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This Invest 98L has been particularly difficult to read and anticipate so far. First several “centers”, then a rectilinear trajectory towards the west, then a merger of the 2 nearby disturbances… in short, it has made models and forecasters sweat for the past 72 hours. It is certainly not over, but things seem much clearer tonight.
In terms of the environment, the shear is still above 15N and doesn't really affect it yet. On the other hand, if it is on a trend of movement more NW it could be confronted with it quite quickly. And given its still somewhat uncertain organization, its chances of resisting it would be quite low.
There is still quite a bit of dry air and sand to its north, but we can clearly see in the image opposite that the deep convection is interposed and that it therefore protects the center quite a bit.
In the end, as often, it is its trajectory that will globally determine the evolution of its intensity. If it goes north quickly enough (hypothesis ofECMWF extension) she will have trouble with the shear, if it continues WNW (assumption ofHWRF) it may strengthen in a storm over the northern half of the arc with favorable conditions, and if it is a little between the 2 (hypothesis of GFS) it could pass on the extreme north of the arc in depression.
There are still 3 hypotheses but they are clearer and more readable than the fog of the last 48 hours.
Even if we can see much more clearly, it is still difficult to assess the real risk for the north of the Caribbean arc. Between the most favorable hypothesis ofECMWF extension and the least favorable of theHWRF, that's a big big gap. As between a lost wave well to the north of the arc and a robust storm at the level of Saint-Kitts. But at least for those who are concerned such as boaters, there is now a clear choice that presents itself and they will have to do it. TheECMWF extension has been very relevant since the start of the season, theHWRF is quite freakish and very aggressive in his forecasts, but over a short time frame and a small area he is one of the best reads for quick reinforcements. And between the 2, we have the GFS which is rarely very wrong but is a little less reliable than theECMWF extension for quite some time already in somewhat complex situations.
Image credits; Tropical tidbits, NHC / Noaa, UW-CIMSS
