Rainfall data of June 2023 of some towns in the Darjeeling -Sikkim Himalaya (along with images of landslides which occurred)

Cyclone 'BiparJoy' (09Jun-16Jun2023)
Formed as a 'low' in the Arabian sea in the first week of Jun2023 and intensified into a cyclone. We watched the storm closely and reported on the movement and forecast track of the storm extensively in our What's App group 'Hazard Alerts'.

 

June Weather
The first 10 days of June were HOT and DRY and the monsoon was delayed by several days.

 

 

The rainy spells for Jun2023 came in 3 spells ie on 11Jun, 17Jun and the last week of June2023.
Taking an example of KALIMPONG rainfall, please note:

• Kalimpong had the highest rainfall among the 4 towns. Kurseong normally has the highest rain. All this rainfall was concentrated in 17 days, 13 days being bone dry.
  
  
• Rainfall on FIVE DAYS ie 11, 17, 26, 27, 28 Jun2023 amounted to 431mm which is equal to 88.8% of the monthly rainfall.
  
  
• And what happened was that this rainfall came in short, intense bursts and so the 431mm of rain must have come down with several hours - NOT days.
  See previous blogs on this here1 and here2
  
  
  

This rainfall, as expected resulted in numerous landslides.

 

 

We will be uploading rainfall data of the previous months in due course.
Thanking all those who contributed the above images in our What's App group 'Hazard Alerts', regretfully the coordinates of the places are not available.

Praful Rao
Kalimpong district,
Darjeeling- Sikkim Himalaya

Rainfall data of some towns in the Darjeeling- Sikkim Himalaya - AUGUST 2020

 Surprisingly:

• Darjeeling town had less rain than Kalimpong town.
  
• Sikkim rainfall (all 4 districts) was much less than that of Kalimpong and Darjeeling.
  

The New Normal : Intense bursts of rain in overnight thundershowers

Graphs from AWS of SaveTheHills show the pattern of rainfall at Kalimpong on 05/06Aug2020 and 26/27Aug2020. In both cases, thundershowers commenced in the late evening or night and got over within a couple of hours with instantaneous rainfall intensities going upto 252mm/hr on 05Aug.

Did we have a cloud burst on 05Aug2020?
Even though we cannot prove it, I do believe we had one. Rainfall intensities reached never before levels of 252mm/hr and the event caused major damage to roads in Kalimpong and infrastructure in W Sikkim.

And it is not as if we have not had cloudbursts earlier

STH has already recorded the extreme rainfall events of AUGUST 2020 and their effects in earlier posts (see 1 and 2).

My thanks to Ms Shreya Gurung for compiling the rainfall data.

Praful Rao
Kalimpong district
Darjeeling-Sikkim HImalaya

 

Reporting an extreme event in the Darjeeling - Sikkim Himalaya (05Aug-06Aug2020)

RAINFALL DATA (24hrs) in Darjeeling- Sikkim -06Aug2020
W Bengal
Kalimpong - 106, Darjeeling - 99.4, Kurseong - 13
Sikkim
Gangtok - 59.2, Khanitar -119.4, Mangan - 104.2, Singhik - 130.8, Gyalsing - 83.6, Damthang - 82
Much of the rain was very high intensity - and came down within a couple of hours

CLOUD IMAGE AND RAINFALL CHARACTERISTICS OF 05/06AUG2020

What is apparent from the above graph and the AWS chart is the intensity of the rainfall - which peaked within hours to an incredible 252mm/hr at Kalimpong resulting in massive volumes of surface runoff from paved areas of urban centres. Videos of torrents of water gushing into residential areas, shops and flooding streets in Darjeeling, Kalimpong and Gangtok went viral. The intensity of the rain was ascribed to vertical buildup of the clouds - reaching well into the stratosphere with cloud top temps being -80 deg C.
While this sort of rainfall data for other towns is not available, similar scales of damage has been widely reported from Darjeeling, Kalimpong and Sikkim.

IMPACT AND DAMAGE FROM THE STORM

WEST BENGAL

Kalimpong suffered a fatality wherein a heavily swollen stream during the downpour in Lamini Gaon, Chota Bhalukhop swept away a 10yr old boy. This area lies in the western face of the Kalimpong ridge line. The body was recovered 3 days later.
A bridge in Dungra village (which lies below the town, on the eastern face of Kalimpong town) was washed away in the deluge

Many subsidences and landslides were reported on NH10 which is a vital link from
Siliguri to Gangtok. Most occurred between Teesta bazar and Coronation bridge.

 

 

SIKKIM - River Rangeet's Rampage 

Rangeet river is the biggest tributary of the Teesta river originating partly in West Sikkim. Older residents of Legship a town on the banks of the river in W Sikkim, recall that the last time the river was in full spate was during the Oct 1968 disaster.

Special thanks to Mr Mukesh Sharma (Kalimpong) for his inputs and photos.

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya