The next Cat 5 U.S. landfall

[HurricaneEnzo]

While a Category 5 hurricane making landfall in New England at that intensity is indeed extremely unlikely - I would say essentially meteorologically impossible in the 21st century, at least, and there is no historical or known paleotempestological evidence for such a storm going back several centuries - a Category 4 hurricane landfalling at that intensity, far north of Hazel's landfall, is very possible, and indeed, has likely happened multiple times over the past few centuries. All it takes is a sufficiently intense hurricane racing northward at approximately 50mph over warmer-than-average SSTs, with baroclinic interaction briefly enhancing intensification or slowing weakening. As noted earlier, the 1635 Great Colonial Hurricane likely struck Long Island and Connecticut as a Category 4 hurricane (yes, some have speculated a Category 5 intensity out at sea, but not at landfall) with a minimum pressure in the 930s and a storm surge of over 20 feet, likely making it the strongest hurricane to hit New England since European colonisation in 1620. (See reanalysis via SLOSH modelling at https://www.aoml.noaa.gov/hrd/Landsea/12Tides.pdf) The 1815 hurricane likely struck Long Island and Connecticut as an upper-end Category 3 hurricane. The 1821 Norfolk-Long Island Hurricane likely struck New Jersey as a Category 3 or 4 hurricane (I would verge on minimal Cat 3 for NJ landfall, based on https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4258685/ and https://esajournals.onlinelibrary.wiley ... -9615(2001)071[0027:LARIOH]2.0.CO;2), and there is sedimentary evidence of a stronger (I would argue considerably stronger, given the thickness of the overwash fan and the indication the storm surge penetrated far deeper inland, due to the coastline being further out back then) hurricane striking New Jersey between 1278 and 1438; based on the comparison to the 1821 Hurricane, I would estimate this prehistoric storm to be a Category 4 hurricane, possibly striking at high tide (the 1821 hurricane struck at very low tide), possibly even more intense than the 1635 hurricane. (See here: http://www.geo.brown.edu/georesearch/es ... Jersey.pdf)

If you want to imagine what such a northern storm might look like on satellite, look no further than Hurricane Ella in 1978, which, thanks to baroclinic instability as it interacted with a mid-latitude system, rapidly intensified into a Category 4 hurricane just south of Nova Scotia, passing the same latitude as New York City. (It became extratropical 24 hours later; the 1938 Long Island Express, a strong Category 3 hurricane at landfall on Long Island, was likely undergoing extratropical transition at landfall, in comparison.) As you can see, it looks rather like a leaner, meaner version of Hurricane Bob.

https://i.imgur.com/lOGd382.jpg

So, in terms of doomsday storms, a Category 5 hurricane weakening to a Category 4 before striking New England is certainly possible and, indeed, a climatological inevitability. But maintaining Category 5 intensity that far north? No.

It doesn't really matter, though; a Category 4 hurricane striking New York City would still likely be the deadliest and costliest American hurricane in history. I recall one meteorologist on this site, Derek Ortt, using SLOSH simulations, minimal lead time (due to racing forward speed of such storms; the Long Island Express was actually slower than most previous New England major hurricanes) and the logistical impossibility of mass evacuations to predict a death toll of hundreds of thousands and half a trillion dollars in damages in such an event, and the insurance company Swiss Re predicted a $107 billion storm if the 1821 storm (which is far from the doomsday scenario) repeated itself.

Not to diminish anything you said but in my opinion sedimentary evidence is far from accurate. I mean it can probably get you within 2-3 categories but as we have seen surge can vary hugely with things such as storm surge, duration of wind, direction of wind, etc.

If Katrina had happened in the 1600s and they found evidence of the 28 foot storm surge they would immediately think it was a monster Cat 5 at landfall. We know that is not the case. Sandy which was not even technically tropical and had a pressure almost in the 930s and created a 13 foot storm surge in NYC.

Sedimentary evidence can help get you in the ballpark but it is far from conclusive IMO. And this is not directed at you personally but some would have you believe it is far more accurate than it is.

