When storms change their mind - Bay of Bengal 26-29July2026

A low pressure area (see above) formed in the Bay of Bengal around the 25/26July2026 which quickly intensified into a depression and thereafter into a deep depression, more or less in the same area. 
The forecast track of the depression was initially in a NWly path:

 

The subsequent path followed by the storm and forecast by the IMD are shown (all images from  https://mausam.imd.gov.in/responsive/cycloneinformation.php):

The latest position of the storm is shown below: it is located South West of where it formed. 

Updated track of the storm as it traversed the breadth of the country (01Aug2026)

Praful Rao
SaveTheHIlls
savethehills@gmail.com
9475033744

Rainfall data of August 2024 of some towns in Sub-Himalayan W Bengal and Sikkim

The National Highway 10 (NH10) which connects Siliguri to Gangtok and is the lifeline for Sikkim and Kalimpong district runs along the river valley almost hugging the banks of the river for almost 50 odd km. The monsoons extracted a heavy price for this closeness in Aug2024 - the highway was closed for almost 20 days due to landslides and erosion.

As per the above data:

• Darjeeling, Kalimpong (in West Bengal), Gangtok, Mangan, Damthang (in Sikkim) recd almost normal rainfall.
• Kalimpong, Siliguri, Jhallong, Alipur Duar (W Bengal) and Dentam in Sikkim recd went deficient in rainfall.
• Most of the rainfall occurred in the first half of the month (see below).
  
  This was undoubtedly due to the low pressure areas and depressions which formed in the Bay of Bengal and moved towards western India, which resulted in surplus rainfall in those parts towards the end of Aug2024 (see above).
  
  

  
  

  

  Major Landslide
  A major landslide occurred in Sikkim on 20Aug2024 at Dipu Dara, just above NHPC Stage V Power House at Baluatar.
  We have covered the entire incident in our previous blog report
  

  
  Documentation of a part of the above report was supported by Royal Enfield, as part of their Social Mission Initiative
  
  
  Praful Rao
  SaveTheHills
  savethehills@gmail.com
  9475033744
  
  

  
  
  
  
  

 

STH stormwatch : A low pressure area in the Bay of Bengal which is likely to form the 2nd cyclone of 2017.

STH will post updates as necessary

Praful Rao,
Kalimpong dist.
Darjeeling-Sikkim Himalaya

STH Stormwatch : Depression in the Bay of Bengal (21Oct2016)

Updates will be posted as necessary

Update 1 (JTWC IR image of two storms in our region)

Predicted storm track (shown in RED) is an approximation (NOT accurate!).

Update 2 (23Oct2016)

Update 3 (23Oct2016) - IMD predicted track

 
Praful Rao,
Kalimpong,
Dist Darjeeling

Onset of SouthWest Monsoon 2016.

 Forecast of the Onset Date of Southwest Monsoon - 2016 over Kerala (Excerpts)

1. Background
The onset of southwest monsoon over Kerala signals the arrival of monsoon over the Indian subcontinent and represents beginning of rainy season over the region. The normal monsoon onset over Kerala is 01 June. Since 2005, India Meteorological Department (IMD) has been issuing operational forecasts for the date of monsoon onset over Kerala using an indigenously developed statistical model with a model error of ± 4 days.

The forecasts of the monsoon onset issued during the past 11 years (2005-2015) except 2015 were proved to be correct. 

2. Advance of monsoon over the Andaman Sea
The southwest monsoon advances over the Andaman Sea normally around 20th May with a standard deviation of about one week. Strong convective activity has been observed over the equatorial Indian Ocean for the last several days. A well marked low pressure area has formed over the Indian Ocean which will concentrate into a depression and move north-westwards. As a result, conditions are becoming favorable for the onset of southwest monsoon over Nicobar Islands, south Andaman Sea and parts of south Bay of Bengal around 17th May and advancement over the entire Andaman Sea close to its normal date. Past data suggest that there is no association of the date of monsoon advance over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country.

