12 May 2023

From Earth, Saturn is tiny and the Moon is large. You can see the huge size difference in Paul Byrne’s (@ThePlanetaryGuy) video of Saturn rising behind the Moon.

Every once in a while, if you time it just right, you can see Saturn rise from behind the Moon. pic.twitter.com/gnRAVQSgyu

— Paul Byrne (@ThePlanetaryGuy) April 28, 2023

In reality Saturn is 95 times larger than our Moon and has 83 moons of its own plus thousands of moonlets. Only seven of Saturn’s moons can be seen through a telescope from Earth.

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

12 April 2023

This morning’s weather forecast includes an unusual warning. There’s a Fire Weather Watch in Pittsburgh today from 11am to 8pm. The relative humidity is low (25-30%), the winds will be gusty (up to 25 mph) and it’ll be hot (almost 80ºF!).

Spring is fire season in Pennsylvania when 85% of our wildfires occur. As the growing season begins, forests and fields are covered in dry leaves and grasses. Under the right weather conditions a cigarette tossed from a car or a trash burn will catch and spread quickly.

That’s probably how this distant wildfire started in Fayette County in March 2011 (photo by Jon Dawson).

Pennsylvania DNCR publishes a daily county-by-county Fire Danger map which shows Allegheny County at elevated risk this morning. The highest risks are in north central PA. (Watch out DuBois and State College!) and in the drought areas in southeastern PA.

So be careful today. Don’t burn trash, don’t drop a burning cigarette on the ground, and if you see a brush fire call the fire department!

Be safe during Pennsylvania Fire Season.

(photos from PA National Guard and Jon Dawson on Flickr via Creative Commons license, weather forecast screenshot from NWS, Fire Danger Map from PA DCNR)

26 January 2023

More fun with maps!

Earlier this month when I wrote about wind speed maps (How Fast Is The Wind Blowing?) Steve Thomas sent a link to the earth mapping website. I remembered green swirling maps on my own blog, Winds On Water, but seven years ago I didn’t look further than the default surface winds.

The earth website is, in their own words, “a visualization of global weather conditions forecast by supercomputers updated every three hours.” Their action maps include high altitude winds, ocean currents, temperatures, fires and more.

Let’s start exploring with today’s map of surface winds, shown below (click here to open it on your own computer). I guarantee it will look different than this image I pulled yesterday.

To see the legend and change the map click on the [earth] icon at bottom left. The default setting is:

• Mode=Air
• Animate=Wind
• Height=Sfc (surface)
• Overlay=Wind

To see winds at higher altitude I chose Height=250. [250 hPa = 250 hectopascals = lower pressure = higher altitude. The lower the hPa number, the higher the altitude above the surface.]

• Mode=Air
• Animate=Wind
• Height=250
• Overlay=Wind

The wind is screaming purple-white at 250 hPa. It looks like the jet stream.

To achieve the map of ocean currents shown at top I chose:

• Mode=Ocean
• Animate=Currents
• Overlay=HTSGW (Significant Wave Height)

Click here to see an action map of the Gulf Stream at the ocean’s surface (screenshot at top). Watch it rounding the tip of Florida, then pumping north and east into the Atlantic, leaving vortices in the Gulf of Mexico.

That strong current near the east coast of Florida is the water “highway” that many creatures use for migrating north. It’s the reason why you can see whales from shore in early spring.

Try out the other options on earth to have more fun with maps.

(all maps are screenshots from earth, base maps for these screenshots can be found at this link https://earth.nullschool.net/#current/wind/surface/level/orthographic=-65.93,34.58,803)

23 January 2023

A green comet that last passed the sun 50,000 years ago set off a flurry of stargazing on the night of the new moon, 21-22 January. Even though Comet C/2022 E3 (ZTF) will pass closest to earth on 2 February it is best to see it now before the moon waxes to full on 5 February.

video from @MrSuperMole on YouTube

Comet C/2022 E3 (ZTF) is so faint that it must be viewed in a dark sky and is best seen via binoculars, telescope, or camera with telephoto lens — for instance, birding equipment. The photo above was taken with a 300mm F/4 lens. Click here for information on where to look.

With magnification and a star map all you need is a dark sky, but finding one is increasingly difficult.

A study published last week in the journal Science examined 12 years of citizen science reports of the constellations seen with the naked eye. The number of constellations seen from 2011-2022 went down as sky glow increased from lights on earth. As Smithsonian Magazine explains, the brightness of light pollution increased at a rate of 9.6 % per year. “That’s equivalent to the brightness doubling every eight years.”

Previous studies used satellites to measure earth lights reaching outer space but they missed the effect of ground lights inside our atmosphere. So the problem is worse than we thought. For a video illustration, see the 2016 article below.

Meanwhile in Pittsburgh, we definitely have light pollution but our impossible hurdle is cloud cover. We have lots of clouds in the forecast for the next 10 days.

Read more about the light pollution study in Smithsonian Magazine: Light pollution is drowning the starry night sky faster than thought.

(photo from Wikimedia Commons, video from @MrSuperMole on YouTube, screenshot from weather.com on cellphone)

17 January 2023

We can’t see the wind but we can guess its speed by watching what it does to leaves and flags …

… and then using the wind speed chart from the National Weather Service (NWS) to make a guess. My guess for the above photos is a Gentle Breeze 8-12 mph or a Moderate Breeze 13-18 mph but it’s hard to tell.

NOAA weather satellites don’t see the wind either but they can see the clouds moving in three layers.

• High level clouds (cirrus) at 23,000 to 46,000 feet
• Mid level clouds at a level of 10,000 to 23,000 feet
• Low level clouds are below 10,000 feet

In their animations of satellite images we can almost see the wind but not its speed.

For instance, in this GOES East animation from last Thursday 12 January 2023 we can see the Atmospheric River pumping into California and a low pressure system moving up the Ohio Valley.

NOAA’s computers use the animated maps to calculate wind speed and direction. The result, called Derived Motion Winds, plots the wind height, direction and speed on a map.

Here’s the same timelapse with Derived Motion Winds. Notice that the layers often don’t move in the same direction or at the same speed. You’ve felt this in an airplane as a “bump” when the plane rises or descends between conflicting layers.

You can “see” the wind anywhere in the Americas by choosing a satellite to view (list on the left) at the NOAA GOES Imagery Satellite Maps. Click on Derived Motion Winds if available.

To view the current GOES East satellite, pictured above, visit these links:

• GOES East satellite, all images: https://www.star.nesdis.noaa.gov/GOES/conus.php?sat=G16
• GOES East satellite, Derived motion winds: https://www.star.nesdis.noaa.gov/GOES/conus_band.php?sat=G16&band=DMW&length=24&dim=1

(photos from Marcy Cunkelman and Wikimedia, maps and animations from NOAA and the National Weather Service)

16 January 2023

Pittsburgh’s skies were oppressively gray on Saturday with thick Lake Effect Clouds but the forecast promised the clouds would break in early afternoon so I planned a walk in Schenley Park for 2:30pm. Hah!

By 3pm the clouds were still thick and gray and the revised forecast predicted they would break up in the 4 o’clock hour. Of course! We were about to get 15-30 minutes of full sun immediately followed by sunset at 5:15pm, a classic Gleam At Sunset. I timed my walk to arrive at Schenley’s golf course by 4:45pm.

My photos show what happened: the classic gleam, an unexpected sun pillar, and a beautiful red sky at sunset.

If you’ve never heard of Lake Effect Clouds and the Gleam At Sunset, find out more in last month’s article:

(photos by Kate St. John)