The Hindu Business Line : Brewing westerly threatens wheat crop

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Thiruvananthapuram March 4 Big-amplitude western disturbances that rained their contents over North and Northwest India during a critical phase last month could spoil the rabi wheat party during March, if forecasts are any indication.

Expectedly widespread rain accompanied at times by hail is the last thing the wheat crop would want at this point of time, say agricultural scientists.

But this is exactly what is feared to result from the `biggie' system rolling in to the Northwest around March 9.

Madhya Pradesh and West Uttar Pradesh are traditionally the most vulnerable to get damaged from a raging hailstorm. The danger is very real as can be judged at this point of time, according to Dr K.J. Ramesh of the Department of Science and Technology.

ROGUE SYSTEMS

Normally, the western disturbance season begins to fade away from early March. But `rogue systems' with mischief potential have been known to arrive during the month holding the prevailing rabi crop to ransom. Those who sowed their winter crop very early during November last have already got their comeuppance from the last round of February rains, Dr Ramesh said.

The European Centre for Medium Range Weather Forecasting (ECMWF) has in its seven-day forecast also supported the forecast for a rogue system hitting the Northwest. Worse, it has gone on to predict another system impacting far Southwest Rajasthan and North Gujarat five days later, on March 14.

FROZEN DROPS

Hail is made up of frozen raindrops - solid chunks of ice more than five mm in diameter. It forms when raindrops are tossed high up by winds inside huge cumulonimbus clouds. They freeze into ice and are continually bounced up and down inside the cloud, building more ice in layers around them.

Hail is the most common in areas with warm summers where there is enough heat to cause the uplift of air and cause large cumulonimbus clouds to form. Brewing weather in the plains of North and Northwest India, where day temperatures are already building, provide perfect foil for hail formation.

LODGING EFFECT

The wheat plants get impacted due the `lodging' effect on the ear-heads from heavy rains and hail. The crop has reached the early dough stage in the Indo-Gangetic plains, a progression from the ear-head emergence and flowering. Unwanted rains could make heavy weather of the crucial `grain filling' stage that follows next.

One favourable factor seen is the temperature regime, which is forecast to hold well within the crucial 35 deg C during the whole of March. The National Centres for Environmental Prediction (NCEP) says 25 deg C should be the normal range for maximum day temperatures in the plains.

The week ending March 9 would see 75 to 100 per cent of the seasonal average of rainfall in Punjab, Haryana, East Rajasthan and onward in Bihar and Jharkhand. At times, it could reach up to 150 per cent above the normal at times. But this forecast does not fully capture the expected realisation from the big westerly system impacting the region from March 9 onwards.

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