Archive

Archive for February, 2010

Aliens In The Clouds!

February 26th, 2010 No comments

The other day I was driving home from work, and on the south side of the Catalina Mountains in Tucson, I saw these clouds:

Tucson Lenticular Clouds

Tucson Lenticular Clouds

Unfortunately, because I took the picture with my iPhone, the clouds are a bit hard to see. But, if you look closely at the clouds in the center of the image, you’ll notice that they’re rounded and somewhat “flying saucer” shaped. Here’s a better picture of the same type of clouds, that I took in Mt Shasta, CA:

Mt Shasta Lenticular

Mt Shasta Lenticular Clouds

These types of clouds are called Lenticular clouds, and they are stationary, lens shaped clouds that form at high altitudes. Typically, these clouds form on the downwind side of a mountain where warm, moist air is flowing, creating a series of large-scale standing waves. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves to the trough of the wave, if it’s warm enough, it may evaporate back to vapor. Under certain conditions, long strings of lenticular clouds can form near the crest of each successive wave, creating a formation known as a wave cloud. And, because these clouds have a characteristic lens appearance and smooth saucer-like shape, they are often mistaken for UFOs (or “visual cover” for UFOs).

The air in the area of lenticular clouds is great for gliders, who seek out and ride the updrafts associated with the standing waves, but not so great for pilots of powered aircraft who are concerned with the turbulence. “Wave lift” often found in areas with lenticular clouds is often so smooth and strong that gliders can sail to incredible heights and distances. In fact, the current gliding world records for both distance (over 3,000 km; 1,864 mi) and altitude (15,460 m; 50,721 ft) were set using such lift.

I’ve always loved how lenticular clouds look. In almost every trip past Mt Shasta in California, where I have been able to see the mountain, lenticular clouds are present. I’ve also noted them quite frequently on the top of Mt Rainier in Washington. They are very beautiful clouds, but you can rest assured there are no aliens hiding in them!

Free Stuff From the NWS!

February 23rd, 2010 No comments

In my last post, I talked a bit about the National Weather Service, and how it contributes to predicting the chances of precipitation. We learned that they send up a radiosonde twice a day, from locations all over the country, to collect data about the atmosphere. Quite a bit of that data they post online for anybody to look at, and combined with other bits of data from things like satellites and ground observations, you can get an amazing picture of how things are shaping up in your area (or almost anywhere in the world!). Let’s take a look at a few of the things you can find online at the National Weather Service web site.

Current observations are an important part of determining what will happen with the weather. If you know how conditions are now, and how they have changed from the past, you can get a clue as to how they might be in the future. One tool that the NWS provides is a Surface Plot graph.

Surface Plot Chart

Surface Plot Chart

The official term for this is Mesonet Observations. According to wikipedia, “a mesonet is a network of automated weather stations designed to observe mesoscale meteorological phenomena. Dry lines, squall lines, and sea breezes are examples of phenomena that can be observed by mesonets. Due to the space and time scales associated with mesoscale phenomena, weather stations comprising a mesonet will be spaced closer together and report more frequently than synoptic scale observing networks, such as ASOS. The term mesonet refers to the collective group of these weather stations, and are typically owned and operated by a common entity.” So, basically, this is a series of stations that report current observations on wind speed and direction, temperature, relative humidity, and other items. If you know how to read these reports, and can spot trends, you can tell when a frontal system moves through, or when you might expect a thunderstorm. It’s good on the ground information.

One area at the NWS site that I spend a lot of time checking during stormy periods is the local weather radar image. This image gives me a great idea of where precipitation is occurring at the moment, and in what amounts and intensity. This is particularly valuable if you are going storm chasing, as you can see where the local thunderstorm cells are dumping their rain. It also provides a time-lapse ability, so you can see what direction the storm is moving. I enjoy watching the radar, especially when storms are headed my way.

Radar Image

Radar Image

Now, let’s say you’re interested in what the current forecast is for your region. The NWS is particularly good at providing that information, and does so in a wonderful graphical format. You can find out great things like temperature, wind speed and direction, dew point (handy in the summer for monsoon prediction), sky cover, precipitation, and more for up to the next week or so. This is very handy for planning activities, and the graphical format of the data is exceptional.

