WEATHER - BEAUFORT SCALE

Beaufort Scale - INTERACTIVE

The Beaufort wind scale is a standard scale, running from force 0 for calm to force 12 hurricane and above for the description of wind speed. Each value represents a specific range and classification of wind speeds with accompanying descriptions of the effects on surface features. It was originally developed as a system for estimating wind strengths without the use of instruments. It was introduced in 1806 by Admiral Sir Francis Beaufort (1774-1857) of the British navy to describe wind effects on a fully rigged man-of-war frigate of the period, and it was later modified to include descriptions of effects on land features as well. It is currently still in use for this same purpose as well as to tie together various components of weather (wind strength, sea state, observable effects) into a unified picture. The Beaufort Scale  (for use at sea) FORCE DESCRIPTION SEA STATE SPEED knots m/s 0 calm like a mirror <1 0.0-0.2 1 light air ripples, no foam 1-3 0.3-1.5 2 light breeze small wavelets, smooth crests with glassy appearance 4-6 1.6-3.3 3 gentle breeze large wavelets, some crests break, some white horses 7-10 3.4-5.4 4 moderate breeze small waves, frequent white horses 11-16 5.5-7.9 5 fresh breeze moderate rather long waves, many white horses, some spray 17-21 8.0-10.7 6 strong breeze some large waves, extensive white foam crests, some spray 22-27 10.8-13.8 7 near gale sea heaped up, streaks of foam blowing with the wind 28-33 13.9-17.1 8 gale fairly high and long waves, crests breaking into spindrift, blowing foam in prominent streaks 34-40 17.2-20.7 9 strong gale high waves, dense foam streaks in wind, wave-crests topple and roll over, spray reduces visibility 41-47 20.8-24.4 10 storm very high waves, overhanging crests, dense blowing foam, heavy tumbling sea appears white, visibility poor 48-55 24.5-28.4 11 violent storm exceptionally high waves, hiding small ships, sea covered with foam, crests blown into froth, visibility poor 56-63 28.5-32.6 12 hurricane air filled with foam and spray, sea white, visibility extremely bad >64 32.7

WEATHER - CLOUDS REVIEW

REVIEW:

The Core Four

While clouds appear in infinite shapes and sizes they fall into some basic forms. From his Essay of the Modifications of Clouds (1803) Luke Howard divided clouds into three categories; cirrus, cumulus and stratus.

	Cirro-form The Latin word 'cirro' means curl of hair. Composed of ice crystals, cirro-form clouds are whitish and hair-like. There are the high, wispy clouds to first appear in advance of a low pressure area such as a mid-latitude storm system or a tropical system such as a hurricane.
	Cumulo-form Generally detached clouds, they look like white fluffy cotton balls. They show vertical motion or thermal uplift of air taking place in the atmosphere. They are usually dense in appearance with sharp outlines. The base of cumulus clouds are generally flat and occurs at the altitude where the moisture in rising air condenses.
	Strato-form From the Latin word for 'layer' these clouds are usually broad and fairly wide spread appearing like a blanket. They result from non-convective rising air and tend to occur along and to the north of warm fronts. The edges of strato-form clouds are diffuse.
	Nimbo-form Howard also designated a special rainy cloud category which combined the three forms Cumulo + Cirro + Stratus. He called this cloud, 'Nimbus', the Latin word for rain. The vast majority of precipitation occurs from nimbo-form clouds and therefore these clouds have the greatest vertical height.

Combinations of the Core Four

Based on his observations, Howard suggested there were modifications (or combinations) of these core clouds between categories. He noticed that clouds often have features of two or more categories; cirrus + stratus, cumulus + stratus, etc. His research served as the starting point for the ten basic types of clouds we observe.

We call these CLOUDS:

 Altocumulus, Altostratus, Cirrus, Cirrocumulus, Cirrostratus, Cumulonimbus, Cumulus, Nimbostratus, Stratocumulus andStratus.

