what the 'bleep' did she say?

7/30/2019 What the 'Bleep' Did She Say?

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What the Bleep Did She Say?

Understanding Your Local Meteorologist

By Anthony Stauffer

Weve all been there; you just got home from a rough day at work and you sit down to

watch the local news. You are excited to listen to the weather because you heard at work that

there is some nasty weather headed your way for the next day. You suffer through the first

twenty-two minutes of news, nothing but mostly bad news, and finally reach the forecast. And as

you watch your resident meteorologist, you hear her say words and phrases like clipper system,

upper level low, ridge of high pressure, isobars, etc. And all you can do is just watch the

greenscreen behind her at the animated weather and do the best you can to decipher what she issaying. Many times meteorologists, especially the local ones, dont use too many terms to

confuse the general public, but, sometimes, there is no choice. When forecasts or weather

explanations are in written form, it is even worse. Take, for example, this excerpt from

Wikipedia detailing the meteorological history ofHurricane Sandy(a.k.a. Frankenstorm).

Hurricane Sandy began as a low pressure system which developed sufficient organizedconvectionto be

classified as a tropical depression on October 22 south ofKingston, Jamaica.[17]

It moved slowly at first

due to aridgeto the north. Lowwind shearand warmwatersallowed for strengthening,[17]

and the system

wasnamedTropical Storm Sandy late on October 22.[18]

Early on October 24, aneyebegan developing,

and it was moving steadily northward due to an approachingtrough.

[19]

Later that day, theNationalHurricane Center (NHC)upgraded Sandy to hurricane status about 65 mi (105 km) south of Kingston,

Jamaica.[20]

At about 1900 UTC that day, Sandy madelandfallnear Kingston with winds of about 80 mph

(130 km/h).[21]

Just offshore Cuba, Sandy rapidly intensified to winds of 115 mph (185 km/h),[1]

and at that

intensity it made landfall just west ofSantiago de Cubaat 0525 UTC on October 25.[22]

After Sandy exited Cuba, the structure became disorganized,[23]

and it turned to the north-northwest over

the Bahamas.[24]

By October 27, Sandy was no longer fully tropical, and despite strong shear, it

maintained convection due to influence from an approaching trough; the same trough turned the

hurricane to the northeast.[25]

After briefly weakening to a tropical storm,[26]

Sandy re-intensified into a

hurricane,[27]

and on October 28 an eye began redeveloping.[28]

The storm moved around anupper-level

lowover the eastern United States and also to the southwest of a ridge overAtlantic Canada, turning it to

the northwest.[29]

Sandy briefly re-intensified to Category 2 intensity on the morning of October 29, around

which time it had a wind diameter of over 1,150 miles (1,850 km).[30]

The convection diminished while the

hurricane accelerated toward the New Jersey coast,[31]

and the hurricane was no longer tropical by

2300 UTC on October 29.[32]

An hour later at about 0000 UTC on October 30, Sandy made landfall near,

Brigantine, New Jersey,[33]

with winds of 80 mph (130 km/h).[34]

