Jakarta, domclub Indonesia
—
Tropical Cyclone Seed 91S
observed to be active in the Indian Ocean west of Lampung Province.Bulk alert
rain
increase in the next few days.
The Meteorology, Climatology and Geophysics Agency (BMKG) warns that in the next 24 hours, Tropical Cyclone Seed 91S is expected to move closer to mainland Sumatra.Then in the next 36 to 72 hours, it is predicted that it will turn southwest and away from Sumatra.
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“You need to be aware of the intensity of the rain on December 11, 12 and 16 due to the influence of Tropical Cyclone Seed 91S. However, please remain calm, alert and maintain preparedness because the potential for this cyclone seed to grow into a tropical cyclone on land is in the low category,” said Head of BMKG Teuku Faisal Fathani in his statement, Wednesday (10/12).
According to BMKG, a number of areas in West Sumatra, Bengkulu and Lampung have the potential to experience moderate to heavy rain caused by Tropical Cyclone Seed 91S.
Based on BMKG analysis, Tropical Cyclone Seed 91S formed on December 7 at 07.00 WIB in the Indian Ocean region southwest of Lampung.On Wednesday (10/12) at 07.00 WIB, the circulation center of Tropical Cyclone Seed 91S was detected at around 4.9°S 96.1°E and was still within the TCWC Jakarta Area of Responsibility (AoR).
The maximum wind speed around this low pressure system is around 20 knots or 37 km/hour observed to the north of the system, with a minimum pressure of around 1008 hPa.
Based on observations of satellite imagery, BMKG said convective clouds were observed to tend to be persistent with a slight tendency to increase.
However, the distribution of clouds is said to be still sporadic and extends to the north of the system and has not yet formed an area of deep convection that is symmetrical and circles the center of circulation.
“This indicates that convection around the system is still fluctuating and not fully organized,” said BMKG in its analysis.
Based on wind analysis per layer, in the surface layer up to 850 hPa, the cyclonic circulation pattern appears to expand eastward from the center of the system.
Meanwhile in the 700-500 hPa layer, the circulation pattern is no longer clear and more resembles wind bends, and in the 200 hPa layer there is an area of divergence in the upper layer around the center of circulation, although the relatively weak wind flow is shifted more towards the northeast.
The activity of Tropical Cyclone Seed 91S is also supported by active Equatorial Rossby waves in the area where the system is located and low frequency waves which are spatially to the east of the circulation center.
Apart from that, 91S is also supported by system conditions that are in an area with warm sea surface temperatures (29-30 degrees Celsius), supportive vortices although not too strong, strengthening top layer divergence, and relatively wet and supportive air humidity in each layer around the center of the system.
Apart from Tropical Cyclone Seed 91S, the climatological aspect estimates that high to very high rainfall (200-500 mm/month) will occur in Tapanuli, Nias, Langkat, Mandailing Natal and Labuhan Ratu in December.Furthermore, in January 2026, rainfall tends to decrease and become medium to high category in Central Tapanuli, Langkat, Mandailing Natal, and Padang Lawas.
(lom/dmi)
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