By convention, clouds are vertically divided into three levels; low, middle, and high. Each level is defined by the range of levels at which each type of cloud typically appears. Divided by their height the ten types of clouds are...

• Cirrus (Ci), Cirrocumulus (Cc), and Cirrostratus (Cs) are high level clouds. They are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon.

Cloud Poster. Click to enlarge.
• Altocumulus (Ac), Altostratus (As), and Nimbostratus (Ns) are mid-level clouds They are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are low enough.
  
  In Latin, alto means 'high' yet Altostratus and Altocumulus clouds are classified as mid-level clouds. 'Alto' is used to distinguish between liquid-based clouds. They are 'high' relative to their low level liquid-based counterpart clouds Stratus and Cumulus.
  
  Altostratus can extend into the high level of clouds. Nimbostratus can extend into the high level as well but the base of the cloud typically decreases into the low level as precipitation continues.
• Cumulus (Cu), Stratocumulus (Sc), Stratus (St), and Cumulonimbus(Cb) are low clouds composed of water droplets. Cumulonimbus, with its strong vertical updraft, extends well into the the high level of clouds.

"Clouds out my Window" book.

by:  John "Dr. Lightning" Jensenius, a NWS Meteorologist in Maine



TEN BASIC CLOUDS
From the World Meteorological Organization's (WMO) International Cloud Atlas, the official worldwide standard for clouds, the following are definitions of the ten basic cloud types.

High Level Clouds

Cirrus (Ci) Detached clouds in the form of white, delicate filaments, mostly white patches or narrow bands. They may have a fibrous (hair-like) and/or silky sheen appearance. Cirrus clouds are always composed of ice crystals, and their transparent character depends upon the degree of separation of the crystals. As a rule when these clouds cross the sun's disk they hardly diminish its brightness. But when they are exceptionally thick they may veil its light and obliterate its contour. Before sunrise and after sunset, cirrus is often colored bright yellow or red. These clouds are lit up long before other clouds and fade out much later; some time after sunset they become gray. At all hours of the day Cirrus near the horizon is often of a yellowish color; this is due to distance and to the great thickness of air traversed by the rays of light.
Cirrocumulus (Cc) Thin, white patch, sheet, or layered of clouds without shading. They are composed of very small elements in the form of more or less regularly arranged grains or ripples. Most of these elements have an apparent width of less than one degree (approximately width of the little finger - at arm's length). In general Cirrocumulus represents a degraded state of cirrus and cirrostratus both of which may change into it and is an uncommon cloud. There will be a connection with cirrus or cirrostratus and will show some characteristics of ice crystal clouds.
Cirrostratus (Cs) Transparent, whitish veil clouds with a fibrous (hair-like) or smooth appearance. A sheet of cirrostratus which is very extensive, nearly always ends by covering the whole sky. During the day, when the sun is sufficiently high above the horizon, the sheet is never thick enough to prevent shadows of objects on the ground. A milky veil of fog (or thin Stratus) is distinguished from a veil of Cirrostratus of a similar appearance by the halo phenomena which the sun or the moon nearly always produces in a layer of cirrostratus.

Mid Level Clouds

Altocumulus (Ac) White and/or gray patch, sheet or layered clouds, generally composed of laminae (plates), rounded masses or rolls. They may be partly fibrous or diffuse and may or may not be merged. Most of these regularly arranged small elements have an apparent width of one to five degrees (larger than the little finger and smaller than three fingers - at arm's length). When the edge or a thin semitransparent patch of altocumulus passes in front of the sun or moon a corona appears. This colored ring has red on the outside and blue inside and occurs within a few degrees of the sun or moon. The most common mid cloud, more than one layer of Altocumulus often appears at different levels at the same time. Many times Altocumulus will appear with other cloud types.
Altostratus (As) Gray or bluish cloud sheets or layers of striated or fibrous clouds that totally or partially covers the sky. They are thin enough to regularly reveal the sun as if seen through ground glass. Altostratus clouds do not produce a halo phenomenon nor are the shadows of objects on the ground visible. Sometime virga is seen hanging from Altostratus, and at times may even reach the ground causing very light precipitation.
Nimbostratus (Ns) Resulting from thickening Altostratus, This is a dark gray cloud layer diffused by falling rain or snow. It is thick enough throughout to blot out the sun. The cloud base lowers as precipitation continues. Also, low, ragged clouds frequently occur beneath this cloud which sometimes merges with its base.
While Altostratus and Nimbostratus can extend into the high level of clouds, Nimbostratus can extend into the low level as well.

Low Level Clouds

Cumulus (Cu) Detached, generally dense clouds and with sharp outlines that develop vertically in the form of rising mounds, domes or towers with bulging upper parts often resembling a cauliflower. The sunlit parts of these clouds are mostly brilliant white while their bases are relatively dark and horizontal. Over land cumulus develops on days of clear skies, and is due diurnal convection; it appears in the morning, grows, and then more or less dissolves again toward evening.
Cumulonimbus (Cb) The thunderstorm cloud, this is a heavy and dense cloud in the form of a mountain or huge tower. The upper portion is usually smoothed, fibrous or striated and nearly always flattened in the shape of an anvil or vast plume. Under the base of this cloud which is often very dark, there are often low ragged clouds that may or may not merge with the base. They produce precipitation, which sometimes is in the form of virga. Cumulonimbus clouds also produce hail and tornadoes.
Cumulus and Cumulonimbus clouds are usually found in the low level category, but their tops may reach into the mid and high levels.
Stratocumulus (Sc) Gray or whitish patch, sheet, or layered clouds which almost always have dark tessellations (honeycomb appearance), rounded masses or rolls. Except for virga they are non-fibrous and may or may not be merged. They also have regularly arranged small elements with an apparent width of more than five degrees (three fingers - at arm's length).
Stratus (St) A generally gray cloud layer with a uniform base which may, if thick enough, produce drizzle, ice prisms, or snow grains. When the sun is visible through this cloud, its outline is clearly discernible. Often when a layer of Stratus breaks up and dissipates blue sky is seen. Sometimes appearing as ragged sheets Stratus clouds do not produce a halo phenomenon except, occasionally at very low temperatures.

http://www.srh.weather.gov/srh/jetstream/clouds/basicten.htm

CLOUD MATCHING - ACTIVITY

WEATHER - LAKE SNOW EFFECT

Lake Effect Snow 

Lake effect snows occur when a mass of sufficiently cold air moves over a body of warmer water, creating an unstable temperature profile in the atmosphere.

As a result, clouds build over the lake and eventually develop into snow showers and squalls as they move downwind. The intensity of lake effect snow is increased when higher elevations downwind of the lake force the cold, snow-producing air to rise even further.

The most likely setting for this localized type of snowfall is when very cold Arctic air rushes over warmer water on the heels of a passing cold front, as often happens in the Great Lakes region during winter.

Winds accompanying Arctic air masses generally blow from a west or northwest direction, causing lake effect snow to fall on the east or southeast sides of the lakes.

Whether an area gets a large amount of snow from lake effect is dependent on the direction of the winds, the duration they blow from a particular direction, and the magnitude of the temperature difference between the water and air.

Since cold air can hold very little moisture and the low level of the atmosphere is quite unstable, clouds form very rapidly, condensation occurs and snow begins to fall. Lake effect snow is lighter than snow that forms from frontal stratus or nimbostratus.

Areas of relatively high elevation downwind of the Great Lakes generally receive heavier amounts of lake effect snow than do other locations in this region.

For example, residents of the Tug Hill Plateau in New York State east of Lake Ontario can spend the winter months digging out of anywhere from 200 to 300 inches of snow. Likewise, the mountains of West Virginia can receive over 200 inches of snow in a winter, helped by the lake effect.

The only other lake that produces significant lake effect snow in the United States is the Great Salt Lake in Utah.

Cape Cod Bay in Massachusetts and Chesapeake Bay in Maryland and Virginia, on occasion, produce what is called bay effect snow. Bay effect snow forms in the same manner as lake effect snow, only over the ocean.

