TROPICAL SYSTEM FORMATION ALERT
DATE: 15TH DECEMBER 2021 | TIME: 6:30PM BST (+6 GMT)
SUB: TROPICAL DEVELOPMENT | PERIOD: 16-20 DECEMBER 2021
(A) Under the influence of an Upper Air Circulation, a Low Pressure Area could form over Southwest Bay of Bengal by 16-17 December 2021.
It could intensify into a Well Marked LPA & then into a Tropical Depression (≥45kph) between 18-20 December over South West adjoining SE Bay of Bengal. Then it could be more marked by moving ENE/Eastward.
▪️Overall confidence in the forecast is high as a Disturbance is present over South West Bay of Bengal & adjoining areas.
But MJO signal found between Phase 6-7 with 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 (⬇️) over the development area & decent outflow aloft along with potentially favourable parameters. And this combination is likely to sustain during the whole forecast period with a slight deviation.
That’s why, It is having chances 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 VWS, Outflow & other favourable parameters are leading High 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 23/24th 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.
Due to the partial effect of the system, Eastern Sri Lanka could have moderate to heavy rain along with isolated heavy to very heavy rain between 16-19 December 2021.
Andaman island could have heavy to very heavy rain after 20/21st Dec.
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.