Monthly Archives: February 2015

Introduction

An air mass is a huge dome of air whose temperature and humidity characteristics remain fairly constant over a horizontal distance. This horizontal distance can extend up to hundreds or thousands of kilometers. Air masses are classified according...

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Introduction

Clouds are often very important indicators of imminent weather changes. When they are observed at various times and regular intervals, even an approaching mid-latitude storm can be recognized. In an approaching storm, a change of cloud structure...

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How clouds are formed

The cloud formations of interest to the mariner are formed in the Troposphere. The Troposphere is a layer of the earth’s atmosphere that extends from the earth’s surface to about 24.000 feet (7.300 meters) above the poles, and to...

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Classification

Clouds are classified by their general appearance and level. Cloud names are Cirrus, Stratus and Cumulus. To indicate the level of a cloud, a prefix is given to the cloud name, like Cirro and Alto. Cirro indicates high clouds with bases above...

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High clouds

High clouds are Cirrus, Cirrostratus and Cirrocumulus. Cirrus clouds are thin wispy clouds, composed predominantly of ice crystals. Thick patches of Cirrus clouds indicate that showers are nearby. Cirrus clouds that are shaped like commas...

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Mid level clouds

Mid-level clouds are Altostratus and Altocumulus. Altostratus clouds are usually grayish clouds that cover part or all of the sky. These clouds are composed of water droplets or ice crystals. At sea, Altostratus clouds are an important weather...

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Low clouds 1

Low clouds are Nimbostratus, Stratus, Stratocumulus, Cumulus and Cumulonimbus. Nimbostratus clouds are dark and quite homogeneous clouds. These clouds are associated with heavy downpours, high winds and sea conditions that are hazardous for small...

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Low clouds 2

Cumulus clouds are cauliflower-like clouds whose contours change constantly. Cumulus clouds can have slight or extensive height. With little vertical growth, these clouds indicate fair weather. With a large vertical extent, these clouds are...

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Introduction

The unequal heating of the earth between equator and poles causes meridional winds. Due to the rotation of the earth, winds are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This movement of great...

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Highs

Highs are also called anticyclones. In the Northern Hemisphere winds blow clockwise around an anticyclone, and in the Southern Hemisphere winds blow counterclockwise. The winds on the outer edges of a high blow stronger than they do towards the...

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Lows

Lows are also called depressions. In the Northern Hemisphere, winds blow counterclockwise around a depression, and in the Southern Hemisphere winds blow clockwise. Winds blow stronger in the center of a low than they do on its outer edges...

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Introduction

Land has the ability to heat and cool far more quickly than the sea. The temperature between the land and the sea can be different at any point during day and night. This temperature discrepancy between land and sea can develop local winds, also...

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Sea breeze

As we know, land masses heat up more quickly than sea masses, especially during the day. As the air heats up, the air parcels begin to rise and create low pressure areas at ground level. At a height of nearly 600 meters (2000 feet) the warm air...

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Land breeze

The converse of the sea breeze is the land breeze. At night the land mass cools more rapidly than the sea and the opposite circulation pattern takes place. The air over the land cools, sinks and raises the pressure. The air over the sea is warmer...

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Introduction dew point

Fog can be a dangerous weather phenomena. Fog may form either when there is a lot of moisture near the ground, or when the air near the ground is cooled to its dew point. But what is the dew point? Scientifically speaking, the dew point is the...

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Expecting fog

When can you expect fog to occur? A simple rule is: when the difference between the air temperature and the dew point is large and does not decrease, no fog is expected. When the difference between the air temperature and the dew point is small...

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Advecation fog

Advection fog, also known as sea fog, is formed when moisture-laden warmer air blows over colder land or water. When the warm air cools down to its dew point, water vapor in the air condenses and fog forms. Advection fog is very thick and...

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Frontal fog

Frontal fog is usually found ahead of warm fronts and occluded fronts, and behind cold fronts. When warm moist air rises over colder air it causes the air temperature of the warm air to fall below its dew point. Frontal fog is not persistent, but...

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