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Posts Tagged ‘Weather’

Weather Word Wednesday : Weather

January 26th, 2011 No comments

As I got to thinking about the word I wanted to discus today, it occurred to me that the very base of what we’re talking about here, Weather, would be the perfect word to delve into!

Weather, according to Wikipedia, “is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy.” Seems pretty basic when you look at it like that! Most weather tends to occur in the troposphere, which is the layer of the atmosphere that we live in. Wikipedia goes on to say that “weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time.” And, unless you’re being specific, the term generally applies to weather on Earth.

Weather basically occurs because of density differences in temperature and moisture between different points on the earth. These differences are generally caused by the varying sun angles at any point on the earth, which varies by latitude from the tropics. The strong temperature differences between the tropics and the poles is what causes the jet stream, which is a fast flowing, narrow air current. Weather systems in the mid-latitudes, like the United States and much of Europe, is caused by instabilities of the jet stream flow. Sometimes the jet stream dips down from the poles, bringing with it cold air. Sometimes it causes a ridge that brings up warm, moist air from the tropics. All this combines to create the weather systems that get reported on each day.

Earth's Weather

Weather on Earth is complex and chaotic!

On Earth, “common weather phenomena include wind, cloud, rain, snow, fog and dust storms.” Less common events include “tornadoes, hurricanes, typhoons and ice storms.” Wind is created by differences in air pressure levels on the planet, with air flowing from regions of high pressure to low pressure. Pressure itself is caused by varying temperatures on the planet, with colder temps producing lower air pressure, and higher temps associated with high pressure systems.

The atmosphere is a hugely complex and chaotic system, where changes to one variable (temperature, pressure, moisture) can have huge effects on the weather in a particular location, or a location remote from where the variable has changed. The dynamics of weather in many cases are poorly understood, which is why long term weather forecasts are so difficult to create. As the years go by and we are able to gather more data about actual weather events, our understanding of weather and climate increase, and that leads to an increased ability to make accurate forecasts. But the weather will always surprise us, and we should be prepared for anything at any time. If you tend to venture outside your home, you should take time to understand what weather events might be headed your way!

Weather Word Wednesday : Glory

January 19th, 2011 1 comment

Have you ever been out hiking and looked down on a waterfall, surprised to see a round, rainbow colored halo? Or perhaps you’ve looked off towards a bank of clouds, with the sun at your back, and seen the same colored halo? If so, you’ve seen what meteorologists call a Glory.

Essentially, a Glory is “one or more sequences of faintly colored rings of light that can be seen by an observer around his own shadow cast on a water cloud (a cloud consisting mainly of small, uniform sized water droplets). It can also be seen on fog and exceptionally on dew.”  The glory can only be seen when the observer is directly between the sun and cloud of refracting water droplets.

Solar Glory

Solar glory at hot springs

Glories are not completely understood. The colored rings of the glory are caused by two-ray interference between “short” and “long” path surface waves – which are generated by light rays entering the droplets at diametrically opposite points (both rays suffer one internal reflection). Glories are often seen in association with a Brocken spectre, the apparently enormously magnified shadow of an observer, cast (when the Sun is low) upon the upper surfaces of clouds that are below the mountain upon which he or she stands. The name derives from the Brocken, the tallest peak of the Harz mountain range in Germany. Because the peak is above the cloud level, and the area is frequently misty, the condition of a shadow cast onto a cloud layer is relatively favored. The appearance of giant shadows that seemed to move by themselves due to the movement of the cloud layer (this movement is another part of the definition of the Brocken Spectre), and which were surrounded by optical glory halos, may have contributed to the reputation the Harz mountains hold as a refuge for witches and evil spirits.

The next time you have your back to the sun and clouds at your front, or are up high with clouds below, try and find a Glory on your shadow. If you have a camera with you, and see a Glory, send us a snapshot!

Source : Wikipedia

Pretty Sky

January 2nd, 2011 No comments

Sky looked pretty this evening around 5PM…deep blue with nice cirrus clouds!

Categories: Clouds, Weather Tags: ,

Changes Coming In 2011!

December 28th, 2010 No comments

Next year I plan on being much better at updating this blog! For starters, every week there will be “Weather Word Wednesday,” which will feature a word that deals with meteorology, with a short discussion of what it means. So, you can count on learning one new thing (hopefully!) each week! In addition, I plan on posting an interesting weather image each week, and will have more long posts about particular topics. If there is something about the weather that has always interested you, please post a comment about it, and I’ll look into writing about it for you!

Here’s to a great 2010, and an even better 2011. May the weather be interesting wherever you live!

Categories: General, Weather Tags: , ,

Water Vapor Imagery

August 24th, 2010 No comments

I recently “discovered” on the local NWS website the Satellite Water Vapor Imagery data for our area, and I’m quite fascinated by it! The official description of this data is as follows:

Water vapor satellite imagery depicts moisture content in the middle and upper layers of the atmosphere. Lower level moisture is not depicted in these images. Moisture transport over large distances generally happens through the middle and upper layers of the atmosphere. Hence these images will depict moisture coming into the Southwest from the Gulf of Mexico or across Texas. Additionally, weak disturbances from the east are best tracked through water vapor imagery.

The imagery looks like this when viewed online. The is a screen capture of one frame of data:

Water Vapor Imagery

Water Vapor Imagery

Basically, what this shows is the amount of moisture that is in the upper atmosphere. This may be in the form of clouds that you see, but often it is not. Water vapor literally surrounds the earth, but is unevenly distributed due to things like oceans, lakes, rivers, deserts, arid areas, etc. For instance, in the image above, you can see a lot of water vapor coming up from the southwest into places like Arizona and New Mexico, which are traditionally dry regions. Areas like the Pacific Northwest, which are usually wet, have much less than normal. This is all due to seasonal shifts in winds and weather patterns, which change the flow of moisture around the planet. By looking at an image like this, you can get an idea of how much moisture is available in your area…moisture that could turn to rain or snow!

Amazingly Quick Storm Development

August 23rd, 2010 No comments

When I drove to work this morning, around 9AM, the sky was almost perfectly clear.  A few high cirrus clouds, but nothing aside from that…just blue sky. Below is a snapshot from my phone on what the sky looked like around 1:30PM today:

Quick Storm Development

Quick Storm Development

Since this picture was taken, our area has seen multiple Severe Thunderstorm alerts, along with several Flash Flood warnings! It absolutely amazes me how quickly the weather can turn in our area of the wood, and why it’s always important to keep an eye on weather when outside doing fun things. Dry washes and rivers can turn into raging torrents without a single drop falling in your particular area. Always know the weather!

Categories: Clouds, Monsoon, Weather Tags: , ,

How To Forecast Weather Without Gadgets

June 2nd, 2010 No comments

I stumbled across this today, and thought it was worth sharing. There are lots of ways to forecast the weather without relying on gadgets. Knowing how to do it old school is a great skill to have, and helps you understand the fundamental properties of weather. Check out this graphic, and have fun learning!

How To Forecast Weather

Picture Of The Week

April 11th, 2010 No comments

Got this with my iPhone while at the airport in Dallas. It’s that time of year!

Categories: General, Tornadoes, Weather Tags: ,

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!