Lucky Weather

The spate of cloudy nights here in Austin, reminds me of the importance of making your own luck with the weather. I would have missed all the sights below without making my own luck.

the International Space Station transiting the Sun

Make time, space, and good weather coincide

Most of the sights in the night sky are visible any time they are above the horizon and the sky is clear and dark. Enjoying them is simply a matter of getting outside when the weather is good and knowing where to look.

There are celestial events that are only visible at specific times and locations. Aurora, eclipses, conjunctions, transits, occultations, and meteor showers can all be spectacular events. Part of their attraction is that you can’t see them from anywhere or on just any night. Many of these events repeat, but waiting for that to coincide with good viewing weather in your location may take years or even decades.

Jupiter and Venus conjunction - long view

Making your own luck

If you are willing to travel and learn how to use astronomical weather forecasts, you can improve your chances of seeing events in the sky. Mother nature is still in charge; so nothing is guaranteed. I've spent some time under grey skies that were supposed to be partly cloudy. Using these techniques I've had more good luck with the weather than bad.

Jupiter and Venus conjunction - close up

Track astronomical weather forecasts

Most weather forecasts are for temperature, wind, rain or shine. All are important to astronomers but they are not enough. Cloud cover, seeing (atmospheric turbulence), transparency (dust, moisture and thin clouds) are also important and not in every forecast.

Transit of Mercury

All weather forecasts start with data from ground weather stations. Locations with dark skies are usually not near many people, these areas usually don’t have as many weather stations to collect data as highly populated areas. As a result these and areas "down weather" from them have less accurate forecasts.

Computing weather forecasts is expensive. To keep computing costs low, longer range forecasts calculate their forecasts on a courser grid. As the date gets closer, better data is used and the calculations are done on a finer grid making them more accurate. There are four time scales that you should know about:

  • seasonal climate - will the next season or moth be wetter or dryer than normal
  • a week ahead - forecasts predict specific weather, but there is a lot of room for change
  • three to two days out - weather models switch to a finer grid and become much more accurate
  • the day before - even more detailed computations are done and there is another big step up in accuracy

Checking forecasts at each of these points will let you incorporate the weather into your plans.

Keep in mind what is unpredictable. We can expect some kinds of weather, e.g., wind, area wide rain, or sky cover to be accurate. Predicting exactly where thunder storms will pop up is well beyond what is possible.

Use more than one weather forecast source. There are some excellent forecasts aimed at astronomers like the Canadian Clear Dark Sky forecast (includes the US) and but these can easily miss local variations. The US National Weather Service detailed forecasts include important information like sky cover and humidity for any location in the US in graphical form or as interactive maps. Most other sources are based on the forecasts of the national weather services, but they often include local weather expertise as variations to these forecasts.

Large area graphical views of forecasts or satellite weather data are useful for picking out patterns to watch for. For example a local forecast may look good, but a larger view may show an approaching change that could radically alter the local weather if it arrives sooner. NOAA Water Vapor (transparency) and IR (cloud cover) images are very useful. During fire season wildfire smoke plume maps may be useful.

Looking at several forecasts is well worth while, because it’s not unusual for a single source to miss something important to you. Keeping a list of forecast bookmarks to check is an easy way to keep this information accessible.

I’ve found that once I picked the sources that worked for me it wasn’t hard to combine them into a dashboard and make sure that I don’t miss anything. If you have a little skill with HTML for web pages, it’s easy to pull this together on a local HTML file that you can bring up in your web browser. Mine is located here. You are free to grab the HTML code for my page and modify it to create your own custom dashboard.

Travel to where the weather is good

If the observing weather looks bad where you live, the forecasts will show areas where it is better. Finding a spot to observe on shot notice, usually isn’t hard. Public access areas like parks, public lands, and rest areas can be great spots for a few hours observing. Semi-public areas like churches, schools, and cemeteries can work well too. Be sensible about safety. A companion and a mobile phone is always a good idea. Many of these areas may have nominal curfews at night. Most of the time you are unlikely to be noticed and if you are a friendly explanation and offer to share the view will get you by.

I’ve been able to see many astronomical events that I would have missed if I’d stayed closer to home by being willing to travel an hour or two. When I traveled to see a total solar eclipse access to easy travel along the path was an important consideration. I used that to move a several hundred miles the night before and increase my chances from 50% to 100%.

2017 Great American Eclipse Revisited, put a ring on it

Adapt your plans to the weather

Sometimes we can live with clouds and make the best of things. If clouds are broken and the winds are moving them along, it’s easy to wait for clear spots, it what you want to observe lasts more than a few minutes.

If you are an astrophotographer, clouds, poor seeing and transparency may spoil plans for long exposures or long focal length close ups. Switching to a wide lens for the big view may work much better with the clouds adding context and interest to the event.

Super Blue Blood Moon Time-lapse Lometa Texas

Content created: 2018-02-08




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Moon Phase