vagaries© of the weather.blog written by rajesh kapadia.concentrating on meteorology of the Indian sub continent and extreme world weather since 55 years For Any Information taken from here, due credit must be given to Vagaries.
Thursday, September 05, 2019
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4th June Night: Uncertainty remains over the formation and track of the first low pressure system of Arabian Sea (AS-1)! A cyclonic circulat...
The low, has literally "whizzed" past,and thru the central regions, and by saturday night, is already over south Rajasthan/Gujarat...
Refer to all:
Vagaries blog had initially given a "Latest Snippet" forecast on 31st Aug Sunday of "increase in rain " from Tuesday 3rd. Again on Monday 2nd, we issued a fresh snippet warning the "One and Half Days Ganapati" of being hampered on Tuesday due to heavy rains FROM Tuesday thru Thursday...Frequency increase was also given in Hindi.
Yes, we estimated (or under estimated ) the quantum...mentioned 30-40 mms...and what we had (average) was 90 mms on Tuesday and 120 mms ( i said average) on Wednesday. The highest being at Scruz with 242 mms and 73 mms at Colaba.
The sudden very heavy bursts in some regions was due to "Micro Weather" Votice forming. Forming in the trough, the Vortice caused by sudden unpredictable divergence in the upper air gives unprecedented heavy rains in large patches. Trough strengthening was expected , but not local Vortex forming embedded in trough.
Vagaries regrets the under estimation inconvenience caused. Though overall rain was expected to increase.
Rains likely to reduce from Thursday thru Friday.
Watching the BB10 coming now.
The highest annual total at Scruz is 3785 mms in 1958 and 3482 at Colaba in 1954.
With 203 mms ending 8.30am today, Matheran achieved 6K mark today.. Seasonal total on 6036 mms
With 188 mms ending 8.30am today, Panvel achieved 4K mark today.. Seasonal total on 4142 mms
Happy Teachers Day Rajesh Sir! :)
We all weather enthusiast are here together due to Vagaries blog only so very thankful to you and has learned lot about the weather dynamics and still have to learn a lot.
And as per mine personal view this avg concept between two IMD stations is unfair policy towards any rain event or seeing how much Rainfall Mumbai got !!
Tuesday morning avg ending 8.30am today was 105 mm (Colaba 80, Santacruz 131)
Wed morning avg was 120 mm (Colaba 122, Santacruz 118)
Thur means today morning avg was 158 mm (Colaba 74, Santacruz 242)
So all three days reflecting 100-160 mms avg which falls in Heavy to Very Heavy Rainfall as per IMD criteria !
As we all know Colaba is least rainy place in whole Mumbai with less avg and has less occurrence of extreme events compare to suburban Mumbai district! Even IMD also agrees on it.
Today's article mentioning same: https://m.timesofindia.com/city/mumbai/mumbai-rains-suburbs-get-thrice-as-much-rain-as-island-city/amp_articleshow/70985736.cms
Below Para from article:
What explains the disparity? Climatologists say wind patterns differ for the city's narrow peninsular south and the wide north, which is almost contiguous with the mainland. The two regions also vary in terms of topography and layout: the suburbs are hilly, greener and have lakes, with the national park being a major climatological influence, while the island city is more densely built up, with thin green cover. Because of these factors, says the weather bureau, rainfall recorded by the Colaba and Santacruz stations are dissimilar.
Accordingly, winds are stronger in the suburban side as compared to the island city," said K S Hosalikar, deputy director general (western region), India Meteorological Department. "Another factor is land mass. This is to be considered as (south Mumbai) is a narrow piece of land compared to the suburban mass." The implication is that it is easier for clouds to pass over a sliver of land, resulting in less precipitation than in a much broader land area. "Then there's topography and the presence of green belts like the national park and Aarey Colony in the suburbs," said Hosalikar, meaning that such factors affect cloud formation.
Additionally, during a heavy rain event, a cyclonic circulation forms near the northern Arabian Sea, owing to which winds blow in a north-westerly direction-as per IMD's classification, Colaba on Wednesday received heavy rain (64.5-115.5mm) and Santacruz extreme rain (over 204.5mm).
Same way if see July 2005 event then Colaba had mere 74 mms & Santacruz had massive 944 mm with further Vihar lake seeing 1049 mms . So here if we take avg of CLB & SCZ then comes to almost half 509 mms !! So this completely makes unfair and events are gets suppressed due to it!
On every occasion this year June,July Aug, Sep Suburban Mumbai dist have saw extreme heavy rainfall events with rainfall ranging between 205 to 500mm with places getting changes.
