Severe storms and heavy rain possible for Tuesday

The National Weather Service’s Storm Prediction Center has mapped out an elevated risk of severe weather and heavy rain over the mid-Atlantic states for Tuesday. Beware of flooding and possible severe thunderstorms Tuesday afternoon into the early evening.

The hourly aviation forecasts are predicting: for Philadelphia, showers with a 30% probability of heavy or severe thunderstorms between 3pm and 6pm on Tuesday. The NYC area forecasts are giving the timing of a 30% probability of moderate thunderstorms between noon and 6pm, with a general moderate rain during that time. After that, both areas have light rain showers into the night.

Any severe thunderstorms will have high wind gusts as their major damaging effect. (In addition to possible very heavy rains.)

Here’s the Weather Prediction Center’s forecast map for Tuesday. Check the site for updates.

Tuesday morning and during the day on Tuesday, check these sources and your local forecasts for updates, especially for when severe conditions may occur.

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Catching a Perseid Meteor – sooner may be better

The 2019 Perseid meteor shower peaks around 10pm on August 12th. But an almost-full Moon will drown out the fainter meteors. So start looking now, even in the evening sky, for early Perseids.

The hours after midnight are typically best to see more meteors. The Earth leads with its morning edge as it orbits the Sun, so we scoop up more interplanetary particles then. But the Perseid shower has two important features: 1) the shower produces many meteors ahead of the peak on the 12th. 2) many Perseids are bright. So, if you are out after dark this week, especially while the Moon is still thin, keep an eye out for meteors!

Another plus is the place were Perseids appear to come from in the sky (its ‘radiant’ in the constellation Perseus) is above our horizon most of the night. That also gives us a better chance to see more Perseids in the evening. Look in the darkest part of the sky to see more meteors. No need to find Perseus to see the meteors.

August sky around 10pm EDT from Westchester County, NY.
Note Perseus rising in the northeast.

For early risers, the mornings are dark until Moon sets after midnight starting on the 8th. Each night the Moon sets about 50 minutes later. But even on the 12th, there is about an hour between moon-set and the beginning of morning twilight. So there is a window of opportunity on the morning before the peak to see more Perseids.

One more interesting opportunity is when the radiant in Perseus rises after evening twilight. Sometimes, when the radiant is low in the sky, we see meteors skipping across the top of the atmosphere that trail across much of the sky.

Perseids are crumbs from Comet 109P/Swift–Tuttle. It takes 133 years to go around the Sun. It’ll be back in July 2126. Swift-Tuttle is 16 miles wide. That makes it the largest object, other than the Moon, to come near Earth. It’s larger than the object that struck the Earth and helped make the dinosaurs extinct. Calculations of Swift-Tuttle’s orbit predict it will come close, but not hit the Earth, for at least two thousand years.

Heads UP! for August 2019

Astronomy is the universe of the seen and unseen.  For me, it’s about finding ways to show the sky to people.  I love things that change.  Jupiter and Saturn have changing cloud bands and dancing moons.  Even our unchanging moon goes through phases modulating the light and shadows that help us see places on the moon, including places we’ve visited.  What about the stuff we ‘can’t’ see? More on that later.

August Summary Jupiter and Saturn call for our attention after sunset.  Venus and Mars hide in the glare of the Summer sun. Mercury peeks out into the morning sky, perhaps to see if it’s safe for Venus and Mars to come out this Fall, and then goes back to tell them.  

More Moon If you missed viewing our Moon in July, the dates for best viewing of the Apollo 11 landing site start in the evening sky on August 6, this month’s date when the sun angle is nearly the same as during the landing of Apollo 11 in Mare Tranquillitatis.

Moon phase at 10pm EDT August 6th. NASA Scientific Visualization Studio illustration.

Oh, Jupiter!  Due south before the end of twilight, the planet looks like it wants to leave town fast.  Take some time with Jupiter and a telescope; it’s as if Jupiter is in the shop for a change of belts and badly out of round tire-shaped Great Red Spot. The Moon sits atop Jupiter on the 9th.