3. Forecast for the 2016 Monsoon Onset over Kerala
The statistical model forecast suggests that the monsoon onset over Kerala in this year is likely to be slightly delayed. The southwest monsoon is likely to set over Kerala on 7th June with a model error of ± 4 days.

Read full article here

Praful Rao,
Kalimpong,
Darjeeling district

STH Stormwatch : Update on depression on 02Aug2015

Above satellite image has been obtained from Nepal MFD since the IMD website is not working from 05.00am till the time of this report.
The storm has moved over Chatisgarh but the image shows significant clouding over south Bengal. I have verified that it is not raining in Kolkata at least.

Praful Rao,
Kalimpong,
Dist Darjeeling

STH Stormwatch : Update on depression (Bulletin 27)

Excerpt from IMD Bulletin 27 (Bay of Bengal) issued at 2000h (IST) on 01Aug2015
'The depression over Bangladesh moved west northwestwards and lay centred at 1730 hrs IST of today, the 01 August 2015 over Gangetic West Bengal and adjoining Bangladesh near latitude 23.80N and longitude 88.40E, about 30 km south southeast of Berhampore (West Bengal). It would move west northwestwards and weaken into a well marked low pressure area gradually.'

Comment by Praful Rao

I wish IMD would give more frequent weather bulletins and analysis especially when we are exposed to severe and extreme weather. It is pathetic that position of the storm has been updated after almost 9hrs (Bulletin 26  and information on the storm position was issued at 11.30am this morning after which there was no update till now).

The state of IMD AWS/ARG stations are no less dismal with most of the AWS/ARG stations either non-functional or giving erratic data.

Thank goodness their satellite imagery is different and works almost flawlessly well.

Praful Rao

Kalimpong,

Dist Darjeeling

STH Stormwatch : Update on depresssion from IMD (1130h, 01Aug2015)

Excerpt from IMD Bulletin No 26 (Bay of Bengal) Issued at 1130h (IST) on 01Aug2015 

'The depression over Bangladesh remained practically stationary during past 3 hours and lay centred at 0830 hrs IST of today, the 01 August 2015 over Bangladesh near latitude 23.20N and longitude 89.20E, close to Jessore (Bangladesh). It would move west northwestwards and further weaken into a well marked low pressure area gradually.'

Rainfall in the past 24hrs 
Kolkata : 133.6mm
DumDum : 131.4mm
Gangtok : 2.5mm
Kalimpong : 2.2mm
 
Praful Rao,
Kalimpong,
Dist Darjeeling

STH Stormwatch : Update on DEEP depression in Bay of Bengal (29Jul2015)

Placed above are images from JTWC (Google Earth) and the latest IR2 image from IMD of the deep depression in the Bay of Bengal.

Excerpt from IMD (0900h, 29July2015)
'The depression over northeast Bay of Bengal and adjoining coastal areas of Bangladesh & West Bengal moved southeastwards, concentrated into a deep depression and lay centred at 0530 hours IST of today, the 29th July, 2015 over north east Bay of Bengal and adjoining areas of Bangladesh near Lat. 21.0 ° N and Long. 91.0 °E, 160 km south­ southwest of Chittagong (Bangladesh). The system would move nearly northward and cross Bangladesh Coast on 30th forenoon between Long. 90.5 °E and 91.5 °E.'

Praful Rao,
Kalimpong,
Dist Darjeeling

NB: Italics are mine.

STH stormwatch : First depression of 2015 in the Bay of Bengal

'The depression over northwest & adjoining westcentral Bay of Bengal off north Andhra Pradesh­south Odisha coast moved northwestwards during past 3 hours and lay centred at 1730 hours IST of today, near Lat. 18.5°N and Long.85.5°E, about 150 km south of Puri.
The system would move northwestwards and cross Odisha coast between Gopalpur and Puri by tomorrow forenoon.'
- IMetD

Praful Rao,
Kalimpong,
Dist Darjeeling

STH Stormwatch (07Nov2014 update) : Track/winds of deep depression in Bay of Bengal

Praful Rao,
Kalimpong,
Dist Darjeeling

STH Stormwatch (05Nov2014 update): The low pressure intensifies into a depression

As per JTWC, 'the potential for the development of a significant tropical cyclone within the next 24hr is upgraded to medium'

Praful Rao,
Kalimpong,
Dist Darjeeling

STH stormwatch (23May2014) : POOF! and the storm disappears!!!

