Windspeed

I reckon this is the most intensification in an initial advisory I can recall aside from Iota last year. This forecast essentially ties that one. 35 kts to 95 kts in 72 hours. I suppose it's warranted based on all the available data, empirical and simulated. Now just to wait and see what recon finds.

Here is the 11AM EDT Discussion for posterity... 044 WTNT44 KNHC 261456 TCDAT4 Tropical Depression Nine Discussion Number 1 NWS National Hurricane Center Miami FL AL092021 1100 AM EDT Thu Aug 26 2021 Early morning visible satellite imagery shows that the circulation associated with the area of low pressure over west-central Caribbean Sea has become better defined. There has also been an increase in the organization of the associated convective activity, and based on consensus Dvorak T-numbers of 2.0 from TAFB and SAB, advisories are being initiated on a tropical depression. The initial intensity is set at 30 kt, in agreement with the subjective satellite estimates. The official reporting station in Kingston, Jamaica, has reported sustained winds of 25 kt with gusts to 35 kt during the past couple of hours. An Air Force Reserve reconnaissance aircraft is scheduled to be in the system later this afternoon to provide more information on the system's structure and intensity. The depression is moving northwestward or 325/11 kt, however the initial motion is a bit more uncertain than normal since the low- level center has only recently formed. The cyclone is forecast to move steadily northwestward around the southwestern portion of a deep-layer ridge centered over the western Atlantic. This track should bring the center near or over western Cuba late Friday, over the southeastern and central Gulf of Mexico Friday night and Saturday, and have the center approach the northern Gulf coast on Sunday. The track guidance is in relatively good agreement, however the average NHC track forecast error at day 4 is around 175 miles, so users should not focus on the details of the long range track forecast. Some shifts in the track are likely until the system consolidates and becomes better defined. The NHC track is near the various consensus model aids and is in best agreement with the GFS ensemble mean. The depression will be moving over the high ocean heat content waters of the northwestern Caribbean Sea during the next 24-36 hours. This, in combination with low vertical wind shear and a moist environment, should allow for steady strengthening. The depression is forecast to become a tropical storm later today or tonight, and could approach hurricane strength as it passes near or over western Cuba. Once the system moves into the Gulf of Mexico, conditions are expected to be conducive for additional strengthening, and rapid intensification is explicitly shown in the NHC forecast between 48 and 72 hours. The NHC intensity forecast brings the system near major hurricane strength when it approaches the northern Gulf coast on Sunday. This forecast is supported by the HWRF and CTCI models, and the GFS, ECMWF, and UKMET global model guidance, which all significantly deepen the cyclone over the Gulf of Mexico. As a result, there is higher-than-normal confidence that a strengthening tropical cyclone will be moving over the Gulf this weekend. Key Messages: 1. Tropical storm conditions are likely in portions of the Cayman Islands tonight and western Cuba Friday and Friday night, with dangerous storm surge possible in portions of western Cuba, including the Isle of Youth, in areas of onshore flow. 2. The system is expected to produce life-threatening heavy rains, flash flooding and mudslides across Jamaica, the Cayman Islands, western Cuba, including the Isle of Youth and northeastern portions of the Yucatan Peninsula. 3. This system is forecast to approach the northern Gulf Coast at or near major hurricane intensity on Sunday, although the forecast uncertainty is larger than usual since the system is just forming. There is a risk of life-threatening storm surge, damaging hurricane-force winds, and heavy rainfall Sunday and Monday along the northern Gulf Coast from the Florida Panhandle to the upper Texas coast, with the greatest risk along the coast of Louisiana. Interests in these areas should closely monitor the progress of this system and ensure they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 16.9N 79.2W 30 KT 35 MPH 12H 27/0000Z 18.2N 80.4W 35 KT 40 MPH 24H 27/1200Z 20.3N 82.0W 45 KT 50 MPH 36H 28/0000Z 22.5N 83.9W 55 KT 65 MPH...INLAND 48H 28/1200Z 24.4N 86.0W 65 KT 75 MPH...OVER WATER 60H 29/0000Z 26.1N 88.1W 80 KT 90 MPH 72H 29/1200Z 27.7N 90.0W 95 KT 110 MPH 96H 30/1200Z 30.5N 92.0W 70 KT 80 MPH...INLAND 120H 31/1200Z 33.7N 91.2W 30 KT 35 MPH...INLAND $$ Forecaster Brown

Unfortunately another landfall under darkness.....

Suspicious low-level circulation evident on visible. NHC must have sniffed out something just SW of Jamaica for TD vs PTC advisories. We'll know more soon enough.

Agreed, even more complicated now by the societal state in the wake of a pandemic, when many have yet been reluctant to travel. There is a mental barrier for some to overcome. It's a tough decision regardless if you live in a rural or urban area.

96 hrs / 4 days... Very little lead time. Also so very typical of intense landfalls. Less than 72 hours from genesis to major hurricane.

Where TCG may occur based on most recent progs. Even that information may change between outlooks as the situation is fluid. The wave axis lifting north can dramatically change location point of genesis. So caution is warranted.

Speaking for rapid organization, the 18z HWRF now has 99L making landfall in western Cuba as a hurricane. That's some pretty rapid TCG and intensification in the short-term, so piles of salt.

