Cyclone Amphan Wind Speeds in Kolkata are the highest Kolkata has seen in last 150 years.

May 25, 2020
Share

Have gone through the last 150 years of Cyclone data and without a doubt the sustained wind speeds (3 mins avg) of 130 km/hr recorded at Dum Dum is the highest Kolkata has witnessed in over 100 years. Cyclone Aila came close but was 30% weaker than Amphan when it was over Kolkata. In Amphan the eyewall passed right over the City. The Maximum Sustained Wind Speeds and Gusts in Kolkata from Cyclones are as follows –

Kolkata Maximum Sustained Winds (60 km/hr and above)
————–
1. Cyclone Amphan (2020) – Dum Dum 130 km/hr and Alipore 112 km/hr
2. Cyclone Aila (2009) – Barrackpore 112 km/hr, Alipore 95 km/hr and Dum Dum 70 km/hr
3. 1971 September Cyclone – Dum Dum 93 km/hr
4. 1937 September Cyclone – Alipore 93 km/hr
5. 1896 June Cyclone – Alipore 83 km/hr
6. 1988 October Cyclone – Dum Dum 80 km/hr
7. 1974 August Cyclone – Dum Dum 74 km/hr
8. 2002 West Bengal Cyclone – Dum Dum 74 km/hr
9. 1916 September Cyclone – Alipore 74 km/hr
10. 1932 May Cyclone – Alipore 74 km/hr
11. 1936 May Cyclone – Alipore 74 km/hr
12. 1940 June Cyclone – Alipore 74 km/hr
13. 1888 August Cyclone – Alipore 68 km/hr
14. 1901 November Cyclone – Alipore 65 km/hr
15. 1889 August Cyclone – Alipore 63 km/hr
16. 1962 September Cyclone – Alipore 60 km/hr
17. Cyclone Bulbul (2019)- Alipore 60 km/hr

Kolkata Gusts (70 km/hr and above)
———–
1. 1937 September Cyclone – Alipore 105 km/hr
2. 1970 October Cyclone – Alipore 105 km/hr
3. Cyclone Aila (2009) – Dum Dum 92 km/hr
4. 1974 December Cyclone – Dum Dum 74 km/hr

Note: 

A Sustained Wind Speed is found by averaging observed values of the wind over a one minute period or above. In India, IMD uses 3 mins average, while in USA they follow 1 mins average and in Japan they follow 10 mins average.

Wind Gusts is quick and sudden increase in the speed of wind (faster burst of wind). A wind gust usually lasts less than 20 seconds.

 

Photos courtesy of Trees fallen in Kolkata due to Amphan – Hindu, Indian Express and Dailyo

Share and Enjoy !

0Shares
0
Related Posts

Action to shift to North Interior Tamil Nadu. Parts of Kerala to get heavy rains, Bangalore in hit or miss heavy rains

May 11, 2021

Before going into the post, it was a month which i would like to forget. For those for here for only weather can skip this part and go to S.No.I.

Day 1 to Day 5 – Few hours fever on day 1 and CT scan on day 5 after breathing difficulties

Its been nearly 35 days since i got Covid-19, it was in April 3rd when it all started with just fever for few hours and the on 3rd day i lost my smell and taste completely, Tea and water there was not much difference in taste, i could not taste the toothpaste nor the smell of sanitizer nor the mysore sandal soap not even a bit. Since many are in denial to accept they got covid, these are some of the symptoms and along with it severe fatigue and body pain with occasional fever for some. There was no fever after 1st day. I was taking prophylaxis medication based on Doctor’s suggestion and all was normal till end of 5th day when i was hardly able to sit and there was breathing issues, immediately i was advised to take CT Chest scan and Blood tests (CRP, CBC and D-Dimer Test). Note the symptoms change from person to person. On the 5th day from 1st sign of symptom, i took CT scan (CT scan is not required for all only based on doctor suggestion for those who have symptoms of cough, fever or breathlessness. If taken immediately after  2nd or 3rd day of symptoms, the purpose of CT scan will be defeated). So note down the 1st day when u get symptoms most likely light fever for few hours 99.5 to 100.5F. Remember some people fever will be just 1 day for others it will be 2-3 days. Its not standard and changes from people to people.

