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LAPAN: Winds of tornadoes sit second place in extreme weather
10 Dec 2018

Tornadoes ranked second in hydrometeorological natural disasters that often occur in Indonesia. The National Aeronautics and Space Institute (LAPAN) states, every year the tornado has increased. It was also recorded by the 2017 National Disaster Management Agency (BNPB) of 30 percent.

Members of climate variability 2018 LAPAN Center for Atmospheric Science and Technology (PSTA), Erma Yulihastin, said the previous year the tornado was the third most frequent natural disaster in Indonesia.

Erma says the tornado can be categorized as extreme weather because it fulfills several criteria as unexpected (unexpected), unusual or very rare, unpredictable, and dangerous (severe) because it causes a material and life-threatening loss.
"There are a number of conjectures that can explain why the frequency of tornadoes increases from year to year. First, due to the increasingly uneven warming of the atmosphere on the surface, especially in urban areas, the drastic effect of land conversion from green open land becomes dense residential land, "Erma said in Bandung on Monday (10/12/2018).

Erma continued, this uneven heating pattern evokes the pattern and character of surface wind, which tends to be different as well so that it generates wind collisions and forms wind shear, as the beginning of the tornado formation. The second guess is that there is an increase in the intensity and frequency of Cumulonimbus cloud formation in an area.

The formation of Cumulonimbus clouds that are very fast can trigger extreme weather, such as thunderstorms and tornadoes, because tornadoes generally occur, due to meetings or collisions between two winds that have different characters or because of the occurrence wind shear.
"This wind is then lifted (updraft) and strengthened by conditions of instability of the surrounding air. This wind is usually formed in areas that have low teropografi or coastal areas, in the months of the transition period (from the dry season to rain or vice versa), "said Erma.

The intense activity of Cumulonimbus or cumulus congestus clouds in one place also needs to be watched out for because of the situation because it has the potential to generate a tornado. Until now, tornadoes are still very difficult to predict. This is because the tornado is called a small tornado, due to its wind power which is still below the Fujita scale (a scale commonly used to measure tornado strength based on wind magnitude and damage effects caused). Based on the scale, a tornado has a turning radius of less than one kilometer and a life span of less than one hour.
"So if we want to predict tornadoes using numerical weather models, we need predictions with spatial scales of less than one kilometer and a time scale of less than one hour. To note, the Sadewa-LAPAN prediction model that has been developed has a five kilometer spatial scale and the time scale per one hour so that it is impossible to detect the phenomenon of tornadoes, "said Erma.
But Erma explained, it was not enough just to increase the dissolution of the space scale and time of numerical weather prediction models. The potential for extreme weather such as tornadoes also requires the support of various equipment such as radiosonde, balonsonde, weather radar, and others to calculate extreme weather indices derived from weather parameters such as wind speed, wind patterns and temperature.

In addition, it also needs to calculate various indices such as CAPE (Convective Availabel Potential Energy), VGP (Vorticity Generation Potential), BRN (Bulk Richardson Number), EHI (Energy Helicity Index) and SREH (Surface Relative Environmental Helicity). From some of these parameters, Erma added, the most important thing to identify tornado-producing storm clouds is CAPE, EHI and SREH.

" Nevertheless, people can still make visual observations to find out the potential for extreme weather, "Erma explained.
One of them is by looking at signs such as morning to daytime temperatures sweltering, then entering the afternoon changes quickly into a gray and evenly cloudy, there is a closed circulation indicated by a gray cloud surrounded by bright or bright sky around it.Different contrasts between cloudy and bright, close together, there are gray clouds that look arranged in layers vertical like a tree.

Source: Kumparan. Image Source: News Okezone

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