Hailstorm -Tan Shang Jien

The hailstorm that hit USJ Subang Jaya,  Selangor, on Sunday and caused panic among  residents is a common phenomenon, said two experts on lightning.Consultant engineer Hartono Zainal Abidin said the  hailstorm was a consequence of thunderstorms and was not  related to extreme weather conditions.

“There is always this misconception about hailstorms, or ice rain. Many think that it is not possible to have hailstorms in a tropical climate. ” “What people don’t understand is that hail is not snow. Just like mini tornadoes that   happen in the country, hailstorms are one of the effects of thunderstorms,” he said.

The hailstorm that hit USJ Subang Jaya   was relayed via social media networks such as Facebook and Twitter on Sunday afternoon.Hartono said hail was formed in thunderclouds, particularly with intense updrafts, whereas snow was formed  because of low temperature  in the atmosphere.He said Malaysia was one of those countries in the region that recorded a higher number of thunderstorms,  so it was common to see hailstorms here.

Hail is formed because of precipitation that occurs  at the beginning of thunderstorms. When  raindrops pass through the belt of cold air, they freeze into small cubes of ice.However, Hartono said, most of the hail either melted or disintegrated in   storms before reaching the ground. Professor Datuk Dr Azizan Abu Samah of   Universiti Malaya’s Geography Department said  hailstorms could even happen in countries with extremely hot climate, such as  Saudi Arabia.

“There was nothing extraordinary about the hailstorm in USJ. And it can’t be associated with extreme weather. It was  a natural phenomenon.” He said   it was possible to see another hailstorm during the monsoon season.The last hailstorm  was in March last year and it occurred for 20 minutes  in  Solaris Mont Kiara, Damansara Uptown and Bukit Kiara here.

Meteorological Department’s centre forecast office director Saw Bun Liong said  hailstorms could happen in any part of the country, but  the west coast of the peninsula was more prone to experience such a phenomenon.The department said scattered thunderstorms and isolated rains were expected in the  Klang Valley this week.

HOw is it Form?

Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0 °C (32 °F).These types of strong updrafts can also indicate the presence of a tornado. The growth rate is maximized where air is near a temperature of −13 °C (9 °F),

Hail is most common within continental interiors of the mid-latitudes, as hail formation is considerably more likely when the freezing level is below the altitude of 11,000 feet (3,400 m).Movement of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporational cooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. Accordingly, hail is less common in the tropics despite a much higher frequency of thunderstorms than in the mid-latitudes because the atmosphere over the tropics tends to be warmer over a much greater altitude. Hail in the tropics occurs mainly at higher elevations.

Hail growth becomes vanishingly small when air temperatures fall below −30 °C (−22 °F) as supercooled water droplets become rare at these temperatures.Around thunderstorms, hail is most likely within the cloud at elevations above 20,000 feet (6,100 m). Between 10,000 feet (3,000 m) and 20,000 feet (6,100 m), 60 percent of hail is still within the thunderstorm, though 40 percent now lies within the clear air under the anvil. Below 10,000 feet (3,000 m), hail is equally distributed in and around a thunderstorm to a distance of 2 nautical miles (3.7 km).



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