It can get exciting or disturbing, whatever floats your boat, when the globals show an intense system. I am guilty of eyeballing intensity as well. But it is best to remind to not rely on them for maximum intensity. Their use is for track guidance and potential environment. If they are resolving a hurricane, that's trouble. The TC models and SHIPs are better suited for intensity guidance. Plenty of intense hurricanes have made landfall that never showed up as a major hurricane near landfall by any of the globals. The shift east is troubling but not only are we still early, there's no vortex yet to track. So patience until TCG occurs.

Knoxville, especially N.Knoxvile area getting a good pounding right now.

The system you are referring to is actually the pv/upper level low retrograding into the GOM this week. This is the system partly responsible for aiding in lift/instability and divergent flow aloft for invest 99L to the south in the Caribbean, and potentially influencing its track into the GOM this weekend. You'll get some gusty thunderstorms, no doubt. Upper cold cores make for some strong lapse rates and convection over Florida this time of year. But any potential for a tropical disturbance developing underneath that feature is negligible.

Well we still don't have a closed vortex to track and initialize more accurate modeling. Arguably, the ECMWF and GFS operationals, though rare to be in such alignment pre-TCG, might be way off if 99L is delayed in undergoing genesis. If it occurs near the Riveria Maya or tracks longer over the Yucatán, that could definitely help as an inhibitor. But we are reaching if this merely crosses extreme NE Yucatán, the channel, or even western tip of Cuba. The aforementioned scenario could help keep the TC a low-end hurricane if there are structural and organizational issues. But the latter would increase the odds of major, perhaps intense hurricane unfortunately.

Dr Papin mentioned this in his latest post. The same PV helping to lift 99L's resultant TC into the central GOM also seems to act as a buffer between airmass evacuation from the potential EPAC system and the same from the GOM system. At any rate, the overall upper environment looks considerably conducive for an intensifying hurricane, especially given the westerly + northerly branch outflow jets.

Uh oh...

That's a big if though. Early genesis in the NW Caribbean could open the door for the TC to be anywhere along the north GOM, not necessarily a Laura redo. Note how the PV anomaly north of 99L evolves through the first 72 hours. If 99L's resultant TC deepens faster than the GFS models here, a stronger stacked system is likely to feel the initial poleward 500-300 mb flow over the eastern GOM until the TC's diabetic heat transfer processes squash it. This could result in more intial latitude gain until a gradual bend back NW with increasing 500 dm heights over the eastern CONUS. Lots of possibilities here with a notable heavy flood threat in a stalling inland deluge with a possible block scenario late next week into the following weekend. This is unfortunately another nasty setup for inland flooding.

Heh, 99L does not appear to be wasting any time getting organized today. Note the sharpening of the wave axis and evident mid level circulation developing. If these trends continue, location of low level vortex / TCG is going to be sooner ahead of schedule than yet modeled. This would give credence to more northerly clusters of track ensembles, but of course still all unknowns until we have a CoC to track and better model initializations.

So boring yet you'll be posting nonetheless, right? lol

Worst time of year for any TC to reach the northern GOM regardless of gulf loop current position and eddy proximity. The entirety of the northern coast from Texas to the Florida Panhandle is ≥30°C; its profile extending several hundred miles out from shoreline with a very large surface area in the western GOM. A slow moving or stalled system can still upwell and lower its maximum potential intensity, but from the highest of known intensity potential here. Even a large TC with decent motion is only limited by the atmospheric environment which it is contained, interaction with airmass, structure, shear, etc.. Thermodynamic profiles such as these are essentially overkill this time of year until we start seeing cold fronts reach the GOM in late September/October, or numerous TCs decrease heat content. That being said, even a slow moving large TC could stall over the central GOM for several days and likely still remain a major hurricane if under a favorable atmospheric environment. The gulf loop current extends all the way up to the Mississippi River's discharge current at present. So there is a very a deep 26°C isotherm from the Yucatán Channel up to the shallow shelf waters near Louisiana. Really the entire GOM has good depth of heat content, but obviously that absurd loop current profile is like the NW Caribbean.

We're in the medium range now. It's becoming very apparent that the upper level pattern will most likely be primed to support a hurricane in the GOM. The question is the latitude where low level circulation closes off. Obviously a lower latitude will spend more time over the Yucatán and will have a longer organizational period of development versus a more northern region of TCG. This matters for if we are looking at a potential major Harvey-like hurricane or something more slow to intensify into landfall. Nothing is in stone until we have that vortex placement regardless of all the crazy outputs we may yet see from the models. That being said, the signal is clearly on the up that we have a TC in the GOM next week. You do a double-take at these outflow patterns in the 72 to 126 hour range.

While we're all going to be looking to the NW Caribbean and GOM for potential development into the weekend, currently there is a nice AEW south of the Cabo Verdes forecast to make its way across the MDR this week. It's not in a horrible environment at the moment, but conditions are only marginal across the MDR. Some SAL and stable air mass to contend, but it bears watching.

Linda is a sheared cyclone, no doubt. But how on Earth is that not a classified TC? It has a closed low level vortex and ASCAT has TS and Gale force winds. Also, Linda has produced nice bursts of convection over the LLC the past 24 hours. Boggles the mind...

This thread.. and I absolutely agree with it. What the hell has the CPHC been doing the past 24 hours?

Yeah NYC and areas just north are in the pivot of a nasty band.