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MFR昨晚热带天气讨论开始提及南印度洋中部热带系统，今晚热带天气讨论继续提及
The basin remains in a Near Equatorial Trough (NET) pattern east of 63E, undulating between 4 and 8S. Convective
activity is weak, few thunder cells near from the Comoros Islands. Convective activity is low, with a few thunderstorm
cells in the northeast of Madagascar and south of the NET.
The large-scale background remains in the first instance mostly unconducive for cyclonic activity due to the MJO's dry
phase. However, we note the presence of an Equatorial Rossby (ER) wave that crosses the basin while the dry MJO
evacuates over the maritime continent, leaving a more favourable context.
The large-scale context remains unfavorable for tropical storm formation. However, conditions for cyclogenesis could
improve with the transit of the ER, which would favor convergence in the lower layers to the southwest of Diego Garcia
at the end of the period. The scenarios suggested by European deterministic and ensemblistic models mostly reject this
possibility, due to strong deep wind shear and non-existent low-level convergence. In contrast, the deterministic GFS
reduces the intensity of the Mascarene High, opening up the possibility of cyclonic development over warmer waters. It
also reduces the deep shear in this zone, which remains very strong with IFS. Finally, the American ensemble model
develops several low-pressure cores corresponding to the deepening of a tropical storm.
A suspicious zone is therefore present to the south-west of Diego Garcia beyond 48 hours.
The likelihood of the formation of a moderate tropical storm becomes very low from Wednesday southwest of Diego
Garcia. The basin depicts a Near Equatorial Trough (NET) pattern east of 60E, undulating slightly between 5 and 7S. Convective
activity remains weak along the southern edge of the NET, as the trade winds slow down. On the other hand, it is much
more developed over the northern half of the Mozambique Channel in the mesoscale low level convergences, currently
surrounding the Comoros archipelago, while developing along the Tanzanian and Kenyan coasts.
The large-scale context remains unfavorable to cyclogenesis overall. This is due to the current dry phase of the MJO,
and the IOD+ phase, which from the middle of next week onwards will generate an anomaly of near-equatorial easterly
winds capable of weakening the current NET. However, between Tuesday and Wednesday, a Kelvin wave will intersect
with an equatorial Rossby wave in the Diego-Garcia area. This short-lived wave interaction could very occasionally
reinforce the low level vorticity, without being totally effective.
Area of low pressure northwest of Diego Garcia :
A vast zone of low pressure is currently present to the north-west of Diego-Garcia. Analysis of the 0419UTC ASCAT-C
pass is not convincing in terms of defining low-level winds, with the presence of multiple secondary vortexes. Maximum
winds are of the order of 15/20kt, far to the south of this zone, due to the pressure gradient with subtropical high
pressure. Environmental conditions seem rather unfavorable at present: low ocean heat potential and lack of low-level
convergence. The only available advantage is still a satisfactory level of mid-tropospheric moist. Coupled with an
equatorial wave crossing between Tuesday and Wednesday, a temporary improvement in low-level convergence could
occur, leading to more orderly convective activity in the precursor's southern semicircle. Deterministic models don't
believe this for a second; only the European ensemble model EPS suggests that an outlier could develop into a
hypothetical storm stage from next Wednesday, northwest of Diego-Garcia.
The likelihood of the formation of a moderate tropical storm is still very low from Wednesday northwest of Diego Garcia. |
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楼主: 理可的呆萌呆毛
发表于 2025-4-13 20:45
发表于 2025-4-27 23:59
