vortex95

Another HU warm eddy RI? Opal in Oct 1995. 80 > 130 kt in 22 hr 130 > 100 kt in 12 hr (100 at landfall). 19951003, 1200, , HU, 22.8N, 91.6W, 80, 968, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951003, 1800, , HU, 23.5N, 91.0W, 85, 965, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 0000, , HU, 24.5N, 90.1W, 100, 953, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 0600, , HU, 25.9N, 89.4W, 110, 935, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 1000, I, HU, 26.6N, 88.8W, 130, 916, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 1200, , HU, 27.3N, 88.5W, 130, 919, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 1800, , HU, 29.0N, 87.7W, 110, 938, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 19951004, 2200, L, HU, 30.3N, 87.1W, 100, 942, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, 50

FL wind reduction to sfc 700 - 90% 850 - 80% 925 - 75% 300 m - 80% 150 m mean layer - 85% However, Sfc-700 mb wind ratios vary from TC to TC and can range from ~70% to >100%. But departures from standard adjustment cannot be determined from just a few sondes b/c of convective vigor, eye wall structure/cycle, RMW, and/or low-level stability/cooler waters. In order for 700 winds to be 100% at the sfc, I think you need an exceptional eye wall ring and the hurricane in RI mode, like Andrew was at landfall. Also, CGs in the eye wall indicating better updraft/downdraft couplets.

For scale, I attached zoomed out WV image,. The CDO/core of Isaias is very small. That makes it much more susceptible to shear and dry air. Also, easier RI. The 12z HAFS A/B shows sig intensification, but the rate of weakening it shows just in the last 9 hr up to landfall is quite remarkable. Just from a wild extreme swing one end to the other, this may be an exceptional event meteorologically. We get lots of big RIs just before landfall (Michael, Otis), but going the other way? I know no Atlantic situation quite like this, at least for an impending landfall. Sure, many HUs elsewhere has got torn apart in short order, but it is so much different when close to landfall and the system is quite strong within say 12-15 hr of landfall. A lot more eyes are on it!

They are reaching IMHO. No drop in pressure and FL winds the same? That tail radar measurement I bet was due to pulsing convection transitory spot wind, rather than true gradient. And the Dvorak does not support 85 kt winds. One observation does not take precedence over several observations that show the contrary. I just find if they can hedge higher for system threading land, they will.

This happened w/ HU Lili in Oct 2002. It ramped up very quickly over the loop current, but once exiting, it weakened even faster in short order. 90 > 125 kt in 24 hr and then 125 > 80 kt in 24 hr at landfall. And the environment for LIli was not nearly as baroclinic w/ a lot of dry air/shear present as Isaias now. 20021002, 0000, , HU, 23.0N, 85.7W, 90, 967, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021002, 0600, , HU, 23.6N, 87.2W, 100, 962, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021002, 1200, , HU, 24.4N, 88.3W, 110, 952, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021002, 1800, , HU, 25.4N, 89.5W, 120, 941, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021002, 2013, I, HU, 25.9N, 89.9W, 125, 938, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021003, 0000, , HU, 26.7N, 90.3W, 125, 940, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021003, 0600, , HU, 28.1N, 91.4W, 105, 957, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021003, 1200, , HU, 29.2N, 92.1W, 80, 962, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999 20021003, 1300, L, HU, 29.5N, 92.2W, 80, 963, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, -999, 10

Isaias is an atypical TC situation esp. for a landfall. In a way it reminds me of Sandy in Oct 2012, but some differences. However, it has similar implications. The models, both global and hurricane, all along have showed very rapid weakening of Isaias the last 9-12 hr to landfall. 12z HAFS-A 09/18z 951 mb /110 kt 10/03z 984 mb / 63 kt 12z HAFS-B 09/18z 964 mb / 99 kt 10/03z 985 mb / 57 kt So there is a serious question if it will be a hurricane at landfall. In addition, looking at the storm structure forecast, it is difficult to imagine it will still be classifiable as a tropical cyclone at landfall. The SHIPS shear value is 35 kt 09/12z increasing to 49 kt 10/00z. It is fully embedded in a 250 jet streak near landfall and all the convection sheared off N of the center at the time. Very dry air (<20% 700-300 RH) is completely wrapped around and over the center (HAFS A/B forecast attached) and clear, defined frontal features apparent on the moisture fields. Since Isaias is rather small and not that strong, it is unlikely to be able to ward off wind shear and dry air intrusion, like Ian did in Sep 2022. Despite all of the above, I do not see any real emphasis currently in the mainstream on this very real possibility. I've seen this before from NHC. They avoid much emphasis on rapid weakening close to landfall b/c they think ppl will not take the warnings as seriously, but I find this disingenuous. They are not being objective and transparent. This was apparent w/ Milton, which is the most rapid weakening for a HU in a short period leading up to a U.S. landfall. Our forecast skill/modeling have come a long way for TCs, so confidence in outlier or atypical scenarios is higher these days and we should take full advantage of this operationally. I know of no Gulf hurricane situation quite like this one where such rapid weakening and quick PT/ET transition occurs near landfall (Milton comes close). And I see no reason why the HAFS weakening forecast would be wrong given the synoptic pattern currently and this model handled the very rapid weakening of Milton. That was a strong baroclinic interaction with high shear impacting the hurricane. So this presents a problem/challenge as to how Isaias could be handled. The concern is that in deference to messaging, it may not be called PT/ET at landfall or below hurricane strength even if it clearly is since within 12 hr of landfall it may be much stronger. From an objective meteorological standpoint? It should not matter where a TC is (close to a landfall or far at sea), how strong it is, or what type of watches/warnings are in effect, it should be treated "as is" operationally. So if goes ET/PT just before landfall, call it for what is it. The atmosphere does not care about our subjective policies/rules, it does what it does. There is nothing that says a TC can not go ET/PT just before landfall, and it has been done before (Sandy). And after Sandy, things were adjusted so tropical watches/warnings remain in place even if a TC goes ET/PT, so things are covered here from a messaging standpoint. This kind of objectivity is important to the meteorological science. A hurricane at landfall or not is significant from a climo standpoint. And in some cases depending on the state, county, or city/town, what something is called/labeled makes a difference from an insurance and legal standpoint. Some may say all what I say above is being pedantic or picayune, but I beg differ. There were significant discussions and controversy in the meteorological and other fields as to what Sandy was called at landfall. I am just proactively pointing out beforehand a similar TC situation currently.