On taking CT scan the spread was seen 60%. I was given Anti-inflamatory drugs (steroids to reduce the inflammation) and Anti-Coagulant drugs (to avoid blood clots) on doctor advise. The coughs on morning were very severe sometimes the coughs went for 5-6 hours continuously.  Same situation prevailed for 6th and 7th day with coughs and no fever. The C-Reactive Protein (CRP blood test) showed 22 on the 6th day.

Day 8-13 crucial days – cytokine storm

I was hoping that fever should not come back but worst fears came true on 8th day and i got Hyper Immune – cytokine storm and fever (not continuous) started from Day 8 and lasted 5 days till Day 13 and it was in these days the CRP values increased to 55 and then close to 100 on the 13th day. I was completely on AC keeping my body cool and was drinking water multiple times to keep myself hydrated. Oxygen levels were fluctuating between 88 to 93 without any support. I was sleeping with proning which helped a lot. With oxygen concentrator support at times for 3-4 days the SpO2 levels was maintained at 97.  On 14th day, the CRP levels came down to 26 after peaking close to 100. Once fever stopped the oxygen levels stabilized from Day 16/17 at 97 levels without any support. The high ldh values in blood test showed that there was tissue damage in lungs during the cytokine storm.

Post recovery period (3 weeks)

Loss of sleep with sleep coming at 1 or 2.00 am or you wake up at 4.00 am assuming 6.00 am, this happened to me many days, confusion, loss of concentration, head aches are common, fatigue you could barely walk for next 5 days.  Complete rest is required with continuing low doses steroids to avoid fibrosis for few more days and then tamper off. Since i had high CRP values i was advised to take Asprin in the recovery period based on doctor advise to avoid blood clots in recovery period. I was in complete rest for these 3 weeks. After three weeks going into shop i could not recollect my credit card pin number for few minutes inspite of trying hard. Entire back from neck had skin rashes red in color and then the head aches are terrible ones which comes occasionally.

After 42 days, i have joined office today, the experience in isolated room and psychological trauma still haunts. If someone comes close to you get that fear. Covid for those who become hyper-immune and get cytokine storm are very vulnerable if inflammation is not reduced by giving appropriate drugs at appropriate time.

Corona is not a another flu. Its dangerous once u get covid pneumonia or if u become hyper immune particularly with co-morbidity it complicates even more. Get vaccinated and at same time dont spend too much time in the crowded hospitals. Try to get vaccinated in places where there is less crowd and good ventilation.

Its Day 40, the taste and smell is yet to return and occasionally i can taste. So when u lose taste, try to eat food hot, its very tough to eat food which is not hot and even at hot you feel its too salty all the foods.

I. Massive Convergence with LWD in the interiors and westerly winds  seen in kerala

So far we have seen lot of action in South TN districts in the past few days and now the convergence shifts to North Interior TN and Mysore – Bangalore region with massive instability seen in the interiors.

In Kerala with the low forming in Arabia Sea, the part of moisture filled westerly winds are pushed into Kerala ghats so for the 1st time this season, the ghat areas of kerala can see heavy rains today.

II. Rainfall areas on Tuesday

  1. 90% probability of rains at widespread places in Kanyakumari district, Valparai belt in Coimbatore and Nilgiris (particularly Gudalur-Pandalur belt since westerlies is seen).
  2. 60% probability of rains at some places in Thoothukudi, , Dindigul, Tiruvannamalai, Ranipet, Vellore, Erode, Krishnagiri, Dharmapuri, Tirupattur, Thenkasi, Virudhunagar, Nellai and Theni districts
  3. 50 % probability of rains in isolated places in Salem, Namakkal, Ramanthapuram, Delta belt of Tiruvarur and Thanjavur belt.

III. Heavy Rainfall of above 65 mm

  1. Hit or miss in Bangalore belt as heavy rainfall is shown by 50% of leading models and balance 50% models show light rains. If it happens, the Bangalore will see its 1st heavy rainfall of the season at many places of its urban area.
  2. Nilgiris belt at isolated places particularly in Gudalur, Pandalur, Devala belt and Kanyakumari region and Valparai belt.
  3. Kerala will see widespread rains with westerlies seen Idukki, Mallapuram, Kozhikode, Kannur, Kasargode (K3) and Wayanad will be back in action.
  4. In Rayalseema there is chance of heavy rains in Chittor and Anantpur districts.

IV. 24hrs rainfall ending 10.05.2021

Meanwhile Kanykumari has been getting daily rains but yesterday evening it was so widespread almost all the places got rains and of which Thiruvattur topped the charts with 75 mm rainfall.

