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Tropical cyclone BELAL :
Information at 09UTC
Position: 21.2.4°S / 55.8°E
Movement: Southeast 9kt
Max wind averaged over 10min: 65kt
Estimated central pressure: 975 hPa
For further information, please refer to bulletins WTIO21 and WTIO31 to be issued at 12UTC.
In the Mozambique Channel:
A tropical low-pressure system is currently located off the coast of Mozambique. This benefits from
an excellent supply of moisture, thanks to a particularly dynamic monsoon flow converging to the
south-west of the Comoros archipelago. Moving eastwards towards Madagascar, this minimum
should gradually guide this dynamic convergence over the aforementioned archipelago, triggering
unstable weather. Low-level convergence on the polar side is absent. In fact, this is what will
prevent it from continuing its deepening phase, despite good oceanic potential and a good polar
evacuation channel. By the middle of next week, the minimum is expected to approach Madagascar,
undermining the system's main source of energy. The main deterministic models are struggling to
make it cross the Indian Ocean. Prior to this phase, only the French ARO model suggests an
intensification into a tropical depression, or even local gale force winds in the convection linked to
the monsoon flow. The French and American ensemble models suggest a low risk from tomorrow
onwards of deepening into a moderate tropical storm.
The risk of a new tropical storm forming in the Mozambique Channel is low over the next 5
days.
East of 90E:
A large low-pressure circulation is currently present, straddling the Indonesian and Australian area.
It is currently being monitored by the BOM, which predicts a high risk (65%) of it developing into a
tropical storm, east of 90°E.
In the short term, however, the environment seems mixed for its development due to slightly
sheared conditions aloft, but these conditions could improve at the margin during next week and
lead to a phase of intensification, but a priori in the Australian domain, close to the east of our area
of responsibility.
Deterministic models agree on this scenario. However, some ensemble models suggest that the
storm will enter our basin from next Thursday, with a low risk, at the stage of a moderate tropical
storm.
There remains a low risk of a new tropical storm entering the eastern part of the basin from
next Thursday.
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Moderate Tropical Storm BELAL :
Informations at 09:30UTC
Location : 23.9°S / 63.4°E
Motion : east-southeast 6kt
Max wind averaged over 10min : 45kt
Estimated central pressure : 987hPa
For more information, please refer to bulletins WTIO20 and WTIO30 to come at 12UTC.
East of 90E (Tropical storm ANGGREK) :
Moderate tropical storm ANGGREK is currently being tracked by the Australian BOM, and is
located around 10°S/94°E this Wednesday with an analyzed intensity of 45kt. Most models forecast
a slow west-southwestward drift of the system, bringing it more or less close to 90°E. Some
deterministic scenarios (especially GFS) and a fairly significant proportion of EPS members suggest
that this system could end up entering our area of responsibility by early next week, but with a wide
dispersion on the intensity and timing of the crossing of the 90°E meridian. Compared with
yesterday, the overall forecast has increased the likelihood of this system crossing into our area of
responsibility.
There is a moderate risk of tropical storm ANGGREK entering from the east of the basin
from Sunday 21st onwards.
Northeast of the Mascarene archipelago :
From this weekend onwards, a strong surge of monsoon flow could enable the development of one
or more vorticity precursors to the north and northeast of the Mascarene Islands. While convergence
looks set to be excellent on the equatorial side, it could be lacking on the polar side due to the
presence of the remnants of BELAL, which are partly blocking the supply of trade winds to the
south of the MT. For the time being, the preferred scenario is the formation of a fairly wide
monsoon low that will have difficulty concentrating its vorticity. Nevertheless, some deterministic
(including GFS) and ensemblist scenarios manage to deepen a more compact low to tropical storm
stage. Probabilities remain relatively low in the ensemble forecast from now until Monday 22nd.
However, they could increase beyond the next 5 days. Regardless of the risk of cyclogenesis, this
low-pressure area could bring disturbed conditions to Rodrigues early next week.
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看看印度洋（主要是南印度洋的gfs预报信息）
1.初始场状况以及相关分析。
从初始场可以看出，在东西方向上，目前印度洋东西的总热带气旋强度上，西侧大于东侧。而从湿区的规模以及气旋的环流大小来看，东侧的水汽条件好于西侧，环流大小也相应偏大。这可能是由于赤道湿区的震荡（mjo）有关。这个趋势在200hr内（自预报初始场起）不会发生明显变化，推测还和iod+事件或是其退化过程有一定关系。
2.目前存在的气旋…
就6hr预报（可以看做初始场）而言，前面提到的anggrek是唯一目前活跃的超过ts级别的气旋。belal目前已经接近于消散。就水汽状况，belal的水汽绝大多数已经被低纬系统以及西风带倒槽吸走了。未来，其将会沿着东南方向移动，强度继续减弱。
继续来看anggrek的状况。目前其位于东印度洋，iod+环流下沉区。在减少水汽供应的同时，也可以减少其所需要进入的暖湿能量，使得其在较少热量条件下还可以维持一个较好强度。
3.未来展望气旋。
首先是出身于西印度洋的巨大系统。从预报来看，这个系统早已在初始场已有雏形。
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Zone of Disturbed Weather 03-20232024 north of the Mascarene archipelago :
Informations at 0930UTC :
Location : 16.1S / 59.0E
Motion : SE, 6 kt
Max winds over 10min : 30 kt
Central pressure: 1002 hPa
For further information, please refer to bulletins WTIO22 and WTIO30 issued at 12UTC and
following.
East of 90E (ANGGREK):
Tropical storm ANGGREK is currently being monitored by the Australian BOM, which located it at
around 12.1S / 91.5E this Monday at 06UTC. The vast majority of numerical models continue to
forecast a slow westward then southwestward drift of the system, bringing it into our area of
responsibility between Tuesday night and Wednesday evening. Under favorable environmental
conditions, this system should maintain significant intensity over the next few days as it moves into
our basin.
The risk of tropical storm ANGGREK entering our basin from the east becomes moderate on
Tuesday then high from Wednesday onwards.
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