Once again it is nothing against you personally. IDK it has always been a little 'pet peeve' of mine when we make assumptions using only sedimentary data. Some of the other cases you listed had supporting evidence which is great. Some people think they can tell us exactly how strong a storm was or exactly what the temperature was 500 years ago by looking at sediment. I'm not saying there is no merit in it but the margin for error is large. It's kinda if someone dumped a 1000 piece jigsaw puzzle in front of you and you think you know exactly what the whole puzzle looks like assembled by looking at just one piece. Should come with an asterik lol.

But I digress, I agree with you about a Cat 4 being able to make it to the NE given the rare occurrence of perfect conditions aligning.

[HurricaneEdouard]

Not to diminish anything you said but in my opinion sedimentary evidence is far from accurate. I mean it can probably get you within 2-3 categories but as we have seen surge can vary hugely with things such as storm surge, duration of wind, direction of wind, etc.

If Katrina had happened in the 1600s and they found evidence of the 28 foot storm surge they would immediately think it was a monster Cat 5 at landfall. We know that is not the case. Sandy which was not even technically tropical and had a pressure almost in the 930s and created a 13 foot storm surge in NYC.

Sedimentary evidence can help get you in the ballpark but it is far from conclusive IMO. And this is not directed at you personally but some would have you believe it is far more accurate than it is.

Once again it is nothing against you personally. IDK it has always been a little 'pet peeve' of mine when we make assumptions using only sedimentary data. Some of the other cases you listed had supporting evidence which is great. Some people think they can tell us exactly how strong a storm was or exactly what the temperature was 500 years ago by looking at sediment. I'm not saying there is no merit in it but the margin for error is large. It's kinda if someone dumped a 1000 piece jigsaw puzzle in front of you and you think you know exactly what the whole puzzle looks like assembled by looking at just one piece. Should come with an asterik lol.

But I digress, I agree with you about a Cat 4 being able to make it to the NE given the rare occurrence of perfect conditions aligning.

I fully agree with you and I thank you for raising the point for the benefit of other readers, particularly given the context in this study that the third-greatest overwash fan was likely deposited during the Ash Wednesday Nor'easter, since no other New Jersey storm matched the indication of a 20th century dating other than that particularly intense 1962 extratropical cyclone; paleotempestological research has difficulty enough distinguishing between tsunamis and storm surge, let alone extratropical and tropical cyclones, so indeed the accuracy is quite low. That said, I think blending sedimentary evidence with SLOSH simulations and other climatological indicators can yield interesting conclusions with some confidence, even if highly speculative (but the speculation is part of the fun!).

Given that the coastline was, if I recall correctly, 1km further out in this time period than in 1821, the overwash fan associated with this event, which is thicker than the overwash fan associated with the 1821 hurricane, does fairly strongly indicate that the storm tide caused by this hurricane was considerably greater than the storm tide of the 1821 hurricane, and penetrated at least 1km deeper inland. Is this indicative of a greater storm surge? Not necessarily; as noted, the 1821 hurricane struck at very low tide, so a storm of comparable or even lesser intensity (as we saw with Sandy) could cause a similar or greater storm tide simply by striking at high tide.

That said, I think Sandy gives us a good benchmark for this. It indicates a gigantic, weaker or hybrid system striking close to high tide can yield a storm tide comparable to the 1821 hurricane, but not considerably greater; I think the sedimentary evidence would indicate a Sandy-like event likely did not cause the seemingly greater storm tide associated with this 13th to 15th century storm, but rather a major hurricane of some sort. A major hurricane striking at high tide and on a different angle of approach (southeast to northwest, for example, rather than skirting the coast as the 1821 hurricane did) could account for the difference, certainly. The private reason I speculate a Category 4 hurricane is likely more responsible for this event than a large, sprawling weaker storm is the discovery that all of the major hurricanes making landfall in New England, going back to the Great Colonial Hurricane of 1635, have had small radii of maximum winds, even the 1938 hurricane, which was undergoing extratropical transition at the time (some argue it was already extratropical). As Brian Jarvinen (former NHC storm surge program leader and SLOSH expert) noted, it is possible that the only way to get a major hurricane that far north is indeed if it has a small RMW; this may be one of the meteorological prerequisites for such an event, alongside 40mph+ forward speed and baroclinic interaction. Although weak evidence as far as tropical climatology goes, taken together I would lean towards the 13th to 15th century event being associated with a major hurricane with a climatologically small RMW, which would weakly indicate its exceptional storm tide may be more associated with greater intensity and better timing (tide-wise) than the 1821 hurricane, rather than greater size.