V. Rainfall so far in Tamil Nadu in the Pre-monsoon Season

Even after these rains, still Tamil Nadu is -25% for the season and strangely the north east interiors districts such as Kallakurchi, Villupuram and Tiruvannamalai have all missed the rains. And north central coastal districts such as Cuddalore, Karaikkal, Puducherry have performed badly too.  In central interiors the unlucky Karur, Ariyalur, Trichy and nearby Thanjavur and Pudukottai has performed badly.

Erode, Nilgirs, Theni, Thenkasi, Virudhunagar have got above normal rains with Erode is excess zone.

Coming week rainfall should reduce the -25% deficit rainfall in TN.

VI. Future massive Sangu Chakkaram in Arabian Sea

With MJO coming into our basin and expected to bring itself rains at the same time it always triggers a Spinner with favorable SST, TCHP and also takes the moisture filled cross equatorial flow.  The spinner aka Sangu Chakkaram aka future cyclone is a monster in making in Arabian Sea. The path needs to be seen with wide range of landfall area seen from Oman, Pakistan and Gujarat.

With the cyclone taking most of the cross equatorial winds in Arabian sea, the other arm of monsoon in Bay of Bengal carries less moisture and strength so the onset of monsoon in Andaman and Nicobar island between 16-20th May might be delayed or might be a weak onset with very less surge seen from the westerly bursts.

There is one good news with the cyclone in Arabian Sea in Mid-May, this makes the offshore winds weak in the Arabian there by saving Tamil Nadu from heat waves though there will be some rise in Temp, it wont be as bad as ones with strong off shore winds. Till now in 1st 10 days of Summer we have escaped Heatwaves and have had blessed summer.

Share and Enjoy !

0Shares
0

North East Monsoon 2020 – Tamil Nadu Weatherman Special

October 11, 2020

North East Monsoon will be here soon, its the lifeline of Tamil Nadu. So lets see whats in store for us this year. Many would have already seen outputs from other weather bloggers who have already given very good articles on the upcoming NEM. As I am getting old, it is getting very tough to put value added posts, apart from the ones already putup by the young energetic weather bloggers like Hemachander, Jaswanth Weatherman, Rainperal Marimuthu, Veeraraghavan, Sri Hari, T.Raja, Samuel Weather, Monsoon of Chennai, Gopinath, Kabir etc, I can go on and on. So I am not going to take class what is North East Monsoon and bore you guys, but will giving a different perspective.  The simple questions of common man.

1. Which places get North East Monsoon rainfall in India and Tamil Nadu ? Why it is ignored in our Country and why it is crucial to Tamil Nadu.

2. North East Monsoon Rainfall wrt Lanina, neutral IOD and Negative IOD ?

3. Why MJO is important for NEM Rains irrespective of the Elnino or Lanina or IOD  and How 2020 NEM is going to be ?

4. Will delayed NEM onset give less rains ?

5. Why North East Monsoon Prediction is difficult and is 50% based on guess ?

1. Which places get North East Monsoon rainfall in India and Tamil Nadu

Only one state (Tamil Nadu) is dependent on North East monsoon with nearly 50% rains of its annual quota. This is one reason this North East Monsoon is not given much importance and ignored. The rains are mostly associated with Low Pressure Systems & Cyclonic storms. Its the season where each Low Pressure captures headline space in Tamil Nadu, Pa groups are in holiday mode already due to Covid-19, they wont be too keen this time to see Collector announcement. Govt will be on their toes with elections nearing and they dont want to take any chances. Farmers keenly watching, it can go on….No where else in our country monsoon rains will be watched so closely than in Tamil Nadu.

In Tamil Nadu, coastal districts like Chennai to Thoothukudi are dependency on NEM varies from 65% to 85%. So in these places if North East Monsoon fails we automatically go into drought zone. And you can see the rainfall reduces as we go inland into Tamil Nadu. Krishnagiri, Dharmapuri, Tirupattur gets the least rainfall during North East Monsoon in the State. So a person in North West Interior Tamil Nadu should not compare their rainfall with that of coastal belt. Most of the rains in interiors happen during October month when transition period is on and after that they depend on rains from cyclone which move from Bay of Bengal via Gulf of Mannar or Comorin Sea towards Arabian Sea.

