Burevi – Caught between the Ridges will move into area of high Shear in GoM will weaken and stall

December 2, 2020
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Why Burevi is taking a South West Dip and goes down

Nivar oda brother “Burevi” moves W-NW for few more hours under the Pacific Ridge and then the grip of the pacific ridge weakens over Burevi. Then it stall over Gulf of Mannar for a day and then the steering ridge from West (Arabian Ridge) steers the system W-SW and makes it move into Arabian as a very weakened system most probably a Depression or a well marked low.

In the above image, we can see why Burevi moves down (W-SW) because of the under steering of the ridge from the west.

Rare cyclone for  Sri Lanka

Even during Nivar, i had mentioned that very few cyclones have made landfall as cyclone over Sri Lanka, not sure what may be the reason, may be the position of the pacific ridge (most likely reason) or the cyclone fear the rugged terrains  (just kidding).  Would you believe if i said the last three cyclones which made landfall in Sri Lanka are in 1978, 1992 and 2000. So after 20 years a Cyclone is moving into  Sri Lanka as a Cyclone.

1st Landfall and Winds

The cyclone Burvei has already started weakening a bit and as the cyclone moves into Sri Lanka it will weaken further and make landfall evening to tonight close to Trincomalle. The area from Trincomalle to northern regions of Sri Lanka till Jaffna will witness winds of 60-70 km/hr tt

2nd landfall, stalling (due to ridge change) and winds in South India

After crossing it moves into Rameswaram belt in Gulf of Mannar later tomorrow morning. Ramanthapuram to Rameshwaram island to Pamban and the near by areas will witness winds of around 50-60 km/hr. Particularly the winds will be high in Pamban to Rameswaram belt compared to other areas. The Cyclone is weaken a lot by now and will become Deep Depression in Gulf Mannar after which it stays  in same location for almost a day because it is not in the control of pacific ridge anymore and shift in steering ridge happens. Then on 4th morning it will further weaken into Depression and will cross coast between Kanyakumari and Pamban close to border areas of Ramanthapuram – Thoothukudi district (plus or minus some kms) as a weakened one with wind speeds of 30 km/hr on 4th morning to noon.

So wind threat of 50-60 km/hr is mostly in the areas Tondi, Ramanthapuram, Pamban to Rameshwaram belt.

South Kerala and Kanyakumari will also see moderate wind speeds of 30 km/hr. Manjolai in Nellai and Kodaikanal in Dindigul will see gusty winds being higher in elevation and with east opening valley.

Stalling for day and Very Heavy to extreme rains in South and South West Tamil Nadu

Because of the ridge change, weakening and caught in no-mans land over Gulf of Mannar on entire 3rd December, the weakened Burevi stays in Gulf of Mannar (GoM) over a Day and as a result Very Heavy Rains will be in Southern and South western districts such as Ramanathapuram, Pudukottai, Sivagangai, Madurai Theni, Kanyakumari, Thenkasi, Virudhunagar, Thoothukudi, Tirunelveli, Dindigul districts. Coonoor, Kodaikanal, Papanasam and Manjolai areas needs closer watch for very heavy to extreme rains as the valley opens from east and are locked valleys. from 3-5th December Delta districts (Nagai, Thanjavur, Tiruvarur) will also get very heavy rains from tonight – 5th December.

As it stalls over GoM for a day, it will send bands after bands up north upto Chennai and Kancheepuram, Tiruvallur, Chennagalpet (KTC belt) and cts will also get rains from tonight for next 3 days, even Pondy, and Cuddalore will get good spells. Even interiors such as Ariyalur, Permambalur, Trichy, Karur, Tiruppur will all get good rains. Salem, Tiruvannamalai, Namakkal, Villupuram, Vellore, Kallakuruchi will also get good rains atleast for 1-2 days.

Western districts such as Nilgiris, Coimbatore and Tiruppur will also get good rains for a day or two, though they are not capture by the models.  3-6 th December will the days for chance of rains.

Only area to get Moderate rains will be in districts very far away in Erode, Dharmapuri, Krishnagiri and Tirupattur.

Storm Surge

There will be some storm surge in areas in Ramanthapuram and Thoothukudi coast where some areas are on par with mean sea level and even below mean sea level.

Overall conclusion – Weakened Cyclone – Heavy rains are threat in South Tamil Nadu, winds are not a problem.

