The Hindu : Karnataka / Bangalore News : Can you spot the difference?

Online edition of India's National Newspaper
Thursday, May 31, 2007
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Karnataka

Karnataka - Bangalore

Can you spot the difference?

Divya Gandhi

Now, after the starters, it's time for the real thing

RAINY SEASON: That umbrella isn't big enough for the three of them. — File photo: S. Subramanium

Bangalore: So the Meteorological Department has declared that the monsoon has arrived. But can you really tell apart yesterday's downpour from tomorrow's rainfall?

What we have experienced this month are pre-monsoon thundershowers, characterised by evening rain and squalls with wind speeds that can go up to as much as 50 kmph, explains G.S. Vijayaraghavan, Director of the Meteorological Centre. Intense but short-lived gusts of wind and spells of rain typify thundershowers, which cannot be underestimated because they can uproot trees even in the few minutes of their lifespan.

`Better behaved'

Rainfall during the monsoon on the other hand is better behaved, largely because the earth, cooled by rain and cut off from the sun's rays by an overcast sky, is not conducive to the vertical development of thunderclouds and thundershowers. The wind speed never exceeds 25 kmph. Monsoon rainfall can occur at any time of the day, but is more predictable in that it is "sustained, significant and large-scale spells of rain that last typically between four to five days", said Mr. Vijayaraghavan.

But pre-monsoon showers and monsoon rainfall are inextricably connected, believes P. Goswami, Centre for Mathematical Modelling and Computer Simulation (CMMACS), and the two are differentiated for the convenience of definition. "The monsoon is not a monolith, and embedded in the large-scale system are several small-scale systems like localised showers, which constantly interact and impact its nature."

The monsoon arrived over the coast of Karnataka and some parts of south interior Karnataka on Tuesday. "The monsoon line is now slightly to the west of Bangalore, at Karwar, Chitradurga and Pamban in Tamil Nadu. Within 24 to 48 hours, the rains will advance into the interiors, including Bangalore," said Mr. Vijayaraghavan.

Normal rainfall for Bangalore in the month of June is 80.8 mm, moving up gradually to 110.2 mm in July and 137 mm in August. September is the rainiest month of the season with 194.8 mm on average, he added.

According to Dr. Goswami, after an initial spell of rainfall, a lull normally follows as the system depletes itself, perhaps by May 31. "But a tropical monsoon is the hardest thing to predict."

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