Again, all of this is highly speculative, but given that we know with fairly good confidence (unrelated to sedimentary evidence; simply simulating storms that produce the wind and storm surge observations in accounts of historical storms) that minimal Category 4 hurricanes can and have struck New England, then I would wager the 15th to 18th century New Jersey event is more intense than the 1821 hurricane, possibly more comparable to the 1635 hurricane, rather than not!

[HurricaneEnzo]

Agreed definitely need that supporting evidence to really nail it down.

[Do_For_Love]

The private reason I speculate a Category 4 hurricane is likely more responsible for this event than a large, sprawling weaker storm is the discovery that all of the major hurricanes making landfall in New England, going back to the Great Colonial Hurricane of 1635, have had small radii of maximum winds, even the 1938 hurricane, which was undergoing extratropical transition at the time (some argue it was already extratropical). As Brian Jarvinen (former NHC storm surge program leader and SLOSH expert) noted, it is possible that the only way to get a major hurricane that far north is indeed if it has a small RMW; this may be one of the meteorological prerequisites for such an event, alongside 40mph+ forward speed and baroclinic interaction

Again, all of this is highly speculative, but given that we know with fairly good confidence (unrelated to sedimentary evidence; simply simulating storms that produce the wind and storm surge observations in accounts of historical storms) that minimal Category 4 hurricanes can and have struck New England

You did an awesome job writing up all this info and with that laid out better than I could do. I also noticed in reading about those strong NE hits that they all moved super fast as you pointed out. I didn't notice that they were mostly small storms but that's interesting also.

So tell me where my logic is wrong here. Take all those ingredients, a small storm, super fast speed, and the fact that in the past they have had Cat 4 impacts. Well, is it really controversial to suggest that the waters off of FL and the Carolinas are now warmer than they were in 1635 and thus could support a stronger storm? And that if the storm is a little stronger than in 1635, which landfalled as a Cat 4...it could instead landfall as a low end Cat 5 instead now?

I mean, maybe i'm wrong with thinking about how much extra energy goes into a Cat 5 v/s a Cat 4 but in my mind it doesn't seem like a ridiculous stretch. 99% chance it doesn't happen either way so it's just academic. But like I said, take the 1635 storm and replace it with Hurricane Dorian following the same pattern instead - could it squeak in at a 156 mph landfall?

[toad strangler]

The private reason I speculate a Category 4 hurricane is likely more responsible for this event than a large, sprawling weaker storm is the discovery that all of the major hurricanes making landfall in New England, going back to the Great Colonial Hurricane of 1635, have had small radii of maximum winds, even the 1938 hurricane, which was undergoing extratropical transition at the time (some argue it was already extratropical). As Brian Jarvinen (former NHC storm surge program leader and SLOSH expert) noted, it is possible that the only way to get a major hurricane that far north is indeed if it has a small RMW; this may be one of the meteorological prerequisites for such an event, alongside 40mph+ forward speed and baroclinic interaction

Again, all of this is highly speculative, but given that we know with fairly good confidence (unrelated to sedimentary evidence; simply simulating storms that produce the wind and storm surge observations in accounts of historical storms) that minimal Category 4 hurricanes can and have struck New England

You did an awesome job writing up all this info and with that laid out better than I could do. I also noticed in reading about those strong NE hits that they all moved super fast as you pointed out. I didn't notice that they were mostly small storms but that's interesting also.

