TROPICAL SYSTEM FORMATION (REVISED)
DATE: 16TH DECEMBER 2021 | TIME: 3:00PM BST (+6 GMT)
SUB: TROPICAL DEVELOPMENT | PERIOD: 18-21 DECEMBER 2021
(A) Under the influence of an Upper Air Circulation, a Low Pressure Area could form over Southwest adjoining South East Bay of Bengal by 17-18 December 2021.
It could intensify into a Well Marked LPA & then into a Tropical Depression (≥45kph) between 18-21 December over SE Bay of Bengal. Then it could be more marked by moving ENE/Eastward.
▪️Overall confidence in the forecast has become moderate as the Disturbance remains disorganized & persists over South West adjoining SE Bay of Bengal & neighborhood.
So the expected intensification will be slow but delayed.
MJO signal found between Phase 6-7 with nearly Robust Amplitude(≤2) & it is likely to interfere destructively with low frequency La Nina base state over West Pacific & weaken subsequently.
Which is not supportive for Tropical development over Bay of Bengal.
While, Sea Surface Temperature is favourable(28-30°C) over most parts of Southern Bay of Bengal, which is conductive for the development process.
Wind shear is currently low to moderate (⬇️) over the development area & decent outflow aloft along with potentially favourable parameters. But this combination is likely to depart for a while during middle of forecast period as shear could increase then.
That’s why, we have downgraded the probability into moderate value to intensify into a Depression.
•Max intensity is dependent on the track & future condition of the Bay of Bengal which is skeptical right now.
Thus, The disturbance, Low to moderate VWS, Outflow & other favourable parameters are leading Moderate confidence in this forecast.
(B) A pulse/disturbance could emerge into southern Andaman sea by 18/19 dec.
Due to High shear, it might not intensify.
★See the Graphic to see visually the development areas & rainfall activity associated with the system track.
◾ LANDFALL & MAX INTENSITY:-
Landfall Probability is skeptical right now & there is a possibility of dissipation over open water of South Andaman Sea.
If not, then it might cross southern Thailand by 22nd December as a weakening System.
•The forecast track is based on the present data analysis & may not remain consistent if any change appears in the future data.
Max intensity is skeptical right now & anticipated with the track & future condition of the Bay of Bengal.
As the system will drift away from Sri Lanka, Rainfall probability associated with the system has withdrawn from Sri Lanka.
Andaman island, Sumatra, Southern Thailand & Malaysia could have heavy to very heavy rain between 17-22nd December 2021.
These informations are based on Present conditions & it might be changed somewhere during the entire forecast period.
So, keep eye on the latest update for better information.
Stay connected, Stay alert, Stay Safe.
Bangladesh Weather Observation Team.