So Colaba is almost sea side reading doesn't portray Mumbai rains at all! Even CSMT, Malabar hill, Byculla in Sobo post more heavy rainfall readings than south-most tip Colaba!
Abhijit: Thanks and all the good wishes for the future to you.
Vagaries has changed the concept of average between Colaba and Scruz from today.
Previously years ago we had only two stations recording rainfall, at Colaba and scruz. In fact Colaba was alone for almost 70 years.
Things are different now,we have many stations to compare, and city has also grown.
Thanks a lot Sir!
Yes indeed Sir Colaba can't be neglected completely as it is old station and still can be used as reference for Sobo representation rather than for complete city..
Yes. IMD also agreed now so at WMO also they depict Santacruz as official stn of Mumbai after city got expanded and suburban seeing huge population now with compare to city !
Avg concept still can be used with South Mumbai & Subarban Mumbai district as different avg then! Same like how IMD calculate rainfall departure district wise analysis
Amboli,Sawantwadi 195 mms rainfall today. Seasonal total on 8054 mms
Though 2 days report missing yet.. So more 100-150mm can get add in total!
With 151 mms ending 8.30am today, Karjat,Raigad also achieved 4K mark today..
Seasonal total on 4052 mms
With 190 mms ending 8.30am today, Tamhini ghat achieved 8K mark today..
Seasonal total on 8130 mms
Rajesh thanks for the explanation of the Micro weather vortex formation. Helps non technical people understand the weather in a simple way.
And one more point. You have expressed regret for your estimate causing inconvenience. Please do not say so. You are already doing a great service to all of us with such detailed forecasts. This is not mandatory but rather voluntary by you and we should all be obliged to you. I know that even well established western weather models struggle to get forecasts right all the time. So in a tropical monsoon environment it is even more complex. That's why you have absolutely no reason to regret.
Blog is sharing excitement every-time any station in Maharashtra breaks records. Below facts are well established with differences in opinion. Request people to debate and bloggers from south should also join.
(1) What is causing 2019 excess Maharashtra rains?
We had 10 Bay lows systems originating from south china have been activated in north Indian Bay. Usually some take route to north - near Japan or come down towards south pacific and Indian ocean - giving rains to low latitude southern islands like Indonesia, Singapore, Sri Lanka and of course good rains to South East India. This time all went directly to north Bay hence torrential rains to Central India,MAHA,GUJ,RAJ. Horrible drought for low latitude southern regions. Timing for north bay low and cyclonic circulation over GUJ,MAHA exactly coincided, with augmented westerlies AS trough, east-west shear zone - leading to blinding catastrophic rains over MAHA. Can't these factors be analyzed earlier for early warnings? And of course Doppler image analytics.
(2) Many places in Maharashtra have broken historical records - with record highs making them wettest places in world beating Cherrapunji. Maharashtra becomes wettest state.
(3) Gujarat, Rajasthan are no longer dry states - last 4-5 years have been receiving excess rains. Geography books needs to be updated. GUJ kutch and RAJ Jaisalmer are no longer deserts.
(4) Excess rains over MAHA,GUJ,RAJ,Central India, late withdrawl of SWM with longer duration has direct impact on North East Monsoon onset. Last 5 years very less NEM has resulted in South East India (entire South Andhra, almost 90% of Tamil Nadu become desert to near deserts. Very late arrival of NEM coincides with arrival of strong Western Disturbances which take low latitude Bay systems to NE India instead of SE India. SE India is driest place and geography text books have to revised.
In-fact IMD is also revising its statistical models, revising its time table of monsoons.
(5) What is causing 2019 excess Maharashtra rains? We have 10 Bay lows systems originating from south china have been activated in north Indian Bay. Usually some take route to north - near Japan or come down towards south pacific and indian ocean - giving rains to low latitude southern islands like Indonesia, Singapore,Sri Lanka and of course good rains to South East India. This time all went directly to north Bay hence torrential rains to Central India,MAHA,GUJ,RAJ. Horrible drought for low latitude southern regions. Timing for north bay low and cyclonic circulation over GUJ,MAHA exactly coincided, with augmented westerlies AS trough, east-west shear zone - leading to blinding catastrophic rains over MAHA. Can't these factors be analyzed earlier for early warnings?
(6) Sad part global world is talking about Tamil Nadu water crisis - desertificaton, people spoke about MAHA torrential floods but blog was bit silent on these facts?
Any updation for Mumbai rain in Comming days as Skymet seems to be updating that rain to pick up pace from. 8 sept
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