No forecast model 100% accurate: IMD

 No forecast model 100% accurate: IMD | India News - Times of India
NEW DELHI: No forecast model 100% accurate With monsoon still eluding the city and its surrounding areas, the Indian Meteorological Department (IMD) forecasts have come under criticism.
No forecasting model in the world has 100% accuracy even with the best of technology, said Mrutyunjay Mohapatra, director-general of Meteorology at the IMD.
Mohapatra argued that the “unpredictable” nature of the monsoon can only provide 55-60% accuracy even with the best of technology and forecasting models in place.
“Our goal is to have the technology which will be able to forecast weather phenomena with 100% accuracy. However, that day is still far. Till then, we need human experience and understanding of the data,” Mohapatra told TOI.
“Our forecasts made on July 1 regarding the monsoon to slow up considerably and come by the middle of the second week of July is on track so far. However, in some cases, the forecasts over a longer duration may not hold true as well. It is extremely difficult to forecast how the monsoon will progress over a period of more than 15 days,” said Mohapatra.
The forecast accuracy is over 80% in a 24-hour period and more than 60% over a five-day period, he added.
According to the IMD, it relies on human intervention to assess models, since dependence on technology alone can leave data open to interpretation in some cases.
Every morning, the IMD holds a video conference where scientists from across the country use their experiences to assess the weather pattern for the next few days, relying on forecast models generated by machines, satellite imagery, and radar technology. Met officials say while the reliance on technology is 70%, the 30% human interpretation plays a critical role in the forecast for the day.
“A combination of machinery, models, and human skills and experience is used each day. A 24-hour forecast is sometimes unable to capture a sudden change in the weather, which may occur within a matter of hours. For that, our nowcast feature, which gives forecasts for every three hours, is the most accurate,” said a Met official.
“The weather is particularly volatile during the monsoon and late summer. There is low pressure due to high temperature. There is a high moisture content in the air as the monsoon gets closer and a cyclonic circulation can lead to cloud formation and rain within hours. This is not always easy to forecast,” the official added.
While one can rely on satellite imagery and radar technology for a short-term forecast of 3-4 hours, the same may not hold true for 24 hours, a scientist who works on forecasting told TOI pleading anonymity.
“Conditions in the tropical belt are more dynamic than in other parts of the country. The monsoon, plus the weather changes during summer are more dynamic, hence a short-term forecast can capture it. Within 24 hours, it can change completely, which is why releases an updated forecast in the morning may not match with that of the previous evening,” said the scientist.
“At times, only a small patch of land across the entire city receives rainfall. While this means the forecast was accurate, it may appear that it did not rain and so the forecast did not hold true,” the scientist added.
For ‘soft’ indicators, the IMD uses terms like “unlikely” (less than 25% chance of occurrence), “likely” (25-50% chance), “very likely” (75% chance), and “most likely” (more than 75% chance) in its daily forecast, according to officials.
“This gives a rough estimate that if rain is forecast, it may not always occur and will depend on the category of the likelihood it is placed in,” they added.
Navdeep Dahiya, an amateur weatherman who runs ‘Live Weather of India’, said climate change has played a key role over the last decade, making weather patterns more unpredictable, despite the best of technologies in place.
“This summer alone, we have seen heatwave days at the end of June and early July, which is unusual. We are seeing more rain in some places and less in other parts. Weather patterns are more volatile now,” said Dahiya.

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