CYCLONE PROGNOSTICS.
We shall first take a typical well formed cyclone. In the accompanying diagram (Fig. 1) the broad features of the relation of cloud and rain to a cyclone centre are shown, the full line indicating the path of the depression, and the dotted line at right angles to it is the trough or locus of the lowest reading of the barometer.
Fig. 1.—Weather in a Cyclone, November 14, 1875.
In the extreme front of the depression there is a blue sky, then, as the barometer begins to fall, and sometimes even before that takes place, a bank of cirro-stratus, preceded by a halo-bearing sky, makes its appearance, which gradually becomes lower and denser, and forms an overcast, dirty sky. In the whole front of the depression the temperature rises, and the atmosphere feels muggy and close. In the right-hand front the clouds assume the cumulo-stratus type, with driving rain later on. In the left-hand front the air is cooler, but still oppressive, with an easterly wind and overcast sky, succeeded by drizzling rain or ill-defined showers. When the trough of the depression has passed the barometer begins to rise, the wind changes and becomes squally, with showers of rain; the air grows cooler, and the clouds break and ultimately clear away.
Now, with regard to the prognostics with reference to Fig. 2, where the characteristic weather in the different portions of a depression are given in a diagrammatic form, it will be seen that the first indication of a coming change is the appearance of a halo round the sun or moon in the cirro-stratus clouds. Hence,
When round the moon there is a brugh,
The weather will be cold and rough.
The moon with a circle brings water in her beak.
Halos predict a storm (rain and wind or snow and wind) at no great distance, and the open side of the halo tells the quarter from which it may be expected.
Mock suns predict a more or less certain change of weather.
Fig. 2.—Cyclone Prognostics.
With regard to the open side of the halo indicating the quarter from which the storm may be expected, it does not appear that this can be much used as a prognostic. It, however, most probably originated in the fact that halos are often seen in the southwest or west, when the sun or moon is rather low, the lower portion of the halo being cut off by clouds banking up in that direction, and that our storms generally come from those quarters. As a specimen of the value of prognostics we give some details of halos. When rain does not fall within thirty-six hours, any subsequent rain probably belongs to a new depression.
During the six years ending June, 1882, one hundred and fifty-five solar halos and sixty-one lunar halos were observed in the neighborhood of London, and they occurred with the following winds:
| N. | NE. | E. | SE. | S. | SW. | W. | NW. | Total. | |
|---|---|---|---|---|---|---|---|---|---|
| Solar halos | 9 | 7 | 17 | 8 | 22 | 28 | 59 | 5 | 155 |
| Lunar halos | 4 | 3 | 8 | 3 | 8 | 11 | 21 | 3 | 61 |
| WITH SOLAR HALOS. | |||||||||
| Rain fell on same day | 3 | 1 | 10 | 4 | 15 | 12 | 36 | 0 | 81 |
| Rain fell on first day | 1 | 2 | 1 | 2 | 2 | 10 | 12 | 1 | 31 |
| Rain fell on second day | 0 | 0 | 1 | 0 | 2 | 1 | 4 | 2 | 10 |
| Rain fell on third day | 3 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 7 |
| No rain | 2 | 3 | 5 | 2 | 3 | 4 | 6 | 1 | 26 |
| WITH LUNAR HALOS. | |||||||||
| Rain fell on first day | 1 | 1 | 3 | 3 | 3 | 9 | 13 | 1 | 34 |
| Rain fell on second day | 0 | 1 | 0 | 0 | 1 | 1 | 3 | 0 | 6 |
| Rain fell on third day | 1 | 1 | 2 | 0 | 3 | 1 | 0 | 1 | 9 |
| Rain fell on fourth day | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 1 | 4 |
| No rain | 2 | 0 | 3 | 0 | 1 | 0 | 2 | 0 | 8 |
After the halo comes the pale or watery sun and moon.
When the sun appears of a light, pale color or goes down in a bank of clouds, it indicates the approach or continuance of bad weather.
If the sun goes pale to bed,
’Twill rain to-morrow, it is said.
A red sun has water in his eye.
When the moon has a white look or when her outline is not very clear, rain or snow is looked for.
From the extreme damp in this part of the depression, while the sky generally is pretty clear, cloud forms round and “caps” the tops of hills, a circumstance that has given rise to numerous local sayings:
When the clouds are upon the hills,
They’ll come down by the mills.
When Cheviot ye see put on his cap,
Of rain ye’ll have a wee bit drap.
If Riving Pike do wear a hood,
Be sure the day will ne’er be good.
When Bredon Hill puts on his hat
Ye man of the vale beware of that.
From the same excessive damp the following may be explained:
When the walls are more than usually damp rain is expected.
Doors and windows are hard to shut in damp weather.
The sailor notes the tightening of the cordage on his ship as a sign of coming rain.
A lump of hemp acts as a good hygrometer, and prognosticates rain when it is damp.
