Advance warning: this is long. If you don't like long posts, skip this, I'm not about to say anything earth shattering, and carry on with your discussion.
Just to be clear, the NHC is staffed by human forecasters--not wizards that set the actual hurricane's wind speed--and forecasting when it comes to intense, high-profile, high-impact events, is an art. The NHC provides an update every 3 hours, they may get an aircraft measurement every 3-6 hours (sometimes they get the benefit of having one or two aircraft in the storm for the entire 3 hour period, other times, like now, there are none). This means, like us, the NHC have to put forth their own best estimate for intensity. Sometimes, they are marginally wrong. I strongly doubt they are ever VERY wrong, but, to be blunt, based on what I'm seeing *right now*, I would bet money that there are not sustained 145 mph winds in the eyewall. To the same degree, storms don't magically become hurricanes, or dissipate, coincidentally always at 3 hour intervals. To further this concept: hurricanes are not single points, and they aren't singular instances of time. When the NHC issues an update, it is for the next 3 hours, and reflects those data received and analyzed over the preceding 3-6 hours (depending on whether it's a completed or intermediate update, early vs late cycle model guidance etc).
A couple hours ago, even an hour ago, a very clear, tight eye was seen that would make a reasonable forecaster conclude persistence to very slight strengthening from the most recent aircraft data, hence 145. Recall basic forecasting principles--your most basic forecast is persistence--things should continue to do what they did before. Tweak that slightly: the eye looks a bit better, the clouds a bit colder (etc etc), and you can as a forecaster bump up your wind guess without an objective measure. I think the NHC has the additional strengthening forecasted pre-Mexico due to the underlying dynamics--very warm SSTs, and modest shear (but it seems possibly a touch more than was expected at this time yesterday). It should be noted that models do not do a great job with compact, intense hurricanes and they wouldn't necessarily show, say, cat 5 winds, well, in this setup. Hence why the NHC is looking at the SHIPS rapid intensification progs to estimate probabilities for further intensification. There has been a trend this season, and over the last few years, for storms to outperform model guidance (given a certain amount of shear, ssts, etc), and the NHC likely factors that into their forecasts as well. Big picture: more heat, low shear, climate change (please don't shoot the messenger!), stronger storms. The NHC knows they're often better betting high than low versus the model guidance. Thus, the main message I'm conveying is--this storm is clearly messy right now. We really need another aircraft to get truly objective data and actually *know* what the current wind speed is, and what the current pressure is. Otherwise, it is a subjective to quasi-objective estimate based on IR/microwave/visible imagery, persistence from earlier aircraft data, mesoscale hurricane model data, and forecaster experience. The NHC's word is not gospel--they do not set the wind speeds/pressure, they provide their best guess. So can you or I, but the NHC is better at it. I look at 156mb and that satellite presentation and (personally) say that the onus for a claim of 145 rests with the claimant--I would need objective measurements from some source for that, otherwise, I'm not buying what you're selling. I also don't jump to cat 5 forecasting either--156 is low, it is not LOW. The storm has not been deepening much for most of the afternoon, it's come up a couple mb. That is not a sign of cat 5 at this time. You can yourself estimate winds subjectively with the right textbook and knowledge to calculate Dvorak numbers and extrapolate estimated winds based on pressure/eye size and other things. The NHC likely correctly assume however that, even if there was or is a temporary slight drop in maximum winds, 145 is likely right in the 3-hour time frame before 8pm, and we are currently seeing conflicting data vis a vis intensity (lots of lightning and good banding but loss of some symmetry and spatial extent of the coldest cloud tops). 155+ therefore remains quite possible before landfall, and the NHC forecast shows that. It should be noted that for anyone who isn't a weather weenie, being WRONG, by being LOW on your wind forecast, is an order of magnitude worse for the public and preparedness than being a touch too high.
Also note that the NHC deliberately tries to make changes slowly. Their job is communicating risk to the public and public safety officials. Meteorologists know how to read models, interpret satellite imagery and understand charts--so the NHC is not necessarily writing explicitly minutia-level changes. No one, sans a weather weenie, stands outside in strong winds with an anemometer, pushes up on their glasses and exclaims: "these winds are 10mph less than the NHC said they'd be!", and after the end of the season, the NHC goes back and reviews the data from all the storms and confirms intensities and other things. The last hour has seen a notable reduction in the symmetry of the coldest -80-90 degree cloud tops, and a clear eye is NOT visible. If the storm continues to be disorganized, they may well lower the winds a touch on the next advisory or hold them steady. Conversely, shear could abate a bit, and a bit more intensity could be added. Almost all intensity guidance now says that the storm should maintain intensity or weaken slightly (sans two models which show a cat 5 peak, but are out to lunch as they keep the storm extremely strong once inland in the US...I question any other things they're projecting as a result). I'm more concerned, personally, about the fact the models lately are keeping the storm at major status to landfall, and the nhc track hints at that. If you overlay a cat 3 landfall slightly west of New Orleans, and then have that strong right side onshore flow into that area, you're gonna have some problems, though the new protection system should help that...in theory.
Cheers all!
