Stormy weather and Hurricanes

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Contents:
Storm Definitions:

Hurricanes:
What, where and when
Hurricanes, Cyclones or Typhoons?
Forecasting Hurricanes
Hurricane force scales

Winds
Beaufort wind scale on sea
Beaufort wind scale on land
Knot/mph conversion
Weather Map Wind Symbols

Monsoons

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All about the hills the hosts of Mordor raged. The Captains of the West were foundering in a gathering sea. The sun gleamed red, and under the wings of the Nazgûl the shadows of death fell dark upon the earth - LoTR

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"There are times when I am riding the wind ... spiralling through the heart of nature ... I feel as if I have pierced the core of
creation." - Storm. X-Factor #101

Afternoon storms

Storm Definitions:

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Hurricanes
What, where and when:

Hurricanes, called typhoons or tropical cyclones in certain parts of the world (see above), form over the world's tropical oceans except in the Southern Atlantic ocean and the South-eastern Pacific.
NB. Hurricanes, typhoons or tropical cyclones never form on the equator due to the absence of the Coriolis effect.
Universally a tropical storm has winds of 39 mph to 73 mph. When winds reach at least 74 mph the storm becomes a hurricane or typhoon/tropical cyclone, depending on its location and after forming a hurricane may hit places as far away from the Tropics as New England and Typhoons, from the tropical western Pacific, frequently hit Japan and Korea.

Tropical storms begin forming during and just after a region's summer when the ocean is at its warmest. Most regions can be threatened by tropical cyclones for ± six months of the year, but the largest numbers of storms are usually concentrated in a ± two month-long period. Similar indications in each region, such as warm ocean water, light winds, extended periods of warm temperatures and high humidity, help create tropical cyclones over more than 60 percent of the world's tropical latitudes.
Tropical storms and hurricanes form between ±5 degree north of the equator to ±5 degrees south due to the fact that at these latitudes the Earth's spin has little effect on organizing clusters of thunderstorms into whirling tropical cyclones.

The official hurricane season begins May 15 in the eastern and central Pacific basin and June 1 in the Atlantic basin, which includes the Gulf of Mexico and the Caribbean Sea but there are normally few storms in the early part of the season. September is peak season in Caribbean, Mexico, U.S. with hurricanes forming and striking land in the Caribbean or northward along Mexico's west coast generally around July.
The biggest threat to the Caribbean and the Bahamas, the U.S. and to eastern Mexico begins in August and lasts through October. In general, places in the southern Caribbean have fewer hurricanes than in the northern Caribbean.

Everywhere in the Atlantic basin is liable to hurricanes, including Bermuda, especially during September when the season reaches its peak. Long-term records show that four times as many storms have formed in the Atlantic Basin in mid September than during mid June.
While September is the peak of the hurricane season in the Atlantic Basin, storms don't hit every year. Typically, several years can go by without a hurricane.

(Coriolis effect: Force generated by the Earth's rotation, capable of generating currents and causing moving bodies to rotate clockwise n the Northern Hemisphere and anti-clockwise in the Southern Hemisphere. The "force" is proportional to the speed and latitude of the moving object. It is zero at the equator and maximum at the poles.

Hurricanes , Cyclones or Typhoons?

Cyclone
In meteorology, A cyclone is an area of low atmospheric pressure around which the winds flow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. However cyclones are responsible for a wide variety of different meteorological phenomena. Because of this, most weather forecasters avoid using the term cyclone without a qualifying term.

Hurricane
Hurricanes are tropical cyclones with winds that exceed 64 knots (74 mi/hr) and circulate counter-clockwise about their centers in the Northern Hemisphere (clockwise in the Southern Hemisphere)

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Hurricane George

Typhoon
An intense tropical weather system with a well-defined circulation and maximum sustained winds of 74 miles per hour (±64 knots ) in the Northwest Pacific Ocean, west of the International Date Line.
NB. The word "Typhoon" has both Western and the Eastern origins. In Greek "Typhoon" is "Tuphon" , meaning whirlwind, and in Arabic "Tufan", meaning Deluge. In Cantonese "Typhoon" is "taaîfung" , meaning great wind.
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Typhoon Odessa

Forecasting Hurricanes:

Forecasts for more than 2 or 3 days ahead are not possible and it is not possible to predict where a hurricane is going to hit more than a couple of days before it actually hits.
While it's possible to say that some years are likely to breed more hurricanes than others, hurricane forecasters have no way of saying a week or two ahead of time that a hurricane is likely to form, much likely where it's likely to hit. Forecasters hope to some day be able to give the odds of a particular place being threatened a week or two before a storm hits. But for now, such forecasts are only a dream.