The depression which was predicted to move northwestwards towards Bangladesh both by the JTWC and IMetD yesterday, seemed to have a mind of its own today and curved southwest wards and quite suddenly weakened into a well marked low and as such has become insignificant.
It's amazing that all the science and technology in the world cannot quite  predict or understand the behavior of these storms as they wax and wane in the ocean.

Praful Rao,
Kalimpong,
Dist Darjeeling

STH stormwatch (22May2014 update) : JTWC changes predicted track

For further details go here
Whereas on 21May2014, the depression was seen moving east towards MyanMar, on 22May2014, the projected track shows the storm moving northwest towards Bangladesh and could well affect W. Bengal as well.
This forecast seems in keeping with the meteorological analysis by IMetD (22May2014) in its ALL INDIA WEATHER BULLETIN (Night), which states :-
'The depression over east central Bay of Bengal moved north-northwestwards and lay centered at 1730 hours IST of today, near lat.17.5°N and long. 92.0E, about 650 km north-northwest of Port Blair. It would move north-northwestwards during next 48 hours'

Praful Rao,
Kalimpong,
Dist Darjeeling

STH stormwatch (21May2014) : TRMM Sees Stormy Bay Of Bengal + Updates

The TRMM website is one of the many that STH uses while keeping a track of the storms that brew up in the Bay of Bengal.
Placed below is an image juxtaposing the latest image of the storm taken from IMD with that on the TRMM website.

* Update at 0830h IST, 21May2014
The low pressure area over eastcentral Bay of Bengal & neighbourhood concentrated into depression at 0830 hours IST of today, the 21st May 2014 near latitude 15.5°N and longitude 90.5°E over eastcentral Bay of Bengal, about 490 km north­northwest of Port Blair.
It may intensify further into a deep depression during next 24 hours. It would move near northwards for some time andthen north­northeastwards towards Myanmar & adjoining Bangladesh coast during next 48 h

For anyone interested in details see here

Praful Rao,
Kalimpong,
Dist Darjeeling

STH stormwatch updates (19/20Nov2013) : Depression pressure intensifies in Bay of Bengal

All India Weather Bulletin (Morning)
The low pressure area over southeast and adjoining central Bay of Bengal has intensified into a depression over westcentral Bay of Bengal and lay centred at 0530 hours IST of today near Lat.14.5° N and Long. 86.5 °E , about 700km east-­north east of Chennai, 600 km east-­southeast of Machilipatnam and 500 km south­east of Vishakhapatnam.
The depression would intensify into a deep depression and move northwestward towards Andhra Pradesh coast during the next 72h

Update of 20Nov2013(0530h IST)
The above depression has intensified into a deep depression

Praful Rao,
Kalimpong,
Dist Darjeeling

STH Storm watch : 21Oct2013 - Low pressure reported over central parts of south Bay of Bengal

We are now at the end of the cyclone season in the Bay of Bengal with winter right around the corner.2013 saw cyclone 'Mahasen' greeting the monsoon season and lets hope 'Phailin' was farewell to the rain bearing winds which are now on their way out of the sub-continent. Having said this though IMetD reported another low pressure over central parts of South Bay of Bengal on 20Oct2013, excerpts from Bulletin are below :

" The low pressure area over central parts of south Bay of Bengal and neighbourhood
persists."
" Prediction of meteorological condition :
The low pressure area over central parts of south Bay of Bengal would move northwestwards and would intensify into a well marked low pressure area during next 24 hours."

