Yellow, orange, red: Weatherman’s false alerts leave Delhiites high and dry

Experts said it is hard to pin down why the agency is issuing false alarms or simply reading the signs wrong, but there is consensus that the miss rate is too high.

Delhi was predicted to receive “widespread and heavy rainfall” midweek. The India Meteorological Department (IMD) first issued a yellow alert, meant to signify the possibility of light showers, on Monday, before it upgraded it to an orange warning for two days, Wednesday and Thursday.

(Hindustan Times)

Come Wednesday, with precipitation being elusive and a smattering of clouds that would not qualify even for overcast conditions, the alerts were withdrawn, representing yet another instance of erratic forecasting by the country’s official weather agency.

Experts said it is hard to pin down why the agency is issuing false alarms or simply reading the signs wrong, but there is consensus that the miss rate is too high.

“I am not saying that IMD is perfect. There is definitely scope for improvement and that is happening every year,” said M Rajeevan, former secretary of the Union ministry of earth sciences (MoES), who defended the agency and said the accuracy of weather forecasts have significantly improved but cannot always be 100%.

IMD also drew flak a little over a month ago when it prematurely declared the arrival of the monsoon over Kerala, the rain-bearing system’s first port of call.

Rajeevan said the announcement could have included some nuance. “There was a weak monsoon current over Kerala and this should have been specified by IMD while declaring the onset. But we need to understand that there is always some uncertainty in forecasts and IMD has been doing this for years”.

Private weather forecaster Skymet issued a statement disputing the onset declaration at the time.

“Declaring monsoon based on single day observation amounts to gross violation of standards, never attempted in the past. Any reputed scientific body can ill afford to bend rules and criteria, just to prove the forecast right. Such a step, if taken knowingly, becomes highly objectionable and if otherwise, amounts to illusion of knowledge,” the statement said.

In a little over a year, this has now been a consistent trend with IMD. Last year, it made a startling assessment in mid-June that the monsoon rains were going to make onset over northwest India a full fortnight ahead of schedule. Eventually, as the days passed, the agency kept pushing its prediction back, and the rains finally arrived in mid-July.

A similar scenario seems to be playing out this year, and experts say the problem could be in the models, as well as the judgement of those interpreting them.

Among other major instances where IMD has got its predictions wrong, the weather agency appeared to have completely missed predicting a massive storm with wind speeds touching 100kmph that wreaked havoc in Delhi on May 30, uprooting trees and causing widespread chaos. Then on June 11, IMD declared the arrival of monsoon over Mumbai before the set criteria was met. This was repeated on June 30 when monsoon arrival over Delhi was declared with only 24 hours of rainfall as opposed to the stipulated 48 hours.

When asked about the missed “orange alert” on Wednesday and Thursday, RK Jenamani, senior scientist at IMD, said the alert was issued but later withdrawn. He also said that in northwest India, heavy rainfall days are limited throughout the season.

“Most of monsoon days in northwest India are marked by high temperatures and high humidity. In 2021, we had the highest number of heavy rainfall days in the last 74 years—which was seven. Many monsoon seasons in the past hardly see a single heavy rainfall day,” Jenamani said.

But Mahesh Palawat, vice-president (meteorology and climate change) at Skymet, contended: “Easterly winds were blowing and the temperatures were also high, in such conditions weather models sometimes catch high moisture content as rain. The models only consider water content and this could have caused the misinterpretation. Maybe the forecasters saw this and issued the orange alert.”

IMD has sought to defend its track record in the past

In a 2020 assessment of its predictions, the department said it got seven of every 10 forecasts of heavy rainfall right between 2017 and 2019, up from under five between 2002 and 2016. They attributed this to superior weather models, better quality of input data, and more computing power.

But experts are not convinced

Akshay Deoras, independent meteorologist and researcher at University of Reading, United Kingdom, said that while IMD possessed advanced technology and models for forecasting, human intervention and the judgement of forecasters becomes a key aspect of getting accurate forecasts.

“Accurate forecasts depend on two primary factors — efficient weather models and the judgement of forecasters. IMD is in possession of advanced weather models but judgement is needed to make better sense of model predictions. This year while declaring the onset over Kerala and the further progression of monsoon in many states, IMD seems to have considered ‘pseudo onsets’ because atmospheric conditions over many areas did not reflect the monsoonal pattern when these onsets were declared,” said Deoras.

Getting the weather right is crucial for any country where large variations such as in India are seen. These predictions become all the more important for a population where thousands every day take precarious mountain routes at risk of landslides in bad weather, and where millions depend on these predictions to get their farm timelines right.