Only two districts are exception in Tamil Nadu who get balanced rains from NEM and SWM and they are Kanyakumari and Tiruvannamalai. All coastal districts are highly dependent on NEM while the two districts in western ghats Kovai and Nilgiris are dependent on SWM.

2. North East Monsoon Rainfall wrt Lanina, neutral IOD and Negative IOD ?

Elnino or Lanina or Neutral ?

I dont want to go too much into Elnino and Lanina or Neutral. The images will explain how it affects the walker cell and in turn affects Global Climate. When the sea surface temperature near the dateline to Peru in Pacific Ocean is warmer than normal we call it as Elnino and when it is colder than normal we call it as Lanina and when it is normal, we call it as ENSO Neural. We follow the ONI Index to determine whether it is Elnino or La-nina or Neutral and how strong the event is – NOAA Elnino / Lanina years . If the Nino 3.4 index three month average crosses above +0.5 we call it as Elnino year and if it is below 0.5 we call it as Lanina. We can see 2015, 1997, 1982 (red color) are strong elnino events in history. The blue ones indicate Lanina years. Elnino happens once in 4-5 years like 2009, 2006, 2002 these are called moderate elnino years. It has nothing to do with Global Warming and its part of climate cycle and have been there for 100s of years. Lanina is opposite and cooling of the nino 3.4 region and it is announced if the sea surface temp anomaly in the nino 3.4 region dips below – 0.5 we call it as Lanina.

Lanina is good for SW monsoon historically and bad for North East Monsoon (note 2016 was an Lanina year and Tamil Nadu got worst North East Monsoon Rainfall in history). The opposite Elnino year are statistically good for Tamil Nadu North East Monsoon rainfall and eg.2015 was an Elnino year and we got massive rains and traditionally SWM rainfall are poor across the country during a Elnino year.

As you can see we are Lanina zone during this NEM 2020. This alone does not decide NEM the correlation to Elnino/Lanina is 0.4. We have seen very good rains in Lanina year too.

The forecasts for ENSO region indicate that for rest of the North East Monsoon, the ENSO will be in Lanina state.

Positive IOD – Warm water to shift towards Africa and this sets up a temperature difference across the tropical Indian Ocean with cooler than normal water in the east near Indonesia and warmer than normal water in the west near Africa.

Negative IOD – Warmer waters to concentrate near Indonesia -Australia. This sets up warmer than normal water in the east (Indonesia) and cooler than normal water in the west (Africa). The images will explain itself.

Lets see the model forecast for IOD, as you can see IOD is going to be in borderline Neutral to Negative zone and this will help in pick up lot of convection in Bay of Bengal. Coupled with Lanina, we are going to see lots of Low Pressure this NEM even in December.

Lets see some of the comparable years with Lanina in Pacific and Neutral to Weak Negative IOD in Indian Ocean and the rainfall in NEM. Years from transition from Nino to Lanina

2008 – TN strong excess with 560 mm and Chennai above normal with 950 mm rainfall
2005 – TN rainfall massive excess 780 mm and Chennai Massive excess with 2100 mm rainfall
1983 – TN rainfall excess with 600 mm and Chennai above normal with 900 mm rainfall
1970 – TN normal rains with 420 mm and Chennai below normal with 630 mm rainfall
1964 – TN normal rains with 480 mm and Chennai above normal with 900 mm rainfall

This combo is not a bad combo, infact with little luck we can even get very good rainfall. Lets hope this combo clicks and we are in for a treat.

3. Madden Julian Oscillation (MJO) – the NEM driver

MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the along the tropics and returns to its initial starting point on a average of 30 to 60 days. There can be multiple MJO events within a season, and so the MJO is best described as intraseasonal tropical climate variability.

The MJO consists of two parts, or phases: one is the enhanced rainfall (convective) phase and the other is the suppressed rainfall phase. Strong MJO activity often dissects into halves: one half within the enhanced convective phase and the other half in the suppressed convective phase. These two phases produce opposite changes in clouds and rainfall. The location of the convective phases are often grouped into geographically based on stages from number 1-8 (refer image)

In the suppressed phase, winds converge at the top of the atmosphere, forcing air to sink and, later, to diverge at the surface and s air sinks from high altitudes, it warms and dries, which suppresses rainfall. So MJO suppressed phase can bring dry weather.