Mid-Day Update (21Oct2013) 
"The well marked low pressure area over southwest Bay of Bengal and neighbourhood may concentrate into a depression during next 24hrs."

Update on 23Oct2013

A well marked low pressure has formed, likely movement - west northwestwards

(Source : IMetD)
Rohan Rao,
Kalimpong,
Dist-Darjeeling,
Email: rohan.rao1313@gmail.com

STH stormwatch: Inconsistencies of Meteorological Science.

Though the track predictions and forecast of IMetD during Very Severe Cyclone Phailin seemed almost flawless, we are now seeing variations in what was predicted and what actually happened.
a. SLIDE 1 above states that the Cyclonic storm much after landfall on 12Oct2013 would move north WESTWARDS.
b. SLIDE 2 concedes the storm (now a deep depression) has infact moved north EASTWARDS and would continue to move in that direction.
In keeping with the heavy rainfall warning  over Darjeeling and Sikkim (in slide2) it has been raining continuously over this area since this morning albeit not too heavily (see IR image above)

Praful Rao,
Kalimpong,
Dist Darjeeling

STH stormwatch (update) : The storm gets a name, Cyclone PHAILIN

09Oct2013 : The deep depression over east central Bay of Bengal has intensified into a Cyclonic Storm "PHAILIN" which is Thai for "sapphire" (for a comprehensive read on how cyclones are named see here). 

IMetD forecast states :-
"The cyclonic storm, Phailin over east central Bay of Bengal moved slightly northwest wards, and lay centred at 0230 hrs IST of today the 10th October 2013 near latitude 14.00N and longitude 92.00E, about 900km southsouth east of Paradip, 950km south east of Kalingapatnam, 1000 km east-southeast of  Visakhapatnam. The system would intensify into a severe cyclonic storm during next 24 hours.It would continue to move northwest wards and cross north Andhra Pradesh and Odisha coast between Kalingapatnam and Paradip by night of 12th October, 2013 as a very severe cyclonic storm with a maximum sustained wind speed of 175-185 kmph".

The Odisha Government has issued a high alert and cancelled Dussehra holidays for employees in 14 districts (Balasore, Bhadrak, Mayurbhanj, Keonjhar, Dhenkanal, Jajpur, Cuttack, Kendrapara, Jagatsinghpur, Puri, Khurda, Nayagarh, Ganjam and Gajapati districts). District Collectors along with the Odisha Disaster Rapid Action Force  have been asked to ensure the safety of the people.
In this regard, Odisha has one of the best State Disaster Management Authorities in the country, see here.

STH has been tracking this storm for some days now and it will be 2 more days before it makes landfall. Several points emerge from this :-

• Thanks to advances in technology and at least for hydrological disasters (floods, landslides and even flashfloods) it is possible to get several days advance warning  and it is rare that such an event will occur suddenly and without any notice.
• Again satellite imagery, doppler radar and other techniques can give us largely accurate forecast on the expected intensity of rain and duration.
• Track predications of storms has also become accurate and our observation has been that severe storms have made landfall more or less as predicted.
• What is of essence, therefore is what we do with all this information which is now available to us?
  • Have we trained and prepared for such an eventuality?
  • How good are our defenses to absorb and withstand intense, heavy rainfall for several days?
  • Do we have a volunteer force of young people who can help in evacuation, search and rescue?
  • Have we identified the vulnerable, landslide prone areas and vulnerable sections of society?
  • Can the drainage system in our urban mountain centres handle the huge volumes of water which the storm will dump?
  • Is the State Disaster Response Force (SDRF) trained and well equipped?
  • Are back - up generators and battery operated wireless communication gear available at control rooms and life-line structures?

These and many more questions will have to be answered where ever Cyclone Phailin hits the shore in few days time.


Praful and Rohan Rao,
Kalimpong,
District Darjeeling,
Email- rohan.rao1313@gmail.com  

STH storm watch (30May2013): Depression update

Source

Praful Rao,
Kalimpong