After long time of practice, our working people have accumulated rich
experience in hailstone prediction. Though these predictions cannot
make a difference on a long-period’s predicting, they are quite useful.
They are summarized below for reference:
- Feel the temperature. In the season when it is supposed to have hails
The hails can be caused by cumulonimbus which is attributed to
a strong cross-ventilation, a result of the humid cold morning
and the strong solar radiation at noon. Thus, as the sayings go,
if it is chill in the morning, your head would be heat in the afternoon;
heavy dew in the morning, fierce hail in the afternoon.
- Distinguish the direction of the wind. Before the hail
there often are gales which change the direction tempestuously.
As the proverb goes, cloud rampantly develops with wind and hail drastically
descends with wind. And some other phrases, such as revolved cloud
by vigorous wind and hail tablets. Besides, if the wind turns to northwest
or north wind after continuous blowing of the south wind, hailstorms
often come along when the wind force increases. Therefore,
there is an argument saying that "no east wind, no rain,
no south wind, no hail".
There are many expressions and sayings about precursors of hail
from cloud color, such as " not afraid of black clouds,
but clouds of black red clip, the worst is of red-yellow cloud
with long white clips”, and "black cloud tail, yellow cloud head,
hail will kill sheep and cattle”. This is because of the dramatic change
of cloud color during the formation of the hail: at first, it is white
on the top and black on the bottle. Then the middle is red with white,
black and red clouds interweaving whose edges looks like yellow.
There are some other arguments about the precursors of hail: "if clouds roll
into a ball in the afternoon, the rainstorm and hailstorm will come together",
"if it is muggy and yellow clouds are rolling, then, you should prevent
a coming hailstorm”, which indicates that the air convection is very strong
and the rapid development of cloud just like the smoke’s soaring,
and the churn of clouds high up will easily create hailstorms.
The ponderous and unbroken thunder
has been called “lasting thunder”, so, there is a saying going,
"the loud thunder makes no difference, while the ponderous
one brings eggs". This is due to the higher and wider range of horizontal
flashes than vertical ones in the hail clouds, which will
mix the thunder and echo of different kinds of flashes
so that it sounds like a continuous feeling.
- Know something about lightning
Generally speaking, the hail lightning
in the clouds are mostly between clouds and clouds of lightning,
namely "cross flash", which explains the the violent formation of hail
in clouds. Therefore, it is said that "vertical flash just comes and
horizontal flash come with hails”.
There are a lot of experience in forecasting hails
by looking around the objects, such as "if the swan goose flies low,
urgent hail will come along” and “willow turns over, hail is closer”
in the saws of Guizhou province, and in Shanxi province, proverbs go that
"if sheep and cattle do not against horizontal beam at noon, then be aware of
hail in afternoon" and "dewdrop on the grass, hail comes in mass”.
Be aware that the above experience cannot serve as the only grounds to
make some conclusion; they deserve a comprehensive analysis and application.