Multiple districts in the higher reaches of Himachal Pradesh and Uttarakhand have received heavy snowfall and rain this week, particularly on Thursday and Friday. This has led to landslides and avalanches. How intense is this precipitation? Is this usual for this time of the year? The gridded precipitation data of the India Meteorological Department (IMD) can help us in answering this question. This is what the data shows.

The IMD’s data for precipitation is generated for 24 hours ending at 8:30 am on the day. This means that the data for February 28 corresponds to the 24-hour-period ending at 8:30 am on Friday, and shows precipitation for parts of both February 27 and February 28. According to this data, almost all of Himachal Pradesh, Uttarakhand, Jammu and Kashmir, and Ladakh received at least 7.5 mm precipitation on February 28, and large parts of these regions received more than 35.5 mm precipitation.

Multiple districts in the higher reaches of Himachal Pradesh and Uttarakhand have received heavy snowfall and rain this week, particularly on Thursday and Friday. This has led to landslides and avalanches. How intense is this precipitation? Is this usual for this time of the year? The gridded precipitation data of the India Meteorological Department (IMD) can help us in answering this question. This is what the data shows.

The IMD’s data for precipitation is generated for 24 hours ending at 8:30 am on the day. This means that the data for February 28 corresponds to the 24-hour-period ending at 8:30 am on Friday, and shows precipitation for parts of both February 27 and February 28. According to this data, almost all of Himachal Pradesh, Uttarakhand, Jammu and Kashmir, and Ladakh received at least 7.5 mm precipitation on February 28, and large parts of these regions received more than 35.5 mm precipitation.

Since IMD classifies rain in the 35.6-64.4 mm range as “rather heavy”, it is clear that large parts of these regions received heavy precipitation. Moreover, some districts – such as Reasi, Doda, Ramban, and Udhampur in Jammu and Kashmir; Lahul and Spiti, Kullu, and Kangra in Himachal Pradesh; and Chamoli in Uttarakhand -- received 64.4-124.4 mm precipitation, which is classified as “heavy” intensity for rain. Parts of Kullu also received precipitation in the 124.4-244.4 range, the second highest intensity category for a 24-hour period. This means that the precipitation on February 28 was just short of extreme in some places. This is consistent with the reports of precipitation in these districts being heavy enough to cause avalanches and landslides.

Is such precipitation usual for this time of the year in these hilly regions? Not of this intensity. As the accompanying maps show, the usual precipitation for February 28 is mostly light (2.5-7.5 mm), although some places average moderate (7.5 mm-35.5 mm).

To be sure, the cause of the current round of precipitation is indeed common in February. The current round of precipitation, as is often the case in winter in India, was caused by a western disturbance, which is a loosely defined term for storms originating west of India. Around 10 western disturbances affect India in the month of February (1971-2020 average), according to a dataset developed by Kieran M. R. Hunt and others, which was first published in the Quarterly Journal of the Royal Meteorological Society in January 2018.

However, western disturbances have been of lower intensity this year or fewer in number after mid-January. This can be seen in the deviation of precipitation for the 29 days ending February 27. Almost all of the two hilly states and two UTs in the north had a deficit of 20% or more in this period. The disaster-causing precipitation on February 28 has decreased this deficit in a big way. In fact, large parts of Himachal Pradesh, have a surplus of over 20%.

These statistics yet again highlight the erratic patterns of precipitation in a changing climate, where rain and snow fall in one short burst instead of being spread over multiple days, which would reduce the chances of disaster. To be sure, as this column highlighted last week, given the long-term decline in snow pack in India’s hilly regions in the north, it remains to be seen how much these bursts of snowfall help India’s snow pack this year.