Sincere apologies for keeping you all waiting. Hopefully the good news ahead is worth the wait. Pretty much you would have all seen the colorful Nippon paint charts from all the bloggers, my charts wont be different too. The upcoming event is more or less a confirmed event so most of the posts will be similar ones. Enjoy the rains from Tomorrow (morning or by night latest) till 18/19th November with some breaks. Rains peak time is late nights to mornings. We can see rains in day time too at times, as the convergence is bit strong and persisting this time.
1. Exciting days ahead for Tamil Nadu, particularly the entire coast from Chennai to Kanyakumari
The last time i was so excited of heavy rainfall event was in November 1st week 2017 and we did get treat of extended rainfall in that spell with a prolonged spell from 31st October to 7th November. This time too rainfall starts from 11th and picks pace the next day on 12th November and extends upto 19th November with varying intensity of rainfall in between.
Unlike the previous two spells where the rainfall was concentrated in North TN (KTC) and West TN, this time Pondy to Delta belt will be getting good rains too. Right from Kavali in South AP to Kanyakumari the rains will be widespread. The above charts shows the accumulation and spread of rains. Dont convert the rainfall shown in the above charts to real values as the rainfall quantum will always be much much higher sides than the models quantum. There has been tight agreement among the models for the upcoming one week. Not only ECMWF, GFS, UKMET, ICON, GEM, JMA, BOM, KMA, all leading models are so unanimous in active phase of rains and out of the next one week spell, one or two days may even end up as a surprise event.
2. MJO the Kingmaker will move into Phase 2 after Diwali. Enhanced Rains – back to back Easterly waves are expected.
We waited for so long for the entry of MJO into our basin in next few days will and is not going anywhere and expected to stay in Phase 2 till mid-november around 24th. Due to which, next two weeks will see enhanced rainfall activity in Tamil Nadu and this enhanced activity can further extend to December 1st week too depending upon progression of MJO.
Even after MJO goes into Phase 4/5, we will not be under suppression and so we can see enhanced rainfall with breaks till Mid-December, if all goes well and even some chakkarams possible while crossing our basin in last week of November or 1st week of December.
4. Inverted Trough associated Easterly Wave on November 11-13
The Ex Typhoon Goni which devastated Philippines sent a pulse (push of moisture) into our Basin (Bay of Bengal) and it slowly developed into an easterly wave and will be in the form of Inverted trough tomorrow close to Tamil Nadu coast with an Upper Air Circulation below Sri Lanka. The rains will be limited to coast and South TN in the first one or two days that is between 11-13. Delta belt will be the 1st to get rains tomorrow from this spell followed by KTC and South TN belts.
Heavy Rainfall alert – On November 12 going into 13th, the winds perfectly converge over KTCC (Chennai and surrounding region), Pondy, Cuddalore, Delta coast, Ramanathapuram and Thoothukudi will all get heavy rains.
Eg: Inverted trough
4. What will happen on Diwali Day ? Chennai and KTC rains to start on 11th and very heavy rains expected on 12th November
For easy reference let me include the meteogram for Chennai and show the rainy days ahead for Chennai City. We can see the rains starts on 11th (if not at morning atleast by night) and then picks up pace on 12th. There is one good news though there is reduction of rainfall for one day on Diwali and then the rains picks up again from 15th. There will be some rains on 14th on and off and early morning too. But compared to other days the rains on Diwali day will be lesser one.
5. After Diwali the rains will further intensify till November 19.
And then after Diwali the rainfall intensity further is expected to increase on 15-18, some some super spells (good divergence indirectly seen from 200 hpa wind charts) seen a can be expected in that period particularly on 15-16th November along entire coastal areas, including Delta, Thoothukudi and South TN areas. With MJO in Phase I/2, the interior parts of TN too will get rains atleast from 13th November.
6. Scorecard of NEM as on 10.11.2020
Tamil Nadu – 140 mm (Normal Target is 450 mm)
Chennai – 370 mm (Normal Target is 850 mm)
Once the rains starts, i will update the now casting (in FB / Twitter page).