WxWatcher007

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

For our Atlantic Canada folks.

12z Ensembles

Let's take a closer look at our latest area of interest that's expected to move into the western Caribbean and Gulf. The NHC now believes that TC genesis is more likely than not, and with increasing run to run consistency from some operational guidance and ensembles, a forecast for TC genesis is coming into view. 3. Northwestern Caribbean Sea: A broad area of low pressure centered over Central America is forecast to move into northwestern Caribbean Sea by this weekend. Some gradual development of this system is possible thereafter into early next week, and a tropical depression could form while it moves slowly northward, entering the eastern Gulf of Mexico. * Formation chance through 48 hours...low...10 percent. * Formation chance through 7 days...medium...60 percent. I've actually been looking at this region and time period for a little over a week now, as a complicated interaction between an EPAC monsoon trough and broader Central American Gyre (CAG) increased the odds that something could form in the EPAC or Atlantic basin. Normally, we see the CAG a few times a season, usually at the beginning or end of the season, but this time we have the setup during the building climatological peak of the season. Much like the monsoon trough in the eastern MDR last week, the EPAC monsoon trough (ribbon of vorticity) is expected to break apart into distinct areas of vorticity, with one lifting north into the western Caribbean and eventually the eastern Gulf under the influence of an upper level trough. This is where the rubber meets the road. We have a clear area of strong vorticity in Central America and that is gradually moving north. For the last week, the guidance had virtually no run to run consistency over whether a tangible feature would move into the Atlantic basin, let alone develop. Usually, the GFS goes wild with CAG TC formation, but has been silent on development. Now, virtually all major guidance has TC genesis taking shape while the GFS, seemingly behind, does put a disorganized area of vorticity into the Gulf a few days from now. At least today, while the GFS and Euro diverge on development, they are closer than it would appear looking at the general setup. Let's look at the next seven days. The GFS, with more shear and less concentrated vorticity making it to the western Caribbean in a few days takes much longer for a surface feature to develop. The Euro on the other hand, has started to show run to run consistency with lower shear and a more concentrated area of vorticity, leading to development in the eastern Gulf even if the area of vorticity spends time over the Yucatan. Even with the upper low nearby, it is expected to shift west, reducing its influence. In addition, over the region we have an upper-level anticyclone allowing for a pocket of low shear and convective activity. That feature is not expected to go anywhere. Unlike other eastern MDR systems, dry air and subsidence has not been as much of an issue further west, and the influence of the SAL had dramatically diminished, as I posted about a few days ago. Alright, so the Gulf is a furnace so that settles it, right? Hurricane coming? I think it's important to look at what could inhibit development, and I think it's land interaction. It's quite possible that if there is a weaker area of vorticity like the GFS predicts and it lingers over the Yucatan or Central America until a northeast trough pulls it north, there may not be enough time for it to organize, much like it was for Harold this week in the Gulf. That said, I think that's an increasingly low likelihood, so let's talk briefly about what happens after potential development. On the 12z Euro you see the trough that is going to kick TS Franklin OTS or toward Atlantic Canada also allows for whatever develops in the Gulf to lift N/NE. On the Euro, the system hugs the coast before swinging out to sea off the Carolina coast. Other guidance has a different trough orientation/timing that allows for it to come further up the coast. What happens is up in the air, but this is looking like something to watch in the Gulf and along the SE coast. We're going to know pretty quickly which guidance is more correct, as the vorticity lifts north. Watch out for where it lands and how consolidated it is in the next 48-72 hours. I've liked the last week of August for close to home activity for a while now and it looks like that's coming to fruition. How strong the activity is and how much of the coast is impacted remains to be seen.

As nice as this summer has been at times, I do feel like we’ve missed out a bit. No big heat while the Midwest and south have baked. Some severe but no region wide high end event like the Mid-Atlantic moderate. We did flood though.