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Archive for the ‘Weather Definitions’ Category

Classic Plains Tornado Outbreak Ingredients

May 24th, 2011 No comments

There was a recent article at weather.com called Classic Plains Tornado Outbreak Ingredients. It gives an excellent overview, along with weather map examples, of what it takes to generate a tornado. This is absolutely worth a read for any chaser.

Tornado Infographic

April 26th, 2011 1 comment

The tornado season this year has been absolutely HUGE so far! So, here’s an infographic dedicated to teaching you more about this amazingly powerful weather phenomenon!

Weather Word Wednesday : Blizzard

February 2nd, 2011 No comments

Seems fitting that the word for today should be Blizzard! Last night a massive snowstorm blanketed much of the Midwest United States, and has left many without power or stuck in places they don’t want to be. Flights have been canceled, schools closed, and general mayhem was experienced by all!

A blizzard, according to Wikipedia, is “a severe storm condition characterized by strong winds and reduced visibility. By definition, the difference between blizzard and a snowstorm is the strength of the wind. To be a blizzard, a snow storm must have winds in excess of 56 km/h (35 mph) with blowing or drifting snow which reduces visibility to 400 meters or ¼ mile or less and must last for a prolonged period of time — typically three hours or more.”

Last night certainly counted as a blizzard. As the people who experienced 25 foot waves crashing on the shores of Lake Michigan in Chicago. Or the literally thousands of motorists stranded on the roads. This was one of the worst blizzards in history, and the full impact is yet to be realized.

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

Weather Word Wednesday : Nor’easter

January 12th, 2011 No comments

I just read a Twitter post from @reedtimmerTVN that said another Nor’easter was bearing down on the East Coast of the United States today. It occurred to me that I really don’t know what a Nor’easter is, so I figured that would be the perfect word for Weather Word Wednesday.

According to Wikipedia, a Nor’easter is “is a type of macro-scale storm along the East Coast of the United States and Atlantic Canada, so named because the storm travels to the northeast from the south and the winds come from the northeast, especially in the coastal areas of the Northeastern United States and Atlantic Canada.”

Specifically, a Nor’easter describes a low pressure area who’s center of rotation is just off the East Coast and who’s leading winds in the left forward quadrant rotate onto land from the northeast. Nor’easters can cause coastal flooding, coastal erosion, hurricane force winds and heavy snow. While they can occur at any time of the year, they are most frequent in the winter months. These systems are known for bringing down extremely cold arctic air from the north.

Satellite image of the intense nor'easter responsible for the North American blizzard of 2006. Note the hurricane-like eye at the center.

Nor’easters generally affect the United States, from Virginia to the New England cost, as well as Quebec and Atlantic Canada. They tend to bring massive amounts of precipitation, high winds, large waves, and marginal storm surges to coastal areas. In general, though, people tend to call any strong rain or snow storm in the Northeast a Nor’easter. The very name brings feelings of dread and anticipation to people in the region!

For more information, visit this Wikipedia article on Nor’easters.

Weather Word Wednesday : Winter Storms

January 5th, 2011 No comments

This is the first of the Weather Word Wednesday series, where each Wednesday I take a word or set of words found in weather reporting or meteorology, and let you know what they mean! My aim is to educate and help you understand what’s really being talked about on your favorite weather report, blog, or publication. Today we are going to talk briefly about Winter Storm advisories, watches and warnings!

Winter Storm Advisory: An advisory is issued by the National Weather Service (NWS) when a significant winter storm or hazardous winter weather is occurring, imminent, and is an inconvenience. This means bad weather is happening right now or will happen soon, but it won’t be as bad as what you get with a Winter Storm Warning.

Winter Storm Watch: A watch is issued when significant winter weather, like heavy snow, sleet, significant freezing rain, or a combination of events, is expected, but not imminent. A warning provides about 12 to 36 hours notice of the possibility of severe winter weather.

Winter Storm Warning: This is issued when significant winter weather is occurring, imminent, or likely, and is a threat to life or property. If you hear a Winter Storm Warning for your area, you should probably remain inside with a nice cup of hot chocolate! But be prepared to dig yourself out later!

During the course of any given winter, you are likely to hear all three of these weather statements issued at one time or another. Even here in Arizona, we get Winter Storm Warnings when the occasional super heavy snowstorm rolls through. It’s good to have a basic understanding of the urgency associated with each of these weather statements, as it ultimately helps you get prepared for the weather ahead. Keep an eye on the TV, or an ear to the radio, and always know what’s happening outside!

Sources : The Weather Channel

Contrail Science

November 22nd, 2010 No comments

I stumbled (by using StumbleUpon!) an interesting website today called Contrail Science. The tagline for the site is “The Science and Pseudoscience of Contrails and Chemtrails,” and the current article on the home page is a very detailed explanation, using pictures, flight info and good science, about the alleged “missile launch” in Los Angeles a few weeks ago. The author of the site has numerous posts detailing the basics about contrails, some good stuff about contrail chemistry, and pictures galore! Contrails come in many shapes and sizes, and there are additional phenomena seen in the weather that act similarly to contrails. If you are at all interested in those trails you see in the sky, or want a lively debate on the “LA missile launch,” you should absolutely check out this site!

"LA Missile Launch"

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

Hook Echo

May 12th, 2010 No comments

I’ve been doing some reading lately on mesocyclones and tornado development, and one of the hallmark signs of a potential tornado forming is a “hook echo” being seen on the weather radar. A hook echo is produced by rain, hail or even debris being wrapped around a supercell, giving the impression of a hook on the radar. Meteorologists consider the presence of a hook echo enough justification to issue a tornado warning for an area. The hook echo has been recognized as a sign of tornado development for most of the history of weather radar. The first hook echo was detected in 1953 by the Illinois State Water Survey during their test to use radar to measure precipitation rates. In the southern US states, hook echos are not always obvious due to the heavier rainfall from the supercell. Instead, the echo will take on a more kidney shape. Here is an example of a classic hook echo – if you see this while checking out the radar, either seek shelter, or head out with your camera!

Classic Hook Echo