So tell me where my logic is wrong here. Take all those ingredients, a small storm, super fast speed, and the fact that in the past they have had Cat 4 impacts. Well, is it really controversial to suggest that the waters off of FL and the Carolinas are now warmer than they were in 1635 and thus could support a stronger storm? And that if the storm is a little stronger than in 1635, which landfalled as a Cat 4...it could instead landfall as a low end Cat 5 instead now?

I mean, maybe i'm wrong with thinking about how much extra energy goes into a Cat 5 v/s a Cat 4 but in my mind it doesn't seem like a ridiculous stretch. 99% chance it doesn't happen either way so it's just academic. But like I said, take the 1635 storm and replace it with Hurricane Dorian following the same pattern instead - could it squeak in at a 156 mph landfall?

Sustained? cray cray
Not happening
Cat 5's DO NOT roam the sub tropics. Period

[HurricaneEdouard]

You did an awesome job writing up all this info and with that laid out better than I could do. I also noticed in reading about those strong NE hits that they all moved super fast as you pointed out. I didn't notice that they were mostly small storms but that's interesting also.

So tell me where my logic is wrong here. Take all those ingredients, a small storm, super fast speed, and the fact that in the past they have had Cat 4 impacts. Well, is it really controversial to suggest that the waters off of FL and the Carolinas are now warmer than they were in 1635 and thus could support a stronger storm? And that if the storm is a little stronger than in 1635, which landfalled as a Cat 4...it could instead landfall as a low end Cat 5 instead now?

I mean, maybe i'm wrong with thinking about how much extra energy goes into a Cat 5 v/s a Cat 4 but in my mind it doesn't seem like a ridiculous stretch. 99% chance it doesn't happen either way so it's just academic. But like I said, take the 1635 storm and replace it with Hurricane Dorian following the same pattern instead - could it squeak in at a 156 mph landfall?

Thank you!

So, I would say there is indeed quite a stretch between a Category 4 and a Category 5 hurricane. Since (HURDAT) records began in 1851, there have been 149 Category 4 hurricanes recorded in the Atlantic basin; only 36 of them are known to have attained Category 5 intensity (although admittedly there were probably multiple missed Category 5 hurricanes between 1851 and 1924), and that will likely continue to be revised downwards as the Reanalysis Project continues. Category 4 hurricanes have reached as far north as 42.50 N latitude, going by the northernmost Category 4 hurricane recorded in HURDAT, the aforementioned Ella in 1978. (Reanalysis might knock its peak winds down from 120 knots, but the winds were a recon measurement in an era when recon measurements were becoming more reliable, and the minimum central pressure of 956 mb would support the recon measurement at that forward speed and in that part of the world, so I doubt Ella was weaker than 115 knots.)

In comparison, the northernmost Category 5 hurricane recorded in the Atlantic basin (Michael) achieved that intensity just north of 30 N; sediment stratigraphic data indicate that 12 hurricanes of comparable intensity (or at least creating a comparable storm surge; some of these could be Katrina-esque large Category 3 or 4 hurricanes with a storm surge, partly retained from peak Category 5 intensity, still reaching the shore) struck the same region during the past 3,400 years, and of course Camille struck Mississippi just north of 30 N as a Category 5 hurricane as well, so there is evidence Category 5 hurricanes around 30 N are not entirely rare, but the historical evidence and paleotempestological evidence sharply drops off north of 35 N; this is because SSTs sharply drop off around 38.5 to 39 N.

The story isn't that much different in the West Pacific, the warmest and most active tropical cyclone basin in the world, which supplies us with so many Category 5 super typhoons that we have a far better dataset (and far more anomalous storms) to go by than the Atlantic. Typhoon Vera in 1959, if we accept the JTWC wind estimate as reliable (it may well not be; recon wind estimates in the 1950s and 1960s were generally too high, and 920 mb in that area of the world in September may well correlate to a Category 4 typhoon), is officially recorded as maintaining that intensity up to landfall in Japan, west of Shionomisaki, at 33.4 N. This may sound extremely northerly by our (or even West Pacific) standards, and indeed Vera might be the northernmost Category 5 tropical cyclone recorded, but this is only the same latitude as South Carolina.

