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As I indicated in a Facebook post, I am extremely skeptical about this system. For 72 hours, forecasting models have not stopped reducing its intensity forecast and retracing its trajectory… and this is not really what we observe when analyzing satellite data. The fusion between the 2 very close disturbances seems to finally take place which changes a lot of thing in its energy potential and its capacity of resistance to the expected degradation of the conditions.
On the other hand, it is still globally around 12N, which is further south than what was envisaged on the latest forecasts for this deadline.
In the end, we have on one side models which are predominantly forecasting a big wave north of the arc on the other nhc that maintains the onset of depression before the arc and in the middle we have our eyes and our brain telling us that it may not be that simple and clear as it sounds and that the complexity of this situation can exceed can be somewhat the resolution ability of forecast models.
In short, it is very vague; we will therefore try to rely on concrete data.
We will start with the visual rendering of this disturbance from satellite imagery. We note 2 things: the first is that there are no longer the 2 zones of deep convection one after the other. It is difficult to say if the 2 disturbances have merged or if one of the 2 has almost dissipated, but we now have, at least visually, to do with a single system which has become very imposing. The second is that it is not organized. The convection goes a little in all directions and the circulation remains very stretched on the EW axis and the vorticity zone seems to be off-center to the east of the large convection zone.
At the visual level we therefore observe a big change of shape with a big disturbance instead of the 2 until last night but it still seems strongly disorganized.
Finally, we will take a look at the available forecasts. First of all we have the nhc which maintains a 90% risk at 48 hours and at 5 days for cyclonic reinforcement. They were very progressive in the risk assessment but they remain very evasive on the evolution. They do not envisage a direct reinforcement in a storm but a classification in depression at 24 / 48h.
We then have Météo France which displays the forecasts of its models, envisaging a passage for the moment of a big wave with a little wind and rain on the north of the arc.
Finally we have the forecast models which are much more divided this morning than yesterday. TheECMWF extension saw almost nothing to happen and saw this disturbance dissipate very quickly by going sharply north to meet the shear. THE GFS for its part, see the passage of a depression over the northern half of the West Indies, between Guadeloupe and the Northern Islands. The HWRF is for its part, and as usual (pessimism is one of its trademarks!) much more aggressive with a Cat1 hurricane in the north of Guadeloupe and the SHIPS maintains continuous reinforcement in good storm at 48-72h. In short, the beautiful unit of yesterday has been shattered.
ECMWF extension
GFS
HWRF
In the end, we have to admit that the situation is extremely complex and that opinions are divergent. In this kind of situation, it is necessary to be careful, vigilant and to be prepared, in case a bad surprise arises. This disturbance can break up and go north, go into a depression on the northern half of the arc or even get stronger and go into a good storm. With such doubt within 72 hours, the only thing to do is to prepare, just in case. I am thinking in particular of people linked to the maritime or coastal environment in the north of the arc. The risk of a large violent system is almost zero, but that of something badly anticipated is not. Afterwards, everyone does as they see fit 😉
Image credits; Tropical tidbits, NHC / Noaa, UW-CIMSS
