Tuesday, June 16, 2020

The landslides of Darjeeling town (13Jun2020) - human factor also a trigger?

The SW monsoons finally arrived over the Darjeeling - Sikkim Himalaya on 12Jun2020.
Darjeeling town, received 105mm of rain over a approx 36 hour period, most of it coming down on 12Jun in intense bursts. Between 11-13Jun, Kurseong clocked an astounding 299 mm of rain and this not unusual since our experience shows that Kurseong certainly receives some of the heaviest rainfall in the region.
Six of the landslides which took place within the Municipal Limits of Darjeeling are shown in the map:-
Coordinates of these landslides and two others which are known to have taken place at Kurseong and Mungpoo are given below:-

Images of the landslides at Mungpoo and Sivitar T.E, Kurseong are placed below:-

Rainfall data of 2020 for our region is placed below:-
From the rainfall data it is very evident that, except for Gangtok ie East and North Sikkim, the whole region has been deficient in rainfall not only in 2020 but from the end of the monsoon season in 2019. As such I wonder how 6 landslips (small landslides) were triggered by the first burst of heavy rain (109mm) in Darjeeling town?
It is not abnormal to receive 100mm of rain over a 24hr period during the monsoons, what is abnormal is that this rain coming after a prolonged dry period caused so many landslips in Darjeeling town.
Each of those slope failures were capable of taking human life and our experience over the years has been that it is these small landslides in an urban setting which cause most of the fatal landslides. Saying so, I am painfully reminded of a fatal landslide barely 5 mins walk from my home in Jun2010, at Tirpai Kalimpong when it rained only 45mm overnight. It snuffed out the lives of a young mother and her 2 school going children.
In saying so, I must point out that occurring in densely populated urban settings, the trigger for the  landslide always has a human component and in most cases it boils down to managing our drainage system well. The high volumes of surface runoff from the intense rain in our towns must be drained away quickly and safely - otherwise they are bound to do mischief.

Praful Rao,
Kalimpong district
Darjeeling-Sikkim Himalaya

Friday, June 12, 2020

Rainfall data of some towns in Darjeeling - Sikkim Himalaya - May2020

The major weather event of May2020 was of course Super Cyclone 'Amphan' (see above). Much more on the storm is covered in earlier posts.

Rainfall data of Sikkim is from IMD Sikkim.
Grateful thanks to Shreya for helping out.
Praful Rao,
Kalimpong district,
Darjeeling - Sikkim Himalaya

Monday, June 1, 2020

STH stormwatch: A cyclone to threaten India's financial hub in the midst of a pandemic

JWTC forecast on the storm in the Arabian sea

Excerpt from IMD forecast
'The Well Marked Low Pressure Area over Southeast & adjoining Eastcentral Arabian Sea and Lakshadweep area concentrated into a Depression over Eastcentral & adjoining Southeast Arabian Sea. and lay centred about 400 km southwest of Panjim (Goa), 700 km south-southwest of Mumbai ( Maharashtra) and 930 km south-southwest of Surat (Gujarat).
It is very likely to intensify into a Deep Depression over Eastcentral & adjoining Southeast Arabian Sea during next 12 hours and intensify further into a Cyclonic Storm over Eastcentral Arabian Sea during the subsequent 24 hours. It is very likely to move nearly northwards initially till 02nd June morning and recurve northnortheastwards and cross north Maharashtra and south Gujarat coasts between Harihareswar (Raigarh, Maharashtra) and Daman during evening/night of 03 rd June,2020.'

Like AMPHAN hitting Kolkata on 20May2020, this storm too comes at a time when Mumbai has the highest rate of COVID19 infections in the country and is under lockdown.


It is still a Depression but will be called Cyclone 'Nisarga', when it intensifies into a cyclone. It is amazing how two consecutive megastorms (Cyclone 'Amphan' and this one) are targeting two megacities (Kolkata and Mumbai), this one with a population of 20 million and both in the midst of a pandemic.


The deep depression has now become a cyclone (NISARGA)  and while the track on the latest RSMC bulletin remains the same as earlier, information on the wind speeds and storm surge is as above.


First warning from JTWC has finally been issued.

Update 4

JTWC issued only 4 warnings for Cyclone Nisarga. The fourth and the last is below:
Rainfall records

Nira devghar,Pune dist - 147mm
Panshet,Pune dist - 137mm
Mahabaleswar - 214mm
Koyna Nagar - 156mm
Bhimashankar,Pune dist - 117mm
Khandala - 88mm

Praful Rao
Kalimpong district
Darjeeling-Sikkim Himalaya