Steps to Lake Effect Snow

• Cold air streams across the warm lakes. Air warms and becomes more humid.
• As the air warms, it becomes less dense and rises.
• As air rises, it cools.
• Cooler, moist air may form clouds and cause precipitation.
• After the air has moved some distance over the lake, convection and turbulent exchange have transported the moisture aloft to form clouds. Snow may fall.
• Once over land, moisture in the air condenses into snow. Snow created in this way is called lake effect snow.
• As the warmed air reaches the shoreline, additional lifting may occur as the air begins to “pile up.” Air moves more slowly over land than over water, due to increased friction.
• Hills and high lands on down-wind lake shores force air upward. Air cools further, encouraging cloud formation and greater snowfall.

As the cold air streams across the warm lakes, it is warmed and becomes more humid. As the air warms, it becomes less dense and tends to rise cooling (as it rises). Whenever moist air rises, as previously noted, clouds may form and precipitation may result. Fog results from the intense evaporation or transfer of moisture from the warm water to much colder air when the cold air initially makes contact with warm water. After the air passes from some distance over the lake, convection and turbulent exchange have transported the acquired moisture aloft to form clouds and snowfall may occur.

WEATHER - JET STREAM

JET STREAM & WEATHER

Jets streams play a key role in determining the weather because they usually separate colder air and warmer air. Jet streams generally push air masses around, moving weather systems to new areas and even causing them to stall if they have moved too far away

Jet streams are like rivers of wind high above in the atmosphere. These slim strips of strong winds have a huge influence on climate, as they can push air masses around and affect weather patterns.

The jet streams on Earth — other planets have jet streams as well, notably Jupiter and Saturn — typically run from west to east, and their width is relatively narrow compared to their length. Jet streams are typically active at 20,000 feet (6,100 meters) to 50,000 feet (9,144 meters), or about 7 miles (11 kilometers) above the surface and travel in what is known as the troposphere of Earth’s multi-layered atmosphere.

While they are fairly narrow, they cover a wide latitude running north to south and often travel a very winding path; at times they can even fade away or break off into smaller “rivers” of air that merge again “downstream.”

The seasons of the year, location of low and high pressure systems and air temperature all affect when and where a jet stream travels. Jet streams form a border between hot and cold air. Because air temperature influences jet streams, they are more active in the winter when there are wider ranges of temperatures between the competing Arctic and tropic air masses.

Temperature also influences the velocity of the jet stream. The greater the difference in air temperature, the faster the jet stream, which can reach speeds of up to 250 mph (402 kph) or greater, but average about 110 mph (177 kph).

Both the Northern and Southern hemispheres have jet streams, although the jet streams in the north are more forceful. Each hemisphere has two primary jet streams — a polar and a subtropical. The polar jet streams form between the latitudes of 50 and 60 degrees north and south of the equator, and the subtropical jet stream is closer to the equator and takes shape at latitudes of 20 to 30 degrees.

While the polar and subtropical jet streams are the best known and most studied, other jet streams can form when wind speeds are above 58 mph (93.3 kph) in the upper atmosphere at about 6 miles (9.6 kilometers) to 9 miles (14.5 kilometers) above the surface. The term is often misused, even by meteorologists giving the weather forecast who sometimes, for the sake of simplicity, call all strong upper-atmosphere winds jet streams.

Jet Streams and the weather

Jets streams play a key role in determining the weather because they usually separate colder air and warmer air. Jet streams generally push air masses around, moving weather systems to new areas and even causing them to stall if they have moved too far away.

While they are typically used as one of the factors in predicting weather, jet streams don’t generally follow a straight path — the patterns are called peaks and troughs — so they can shift, causing some to point at the poor forecasting skills of meteorologists.

Climatologists say that changes in the jet streams are closely tied to global warming, especially the polar jet streams, because there is a great deal of evidence that the North and South poles are warming faster than the remainder of the planet. When the jets streams are warmer, their ups and downs become more extreme, bringing different types of weather to areas that are not accustomed to climate variations. If the jet stream dips south, for example, it takes the colder air masses with it.