The remnants weakened over western

Pennsylvania, degenerating into a remnant trough on October 31.[35]
http://en.wikipedia.org/wiki/Hurricane_Sandyhttp://en.wikipedia.org/wiki/Hurricane_Sandyhttp://en.wikipedia.org/wiki/Hurricane_Sandyhttp://en.wikipedia.org/wiki/Convection_(meteorology)http://en.wikipedia.org/wiki/Convection_(meteorology)http://en.wikipedia.org/wiki/Convection_(meteorology)http://en.wikipedia.org/wiki/Kingston,_Jamaicahttp://en.wikipedia.org/wiki/Kingston,_Jamaicahttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Ridge_(meteorology)http://en.wikipedia.org/wiki/Ridge_(meteorology)http://en.wikipedia.org/wiki/Ridge_(meteorology)http://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Sea_surface_temperaturehttp://en.wikipedia.org/wiki/Sea_surface_temperaturehttp://en.wikipedia.org/wiki/Sea_surface_temperaturehttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/North_Atlantic_hurricane_naming_listhttp://en.wikipedia.org/wiki/North_Atlantic_hurricane_naming_listhttp://en.wikipedia.org/wiki/North_Atlantic_hurricane_naming_listhttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-18http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-18http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-18http://en.wikipedia.org/wiki/Eye_(cyclone)http://en.wikipedia.org/wiki/Eye_(cyclone)http://en.wikipedia.org/wiki/Eye_(cyclone)http://en.wikipedia.org/wiki/Trough_(meteorology)http://en.wikipedia.org/wiki/Trough_(meteorology)http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-19http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-19http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-19http://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-20http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-20http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-20http://en.wikipedia.org/wiki/Landfall_(meteorology)http://en.wikipedia.org/wiki/Landfall_(meteorology)http://en.wikipedia.org/wiki/Landfall_(meteorology)http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-21http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-21http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-21http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-SandyTCR-1http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-SandyTCR-1http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-SandyTCR-1http://en.wikipedia.org/wiki/Santiago_de_Cubahttp://en.wikipedia.org/wiki/Santiago_de_Cubahttp://en.wikipedia.org/wiki/Santiago_de_Cubahttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-22http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-22http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-22http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-23http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-23http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-23http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-24http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-24http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-24http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-25http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-25http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-25http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-26http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-26http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-26http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-27http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-27http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-27http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-28http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-28http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-28http://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Atlantic_Canadahttp://en.wikipedia.org/wiki/Atlantic_Canadahttp://en.wikipedia.org/wiki/Atlantic_Canadahttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc28-29http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc28-29http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc28-29http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-30http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-30http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-30http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-31http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-31http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-31http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-32http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-32http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-32http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-33http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-33http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-33http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-34http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-34http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-34http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-35http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-35http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-35http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-35http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-34http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-33http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-32http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-31http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-30http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc28-29http://en.wikipedia.org/wiki/Atlantic_Canadahttp://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Cold-core_lowhttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-28http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-27http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-26http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-25http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-24http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-23http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-22http://en.wikipedia.org/wiki/Santiago_de_Cubahttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-SandyTCR-1http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-21http://en.wikipedia.org/wiki/Landfall_(meteorology)http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-20http://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/National_Hurricane_Centerhttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-19http://en.wikipedia.org/wiki/Trough_(meteorology)http://en.wikipedia.org/wiki/Eye_(cyclone)http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-18http://en.wikipedia.org/wiki/North_Atlantic_hurricane_naming_listhttp://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Sea_surface_temperaturehttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Ridge_(meteorology)http://en.wikipedia.org/wiki/Hurricane_Sandy#cite_note-disc1-17http://en.wikipedia.org/wiki/Kingston,_Jamaicahttp://en.wikipedia.org/wiki/Convection_(meteorology)http://en.wikipedia.org/wiki/Hurricane_Sandy


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*NOTE: the numbers in brackets indicate references the Wikipedia article used to verify proper information,

and those links remain active for this article.*

That is a quite an explanation, with a lot of concepts which seem complex. To add some

sense to what the above was saying, below is a series of satellite photographs plotting Hurricane

Sandy over its course from Florida to its dissipation over New England.

Photos are courtesy of theNASA

GOES Projectand theNOAA.
http://goes.gsfc.nasa.gov/http://goes.gsfc.nasa.gov/http://goes.gsfc.nasa.gov/http://goes.gsfc.nasa.gov/http://www.noaa.gov/http://www.noaa.gov/http://www.noaa.gov/http://www.noaa.gov/http://goes.gsfc.nasa.gov/http://goes.gsfc.nasa.gov/


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What is Weather?

We may as well start at the beginning and figure out what weather is and what drives it.

As we all are familiar with, Earths axis of rotation is tilted. This translates to the following; no

matter where on the Earth you are, over the course of time you will see the Suns maximum

height in the daytime sky change, and the length of a day change with it. As a result, temperaturedifferences and moisture content in the air change rapidly. Thus, we end up with the driving

force behind the weather, differences in air pressure from one locale to another. The other factor

that sets up the weather is the spin of the Earth. Because there is friction between air and the

Earths surface, and the added effect of Earths gravity on the mass of the atmosphere, as the

planet spins the atmosphere goes with it. Thus, we end up with theCoriolis Effect, whereby the

cold air coming down from the poles flows toward the Equator and is, from ourstationary

frame of reference on the ground, deflected towards the west. This produces circulating air

masses as the cool air from the poles warms and the warm air from the equator cools, as shown

in the picture below.

