The phenomenon of hail occurred around Jalan Dewi Sartika, Cawang, East Jakarta on Saturday (17/12) afternoon. Events like this are quite a scene because it rarely happens. A number of motorists who were passing immediately pulled over to avoid the hail.
Actually, the phenomenon of hail is a natural weather phenomenon that usually occurs. Quoted from the Meteorology, Climatology and Geophysics Agency (BMKG) website, rain events that produce ice accompanied by lightning, lightning and strong winds of short duration are more common during the transition/transition seasons, either from the dry season to the rainy season or vice versa.
There are a number of indications of heavy hail accompanied by lightning, and strong winds of short duration:
One day before the air at night until the morning was hot and sultry
The air feels hot and stifling due to the presence of strong solar radiation as indicated by the value of the difference in air temperature between 10.00 and 07.00 LT (> 4.5°C) accompanied by quite high humidity indicated by the value of air humidity in the layer 700 mb (> 60%)
Starting at 10.00 in the morning you can see cumulus clouds (layered white clouds), among these clouds there is one type of cloud that has very clear gray edges soaring high like cauliflower
The next stage of the cloud will quickly change color to gray or black, known as Cb (Cumulonimbus) clouds.
The trees around where we stand have branches or twigs that start to sway quickly
Feels there is a touch of cold air around where we stand
Usually the first rain that falls is a sudden downpour, if the rain is drizzling then strong winds are far from where we are
If there is no rain for 1-3 consecutive days during the transition/transition/rainy season, then there is an indication of the potential for heavy rain to fall for the first time followed by strong winds, both those that are included in the typhoon category and those that are not.
The characteristics of a tornado/strong wind of short duration are as follows:
Very local
Its area ranges from 5 - 10 km
The time is short about less than 10 minutes
More often occurs at the turn of the season (transition)
More often occurs in the afternoon or evening, and sometimes at night
Move in a straight line
Cannot be predicted specifically, can only be predicted 0.5 - 1 hour before the incident if you see or feel the signs with an accuracy level < 50%
Only comes from Cumulonimbus clouds (not from monsoon wind movements or wind movements in general), but not all Cb clouds cause tornadoes
It's less likely to happen again in the same place.