Jet streams also have an impact on air travel and are used to determine flight patterns. An airplane can travel much faster, and save fuel, by getting “sucked up” in the jet stream. That can also cause a bumpy flight, because the jet stream is sometimes unpredictable and can cause sudden movement, even when the weather looks calm and clear.

Who discovered jet streams?

Aeronautics played a role in the discovery and mapping of jet streams. Many credit bomber pilots flying missions during World War II with much of the knowledge we have today about the jet streams. They were able to quicken their missions and beat hasty retreats over the Mediterranean Sea by making the most of the jet streams.

But even before WWII bomber pilots used the jet streams. Wiley Post, an American pilot and the first to fly solo around the world in 1933, contributed to our knowledge of these forces of nature. He developed a pressurized suit to fly higher in the atmosphere and noted the differences in pressure at various levels. This set the stage for the understanding of the jet stream and pressurized flight.

German meteorologist H. Seilkopf is often credited with coining the phrase "jet stream," as he used in a research paper published in 1939.

Volcanoes have also played a role in understanding of the jet stream. Observers of the 1883 eruption of the Krakatoa volcanic island in Indonesia documented its effect on the sky, and in the 1920s Japanese meteorologist Wasaburo Oishi used aviator balloons to identify the jet stream from a site near Mt. Fuji.

More recently, many European flights were grounded after the 2009 eruption of Iceland's Eyjafjallajokull volcano —further proof that plumes of volcanic ash have a tendency to get sucked into the same jet stream that airplanes use for travel.

Iceland Eyjafjallajokull Volcano - April 2010

SCIENCE WORLD

SCIENCE WORLD

• Carefully read the articles & take notes for discussion.
• You can check-out a magazine or read online (click on the highlighted links)

SCIENCE WORLD - MARCH 24

SCIENCE WORLD - MARCH 3

SCIENCE WORLD - FEBRUARY 3

SCIENCE WORLD - JANUARY 13

SCIENCE WORLD - DECEMBER 9

WIND & LEEWARD VS. WINDWARD

What is wind? 
Wind is air in motion. It is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s radiation unevenly. Two factors are necessary to specify wind: speed and direction.

What causes the wind to blow? 
As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow.
Wind Direction

Although wind blows from areas of high pressure to areas of low pressure, it doesn't blow in a straight line.  That's because the earth is rotating.  In the northern hemisphere, the spin of the earth causes winds to curve to the right (to the left in the southern hemisphere). This is called the coriolis effect. So in the northern hemisphere, winds blow clockwise around an area of high pressure and counter-clockwise around low pressure.

How Fast Is It? You can estimate wind speed with the Beaufort Scale.  It was developed in 1805 by a Navy admiral to measure wind at sea.  But we can also use it to measure wind on land.

ESTIMATE WIND BY WATCHING OBJECTS MOVE!

Miles Per Hour   Effects <1  Smoke rises straight up, no motion
1-3        Smoke drifts slowly, tree leaves barely move
4-7        Leaves rustle, wind felt on face

8-12      Leaves and twigs move, dust raised from ground

13-18    Small branches move, dust and paper blown away.

19-24    Small trees and large branches sway

25-31    Big branches move a lot, wind whistles, umbrellas
             turn inside out.
32-38    Whole trees sway, hard to walk
39-46    Tree twigs break, very hard to walk
47-54    Branches, roof tiles blown down
55-63    Trees uprooted, severe building damage
64-72    Severe destruction