The above is done based on personal interpretation of charts and also based on experience. Follow the official agency and disaster management for any precautions.

Tomorrow a special post on neglected Historic South Tamil Nadu Cyclones.

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Another very good day for Thunderstorms in Tamil Nadu

June 29, 2020

Thunderstorms to continue in Tamil Nadu

The dream days for Tamil Nadu thunderstorms has been continuing, today too pop-up has been seen at many districts. Earlier in the day, Ramanathapuram got surprise rains.  The UAC in South Andhra has slightly moved up, has become  elongated and has merged with east-west shear zone with two UAC in either side of the zone.

Reason for Rains

For rains in Tamil Nadu in leeward side, heat always matters irrespective or UAC or whatever. Without heat no rains will be seen in Tamil Nadu leeward side regions most of the times. In Break monsoon period like now, an UAC in southern Bay of Bengal always forms, but it wont give rains like north east monsoon, instead  an UAC presence nearby can enhance the longevity of the thunderstorms with supportive atmospheric conditions.

How long will this dream Thunderstorms last in Tamil Nadu leeward side

The monsoon winds in Arabian sea are going to get activated from July 3rd with a monsoon low moving into land via Chattisgarh—>Maharashashtra/Madhaya Pradesh  –> Gujarat. This will make wind unfavorable for convergence in Tamil Nadu Veppa Salanam rains, though there will be some thunderstorms we can expect them to be widepread ones.

KTC Rains to continue till 2nd July

With KTC having convex shoreline, we always have advantage with respect to convergence of winds when sea breeze enters after a hot day, the rains may happen in northern suburbs or southern suburbs or even right over like yesterday.  So next 2 days (till 2nd July) and today we have chance for rains in KTC belt. As usual, which place will get rains is decided by luck.

Tomorrow massive rains has been picked by models for KTC zone, lets wait and see if they retain the rains and change it to a lesser quantum.

Rainfall in Chennai and KTC (100 kms zone) on 29.06.2020

in mm (min 5 mm)

Sholingur – 58
Uthukottai – 43
Tiruttani PTO – 37
Kaveripakkam – 33
Madhavaram – 36
RK Pet – 35
Kolapakkam – 21
Walajah – 18
Nungambakkam – 17
Gumdipoondi – 17
Mugalivakkam – 16
Tiruttani – 14
Anna University – 15
Thiruvottiyur – 15
Taramani – 11
Perungudi – 10
Madurantagam – 7
KK Nagar – 6
Ponneri – 6
Meenambakkam – 6
Alandur – 6
Shenoy Nagar – 6
Ennore – 5
Shollinganallur – 5
DGP Office Marina – 5

 

Due to time constraints, rainfall data was not updated in the respective page. It will be done by tonight.

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Monsoon clouds cross the Ghats to Kovai, 2nd spell for South Chennai and Squall in Delta

July 3, 2020

Synoptic Analysis

Monsoon winds has been very active from yesterday and will continue to be so for next few days which means active days for Kerala, Karnataka, Goa, South Gujarat and Maharashtra side facing Arabian sea.

In the other side, in leeward regions it will windy at the same time we can see fast moving rains. Because of active monsoon, we cant see widespread rains like what we saw in the last week during the break monsoon.

Summary of Today

  1. For the 1st time, clouds have crossed ghats and have reached Coimbatore – Erode belt
  2. Rains in Erode, Salem, Namakkal, Coimbatore, Pudukottai, Delta belt (Thanjavur-Nagai-Tiruvarur belt)
  3. Chennai (South Chennai) got two spells (rare indeed)
  4. It will be windy due monsoon active, we wont be widespread thunderstorms which we see in break monsoon.
  5. Overall the leeward side will be seeing windy days with fast moving thunderstorms here and there.
  6. Heavy rains in Kerala to continue but nothing fearsome as of now.

Nowcasting (8.00 pm on 03.07.2020)

As you can see rain clouds in dry regions of Covai, Erode, Tiruppur  in West Tamil Nadu and squall is moving in delta. Nagai and Tiruvarur will see high winds followed by fast moving rains.

Next active phase for Thunderstorms in Tamil Nadu

Though we might see daily fast moving rains overall for Tamil Nadu, the next active phase for Thunderstorms will start from July 8/9, 2020 after the UAC over Gujarat moves away and merges with heat.

Chennai

Chennai will continue to see hit or miss fast moving rains like today in the evenings and late nights.



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