Saturn follows Jupiter, highest 10 to 11pm. Titan, Saturn’s largest moon, swings out widest from the planet on the 3rd, 11th, 19th, 27th.  The rings tilt 24½ degrees wide from Earth’s point of view.  Saturn appears to scoot across the Moon’s north pole on the 12th and 13th.

Saturn and Jupiter on each side of Sagittarius.

August’s Super New Moon On the 30th, a “super” new moon is closest to Earth only five hours after new moon.  Let’s hope no hurricanes approach land during this and the following days of already larger-than-normal tides.

The Perseids meteors peak on the 12th/13th, but the moon is almost full that night. Take advantage of the many Perseids that arrive before the peak.  Go out early in the month, when the moon is less bright, get the bright lights out of your eyes, and look for Perseids and other meteors then.  Viewing after twilight may be better for this shower than most.  Generally, the Earth runs into more meteors during the morning, but the apparent source in the constellation Perseus is above the horizon most of the night.  You might even see some bright, long trail meteors at the shower’s peak just after evening twilight on the 12th.  

Satellite Sightings The International Space Station is visible evenings through the 8th, and mornings starting on the 24th.  China’s Tiangong 2 was coaxed to reenter into the Earth’s atmosphere over the Southern Pacific Ocean on July 19th, 40 years after the USA’s Skylab fell into Indian Ocean and some parts showered Australia July 11, 1979.

Solar Limbo Dancing Mercury is low in the morning sky, actually getting brighter even as it moves further away from us. Even though its size shrinks, more of the innermost planet is illuminated as the month goes on. It swings farthest out from the Sun on the 9th.  Venus reaches superior conjunction in back of the Sun on the 14th.  Mars has one more month to reach its solar conjunction.

As for the stuff we can’t see.  Sometimes it’s looking deeper in a larger telescope or catching the light taken from professional telescopes around the world and in space.  I keep going back to the SOHO satellite.  It’s life has been extended several times by creative folks at the Goddard Spaceflight Center and the European Space Agency.  This month, it lets us see the planets in the traffic jam in the solar glare.  At star parties, we get questions about the planets – “When’s Mars coming out?”  Too close to the Sun, we tell them.  But, for the last third of the month, Venus and Mars hang together near the Sun in the SOHO view, as close as a third of a degree apart on the 24th.  Regulus sits in the background.  Mercury joins the club late in the month.

Moon landing and Moon rise

By coincidence, the moment of the anniversary of the first step on our Moon by humans is about the same as the time of moon rise here in the Mid-Atlantic states of the United States.

At 10:56:20 pm EDT, Saturday, July 20th, we celebrate exactly 50 years since Neil Armstrong stepped on our moon’s surface. At a specific set of places across the world tonight, the Moon will rise at or around that time.
For New York City, moon rise is 10:47pm. EDT, 10:58 in Washington, DC, 10:57 in Philadelphia, PA. Data from USNO site.
If I understood the moon-rise math and geometry better, I could figure out which specific places the moon will rise at the time of the first step in that time zone’s standard time.
Note that since the dates of the phases of the moon change from month to month (see Scott’s blog on this: https://scottastronomy.wordpress.com/…/apollo-11-a-moon-ph…/ ) the moon is not where it was the night of the first moon landing.

It might be nice to commemorate the anniversary of the ‘small step’ / ‘giant leap’ with the view of our moon coming over the horizon.

July 17, 1969: The New York Times Corrects an Error

In 1920, the New York Times castigated Robert Goddard for not knowing that a rocket ship would need “something better than a vacuum against which to react”.

On July 17, 1969, the New York Times corrected that error.

Even more interesting, several days later in July 1969, Robert Goddard’s widow chided the Times that it should not have “took the trouble to disinter this item”.

Copies of the Correction, the relevant piece of the original article, and Mrs. Goddard’s letter, are below for your inspection.

Moon Dust, Sahara Dust, Storms and Air Quality Problems. And, Bring the Heat for the East.

With the 50th anniversary of the first landing on the moon coming up, everyone’s talking about the Moon. Including me at the Greenburgh Public Library in Elmsford, New York, tonight at 7pm. Come and find out the many (less mentioned) ways we almost never landed on the moon and how they worked around those problems.

