Monday, July 11, 2011

Monsoon run complete amid ‘La Nina rebound' cues

India Meteorological Department (IMD) has declared that the southwest monsoon managed to cover the entire country by Saturday, at least a week ahead of schedule.
In a fortuitous coincidence, latest update from the Climate Prediction Centre (CPC) of the US National Weather Services seemed to suggest the re-emergence of a monsoon-friendly La Nina in the east equatorial Pacific later this year.
Over the last couple of weeks, forecasts created by the Climate Forecast System of the National Centres for Environmental Prediction have begun to indicate the re-emergence of La Nina during northern hemisphere autumn, the CPC said.
Combined with the recent weakening of the positive ocean anomalies and the lingering La Niña state of the atmosphere, the possibility of a return to La Nina has increased over the past month.
However, it added the caveat that most other models and all multi-model forecasts have been predicting ‘neutral' (conditions), suggesting neither La Nina nor El Nino, during the season ahead.
Out of more than 20 such forecasts monitored by the International Research Institute for Climate and Society at Columbia University, only six plumped for the ‘La Nina' option, it said.
Back home, the monsoon ran ahead of time to cover the entire mass after a ‘pulse' from the Bay of Bengal ended the ‘break monsoon' phase that had manifested during the first week of July.
Break monsoon is the term referred to the inevitable pause that the monsoon allows itself after a hectic run that, in the instant case, lasted almost the whole of June.
This pulse had also triggered the formation of a low-pressure area over land in east India. It travelled west for a day, before losing most of the sting over northwest Madhya Pradesh.
But it had also helped consolidate the easterly monsoon flows by coercing the all-important land-based monsoon trough across northwest-to-southeast India to revert to its normal position to sustain the flows.

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