Melissa stalled, catastrophe looming for Jamaica, Haiti

Although Melissa is still struggling to organize this morning, the expectation is that the storm will intensify into a hurricane this weekend and become a Category Four storm by early next week as it does a loop just south of Jamaica …

If this forecast holds up, Melissa’s impacts will be felt over Jamaica for about four days. The US National Hurricane Center’s “Key Messages” products is increasingly apocalyptic … here the links: Key messages regarding Tropical Storm Melissa (en Español: Mensajes Claves). The potential damage swath doesn’t really do justice to the situation:

As you know, I don’t like some of the new terminology used in NWS forecasts, especially the term “life threatening,” which I feel is over-used and should be reserved for truly dangerous (rather than hazardous) situations. Well, in this case, it is appropriate. This is a potentially catastrophic situation. In the late 1990’s I helped Jamaica develop their first comprehensive hurricane disaster plans, and spent a lot of time studying the island. A lot of visitors don’t see much beyond the “all inclusive” resorts in Montego Bay or Ocho Rios. The mountains (where the rightly famous Blue Mountain Coffee is grown) are steep, with many “gullies” (ravines) that act as funnels in heavy rain. And heavy rain is exactly what is in store: it will not be surprising to see totals of over five feet in the next week! Debris from the high winds will clog the drainage even further, creating temporary dams and exacerbating the problem.

The Tiburon Peninsula of Haiti (the southern bit sticking out to the west) will also see catastrophic flooding, and given geometry of the storm the southern half of the country is also likely to be flooded. Here too a catastrophe is imminent – in a country wracked by turmoil that has still not recovered from the great earthquake over a decade and a half ago. The humanitarian situation is likely to be horrific.

As noted, Melissa is struggling to organize. Here is the overnight IR view (the sun is just rising over the storm) …

Here is an analysis of the storm and the wind shear. Notice that in the area north and west of the center (where the AL132025 label is located) the magenta and cyan arrows are pointed in different directions. The low level winds are in a nice circular pattern, but the upper level winds are “fighting” development.

This isn’t as bad as it was yesterday, it seems the shear is weakening, and the water temperatures are so warm there is enough energy to support whatever intensity the atmo will allow. This is why NHC is forecasting at least a Cat 4.

The track models are mostly in agreement that the storm is going to do a loop near Jamaica over the next five days. The one outlier is the primary GFS run, seen here in the dark blue line …

This has caused a lot of people to criticize the model, but I think that it’s a bit early to say that. For one thing, the GFS ensemble is in the middle of the other models, and for another, we don’t know what is going to happen yet. Here is the GFS primary, ensemble mean (AEMN), and individual tracks:

Either way, the storm isn’t going anywhere for the next week, which is catastrophic news for Haiti and Jamaica. Will post an update this afternoon with more on model performance statistics, which as you might expect is complicated …

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