WxWatcher007

Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 AM EDT Sat Aug 26 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 several hundred miles south of Bermuda. Northwestern Caribbean Sea and Eastern Gulf of Mexico (AL93): Shower and thunderstorm activity continues to show signs of organization in association with an area of low pressure located near the Yucatan Channel. Environmental conditions appear conducive for further development of this system, and a tropical depression is likely to form within the next day or two while it moves generally northward over the southeastern 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...high...70 percent. * Formation chance through 7 days...high...90 percent.

988.9mb extrapolated pressure with a peak FL wind of 57kts. Some SFMR have been over 64kt, but apparently SFMR readings have been high in Franklin before. If it's not a hurricane, it's getting close.

Certainly possible, though this one looks a little ahead of the modeling schedule for organization, at least at the mid levels. Of course, any early "progress" could be lost if this slides and sits over the Yucatan today, but the eastward development of a possible vigorous MLC is intriguing.

Recon approaching the eye.

Invest 93L continues to organize this morning under an ULAC. It's very hard to get a sense of how much organization we have of the low levels without visible satellite and microwave imagery, but looking at a much longer version of IR just now, it looks like at least the mid-level circulation is developing east of the Yucatan. You can see it a bit with those towers rotating in the image above. Even if an LLC isn't under the convection currently, the consistent and strong convection we see this morning could either work to the surface with sufficient time or pull a misaligned LLC east. SW IR presents a similar picture. You can see a clearly consolidating circulation, but it's hard to tell if there's a true LLC and where. There may be evidence of outflow developing, another sign of organization. There has been consistent convection through the night, which has become more organized the last few hours. First light will be telling, but given the convective activity and appearance if this holds we probably see at least a PTC today to cover the Yucatan.

Speaking of odd structure—it’s got a partial eyewall going at first light and possible eye. Recon en route but this could be a hurricane today if that keeps up.

Keep in mind that the HWRF is in the process of retirement so I’d look at HAFS-A/B now. (and that the hurricane models are prone to large errors when there isn’t a well defined LLC)

Tropical Storm Franklin Discussion Number 22 NWS National Hurricane Center Miami FL AL082023 1100 PM AST Fri Aug 25 2023 Westerly shear continues to affect Franklin tonight, as evidenced by the sharp edge to its cold cloud tops on infrared satellite images. However, the low-level center that was exposed earlier today appears to have moved under the western edge of the convective canopy. An Air Force Reserve Hurricane Hunter aircraft flew the storm at 700 mb this evening and reported peak flight-level winds of 56 kt, with believable SFMR winds in the 45-55 kt range. These data warrant a slight increase to the initial intensity (50 kt), especially given a recent dropsonde that suggests the surface pressure has fallen to 996 mb tonight. A recent ASCAT-B pass over Franklin further supports this, with peak wind vectors slightly above 45 kt. Note that the initial intensity of Franklin is more uncertain than normal, with there being a large spread between some of the aircraft data and the various objective and subjective satellite estimates. The intense convection closer to the center of Franklin appears to have drawn the surface center more northeastward, and the initial motion is an uncertain 60/7 kt. A high pressure ridge building to the east of Franklin is expected to steer the cyclone more northward and north-northwestward this weekend and into early next week. Then, a deep-layer trough is forecast to move across the northeastern U.S. and eastern Canada by midweek. This should cause Franklin to accelerate northeastward deeper into the mid latitudes through the end of the forecast period. The updated NHC track forecast lies to the east of the previous one during the first 60-72 h of the period, mainly a result of the eastward adjustment to the initial position of Franklin. There are some notable forward speed differences beyond 72 h, with the GFS significantly faster than the rest of the global and regional models. With the NHC forecast remaining near the multi-model consensus aids, no notable changes were made to this portion of the track forecast. The westerly shear that has plagued Franklin for the past couple of days is expected to decrease during the next 24-36 h. So while only modest strengthening is forecast in the near term, more significant strengthening seems likely thereafter as the cyclone moves over very warm SSTs (29-30 deg C) and within a more favorable dynamic environment. The updated forecast shows Franklin becoming a hurricane by 48 h and peaking near major hurricane intensity in 72-96 h, in good agreement with the latest HCCA and IVCN aids. As Franklin accelerates to higher latitudes, cooler waters and increased deep-layer shear will induce weakening and eventually extratropical transition beyond the end of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 22.4N 66.2W 50 KT 60 MPH 12H 26/1200Z 23.0N 66.0W 55 KT 65 MPH 24H 27/0000Z 23.9N 66.3W 55 KT 65 MPH 36H 27/1200Z 25.3N 67.0W 60 KT 70 MPH 48H 28/0000Z 27.0N 67.9W 70 KT 80 MPH 60H 28/1200Z 28.8N 68.4W 80 KT 90 MPH 72H 29/0000Z 30.5N 68.4W 95 KT 110 MPH 96H 30/0000Z 34.7N 66.5W 95 KT 110 MPH 120H 31/0000Z 40.0N 60.0W 75 KT 85 MPH $$ Forecaster Reinhart

18z EPS

Right. Having a higher ceiling doesn’t mean it gets reached. Land interaction and sneaky shear imparting dry air, along with limited time over the Gulf could easily hold this back. Also, it takes time to organize an inner core, which is an absolute essential for higher end development. It’s too early to say exactly where this is headed.

Somewhat divergent steering pattern that needs to be worked out.

Maybe a little more lopsided verbatim at 90 & 96, but it’s probably going to end up another relatively strong run.

No surprise, but the GFS is a little tighter with vorticity at 24 given the organizational trend we’ve seen today.

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.