In each hemisphere, this leads to the creation of three distinct air masses; they are the

tropical (equatorial), sub-tropical, and polar. The boundaries of these air masses are known as the

jet streams. The cooler air from the north dives beneath the warmer air coming from the south; it

sets up a low pressure at the surface and a high pressure in the upper altitudes. In regards to the

polar and subtropical air masses, the high pressure in the upper altitudes at the boundary clashes

with the low pressure in the upper altitudes of the pole. Therefore, with lower friction at high

altitudes, it causes the warmer air to be caught up strongly in the Coriolis Effect and flow quickly

eastward. This jet stream is known as the Polar Jet, and is the driver behind most of the weather

we experience.

Schematic representation of inertial

circles of air masses in the absence of

other forces, calculated for a wind

speed of approximately 50 to 70 m/s

(110 to 160 mph).

Picture courtesy of Anders Persson
http://www.youtube.com/watch?v=aeY9tY9vKgshttp://www.youtube.com/watch?v=aeY9tY9vKgshttp://www.youtube.com/watch?v=aeY9tY9vKgshttp://www.youtube.com/watch?v=aeY9tY9vKgs


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In regards to the subtropical and tropical air masses, things are slightly different and more

mathematical. In this case, the warm air is driven to high altitudes and northward by the constant

supply of thunderstorms in the tropical air mass. Due to theconservation of momentumand the

Coriolis Effect, the cooling, sinking air is deflected to the right and the Subtropical Jet is formed.

At around 30 latitude the Subtropical Jet reaches a maximum speed, and, were it to move any

further northward, the air stream would become unstable and fall apart.

Comparatively, the Polar Jet flows faster (both jets flow at speeds greater than 57 mph,

but the Polar Jet has been known to be as fast as 247 mph) and at a lower altitude (23k-39k feet

vice 33k-52k feet) than the Subtropical Jet. Overall, it is the interaction of these air masses and

the flow of air that leads to all the weather that we see.

Chaotic Behavior

For the rest of this article we will focus on the North Polar Jet, mainly because Im biased

and live in Pennsylvania. Now that we understand what sets up weather patterns, we need tounderstand how these weather patterns form. Even though all seems orderly in the production of

the jet streams, the atmosphere is a VERY chaotic place, and the jet streams do not flow nicely in

a big circle around the planet. To give you an idea of what I mean, get a large pot and fill it with

water. Let it settle to a nice orderly and non-moving state. Now, get a handheld mixer, using only

one whisk, and turn it on at a low speed. Again, the whisk on the mixer is turning in a nice,

orderly fashion in the clockwise direction. Finally, place the whisk in the center of the pot of

water and watch. You will see that we have brought two, orderly systems together and we now

have a one very chaotic system. So chaotic, in fact, that you will notice vortices (i.e. whirlpools)

forming in the water that actually spin in the opposite direction that the whisk is spinning! These

represent the low pressure weather systems that we see here on Earth.

The turbulence in the atmosphere causes the Polar Jet to follow a north-south curving

path, and for the most part is continuous around the planet. It is this north-south meandering that

lead to the first terms to be discussed, troughs and ridges. Where the Polar Jet dips to the south,

this is called a trough, and is usually characterized by advancing low pressure systems.

Conversely, where the Polar Jet makes its way north is called a ridge, and is usually

characterized by, you guessed it, an advancing high pressure system. As mentioned before, high

pressure systems rotate in the clockwise direction, and low pressure systems rotate in the counter

clockwise direction. This aids in the maintenance of the jet stream since, where these systems

meet, the air flow is usually in the same direction (this is for regional size air masses; localizedair masses dont necessarily follow this rule).

It can then be seen that Polar Jet troughs give rise to cold fronts, where cooler air masses

flow, generally, south and east. Once a trough passes and allows the inflow of warmer, more

moisture-laden air from the south, this will give rise to warm fronts and eventually lead to more

beautiful weather as the next ridge of high pressure settles in. This can be seen on weather maps
http://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentumhttp://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentumhttp://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentumhttp://en.wikipedia.org/wiki/Conservation_of_momentum#Conservation_of_linear_momentum


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as the blue lines with semicircles (cold fronts) and the red lines with triangles (warm fronts).

