian approached Florida on Labor Day afternoon and a storm band dowsed the area with wind and rain, my sister-in-law went into her garage in Boca Raton and found a bird, 15-18″ tall, perched high near the ceiling. She texted me a photo. “What is it?”
This immature Cooper’s hawk is too young to have seen a hurricane before, but he knows that the weather is bad and he can feel it’s going to get worse. If he’s a skillful hunter he’s already eaten a lot in anticipation of the storm and just needs a safe place to wait out the weather, so he picked the best available option. He came indoors.
Cooper’s hawks don’t breed in South Florida but they spend the winter there (see range map). This youngster arrived recently and is improvising in bad weather. So far so good.
The bird may have to wait in the garage for a while. Hurricane Dorian could take 24 hours to move out of the area.
When the storm is over this bird will be glad to leave.
UPDATE, 3 Sep 2019, 8a: The storm isn’t bad in Boca Raton. The hawk left.
(photo by Natalie Mitchell, range map from Wikimedia Commons)
When we say we’re “in the doldrums” we feel depressed, dull and listless. Those with Seasonal Affective Disorder (SAD) — a type of depression related to the change of seasons — may be in the doldrums already though it’s only late August. They’re aware that Pittsburgh has lost an hour and 48 minutes of daylight since the June 21 solstice.
You can see the ITCZ from satellite as a band of clouds near the thermal equator (photo at top). At this time of year there may be a dense circle in the line of clouds, a newly forming tropical depression.
The ITCZ moves north in the summer especially over land (which is warmer) and south in the winter, causing rainy and dry seasons in the tropics. The map below shows where the ITCZ usually goes; its path in the Pacific is affected by El Nino.
Five years ago today on 17 August 2014 Terry Lovejoy scanned the heavens from his home near Brisbane, Australia and found a new long-period comet.
Originating from the Oort Cloud, Comet C/2014 Q2 was in the southern constellation Puppis when Lovejoy first saw it. It wasn’t very bright at the time (apparent magnitude 15) but by mid-December it became so bright that you could see it naked-eye in a dark sky if you knew where to look. In January 2015 it crossed the celestial equator and became brighter still, soon passing close to the sun. Diminished by the sun’s power it won’t return for another 8,000 years.
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.
Airplanes can create elongated fallstreaks when they pass through the cloud layer. This cavum has an added bonus. There’s a sundog inside it.
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.
Gavin Pretor-Pinney loves clouds so much that he started the Cloud Appreciation Society in 2005. In this 11 minute video he shows how clouds are fun and fascinating and urges us to slow down and take a look at them.
Keep looking up!
p.s. The embedded video begins at 1:19 minutes in. Click here to see the whole video from the beginning.
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 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.
If you were out in the UK today, this will not be hard to work out. Infrared shows the temperature difference between areas with trees, and those without. Thanks to Meg Caffin and the City of Geelong, Australia, for the insight. This is what’s coming and we’re not ready for it! pic.twitter.com/N5PrCvIhYB
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.
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.
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.”
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)