Saturday, September 09, 2017

Crisis of Faith

Irma is creeping WNW along the Cuban coast, and will do so most of Saturday. The models indicate it will start turning north after sunset towards Naples.

Latest weather maps are out. Both NVG and GFS bring Irma right up Florida's west coast, with Irma's sharp northerly turn coming around sunset this evening.
Jose is becoming a nuisance. After dithering for a long time off the Bahamas, more than a week, it may head towards the northeast United States. Currently models point it at New York City, but it could go lots of places.

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I'm having a crisis of faith with the models. My instinct is Hurricane Irma won't turn much, if at all. I worry the models have simplifications that mislead them. Specifically, the basis of the models, the Omega Equation, may be oversimplified.

The models are equating the fast-moving cyclonic vorticity advection heading south from the Dakotas with the slow, northerly-moving but intense cyclonic vorticity advection of Irma, setting up a common center, and forming a cutoff low. It's a neat, clever resolution. Maybe too neat and clever.

Irma has a freakload of inertia. The Omega Equation drops inertial terms though.

Why should Irma respond to the fast-moving but evanescent Dakota fluffballs? Why shouldn't the Dakota fluffballs respond to Irma instead? The East Coast trough has largely moved on. Why should Irma respond to it? Irma is a vertically-organized vorticity machine with almost the entire tropospheric column of air under its control. Irma IS the vorticity queen! Plus, the tropical easterlies don't move quickly - not nearly as quick as the Jet Stream. Why should the tropical easterlies form a cutoff low now? It's perplexing.

My instinct is the storm will shift north, perhaps heading northwest, but not turn sharply north like the models say. Irma could head to sunnier shores where large hurricanes are always welcome, like New Orleans or Houston.

But we won't have to wait too long. In a day, either way, Irma will make its path, and we will find out.

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