When clouds look like black smoke ::
When clouds look like black smoke ::
A wise man will put on his cloak Thick, moisture-laden storm clouds absorb sunlight. It gives them an appearance that somewhat resembles black smoke.
Red sky at night probably means dry weather the next day. ::''Red sky at night, shepherd's delight.'' ::''Red sky in the morning, shepherd's warning.'' (In a common variation, "shepherd" is replaced by "sailor") A red sky – in the morning or evening – is a result of high pressure air in the atmosphere trapping particles of dust or soot. Air molecules scatter the shorter blue wavelengths of sunlight, but particles of dust, soot and other aerosols scatter the longer red wavelength of sunlight in a process called
Rayleigh scattering. At sunrise and sunset, the sun is lower in the sky causing the sunlight to travel through more of the atmosphere so scattering more light. This effect is further enhanced when there are at least some high level clouds to reflect this light back to the ground. When weather systems predominantly move from
west to
east, a red sky at night indicates that the high pressure air (and better weather) is westwards. In the morning the light is eastwards, and so a red sky then indicates the high pressure (and better weather) has already passed, and an area of low pressure is following behind.
Low-pressure regions ::
When the wind is blowing in the North ::
No fisherman should set forth, ::
When the wind is blowing in the East, ::'
Tis not fit for man nor beast, ::
When the wind is blowing in the South ::''It brings the food over the fish's mouth,'' ::
When the wind is blowing in the West, ::''That is when the fishing's best!'' In western European seas, this description of wind direction is an excellent illustration of how the weather events of an active
low pressure area present themselves. With the approach of a low, easterly winds typically pick up. These gusty winds can be unpleasant for a number of reasons; they are often uncomfortably warm, dry, and dusty in the summer and bitterly cold in the winter. Northerly winds, which follow around a low, are cold and blustery.
Sailing in conditions of northerly winds requires expertise and a
boat capable of handling heavy waves. Southerly winds usually bring warm temperatures, and though they may not necessarily feed the fish, they do provide pleasant fishing weather. Wind and weather observations will be different for a low passing to the north of the observer than for one passing to the south. When a low passes to the north, the winds typically pick up from the east, swing to southerly (possibly accompanied by light precipitation, usually not) with the passage of the low's warm front, and then switch to northwesterly or westerly as the cold front passes. Typically, if there is any heavy precipitation, it will accompany the passage of the cold front. When a low passes to the south, on the other hand, winds will initially pick up from the east, but will gradually shift to northerly. Overcast skies and steady precipitation often occur as the center of the low passes due south, but skies will clear and winds will gradually become westerly as the low moves off to the east. No observer will experience all the weather elements of a low in a single passage.
Calm conditions :
No weather is ill if the wind be still. Calm conditions, especially with clear skies, indicate the dominance of a
high pressure area. Because highs are broad regions of descending air, they discourage the formation of phenomena typically associated with weather, such as clouds, wind, and precipitation. Calm conditions, though, may also result from a circumstance known as "the calm before the storm," in which a large thunderstorm cell to the west may be updrafting the westerly surface wind before it can arrive locally. This situation is readily identifiable by looking to the west – such an approaching storm will be close enough to be unmistakable. In winter, though, calm air and clear skies may signal the presence of an
Arctic high, typically accompanied by very cold air, and it is difficult to imagine describing a temperature of –35 °C (–31 °F) as pleasant.
Ring around the Moon ::''When halo rings the Moon or Sun, rain's approaching on the run'' A
halo around the Sun or Moon is caused by the
refraction of that body's light by
ice crystals at high
altitude. Such high-level moisture is a precursor to moisture moving in at increasingly lower levels, and is a good indicator that an active weather system is on its way. Halos typically evolve into what is known as "milk sky", when the sky appears clear, but the typical blue is either washed-out or barely noticeable. This high, thick cirrostratus cloud is a clear indicator of an approaching low. In the coldest days of winter, a halo around the Sun is evidence of very cold and typically clear air at and above the surface. But
sun dogs are indicators that weather conditions are likely to change in the next 18 to 36 hours.
Humidity indicators :''When
windows won't open and the
salt clogs the shaker,'' :
The weather will favour the umbrella maker! Moisture in the air causes
wood to swell, making doors and windows sticky, and salt is a very effective absorber of
moisture. With a high level of moisture in the air, the likelihood of precipitation is increased. The
magnesium carbonate and later
calcium silicate in iodized salt acts as an anti-clumping agent in humid conditions, leading to
Morton Salt's umbrella girl logo and slogan "When it rains, it pours".
Fog :
A summer fog for fair, :
A winter fog for rain. :
A fact most everywhere, :
In valley or on plain. Fog is formed when the air cools enough that the
vapour pressure encourages
condensation over
evaporation. In order for the air to be cool on a summer night, the
sky must be clear, so excess
heat can be radiated into
space. Cloudy skies act like a blanket, absorbing and reradiating the heat, keeping it in. So if it is cool enough (and clear enough) for fog to form, it will probably be clear the next day. Winter fog is the result of two entirely different circumstances. Above the ocean or a large lake, air is typically more humid than above land. When the humid air moves over cold land, it will form fog and precipitation. (To the east of the
North American
Great Lakes, this is a common phenomenon, and is known as the "
lake effect.") In northerly climates,
ice fog may form when the temperature drops substantially below freezing. It is almost exclusively an
urban phenomenon, when the air is so cold that any vapor pressure results in condensation, and additional vapour emitted by automobiles, household furnaces, and industrial plants simply accumulates as fog. , in the
Pacific coast of
Costa Rica.
Cloud movement :
If clouds move against the wind, rain will follow. This rule may be true under a few special circumstances, otherwise it is false. By standing with one's back to the ground-level wind and observing the movement of the clouds, it is possible to determine whether the weather will improve or deteriorate. Other studies gave accuracy percentages, but differing figures. and some of the numbers were slightly better than hazarded guess (33% accurate), according to one source. == Calendrical lore ==