Advisories started on PTC4

NHC started advisories on PTC4 at 11am, and has raised tropical storm watches and warnings for the southwest coast of Florida …

So, just what is a “Potential Tropical Cyclone” anyway? To quote from the NWS guidance on the subject:

Since 2017, TPC has the option to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours.

In other words, it is a developing system that doesn’t yet meet the technical definition of being a tropical cyclone, but might before it reaches land. So it’s a mechanism that allows the hurricane center to start advisories and issuing bulletins using the normal format for a tropical system, so other agencies as well as the meteorological community can start preparing and using the established tools.

That also means we have an official forecast, which means we now have official Key Messages regarding Potential Tropical Cyclone Four (en Español: Mensajes Claves) which are your best quick look at what is going on and what to do. As we have seen in past years with storm paralleling the coast, they are miserable to forecast because even a little wobble left or right, or an otherwise minor change in intensity, can mean a huge difference in impacts. The current NHC forecast is about in the middle of the forecast guidance, perhaps shaded a bit towards the coast. Here is what the impact swath looks like using my award winning TAOS(tm) model and graphics (:P) …

On this track the Keys will get blustery wind and rain, SW Florida might get low end tropical storm conditions, and farther north, Tampa, Clearwater, etc. might see increasingly stronger tropical storm like conditions. But on this forecast, no hurricane conditions, so the main threat in western and north Florida is from flash flooding, the odd tree or two down, and scattered power outages.

OK, so what about Georgia and the Lowcountry? Yes, there is a scary tropical storm icon just off of Savannah at the 84 hour mark, which translates to 8pm on Monday night. However, at that point the storm (which will be called Debby if this all goes as predicted) will only be a minimal tropical storm, impacts shouldn’t be too significant if nothing breaks that shouldn’t: some thunderstorms, rain, breezy right on the coast, but we will be on the weak side of a storm that has spent almost a day traveling over north Florida, something that will exhaust anyone, as those who travel on I-10 know. It may last a while as the storm looks to slow down at that point, but that remains to be seen. We will need to watch the timing of onshore winds and the tides, so some shallow coastal flooding in the usual spots might be an issue, but nothing at all like Matthew, etc.

As those of you familiar with the area know, for this kind of storm conditions will be worse to the south around Jacksonville, then get better (and peak later) as you move north. Although it will be moving offshore as it moves north and gaining strength, again the coast will be on the weaker side so that all balances out.

So, in short, stormy weekend for Florida but with some common sense preparations nothing terrible. Less stormy for the Georgia/SC coast, only we have more common sense. Maybe. I hope.

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