Probably b/c of it small size. Global models had trouble picking it up.

The 00z ECMWF still has a stark 700-300 mb RH gradient early on that just intensifies as it heads N. The pattern/structure at 108 hr for this parameter looks more like a baroclinic leaf than anything. It dependents it to 998 mb, 9 nm weaker than the 00z, which is in line w/ the 1992 and 1994 early Oct events as to am ET low development in the Gulf making landfall. The HAFS-B is much deeper, but also look at its 700-300 mb RH fcst (attached). That configuration strongly suggests a frontal structure and baroclinic leaf. I would find it hard to believe it could drop into the 970s from largely baroclinic forcing. The deepest ET low in the Gulf ion record s 980 mb from the Bliz of 1993 and that had unreal baroclinic support! The GFS does the opposite of the HAFS-B, it makes it strong as a TC early, and *then* weakens is as it heads N. That coulld happen.

That much snow already made on Whiteface Mtn trails? https://www.facebook.com/share/p/19m3Gzn9Z8/ It did snow: https://www.instagram.com/p/DeH8zc0ylm9/?utm_source=ig_embed&utm_campaign=embed_video_watch_again But is that FB image current?

And "one more hour of cooling so it can snow easier!" You actually see this nonsense posted. Some are trolling but some actually believe it. I see the same thing for svr wx. Extra hour of heating after late March in the Plains!

Given the fcst 850-200 mb wind shear over the northern Gulf is fcst in excess of 50 kt and how the global models depict the storm structure, I have a tough time thinking this can sustain a tropical status once farther N. Sfc winds E of the center will likely get quite strong, but due to baroclinic deepening. If this were a well-established strong TC already, I would not be as concerned about the shear here. Here are two storms in early Oct 1992 and 1994 that fit this scenario. The 1992 event deepened to 996 mb and and 1994 to 1000 mb from baroclinic processes.

Posted this on the Tropical Forum, but will do so here b/c this could some "fun ' games" as to what is what when it comes to a TC or not! ----- Something doesn't seem right. I was surprised the 18z ECWMF suddenly went the GFS route. The 700-300 mb RH fields and PWAT anoms tell the story. I attached 18z ECMWF 72, 105, and 114 hr 700-300 RH. Even when it is still the Bay of Campeche, it is "halved" from a strong moisture gradient, and it just gets stronger w/ time. looking like a typical ET low development. And look at the 114 hr fcst PWAT anomaly. That clearly shows a frontal structure, and compare the PWAT anomalies to Simon in the EPAC. That's not nearly the anomaly you'd see in a typical TC. I can see NHC "playing games" here. Calling it something that it is not b/c of non-meteorological factors (social media nonsense, its sensible wx impact, etc). But ET low can and do form in the Gulf in Oct (see the 1992 case I posted about earlier) and given the strength of El Nino, it makes ET lows this early even more likely. In fact, by 36 hr, the 250 mb STJ become quite apparent near the Gulf Coast, and in 5 days close to landfall, a strong 250 s/w is present in the region, obviously aiding in the system's development. Some might go, "but the simulated IR from the GFS shows an eye!" Well, it is the GFS, and yes, initially it could be a TS/STS but here lies another issue, transition to a PT/ET low when it is approaching a landfall. Sandy anyone? You see the problem here. But I say, in the end, it is what it is, and call it as such. Don't let external pressures and nonsense contaminate the met science!

CAR 2.5" Sep 29-30, 1991 for its first measurable snow on record in Sep. 2" at Glen NH Sep 16, 1986 as a spinner occurred at the same time in Scituate MA. @CoastalWx be like, "how can that be!?"

One could say that Miller A having higher LEQ and lower snow ratios due to their warmer nature, they likely have more underestimation due to compaction.

40"+ was common N&W of BOS for 78.