There are two more types of major fronts that we can see on the weather map, and both of them

look like a combination of a cold front and a warm front; however, one is red and blue with the

semicircles and triangles alternating and on opposite sides of the line, and the other is purple

with the alternating shapes on the same side of the line. The purple one is what is known as an

occluded front. Here, a cold air mass has enough energy to overtake a warm air mass, which is a

typical indication that the low pressure system driving the occlusion has matured. When the cold

air mass associated with the cold front is cooler than the cold air ahead of the warm front, the

colder air will plow underneath both air masses (a cold occlusion) leading, more often than not,

to the development of a strong line of thunderstorms. When the advancing cold air mass is

warmer than the cold air ahead of the warm front, the air mass will ride over the warm air mass

and the preceding cold air mass (warm occlusion); again, storms may be produced, but not as

severe as in a cold occlusion. Following an occlusion, the weather usually becomes dryer and

calmer.

The second type of hybrid front is the stationary front. Here, neither air mass has the

energy to replace the other causing the frontal boundary to stall. Weather associated with these

fronts can last over a period of days with prolonged cloud cover and precipitation. These fronts

may eventually form full cold or warm fronts if conditions above the front change, but they will

typically dissipate or form shear lines.

Bars, Therms, and Gradients

The determination of where weather fronts form, their direction of advance, and the most

probable type weather to be seen from these fronts comes from the use of graphs. The bar is a

measure of pressure, and when a map is produced that shows lines of equal pressures, this isreferred to as an isobar graph. These graphs are used to pinpoint sources of low pressure systems

and high pressure systems. When we use graphs which show lines of equal surface temperatures

(i.e. therms), we refer to them as isotherm graphs; and these graphs are used to determine the

location of frontal boundaries. Finally, graphs that show lines of equal wind speeds are called

isotachs (tach is here used in the same way as in tachometer, the gauge in your car used to

measure how fast the camshaft in your vehicle engine is spinning). These graphs are used to

determine how fast frontal boundaries are advancing.

The isobar and frontal boundary graph below shows the weather systems for

the Tornado Superoutbreak of April 3rd

and 4th

, 1974, in which 148 tornadoes in

13 states, extending from the Canadian border to the Gulf of Mexico, killed 330

people and injured over 5,000. It was determined that the total travel distance

of all 148 tornadoes was approximately 2,014 miles, with a mean travel

distance of 18.7 miles and six tornadoes classified as F5. Picture courtesy of

Taylor & Francis:

http://www.weathergraphics.com/edu/forecastcenter/fc_2010-0708.shtml
http://www.weathergraphics.com/edu/forecastcenter/fc_2010-0708.shtmlhttp://www.weathergraphics.com/edu/forecastcenter/fc_2010-0708.shtmlhttp://www.weathergraphics.com/edu/forecastcenter/fc_2010-0708.shtml


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In the picture above we see the isobars, and several weather fronts forming off of the low

pressure center over northwestern Missouri. Notice how the isobars are at varying distances from

each other. These distances represent the gradients of pressure, and tell us how much the

pressure changes over a given distance and give us an idea of how fast the air is moving and the

intensity of the winds. And, of course, gradients are also measured for isotherm and isotachs

graphs to give us an overall picture of how the surface weather is behaving and aid in the

forecasting of future weather.

Other Frontal Systems

The picture above also shows us two additional types of frontal boundaries, the dry line

(the orange line with scallops) and the surface trough (the red and black dashed lines). Not

pictured here are the squall line (represented by repeating red double dots and a dash) and the

tropical wave (a solid orange line).


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Dry lines are areas where two air masses meet that have a large difference in moisture

content. In the United States this is most commonly seen in the Great Plains and eastward to the

Mississippi River. To form a dry line, the warm moist air from the Gulf of Mexico wedges itself

under the warm, dry air coming from the deserts of the southwest. This forms a boundary similar

to a cold front, and sets up for the formation of severe weather, including the tornado-producing

supercell thunderstorms. A key indication of dry line formation is to look for indications of a

forming front along the 55 dew point line (isodrosotherm).