CORIOLAS EFFECT

Coriolis effect

The Coriolis effect is a (fictitious) force which acts upon any moving body (an object or an parcel of air) in an independently rotating system, such as the Earth. In meteorology, the horizontal component of the Coriolis force is of primary importance, as the most well known application of the Coriolis force is the movement or flow of air and ocean currents across the Earth. The effect is named after the French physicist Gaspard de Coriolis (1792-1843), who first analyzed the concept mathematically. The Earth rotates about its axis from west to east once every 24 hours. This daily rotation of the earth means that in 24 hours a point on its equator moves a distance of some 40 000 kilometres, giving it a tangential velocity of about 1670 kilometres per hour (or roughly 1000 mph). A point at the latitude of, say, Rome, travels a shorter distance in the same time and therefore has a lower tangential velocity - about 1340 kph (840 mph), while the relative tangential speed at the poles is zero. Consequently, an object or current moving above the Earth in a generally northerly or southerly direction (away from the equator) will have an greater eastward velocity than the ground underneath, and so will appear to be deflected in relation to the rotation of the Earth. This deflection acts towards the right (or clockwise) in the, in the Northern Hemisphere and towards the left (or anti-clockwise) in theSouthern Hemisphere. Moving air undergoes an apparent deflection from its path, as seen by an observer on the Earth. This apparent deflection is the result of the Coriolis acceleration (or Coriolis force). The amount of deflection the air makes is directly related to both the latitude and the speed at which the air is moving. Therefore, slowly blowing winds will be deflected only a small amount, while stronger winds will be deflected more. Likewise, winds blowing closer to the poles will be deflected more than winds at the same speed closer to the equator. The Coriolis force is zero right at the equator and becomes a maximum at the poles. The Coriolis force only acts on large objects like air masses moving considerable distances. Small objects, for example ships at sea, are too small to experience significant deflections in direction due to the Coriolis force. Therefore the Coriolis force is particulary significant with regards to winds, ocean currents and tidal streams. The idea of the Coriolis effect was developed independently by William Ferrel in America.

WIND/ENERGY ENGINEER

• Read the article; work through the tabs at top of the page
• take notes
• we will discuss this career in class

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Windward: The side of a mountain or any object facing the wind.

Leeward: The side of a mountain or any object sheltered from the wind.

Prevailing wind: The direction from which the winds blow most of the time. Average wind direction. In N.Y.S. the prevailing winds are from the southwest.

1. Large bodies of water will :
   1. Moderate temperatures extremes.
   2. Water is slow to warm up (cools hot air) and slow to cool off (warms cold air).
   3. Provide a source of moisture for the air, precipitation tends to be higher.
2. Near the center of a land mass :
   1. Temperatures are more extreme (very hot or cold).
   2. Precipitation tends to be lower (no water sources).
3. Elevation changes:
   1. Denser air can contain more heat energy.
   2. Temperatures decrease as elevation increase.
4. Near mountains:
1. As air approaches the mountains (windward side), it rises to go over them.
2. As it rises, it expands and cools to the point where the air can not hold water vapor anymore.
3. This is called the dew point and clouds form. Precipitation occurs.
4. Most of the moisture is taken out of the air raby the time it gets over the mountain summits.
5. As the air descends down the mountain's leeward side it compresses and warms.
6. The warming air absorbs moisture from the ground and dries the leeward side (rain shadow).
5. Rain Shadow

A rain shadow is a patch of land that has been forced to become a desert because mountain ranges blocked all plant-growing, rainy weather. On one side of the mountain, wet weather systems drop rain and snow. On the other side of the mountain—the rain shadow side—all that precipitation is blocked.

In a rain shadow, it’s warm and dry. On the other side of the mountain, it’s wet and cool. Why is there a difference? When an air mass moves from a low elevation to a high elevation, it expands and cools. This cool air cannot hold moisture as well as warm air. Cool air forms clouds, which drop rain and snow, as it rises up a mountain. After the air mass crosses over the peak of the mountain and starts down the other side, the air warms up and the clouds dissipate. That means there is less rainfall.

You’ll often find rain shadows next to some of the world’s most famous mountain ranges. Death Valley, a desert in the U.S. states of California and Nevada, is so hot and dry because it is in the rain shadow of the Sierra Nevada mountain range. The Tibetan Plateau, a rain shadow in Tibet, China, and India has the enormous Himalaya mountain range to thank for its dry climate.

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