The day we have waited has arrived. Onset bands for KTC & Rains to continue in STN

Onset of North East Monsoon & Synoptic Analysis

When you wake up today morning, the much awaited North East Monsoon rain bands would have touched Chennai coast from NE and with an Upper Air Circulation seen close to TN coast, the bands will be keep on coming for next two days with morning being peak time for rains with short brisk spells continuing with breaks. The below wind pattern should help you to understand the onset pattern this year along with the synoptic systems in Bay, Arabian Sea, Indian Peninsula and West Pacific.

KTC falls in Dryline – Wetline winds converging zone

Not only that there is a dryline and wetline winds meeting is taking place along with the onset. These type of rains are totally un-predictable, if we fall over the dry area influence we will miss the rains, if we meet exactly over the converging area, there will semma rains. So this adds to the excitement of the onset. Lets hope we fall in the moist converging side and have a good start to monsoon.

Lets see where the rains will happen in Tamil Nadu in the next two days

The rains will be slow on and off to start with as the UAC is little far away in Sea from TN coast. But on 29th October is moving much closer, so an increased rainfall activity can been seen on 29th. On 28th the rains can bee seen in North TN coast and slowly extending down to Central TN coastal belts of Delta. Chennai, Tiruvallur, Villupuram, Pondy will all get onset 1st in the state. Remember in most cases, night to mornings rains will be along coast, as we move into day time the winds will move into Land giving sharp showers to districts which are slightly interior from coast.

Down south the scenario its completely different, they are far away from the dryline zone, a trough from Arabian sea extends to South TN and the winds from the UAC in Bay create LWD kind of scenario with an temp ciruclation seen in Lakshwadeep Sea. Kanyakumari, Tirunelveli, Tenkasi, Virudhunagar, Thoothukudi, Theni and Madurai all fall in this zone.

Waterspout seen in Ramanathapuram last week, which is a very rare event in Tamil Nadu

June 13, 2021

1. Tornado

A tornado is a violently rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as twisters. Tornadoes come in many shapes and sizes, but they are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 180 km/h. Most extreme tornadoes can attain wind speeds of more than 480 km/h. The scale of intensity for Tornado are EF0, EF1..EF5 with EF5 being deadly with winds over 320 km/hr. The wind scales of Tornado are given below –

2. Tornado in India

The areas of occurrence of tornadoes in India are given in fig below. About 72% of the reported tornadoes in India have occurred in northeast India and Bangladesh.

About 76% of the tornadoes in India occur during March to May, the most favored month being April (see fig below) More number of tornadoes have occurred in the afternoon and evening. 72% of tornadoes are associated with “KalBaishakhi”.

3. F-3 Tornado in Odisha on March, 2009 – Strongest ever Tornado in India

During noon of 31st March 2009, A Tornado ravaged Odisha, a high winds damaged the villages in a narrow track of about 600 metres wide upto 6 kilometers long from the origin. The intensity of the tornado increased gradually and was maximum over Baghabuda. The tornado also passed over the water bodies like ponds in the villages, as fishes weighing 1-2 kg were found scattered. The photo of the the Tornado was put up in Odisha Diary.

Odisha March 2009 EF3 category Tornado which killed 20 people – https://www.youtube.com/watch?v=Caq08IAhNP0

Recent Tornado on March 25,2021 in West Bengal – https://www.youtube.com/watch?v=xFckYJ5PKUw and https://www.youtube.com/watch?v=5vkdMinMg_U

4. Tornado vs Waterspout

The main distinction between a tornado and a waterspout is that a tornado occurs over land while a waterspout occurs over water. Both have a rapid rotation of air and hence they are both classified as tornadoes, so a waterspout being a type of tornado. There is a difference between the two that is the waterspout tends to be weaker. The force of friction is weaker over water thus there is less air available to be drawn into the circulation. An exception to a waterspout tending to be weaker is when a mesocyclonic tornado over land moves over water such as over a lake or sea.

5. Waterspouts fall into two categories: Fair weather waterspouts & Tornadic waterspouts

Waterspouts don’t need a powerful storm to create them. They seem to thrive on the warm, moist air above water, especially when there is little wind shear, and when air above the clouds is cooler than averages.