A surface trough is a smaller, more localized form of a cold front. They are generated by

two air masses, whether they are two cold air masses, two warm air masses, or a degenerated

cold front, which have enough of a temperature difference to take on the characteristics of a

frontal boundary. Typically, though, surface troughs are seen as isobar extensions away from a

low pressure center. A surface trough can also form when the jet stream above a frontal

boundary splits into two. At these locations the associated weather can outrun the cold front that

generated it and become asquall line. These can be seen as a long line of severe thunderstorms

as evidenced by ashelf cloudpreceding the storm activity. For those of you living in the desert

southwest, these squall lines can also producehaboobs, or large, intense dust storms. Another

type of surface trough is the tropical wave. Mostly seen in the Atlantic as low pressure systems

coming from Africa, these waves are the initial drivers to the formation of hurricanes. In

subtropical latitudes, inverted troughs may form that have the characteristics of tropical waves,

but are typically referred to as easterly waves, referring to the direction from which they came.

Seasonal Weather Systems

Common types of weather systems have received their own nomenclature, and can be

expected during certain times of the year. This is due to the fact that, as the Suns maximumheight in the sky changes with the seasons, the Polar Jet tends to follow. Spring and summer sees

the Polar Jet in the higher latitudes and lends to the formation of supercells, dry lines, and squall

lines that produce summer thunderstorms. Additionally, this time of year warms the ocean waters

of the mid-Atlantic, setting up for the formation and longevity of hurricanes. Autumn and winter

sees the Polar Jet in the lower latitudes and lends to the formation of Alberta Clipper systems and

the ever-dreaded Noreaster.

As stated above, the first ingredient for ahurricaneis the passage of a tropical wave from

northern Africa into the Atlantic Ocean. The warmer waters serve to ignite a heat engine within

the low pressure system. The warm moist air above the ocean water feeds into the center of thelow pressure system, causing low level cyclonic action. If enough cyclonic action is produced,

the low pressure center organizes and begins creating a wall cloud. Continued feeding intensifies

this low pressure center, dropping the barometric pressure inside it to the point where large scale

cyclonic action begins, increasing the intensity of the winds flowing around the center and

developing lines of severe thunderstorms and heavy rains. Once the winds intensify enough (75

mph) the low pressure system (having progressed through the titles of tropical depression and
http://www.crh.noaa.gov/lmk/soo/docu/bowecho.phphttp://www.crh.noaa.gov/lmk/soo/docu/bowecho.phphttp://www.crh.noaa.gov/lmk/soo/docu/bowecho.phphttp://physics.illinois.edu/news/story.asp?id=1085http://physics.illinois.edu/news/story.asp?id=1085http://physics.illinois.edu/news/story.asp?id=1085http://www.dailymail.co.uk/news/article-2179556/Enormous-haboob-dust-cloud-2-000-feet-tall-covers-city-Phoenix-cuts-power-9-000-homes.htmlhttp://www.dailymail.co.uk/news/article-2179556/Enormous-haboob-dust-cloud-2-000-feet-tall-covers-city-Phoenix-cuts-power-9-000-homes.htmlhttp://www.dailymail.co.uk/news/article-2179556/Enormous-haboob-dust-cloud-2-000-feet-tall-covers-city-Phoenix-cuts-power-9-000-homes.htmlhttp://www.youtube.com/watch?v=xMWIGfaYDhohttp://www.youtube.com/watch?v=xMWIGfaYDhohttp://www.youtube.com/watch?v=xMWIGfaYDhohttp://www.youtube.com/watch?v=xMWIGfaYDhohttp://www.dailymail.co.uk/news/article-2179556/Enormous-haboob-dust-cloud-2-000-feet-tall-covers-city-Phoenix-cuts-power-9-000-homes.htmlhttp://physics.illinois.edu/news/story.asp?id=1085http://www.crh.noaa.gov/lmk/soo/docu/bowecho.php


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tropical storm) becomes a full-fledged hurricane, with the formation of an eye in which the

weather within is calm and comfortable.

The winter time sees the formation of Alberta Clipper systems. These are small, intense

low pressure systems that originate in western Canada (typically in the region of Alberta, duh)

that move rapidly southeast into the US and bring little precipitation. But, what makes thesesystems notable is that they tend to precede arctic air masses. So, when you hear your local

forecaster talk about an incoming clipper system, you know that the weather is going to become

very cold. The big hitter in the wintertime, however, is the noreaster. Of late, they have become

intense enough and numerous enough to be named, as hurricanes are.

