WxWatcher007

12z ensemble guidance shifted significantly today toward no land impacts. Won’t really get talked about much because it means no impacts but it’s really interesting to see on ensemble and operational guidance. Still worth watching in Atlantic Canada.

Here’s the first super ensemble The big caveat early is that until we have a well defined LLC this can shift. The caveat for the Atlantic is that we still don’t know what will happen with late period troughing and Atlantic ridging—though I’d strongly favor OTS off the Carolina coast even at this stage due to climo.

Euro has the low head offshore eventually, but it's left behind by the trough, similar to 12z yesterday. That tells me there's some uncertainty with the long term track, though I'd favor OTS with either the original trough or a future one. 72 to 192 on the 12z Euro

Right off the GA/SC border at 132. Not really worth opining much on right now, but I've noticed that the steering trend has kind of been all over the place with regard to the NE trough.

There are probably some folks in this thread saying "woah woah slow down this hasn't even developed yet", and wondering why the thread is starting to take off after the early 12z guidance. There are a few reasons. First, although we don't have a well defined low yet, there's increasingly high confidence that one will form. You see that in the NHC outlook at 2pm but let's talk about why. With the latest satellite image above, you can see a clear, but broad circulation that is already in place. It's less broad than 18 hours ago, however. This is why the NHC has designated Invest 93L--with a viable area of focus we can get additional model guidance. The first thing you may hear a lot of people say is that the exceptionally warm waters in the western Caribbean and Gulf are the reason this has a higher ceiling. It's more complicated than that. In order to get a sense of the ceiling for a tropical system, you need to look at the entire environment, which consists of a few major elements. 1. Thermodynamic environment (SSTs, OHC) This is the easiest one to look at. Anomalies matter, but for in-situ analysis it's most helpful to examine current sea surface temperatures and oceanic heat content IMO. Both are exceptionally high. You can have boiling water, but if you don't have thunderstorms that can fire consistently without getting blown away, you won't have any kind of strong tropical system. We're currently seeing this with Tropical Storm Franklin in the Atlantic. 2. Wind Shear Shear can be complicated, because there are a number of ways it can be imparted and it can happen at various levels of the atmosphere. With shear, thunderstorms cannot organize efficiently, if at all, around a low pressure. An upper level low is producing a ribbon of shear just to the north of the invest, but that ULL has pulled west in the last 24 hours. Even more significant, there is an upper level anticyclone (ULAC) that promotes ideal low shear conditions and thunderstorm development. I believe this is why we're seeing the organization we have thus far. The guidance in the last 24 hours has trended away from higher shear, which would allow for modest to significant organization even if there is some land interaction with the Yucatan, which the guidance thus far has shown. With more shear, this could remain a more messy system, with convection unable to wrap around a low allowing it to develop an inner core. An inner core is key to significant intensification, and while it is unclear whether 93L attains that level of organization in the Gulf, it's something worth watching given the shear trends. On other flag is looking at the vorticity here. I posted it earlier, but look at how aligned the 850mb and 925mb areas of vorticity are. Having that kind of alignment allows for more efficient thunderstorm and low pressure organization. I would watch that ULL closely. While it could influence 93L negatively if closer, it could also allow for ventilation of an outflow channel as it heads north or NNE. 4. Dry Air Anytime you are talking about a US landfall, you have to watch for continental dry air entrainment. Dry air is like putting water in a gas tank. It'll cause problems with the engine. On the guidance we see dry air lurking, which could arrest development. However, if there's no shear to impart the dry air it won't slow organization down. The 00z Euro had the dry air lurking while today's GFS did not. The bottom line is that this is something worth watching if you are in the eastern Gulf and SE coast. No one is locking in a hurricane, but given the signals in the environment, any faster organizational pace increases the ceiling for 93L. At this time, it looks like a minimal tropical storm is the floor, which could happen if this hangs up over the Yucatan and finds a more sheared environment in the Gulf. That looks less likely given the current environmental analysis. It's also important to note that while everyone will be talking about wind, the potential track of this could bring storm surge into surge prone areas. That's something to watch closely as well for folks along the coast.

Thought we'd see 40/80 at 2pm. A lot of clues in this one. Tropical Weather Outlook NWS National Hurricane Center Miami FL 200 PM EDT Fri Aug 25 2023 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: Active Systems: The National Hurricane Center is issuing advisories on Tropical Storm Franklin, located a couple of hundred miles east of the Turks and Caicos Islands. Northwestern Caribbean Sea and eastern Gulf of Mexico (AL93): Satellite images indicate that the area of low pressure over the northwestern Caribbean Sea is gradually becoming better organized, with increasing thunderstorm activity and a better-defined low-level circulation. Environmental conditions appear conducive for further development during the next several days, and a tropical depression is likely to form late this weekend or early next week while it moves generally northward over the eastern Gulf of Mexico. Interests in the Yucatan Peninsula of Mexico, western Cuba, and Florida should monitor the progress of this system. * Formation chance through 48 hours...medium...40 percent. * Formation chance through 7 days...high...80 percent.

Well I think we'll have to see what kind of consolidation and organization there is in the next 24-48 hours, and how much a consolidating low gets over the Yucatan. The analysis above has it a little more consolidated than I would have expected thus far but it still has a ways to go IMO.

Very different, but it's one run. Let's see how much the ensembles follow the op. It's a very different intensity and steering forecast. One thing is clear, however, it has been trending toward something more consolidated as it lifts into the Gulf. Here are the last 9 runs.

Well that GFS run is different

GFS quite a bit stronger with a further west track between 84 and 108.

GFS still playing catch up with a faster consolidating low. Still pretty broad lifting into the Gulf at 84. Going to be stronger though as it tightens in the Gulf.

Even though the motion has been erratic, the second trough is a virtual lock to kick this northeast later in the period, much like the current W. Caribbean AOI. It would take a medium range guidance bust of historic proportions—across all guidance for Franklin to become a threat to the US. Atlantic Canada should certainly pay close attention, however.

I can’t tell after the last few seasons

Considering that virtually every other region has baked well over 100 this season, it’s incredible we didn’t see higher highs. Never got the heat dome east.

There was basically no development and no people (relative to the population now) there. As long as they were away from water many probably would have been ok. Not sure but here’s what they did for the more recent record. https://www.aoml.noaa.gov/hrd/data_sub/re_anal.html

It’s hard to imagine anything close to that rolling up the coast. Just insane.

.02 today

Throwback to the OG hurricane in New England

Took the GFS a while to get on board but now it essentially is. Now the questions are how long it takes for consolidation to occur, which obviously has significant implications on intensity in the Gulf, and how likely is this to scrape the SE coastline before likely getting kicked OTS. There’s vorticity, but not much in the way of convection this morning. https://tropic.ssec.wisc.edu/real-time/atlantic/movies/wg8vor4/wg8vor4_loop.html

All the Cat 5’s to hit the US were TS three days before landfall. That’s incredible to me.

First time the GFS has a quicker consolidation of vorticity in the Gulf. Still delayed development until it’s right on the FL coast, then basically OTS.

PRE?

For posterity when this slides harmlessly OTS after Florida