There are growing signs that a portion of the east coast could face a serious hurricane hazard around Sept. 12 or 13. Nothing can possibly be conclusive this far in advance (I'm writing this on Sept. 6), but the evidence for such a threat is gaining traction in the models.
The National Hurricane Center appropriately takes a more conservative approach, generally not venturing beyond the five-day range. They cannot be faulted for this because forecast skills beyond five days are very limited. There are notable exceptions, such as Sandy, when the European model made the call on that uncommon hard left turn into the east coast beyond the five-day range.
As of this writing, NHC discusses the high uncertainty on early Thursday, Sept. 6 as to how far west current Hurricane Florence will travel in the Atlantic; whether it will be forced west under a stacked up ridge of high pressure to the north or be "captured" by a linear trough of low pressure moving out into the Atlantic and recurved out to sea.
Here was their path projection on Thursday. The circle "M" indicates a Major hurricane, at Category 3 or higher.
The vaunted European model began offering a more westward path Wednesday and reinforced that westward path in its latest Thursday run.
In this particular run of the model, if verified next week, this would indeed be an ominous development for the Outer Banks and eastern North Carolina, as the tightly packed isobars and very low pressure suggest, for storm surge, destructive winds and flooding rains.
If it were just one model making such an ominous forecast, I wouldn't be writing this article. But here, again, is the Canadian model. No two models, let alone runs of any given model, are going to be identical, but the Canadian shows some good general agreement.
The central pressure isn't as deep as the European, but it is still a powerful hurricane.
There is more. The American GFS had been recurving Florence out to sea in its previous runs. But this morning, it takes Florence on a more westward path. It is nowhere near the locations of the European or Canadian models, but instead brings a monster close to the landfall location of Sandy, instead of out to sea.
The fact the GFS has now taken on the more westward trend raises at least my eyebrow.
A model from the Japan Meteorological Agency does not go quite so far west today, but it's awfully close.
Even a newer experimental model, ICON, from the Max Planck Meteorological Institute in Germany joins in with a pessimistic forecast.
There is nothing approaching unanimity here, or even general good agreement when all models are factored in. This is what's referred to as a "spaghetti chart," in which the projected paths from many models are overlayed onto a map. This data was made available to the South Florida Water Management District via the NHC.
However, this spaghetti graphic was showing more models picking recurvature to the NE yesterday and the day before. More models, besides those I've shown you, are now trending west. And several of them are projecting deep intensity for the hurricane. I have to quickly add that intensity forecasts have not improved in recent years nearly as much as track forecasts.
If I forecasted somewhere on the east coast, I might have waited another day before composing this article. Paths and intensities will change over the next several days. Due to logistics and costs, most emergency managers and FEMA know not to begin pushing buttons just yet. All we can hope is the future changes in track and intensity forecasts begin moving back in the other — better — original direction.