Lots going on around Mexico this morning. No TL;DR this morning – it’s a complex situation, and as noted Friday today is the day to start paying attention so you’ll just have to read the whole thing 🙁 …
CAUTION: at 11am NHC upgraded the forecast for John to be a hurricane at landfall, and started advisories on AL97 as Potential Tropical Cyclone Nine (link). The discussion on John is outdated, but the longer discussion below on AL97’s possible impacts applies to PTC Nine. Next PTC Nine update in the morning (Tuesday around 6:30am).
Here’s the official forecast and warnings on Tropical Storm John, which is on the Pacific side of Mexico and moving northeast; also note Invest area AL97 on the other side of Central America, off the coast of Honduras:
As I constantly emphasize, the best summary of the official forecasts are found in the “Key Messages” products from the National Hurricane Center. Here are links to the products: Key Messages regarding Tropical Storm John (en Español: Mensajes Claves), and Key Messages for the system in the NW Caribbean (AL97) (don’t know why there isn’t a KM for it it Spanish). Here is the forecast damage swath from John, which should make landfall Tuesday.
Not to be dismissive as if you are in the path you should certainly take precautions and prepare for a tropical storm, especially for heavy rain, flash flooding, and mudslides. But the big potential even will be later in the week, as the invest area seems certain to develop into something.
The system that is now invest area AL97 has been on the horizon for a long time. The models have been spinning it up for a long time, and some are gloating they “forecast” it a week ago. But the thing to remember is for every instance where a situation like this develops, there are probably three or four that didn’t – that’s why I don’t get excited about them until there is something real to talk about. And now we’ve reached that point. So what do the forecasts say? Here’s a preview, with the caveat we don’t actually have a storm yet so it’s a bit fuzzy and likely won’t be clear until the storm actually enters the Gulf late Tuesday or even Wednesday morning, only 36 hours or so before landfall!
The model guidance is fairly tightly grouped, crossing Yucatan as a disturbance or depression. It’s likely that NHC will start advisories on it as a potential tropical cyclone (PTC) before it actually becomes a system, given the proximity to to land and potential for the storm to move quickly across the Gulf. But at the moment we don’t have an official track, so here is an infamous “spaghetti map” …
This puts a potential landfall Thursday. But of course the track is only half or less of the story: the size and intensity. To examine that we have to use a tropical storm impact model, and of course by far the best (immodest cough) is the TAOS model (Here’s a reference link for those interested, from the Bulletin of the American Meteorological Society). Using the GFS forecast, here is what that looks like:
If the GFS forecast pans out, this is an $8 or $9 Billion dollar event, with 16 Million people in the tropical storm wind swath. Using other models gives totals in the $15 Billion range, so it has the potential to be a major event for the Florida panhandle. On this track and timing, expect watches and warnings for Yucatan and Western Cuba perhaps as early as today but certainly tomorrow, and by Wednesday there should be watches and warnings up for the mainland US. As noted above, those in the impact swath should review their hurricane plans and supplies, and be ready to start preparations if warned.
Yeah, yeah, what about Frogmore and environs? This looks to be a “back door” storm, with the core staying inland and going across Macon. The worst of the impacts in coastal Georgia and South Carolina should be overnight Thursday into Friday. The GFS shows higher winds (tropical storm force) along the coast and inland across a wide swath to about halfway between Macon and Atlanta. We all know what that means, power outages, limbs down, a bit mess, hazardous, but if you are in a well built structure not especially dangerous. Mobile homes on the other hand will need to consider seeking shelter. The European model is more sedate, with a weaker storm at landfall, and winds below tropical storm strength across most of Georgia. Here’s the cool slider thing to compare:
Rain is a big concern, especially given the experience of Debby a few weeks ago. The storm looks to be moving fast enough for catastrophic rains to not be a factor, but flash flooding is always a possibility. Here’s the GFS forecast for rain:
That will cause a surge of water down the rivers, but nothing like Debby. As usual with a landfalling storm tornadoes might be an issue.
A lot can change between now and Friday. Again, we don’t really have a storm yet, it’s just spinning up. But that’s what it looks like this morning: hazardous if you don’t take precautions and use common sense, but not a dangerous or catastrophic situation except potentially right on the Gulf coast.
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