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Hurricane Ivan, scale #4, September 15 2004 hitting the US. New Orleans is expecting a scale #5 in the new future

Hurricane force scale ranges:

Hurricane scales are calculated using the 'SAFFIR-SIMPSON' hurricane scale ranges*
*(The scale was formulated in 1969 by Herbert Saffir, a consulting engineer, and Dr. Bob Simpson, director of the National Hurricane Center. The World Meteorological Organization was preparing a report on structural damage to dwellings due to windstorms, and Dr. Simpson added information about storm surge heights that accompany hurricanes in each category. )

(NB. Click on the title 'Damage' to the the damages caused at the different levels of severity)

From this two general formulas are obtained for calculating wind speeds from the minimum central pressure of a hurricane. However, there is an actual formula using the more accurate cyclostrophic balance, but these general ones can be used more easily, because the require knowing only the minimum general pressure:

1. WIND SPEED = 33 X {CUBE ROOT OF (1005-MIN. CENT. PRESS.)}
2. WIND SPEED = 35 X {CUBE ROOT OF (1000-MIN. CENT. PRESS.)}
*AVERAGING THE TWO CAN GIVE A RELATIVELY ACCURATE APPROXIMATION*

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Winds

Generally speaking high or strong winds are announcers, in tropical/subtropical regions, of the arrival of bad or severe weather such as Hurricanes, Tornados... However, high or strong winds are found in every region of the planet, and as 'Stand alone' phenomena, from the Poles to the deserts, and do not spare the more temperate zones such as Europe.
In December 1999 France and Germany witnessed 2 Severe storms in the space of a week that came in from the Atlantic, hit the French Brittany coast at with winds gusting up to ± 200Kph (107 Knots or < Force 12 on the Beaufort scale) crossed into Germany devastating everything it their passage and causing the death of 84 people between Dec 26th and 27th.

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The reason? The extremely bad prevision and announcement of an exceptionally bad storm. Apparently European agencies were not as used to such 'Severe weather' phenomena as their American counterparts. Weather forecasters, at the time,* had no way of anticipating the storms and they had been handicapped by the loss of one of their traditional sources of information: Fishing boats. The fishing boats**, had been forced to stay at home... due to bad weather!
* Since then the Europeans have launched Geo-stationary weather satellites to cover such eventualities.
** At the time the fishing boats provided the meteo' services with a ± 2 day weather forecast from their fishing zones but they were incapable of doing any more than informing of what was about to start. They had no way of anticipating or, more importantly, analyzing the causes and no sooner had the 01st storm passed... the 02nd hit leaving the weather forecasters totally at a loss..

Beaufort wind scale for the open sea

Beaufort wind scale for land

Beaufort wind scale for the open sea
The scale is presently maintained by the British Meteorological Office, who publish a version illustrated with very instructive photographs.

A version currently used by mariners is shown below. Please refer to the warnings following the table.
Column 1 is the Beaufort Number or Force Number.
Column 2 is the range of wind speeds in knots, measured at a height of 33 feet above sea level.
Column 5 is the probable height of waves in feet in the open sea, remote from land. In enclosed waters, or when near land with an offshore wind, wave heights will be smaller and the waves steeper.
Column 6 is the probable maximum wave height in feet in the open sea (rules for column 5 apply here as well)

NB
Estimating wind force by the sea criteria is difficult at night.
An increase of wind does not immediately produce an increase of sea.
Fetch, depth, swell, heavy rain and tide effects should be considered when estimating the wind force from the appearance of the sea.
WARNING: For a given wind force, sea conditions can be more dangerous near land than in the open sea. In many tidal waters wave heights are liable to increase considerably in a matter of minutes!!!

Knot/MPH conversion:

1 knot = 1 nautical mile per hour = 6076 feet per hour = 1.15078 mph
1 mph = 1 mile per hour = 5280 feet per hour = 0.86898 knots per hour

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Beaufort wind scale on land
In June, 1939 the International Meteorological Committee adopted a correlation with wind speeds measured at a height of 6 meters. Great Britain and the United States, however, had already standardized on measuring the wind speed at 11 meters above ground level, which is shown in column 2 below, in miles per hour.

Weather Map Wind Symbols:

Monsoons

Particular to the Indian sub-continent, Monsoons stretch from the Northern tip of Australia to the Atlantic and from the Sub Siberian region to Madagascar.
Monsoon are divided into 2 types:
1- Dry Monsoon
The dry, or winter, monsoon of Asia is largely the result of an area of high pressure that develops over S Siberia. From this area dry winds blow outward, crossing India from northeast to southwest and SE Asia from north to south the dry, or winter, monsoon of Asia is largely the result of an area of high pressure that develops over S Siberia. From this area dry winds blow outward, crossing India from northeast to southwest and SE Asia from north to south.
2- Wet Monsoon
The wet, or summer, monsoon is caused by low pressure that develops over S Asia as the landmass warms. Moisture-laden air over the oceans is drawn toward this center of low pressure. The air cools as it ascends the slopes of mountain barriers; it can no longer retain moisture, resulting in heavy rainfall.

NB. The Indian Ocean version of the hurricane, called a "cyclone", can also occur and move ashore in association with the onset of the monsoon. These cyclones have at times killed thousands of people who live in the low-lying areas along the eastern coast of India and Bangladesh. A weaker version of this monsoon occurs over the normally dry southwestern United States in the later summer when more humid air, accompanied by thunderstorms, invades the region.

Monsoon regions

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