Noreasters require a special mix of ingredients to form, and it all starts with a large,

cold, and dry air mass sweeping southeast out of eastern Canada. When that air mass reaches the

warm waters of the Gulf Stream off of the coast of the southeastern US, it can develop a strong

low pressure center. If the Polar Jet at the time is flowing northward over the eastern US, it can

strip away the rising warm air at a faster than normal rate, which leads to the formation of thestorm. As the storm makes its way up the east coast, the continued feeding of warmth and

moisture in the storm will intensify it and begin large scale circulation of the system, very similar

to a hurricanes motion. This circulation will aid in the continued siphoning of cold air out of the

north. The regions on the western and southern sides of the storm will receive high winds and

blasts of cold. The regions to the east and north, where the moisture content is heaviest, will

receive the bulk of the precipitation in the form of heavy rain and snow. If there is a ridge of high

pressure to the east of the storm, this can further intensify the noreaster by feeding it with warm,

moisture-laden air while, at the same time, slowing the storms progression eastward, keeping it

settled over eastern US and Canada.

Not so much a seasonal system as an aberration, acut off lowor high pressure system can

also produce unwanted weather. These cut off systems are formed when rapid shifts in the jet

stream lead to a low- or high-pressure system being cut off from the normal west-east flow of the

jet stream. For example, in June of 2007, the Polar Jet dipped low into the Midwest, all the way

down into Texas, and quickly rose northward due to a strong ridge of high pressure over

Georgia. A sudden break and reformation of the jet stream in the northern US caused the upper-

level low in Texas and the upper-level high in Georgia to become relatively stationary. The low

in Texas brought prodigious amounts of rain and flooding, while the high in Georgia led to

severe drought conditions. So, while cutoff systems may not be intense weather systems, they are

long term weather systems that may lead to very undesirable results.

El Nio and La Nia

The mechanics of the El Nio-Southern Oscillation (ENSO) system are becoming more

and more known, but the origins of its development are still a mystery. ENSO is a long-term,

periodic, worldwide climate-affecting phenomenon that can have devastating effects. With a
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9/9

periodicity ranging from 2 to 12 years (typically around five years), and a longevity of 9 to 21

months, this oscillation of the eastern tropical Pacific ocean water temperature can lead to long

term droughts or monsoonal type weather systems in areas where these types of weather are

uncommon.

El Nio begins with the Pacific water temperatures off of the coast of Central and SouthAmerica rising upwards of 1 F over the average. Its effect on North America is as follows:

during the winter months, it is noted that, in the northern US, from the Pacific to the Atlantic, are

milder and drier than normal; meanwhile, the southern US is wetter than normal, with the

southeast US also being cooler than normal; as for the Atlantic hurricane season during this time,

added vertical wind shear off of the Eastern US leads to less hurricane activity, as the storms are

unable to stay stable as it approaches the coast.

As expected, during La Nia episodes, the effect is just the opposite of what was

described above. But, for either case, large scale effects can be seen in the agricultural and

fishing industries during these times, which can lead to economic hardships and downturns. Formore global effects of ENSO, see this link:http://www.esrl.noaa.gov/psd/enso/.

Be Nice

As you can clearly see, weather is a complex and chaotic part of our world; and

regardless of the number of supercomputers we use, or the amount of pre-existing data we input,

or even the number of real-time weather instruments we put in place, the ability to accurately

determine the weather for tomorrow, or next week, will always be in the hands of the best

guesser. We can run the same computer models as many times as we want, and build up the most

accurate probabilities we can, and your local forecaster may still say that tomorrow will be warmand partly cloudy while reality shows you that it is cool and rainy. It all comes down to best

guess. So, be nice to your local weather man or woman the next time they get the forecast wrong,

for they are trying to make order out of chaos. But, at least you will have a better idea of all the

information they are looking at and the lingo they use to convey that information to us. For more

information on weather-related terms that you may hear often, such as microburst, confluence,

heat index, wind chill, etc., visit the following link:http://www.erh.noaa.gov/box/glossary.htm.
http://www.esrl.noaa.gov/psd/enso/http://www.esrl.noaa.gov/psd/enso/http://www.esrl.noaa.gov/psd/enso/http://www.erh.noaa.gov/box/glossary.htmhttp://www.erh.noaa.gov/box/glossary.htmhttp://www.erh.noaa.gov/box/glossary.htmhttp://www.erh.noaa.gov/box/glossary.htmhttp://www.esrl.noaa.gov/psd/enso/

what the 'bleep' did she say?

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