So, long story short, there is no reliable/recent evidence from any tropical cyclone basin, even the West Pacific, that a Category 5 tropical cyclone can persist as far north as New England. There is also no historical evidence, or paleotempestological evidence obvious enough for a report to be made espousing such (and there have been quite a few paleotempestological studies in New England at various sites, e.g. A multimillennial record of intense hurricanes in New England, P. Lane, 2007, going back over 3,200 years), that a Category 5 hurricane has ever made landfall in New England; the most intense hurricane to ever strike New England since European colonisation in 1620 does appear to be the Great Colonial Hurricane of 1635, which SLOSH simulations indicate was possibly a borderline Category 4 hurricane with 115 knot winds. In the context of the general meteorological consensus (I'm not a meteorologist myself, but that is the consensus among tropical cyclone specialists) that the atmospheric conditions and SSTs are simply too hostile in all basins to support Category 5 tropical cyclones at so far north a latitude, I do think absence of evidence is fairly good evidence of absence.

As for whether warmer SSTs, or, in a nutshell, climate change, might allow for a hurricane considerably more intense than the 1635 hurricane anytime soon, I doubt it. Without wading into the debate as to whether the net effects of climate change are more likely to suppress or enhance Atlantic activity (and the variability within that debate between enhancement/suppression of frequency versus intensity), I will note that, per the reanalysis report linked earlier, SSTs were likely 80 degrees F or warmer up to about the latitude of southern New Jersey in late August 1635 (when SSTs off the Mid-Atlantic Coast and New England are at their warmest); this is comparable to or greater than periods of anomalously high SSTs off New England over the past few decades, e.g. in August 1991 (Hurricane Bob), not significantly lesser. Paleotempestological studies of hurricane strikes in New England go back millennia, and the paleotempestological indications in New England and the northern Gulf Coast indicate a hyperactive Atlantic regime from circa 1200 BC through 980 CE featuring far more frequent and intense hurricanes than in the period 1000 CE to present. In other words, even if climate change does amplify tropical cyclone intensity and poleward persistence, and its effects continue to coincide with the seemingly ongoing AMO+ phase, this is no reason to toss out historical or paleotempestological data.

I think the sort of scenario you're talking about has happened - the 1635 hurricane may well have been as intense as Hurricane Dorian out at sea, and potentially at a higher latitude than Dorian, and we know the 1938 hurricane achieved Category 5 intensity in a similar part of the world before racing northward - but the "perfect conditions" you're talking about is what allows for a hurricane (small RMW, extremely high SSTs, racing even faster than the 1938 hurricane, baroclinic interaction) to "squeak in" a marginal Category 4 landfall, not a marginal Category 5 landfall. In other words, the reason why a Category 4 landfall in New England is so rare, and hasn't happened since at least 1821, is because it takes essentially perfect conditions. These hurricanes are undergoing, or close to undergoing, extratropical transition as they make landfall, and are likely enhanced by baroclinic instability; their extreme winds edge into Category 4 because they are racing so fast that 1. they are able to just barely maintain their intensity at a latitude that would otherwise not support this intensity and 2. the forward speed adds to their windspeed in the right quadrant of the storm (and subtracts from the left quadrant). But these storms themselves are already so marginal and unlikely (indeed, the 1938 hurricane may not have even been tropical when it made landfall), essentially just functions of troughing causing extreme rapid forward speeds and baroclinic interaction enhancing windspeed, that I really do believe it is impossible for a Category 5 hurricane, a few hours from extratropical transition, to make landfall at that intensity in New England; the "perfect Category 5 monster" you're talking about is likely precisely what allows for that "freak," extremely rare Category 4 landfall.

[Evan_Wilson]

It would definitely not be out of the realm of possibility for a Category 5 to reach as far north as North Carolina this year given the extremely high heat content.

[Do_For_Love]

I appreciate you taking the time to write up your thoughts on that HurricaneEdouard, very informative and interesting post. Honestly I learned a lot haha.

