Weather Bee | How unusual is snowfall in late April? - Hindustan Times

Weather Bee | How unusual is snowfall in late April?

Apr 17, 2024 09:13 PM IST

India's snowpack season in 2024 is marked by unpredictability, with current levels far below what they should be at this time.

As expected from an Indian summer, severe heatwave conditions were reported from pockets of Saurashtra, Gangetic West Bengal, Odisha, and north Konkan on April 16, according to an April 17 press release by the India Meteorological Department (IMD). The same press release, however, talks about a weather event not many Indians expect to hear about in the summer: snowfall. How unusual is this? An HT analysis shows that while snowfall at this time in India is not unusual, there are indeed some unusual trends prevailing in India’s snowpack (the mass of accumulated snow) currently.

Ganderbal [J&K], Apr 16 (ANI): Vehicles covered in snow as Sonamarg receives fresh snowfall, in Ganderbal on Tuesday. (ANI Photo)(ANI) PREMIUM
Ganderbal [J&K], Apr 16 (ANI): Vehicles covered in snow as Sonamarg receives fresh snowfall, in Ganderbal on Tuesday. (ANI Photo)(ANI)

The reason why IMD is talking about snowfall in the summer is that it has forecast “rainfall/snowfall” in different parts of the Himalayas in the coming days. The intuitive expectation from this ambiguous forecast might be that these regions are going to receive rain and not snow. However, this expectation is not based on facts. One can confirm this from an X (formerly Twitter) post by news agency ANI, uploaded on April 15, showing fresh snowfall in Sonamarg in Jammu and Kashmir.

To be sure, ANI’s X post is not the only proof of snowfall in summer. The first edition of this column talked about the seasonality of India’s snowpack using satellite data. This analysis showed that the snowpack over India’s hilly states usually (taken as the 2000-2019 average throughout this analysis) peaks only on April 20, although snow is limited to the higher reaches of these states in late April.

With data and visual confirmation, it should not be a surprise that the IMD is talking about snowfall in the second half of April. However, there are noteworthy trends in India’s snowpack at this time. Data on snowpack from NASA’s Giovanni portal is available up to April 14. This shows that the snowpack over India’s hilly states is far from the usual peak achieved by April 20. The gap from the peak on April 14 was 91.1 mm (20.4% of the peak value of 446.6 mm) in terms of the water content of snow or Snow Water Equivalent (SWE). The deficit compared to the usual snowpack on April 14 was 88.7 mm or 20.0% as we are already close to the usual peak.

To be sure, the deficit in the snowpack at this time is a slight improvement compared to the level of deficit seen earlier during the 2023-24 snowpack cycle (it runs from October to September over India’s northern states). On February 17, the deficit (compared to the normal for the day) was 25.8%, the highest seen on any day of the 2023-24 cycle so far. However, the 20% deficit on April 14 is not the lowest deficit either. At the beginning of the season in October – when snowpack is low – the deficit was around 15%. For a brief period even later in the season (March 3 to March 7), the deficit had decreased to 18%. Nonetheless, as both the highest and lowest values of the deficit this season suggest, this has not been a good season for India’s snowpack. It is at its fourth lowest level for April 14 since the 2000-2001 season, the earliest season for which the Giovanni portal has data.

Do the above trends mean that India’s snowpack cannot improve any further? Not necessarily. While historical averages suggest the peak snowpack is expected on April 20, individual years expectedly show variation. The peak arrived at least a week later in 11 of the past 23 cycles for which data is available, and at least two weeks later in nine of the 23 cycles. In 2009-10, the peak arrived only on June 8, the latest in any year.

The discussion above highlights that there are only a few probable scenarios given the conditions so far this season. These are: the peak reaches a level close to earlier years but arrives late; does not reach historical levels but arrives on time; does not reach historical levels and arrives late; reaches historical levels on time due to heavy snowfall. As is obvious, none of these scenarios are anywhere close to a normal snowpack season.

Abhishek Jha, HT’s senior data journalist, analyses one big weather trend in the context of the ongoing climate crisis every week, using weather data from ground and satellite observations spanning decades.

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