Tornadic waterspouts are tornadoes that form over water or move from land to water. They have the same characteristics as a land tornado. They are associated with severe thunderstorms and are often accompanied by high winds and seas, large hails and frequent dangerous lightning.

Fair weather waterspouts usually form along the dark flat base of a line of developing cumulus clouds. This type of waterspout is generally not associated with thunderstorms. While tornadic waterspouts develop downward in a thunderstorm, a fair weather waterspout develops on the surface of the water and works its way upward. By the time the funnel is visible, a fair weather waterspout is near maturity. Fair weather waterspouts form in light wind conditions so they normally move very little.

6. Tornados in Tamil Nadu

September 12, 2013 in Chennai (Uthandi) – It was in Uthandi in Chennai Robert Gagarin of Uthandi happened to be on the rooftop of his house in time to catch a glimpse of a tornado in the distance. He had taken photo of the same and was published in newspapers. IMD chennai, found a tornado vortex signature (TVS) on the Chennai Doppler radar on September 12, 2013. It was absolute a rare rare rare event.

Uthandi (Chennai) Tornado in September 2013

7. Waterspouts in Tamil Nadu

The morning on 27th October saw intense cloud bands (though not big) move into sea around 8.30 am in north Chennai sea side and then people spotted a funnel cloud (which does not touch land or water) and slowly the leg of the cloud climbed down and touched the water. The video clearly shows the leg of the waterspout visible in the sea. Yes it was Waterspout and since a dense clouds was seen during the period, i would say it as a Tornadic waterspout and this like the 2013 Tornado, it was a rare rare event.

Ennore, Chennai Water Spout in October 2017

Mr.S.Dhanasekar and my friend Karthic Sreenivasan has captured the video of the waterspout in Ennorre and sent them to me. The video link is given below

8. Recent Waterspout in Ramanathapuram and others in South India in last 5 years

On 4th June, 2021, a rare Water Spout was captured by Mohamed Jasir M in Periyapattinam in Ramanathapuram. The video is also available in the links below.

Water Spout in Ramanathapuram in June 2021

4th June 2021 in Ramanathapuram – https://www.youtube.com/watch?v=IJkm97aAlEM and https://www.youtube.com/watch?v=YKoejobpmvE

25th November 2020 at OMR, Chennai – https://www.youtube.com/watch?v=TBBMsuMyB1Y

22nd November 2018 at ECR, Chennai – https://www.youtube.com/watch?v=GrxU_vOF-54

27th October 2017 at Ennore, Chennai – https://www.youtube.com/watch?v=vejPxR_Wh2g

26th November 2017 at Trivandrum – https://www.youtube.com/watch?v=-OPVk6p2fXw

Recently even in last week in Goa, two Water Spouts were seen.

8th June 2021 at Goa – https://www.youtube.com/watch?v=h1cUlL0f38Q

7th June 2021 at Goa – https://www.youtube.com/watch?v=_Q3kszYfvJ4

9. What should a fisherman do if a waterspout is sighted ?

Simple, never try to drive your boat through a waterspout. Although waterspouts are usually weaker than tornadoes, they can still produce significant damage to you and your boat.

10. Dust Devils are mistaken as Tornado by People and Media

Dust devils form in an upward motion from the ground to the sky. They are short-lived whirlwinds that are mainly harmless. Dust devils form when hot air at the surface begins to rise rapidly with much cooler air above it and higher up into the atmosphere. The hot air then stretches and causes a spinning motion much like a tornado. They are short-lived because cold air eventually gets pulled in and dissipates the dust devil. Dust devils become visible when they form over barren terrain, tarmac, and desert-like terrain. For dust devils to form, you usually need plenty of sunshine, little to no wind, and a very cool atmosphere above. Dust Devils will not have any funnel clouds and there will be no connection from the clouds to land.

We would have seen Dust Devils in open grounds in schools and playgrounds often Eg of dust devil in Tamil Nadu – https://www.youtube.com/watch?v=F_XcoBbVprk and https://www.youtube.com/watch?v=z0sUkM1mhr4

The day we have waited has arrived. Onset bands for KTC & Rains to continue in STN

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