Graphical Forecast

Graphical Forecast

Finally, though by no means even close to the end of the great things you can get from the NWS, is the Weather Story that they produce from time to time. In Tucson, I tend to see these when a weather event is on the way, and right after an event. Any significant change in the expected weather pattern also seems to generate a Weather Story. Essentially, these are a couple slides that show the basics of what’s going on in the area, and what to expect in the near future. I find them interesting because it’s a good synopsis of what’s going on. I don’t know if all major locations produce weather stories, but I suspect they do.

Weather Story

Weather Story

So, there you have it…some of the free products that you can get from the NWS. These items only touch on the rich repository of information that is the National Weather Service. If you are interested in weather, I encourage you to take some time and look around. You’ll find data on things that you didn’t even know they collected data on!

a mesonet is a network of automated weather stations designed to observe mesoscale meteorological phenomena. Dry lines, squall lines, and sea breezes are examples of phenomena that can be observed by mesonets. Due to the space and time scales associated with mesoscale phenomena, weather stations comprising a mesonet will be spaced closer together and report more frequently than synoptic scale observing networks, such as ASOS. The term mesonet refers to the collective group of these weather stations, and are typically owned and operated by a common entity.

Chance of Rain

February 22nd, 2010 No comments

It’s raining outside in Tucson today, which leads me to think about what they mean when they say there is an X percent chance of participation. This morning, Weather Underground says there is an 80% chance of precipitation in Tucson. Does that mean 80% of the area will get rain? That it will rain 80% of the day?

I did some research, and the answer is pretty simple : out of 100 days where the weather conditions were exactly or similar to how they are today, it rained 80 times. Pretty simple!

The questions becomes, then, how do they get that data to make such a calculation? The answer lies with the National Weather Service. Each day the NWS releases several balloons into the atmosphere from locations across the country. Those balloons, called radiosondes, are released twice a day and the information they collect is radioed to the ground where it’s collected by the National Meteorological Center near Washington, D.C, where it’s processed by computer. All the information the radiosonde collected during its rise in the atmosphere – pressure, humidity, wind speed and direction, temperature – is fed into the computer and used, in conjunction with data from ground sources, to create a 3D model of the atmosphere. That model is evaluated against various laws of fluid mechanics to predict future conditions.

Chance of precipitation for 22 February 2010.

Chance of precipitation for 22 February 2010.

Unfortunately, given the nature of precipitation, these percentages are really just educated guesses based on previous conditions. The atmosphere is a very fluid and dynamic entity, and many things can trigger an unexpected change in conditions. A wet day can suddenly turn sunny, just like a sunny day can suddenly turn severe. Weather forecasters have a difficult job at best, and providing a chance of precipitation number is just one way that they can help you plan your day.

By the way…a 100% chance of rain does not mean that it’s raining right this moment (unless, perhaps, you live in the Pacific Northwest). Again, it simply means that out of 100 previous days where conditions have been similar to those today, it rained every time. And of course that begs the next question…what is rain? We’ll save that for a later post!

National Weather Service (NWS)

February 22nd, 2010 3 comments

If you plan on following the weather seriously, you should bookmark the National Weather Service. Operated by the National Oceanic and Atmospheric Association (NOAA), the NWS web site provides you with detailed weather information for all of the United States. Of particular interest to those who love to track the weather are:

  • Detailed warning information
  • Forecast discussions
  • Graphical forecasts
  • Forecast discussions with a glossary to help you understand terms
  • Radar
  • Satellite
  • Severe weather

There is tons more there, and it’s all worth a look. You can get local forecasts, with great discussions about them, for your local area. You can also monitor severe weather in the event that you’re looking to do some storm chasing. And, you can watch the satellite to see when that next rain or snowstorm will hit your area. The NWS site is a treasure trove of information for people like me who love the weather. Check it out, and I’m sure you’ll find it interesting as well!

Bad Weather On The Horizon!

February 20th, 2010 No comments

I’ve been thinking about this blog recently, and decided to take it in a new direction. I’ve really wanted to do a blog about weather related subject, and while thinking about a blog name, I realized I already had the perfect one in “Thunderstruck!” So, starting in the very near future, you can expect this blog to be almost 100% weather related. I’ll focus both on weather basics, as well as severe weather subjects. I’m really hoping to go storm chasing in Tornado Alley this spring or summer, and expect to return back with tons of pictures like the one below (not taken by me).

I hope you like the new direction of this blog, and I look forward to and welcome your comments. Thanks for visiting “Ive Been Thunderstruck!”

An awesome looking supercell!

An awesome looking supercell!