For many days now, the skies have been full of towering rain clouds, bringing the seasonal rains to southern Thailand, Peninsular Malaysia and Sumatra; but this rain is heavier than normal.

On December 23, 200 prisoners were forced to evacuate a prison in Lhoksukon, Aceh - The Indonesian police and prisoners waded through flood waters two metres deep.  Jakarta and Bandung have both suffered swift street floods.

The National Park in Kuala Tahan, Pahang was underwater by December 24, 2014 as the worst flooding in decades continued.  More than 100,000 people have been evacuated by authorities in five northern states of Malaysia.

The streets of Yala province in southern Thailand are temporarily broad, shallow rivers running with muddy water. Sri Lanka, suffering the same bout of heavy rain, has seen deaths from mudslides.

But why is the rain so heavy this season? As is often the case, many factors act in concert for an event this extreme: The southeast monsoon is blowing across the South China Sea and this sea is warmer than normal.

That alone would make the showers bigger and the rain heavier. Then mankind creates infrastructure which channels and contains floods – hydro management problems are being cited in Thailand.

Maybe the straw that broke the camel’s back is what is happening eight kilometres up in the sky. Above this part of Southeast Asia is a thing called the Madden-Julian Oscillation. http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml It’s not always there but when it is, it makes big showers into giant showers.

The good news in this event is that this oscillation, this hole in the sky that makes flood-bearing clouds, is on its way east. By the end of the year, the monsoon showers will be merely “normal”.

Source: Al Jazeera