In the convective phase, winds at the surface converge, and air is pushed up throughout the atmosphere. At the top of the atmosphere, the winds reverse and Such rising air motion in the atmosphere tends to increase condensation and rainfall. MJO also helps in tropical cyclonegenesis preferentially during the convective phases.

Example of how MJO is everything for NEM rainfall
—————–
2015 saw prolonged MJO presence in our basin and Tamil Nadu / NEM ended in massive positive side.

In 2016, MJO was completely absent in our Basin and NEM went for a toss with worst ever rainfall.

Right now MJO is in Maritime Continent and sending pulse after pulse via Indo-China into Andaman Sea and not allowing the SWM to withdraw from remaining areas of Andhra /Odisha /East India. This is not allowing the monsoon axis /trough to dip down and westerlies continue to persist thereby delaying the onset of North East Monsoon.

It is been a while since we had prolonged MJO presence in November in our Basin, though weak in amplitude, MJO is coming into our Basin in 2020 by 1/2nd Week of November. The presence of MJO is enough for enhanced rains and not be in higher amplitude.

What is that we can conclude from the above, there is one key point to be noted  be it any years, if November month sees good rains very rarely that North Monsoon has failed. “A good November always ended the monsoon in normal to excess category”. And with MJO seen active in November, this year we can expect Normal to above normal rains for Tamil Nadu (450-470 mm of rainfall) + or – 10% around these figure.

4. Will delayed NEM onset give less rains ?

There is always a opinion that onset on time would result in good rains and delayed onset means less rains. I have taken the last 30 year analysis with Tamil Nadu and Chennai City Co-relation with respect to onset. Lets see the results

You can see from the above table, on time onset has been a curse for Chennai resulting in 8 years in failure.  While for both Tamil Nadu and Chennai if the onset has happened before October 15, most of the time it has ended in excess.  Even on 3 years on delayed monsoon onset, we have ended in excess with the last great flood on 2015 was also a delayed onset. There is no fool proof correlation and one cant be sure to predict monsoon with onset dates.

We already saw 1st week October Low Pressure giving rains to Andhra/Odisha, this came from from Pacific too. The present Depression came as pulse from Pacific and expected to cross India peninsula at Andhra Coast and move into Arabian Sea.  Next week another pulse is moving into Andaman sea, while entering Andaman Sea itself the low is above the latitude of Chennai and so this too wont give much rains to Tamil Nadu. We are yet to even see the pseudo easterlies and so monsoon onset is going to be delayed till month end.

5. Why North East Monsoon Prediction is difficult and 50% is based on guess ?

As you all are well aware that North East Monsoon has one small corelation with Elnino, most of the Elnino years Tamil Nadu has got above normal rains. Almost in all the recent Elnino years both Tamil Nadu and Chennai has seen above normal rains. Other than that there is very little corelation. In positive IOD years we see very active Arabian Sea while in negative IOD years we see very active Bay of Bengal. The NEM rains are dependent on low pressures and cyclonic systems. The time period is short if one cyclone misses and moves away from Tamil Nadu, there will be break in rains for 4-5 days to week since next system should develop.  Eg 2013 we missed 3-4 cyclones and all went to Andhra and our NEM went for a toss. At the same time, if one good Depression or low pressure gets stuck in Gulf of Mannar and gives 4-5 days of rains we nearly can get 30-40% of the total NEM rains.  Eg, in 2008 we all lost hope of monsoon, almost first 20 days of November was dry, it was peak monsoon days and then in the last week came Cyclone Nisha and it dumped so much rains we jumped from deficit to excess in that 5-6 days of rains. Orathanadu got 1200 mm rains in 4 days which is more than 500 mm of its total NEM quota.  One good system is all what required for monsoon to swing. And no one predict these extremes months in advance. So North East Monsoon be it the official agency or the weather bloggers incl me, its always 50% based on some intuitions / guesses. The 2008 Nisha is one dream rain filled system which bloggers dream till now.

Hope some of the basic questions of NEM are answered. Lets hope November rocks this monsoon and active pacific is seen in December too and many low pulses will be sent into Bay of Bengal in December too and in December systems move in low latitude, though models show bleak picture, my 50% of the guess says this monsoon will be Good for Tamil Nadu particularly for coastal Tamil Nadu. Further with Lanina mode, we can see monsoon extend well into late December.

Just waiting eagerly for the 1st easterly wave to hit Tamil Nadu, that sight itself is special.

Share and Enjoy !

0Shares
0