When walls built of stones which have been quarried below high water mark become damp, wet weather is at hand.
Also, owing to excessive moisture, clouds appear soft and lowering, and reflect the glare of iron-works and the lights of large towns:
The glare of the distant Ayrshire iron-works being seen at night from Cumbræ or Rothsay, rain is expected next day.
In Kinkardine of Monteith (Perthshire) and in all that district the reflections from the clouds of the furnaces of the Devon and Carrow works (to the east) foretell rain next day.
Also:
When the flames of candles flare and snap or burn with an unsteady or dim light, rain, and frequently wind also, are found to follow.
This is especially applicable to oil-lamps or tallow candles.
As the depression approaches and the atmosphere becomes gloomy, close, and muggy, some people are troubled with rheumatic pains and neuralgia, old wounds, and corns are painful, animals and birds are restless, and drains and ditches give out an offensive smell:
When rheumatic people complain of more than ordinary pains in the joints, it will rain.
If corns, wounds, and sores itch or ache more than usual, rain is to fall shortly.
A coming storm your shooting corns presage,
And aches will throb, your hollow tooth will rage.
When animals seek sheltered places instead of spreading over their usual range, an unfavorable change is probable.
Hark! I hear the asses bray,
We shall have some rain to-day.
If oxen turn up their nostrils and sniff the air, or if they lick their fore feet, or lie on their right side, it will rain.
Goats leave the high grounds and seek shelter before a storm.
Hogs crying and running unquietly up and down with hay or litter in their mouths, foreshow a storm to be near at hand.
When birds of long flight—rooks, swallows, or others—hang about home and fly up and down, or low, rain or wind may be expected.
This tumbling of rooks is amongst the best known signs of rain in places where those birds are found.
When the peacock loudly bawls,
Soon we’ll have both rain and squalls.
If toads come out of their holes in great numbers, rain will soon fall.
If glow-worms shine much, it will rain.
When gnats bite keenly, and when flies keep near the ground, we look for wind and rain.
When spider webs are seen floating about in the air, farmers regard it as a sign of coming rain.
When many bees enter the hive and none leave it, rain is near.
Also, from cloud and gloom, plants shut up their petals early:
The Convolvulus arvensis (small bind-weed), Anagallis arvensis (scarlet pimpernel), and Calendula pluvialis shut up their flowers before approaching rain. (The pimpernel has been called the poor man’s weather-glass.)
Dr. Jenner’s well-known lines are very good, as they contain references to most of the natural prognostics. (See page [110], General Prognostics.)
It will be seen, however, later on, that the sayings about the rainbow, distant hills, and whirling dust, though good prognostics, do not belong to a depression.
As the depression centre approaches still nearer, rain sets in and continues till the barometer turns to rise. The passage of the trough is often associated with a squall or heavy shower, commonly known as “a clearing shower.” Immediately the air becomes cooler and loses the former muggy sensation, and soon small patches of blue sky appear.
When as much blue sky is seen as will make a Dutchman a jacket (or a sailor breeches) the weather may be expected to clear up.
A small cloudless place in the northeast horizon is regarded both by seamen and landsmen as a certain precursor of fine weather or a clearing up.
The steady rain breaks up into showers or cold squalls, which are followed by hard detached cumulus or strato-cumulus till the sky becomes blue again:
When after a shower, the cirro-strati open up at the zenith, leaving broken or ragged edges pointing upwards, and settle down gloomily and compactly on the horizon, wind will follow, and will last for some time.
This is a description of a clearing up before the windy portion of a depression has passed.
In the south of the depression near the outskirts, windy cirrus and “mare’s tails” are observed, which indicate wind rather than rain, as they are south of the rainy portion.
The cloud called goat’s hair or the gray mare’s tails forebodes wind.
If clouds look as if scratched by a hen
Get ready to reef your topsails then.
Mackerel sky and mare’s tails,
Make lofty ships carry low sails.
The shift of the wind is different in the right-hand portion of the depression to what it is in the left-hand portion. In the former, on its first approach, the wind backs to south and falls very light to an almost ominous calm. The first puffs or “paws” of wind give rise to a noise in tree tops without much wind, and little eddies of dust, or to a whistling of the wind indoors, which are all well-known signs of rain. Then, as the depression passes along, the wind gradually veers to southwest and west, with increasing strength. Hence,
When the wind veers against the sun,
Trust it not, for back ’twill run.
When the wind is in the south
It is in the rain’s mouth.
In the left-hand side of the depression the wind will back right round from south through east to north and northwest. In the rear of the depression on the left-hand side the wind blows from the northeast and then north, when the clouds begin to break and the weather to clear. When the depression has nearly passed away the wind in the rear draws round to the northwest, and gradually abates, and the weather becomes fine. Hence the saying:
Do business with men when the wind is in the northwest.
This bringing the finest weather is said to improve men’s tempers, as opposed to the neuralgic and rheumatic sensations felt in front of a depression.