Today’s national weather map has the remains of tropical system Barry bringing moisture to the northeastern quadrant of the USA. Watches are posted for heavy rain.

National Weather Service Weather Prediction Center Forecast Weather Map for Wed July 17.

Also watch out for the intense weather forecasted for Iowa and Wisconsin today.

A classic high ozone day for the northeast yesterday. Emissions of nitrogen oxides and volatile organic compounds cooked in the summer sun peaked downwind of major urban areas.

State agencies report ozone air quality from Tuesday, July 16th.

Highest concentrations, over the 85 parts per billion code red limit, unhealthy for everyone, were at the end of the northeast corridor in Connecticut.

Wind direction and speed analysis for 3pm Tues July 16. Shows winds in the northeastern urban corridor from the southwest and west-southwest moving emissions from urban centers down the urban corridor.

Waves from Africa bring tropical moisture, and later in the year, hurricanes, to Puerto Rico and the Virgin Islands. At this time of year, trailing the waves are areas of dry air and dust from the Sahara Desert.

Analysis of dry air and dust (yellow, orange and red) from satellite data.

The National Weather Service says the next wave will have enough moisture to give the islands much needed rain, but will be followed by a large area of dry and maybe dusty air.

Last, and not least, Wednesday’s heat and humidity will be a practice run for the extensive area of extreme temperatures to occur over much of the USA this upcoming weekend. Remember that sometimes the worst heat problems are when the temperature remains high at night. Go to the maps.

Heat waves can give us clear, if haze, but steady skies for watching the planets. Jupiter and Saturn are low in the southern sky after sunset. See Sky and Telescope’s Sky at a Glance for weekly updates.

In the meantime, use this chart to find Jupiter and Saturn. The moon has moved on, rising later in the evening, but the chart will be good for the planets and stars for July.

Click on the links to get the latest updates.

And, as always, sorry for the gross ads that wordpress uses to pay the bills.

Celebrate the Apollo Landings – see for yourself

Monday morning, July 8, 2019

Are you ready for the 50th anniversary of our first moon landing on July 20th?  Start the celebration early by looking for our moon in the afternoon or the first half of the night now in early July.   Did you see our Moon in the afternoon sky yesterday, between the cumulus clouds floating around?

Today, July 8th, the Moon will be at the same phase as when the Apollo 11 astronauts landed on the Moon on July 20, 1969, fifty years ago.

Of course, you can’t see the equipment left behind on the Moon by the American Apollo moon landing missions, but you can see the areas where they landed, with a bit of direction. And, looking at our Moon is fun, with no optical aid or any at all.

You’ll be able to see this almost-half-moon after sunset tonight, but take a look this afternoon. The moon will rise just after noon local daylight time today and set about 1am. So, by late afternoon, our Moon will be about half-way up in the southern sky.

Here’s a sky chart for 5pm LDT:

5pm July 8, 2019. Sky chart from Heavens-Above.com
Moon phase for Tuesday, July 9th, 2019. For WAA talk at Yonkers Library.

Get your own view at for different dates and times at : https://svs.gsfc.nasa.gov/4442, via NASA’s Scientific Visualization Studio.  Scroll down further at this site to learn more about how the moon looks at different times of the month and when you can see it.

All of the Apollo landing sites will be (just barely) sunlit by Thursday night through the 21st, when the sun will be setting on the easternmost sites. Ask yourself, “Self, what is special about the order in which they landed at these landing sites.” The answer gives us lots of insight into the Moon itself. We can see the darker areas, where the first landings, Apollos 11 and 12, occurred are less bumpy. It turns out, these darker areas are younger and the brighter, heavily cratered parts are older. By landing in flat areas first, the Apollo program gained confidence. By going to both kinds of areas, we learned more about our Moon. You can see the differences between these two kinds of terrain (lunain?) without any optical aid at all!

Here’s the map for then. It shows what the Moon will look like at the time of Ardsley/Elmsford summer reading club moon presentation, but it’s good for everyone on Thursday evening.

Moon phase for Thursday afternoon/evening July 11th, 2019.

Happy moon viewing!