I personally do think that TCs are starting to get stronger overall and at higher latitudes. Sadly I think the science has moved in that direction recently, especially with the Cat 5 streak we're on in the last few years. Here's an abstract from a study in a prestigious journal from this year that came to that conclusion as an example: https://www.pnas.org/content/117/22/11975.

So I don't think climo is useless at all, but I do think it might become less relevant moving forward. I guess where I come at this from is just that at this point I expect the unexpected when it comes to weather. I mean thinking about the heat in Siberia this year, to the wildfires in Australia, to just how crazy it was when Dorian bombed out last year or when Harvey dropped Noah's ark levels of rain...idk, it just feels like the rules are being bent more and more in my opinion.

Maybe a Cat 5 in New England is pushing it on my part lol. However, I bet that Michael's current record for highest latitude Cat 5 Atlantic landfall won't hold up another 50 years if we continue on the road we're on with climate change. it might even fall a whole lot sooner than that IMO!

[HurricaneEdouard]

I appreciate you taking the time to write up your thoughts on that HurricaneEdouard, very informative and interesting post. Honestly I learned a lot haha.

I personally do think that TCs are starting to get stronger overall and at higher latitudes. Sadly I think the science has moved in that direction recently, especially with the Cat 5 streak we're on in the last few years. Here's an abstract from a study in a prestigious journal from this year that came to that conclusion as an example: https://www.pnas.org/content/117/22/11975.

So I don't think climo is useless at all, but I do think it might become less relevant moving forward. I guess where I come at this from is just that at this point I expect the unexpected when it comes to weather. I mean thinking about the heat in Siberia this year, to the wildfires in Australia, to just how crazy it was when Dorian bombed out last year or when Harvey dropped Noah's ark levels of rain...idk, it just feels like the rules are being bent more and more in my opinion.

Maybe a Cat 5 in New England is pushing it on my part lol. However, I bet that Michael's current record for highest latitude Cat 5 Atlantic landfall won't hold up another 50 years if we continue on the road we're on with climate change. it might even fall a whole lot sooner than that IMO!

Thank you again! It was a very interesting discussion!

I think it's too early to say whether Atlantic tropical cyclones are getting stronger and at higher latitudes, at least relative to the background climatological trend of what would be expected from the AMO (which, for example, the study above isn't able to account for in the Atlantic, as it only goes back to 1979 - when the Atlantic was in AMO- and far less active than the 1920s-1960s). Sadly, AMO notwithstanding, I find that the compartmentalisation of meteorology and climatology means otherwise fascinating studies often cite official activity and intensity records (e.g. HURDAT) to reach their conclusions without mentioning that these records are likely incomplete, inaccurate and overall unrepresentative for comparison purposes, even in light of the (necessarily conservative, because they can't change Best Track data based on pure speculation) Reanalysis Project.

We just don't have enough climatological data; in terms of semi-reliable records, we really only have two AMO+ phases (1920s through 1960s, and the current one 1995 onwards) and one AMO- phase (1970s through early 1990s) to go by, and the most recent AMO+ phase seems roughly comparable to the present in terms of seasonal activity, intensity of storms and devastating/damaging landfalls. For example, in terms of activity, 1933 still stands as the second most-active season in terms of total named storms, after 2005, and reanalysis gave it multiple Category 5 systems.

In terms of intensity, the 1935 Labor Day Hurricane is officially recorded as 892 mb and 185 mph, but this is likely conservative; its extremely tiny RMW (far tighter pressure gradient = far higher windspeeds) and witness accounts of the windspeed and its unprecedented effects (sand blasting) make me think it was likely a Patrica-like micromonster (and likely intensified at a similar rate to Patricia and Wilma, bombing from a tropical storm to the equivalent of a "Category 7" in a day, as it made landfall in the Keys) even smaller than 2001's Iris, with sustained winds in excess of 200 mph and a minimum central pressure in the 880s, possibly more intense than Wilma. The 1932 Cuba Hurricane was probably far more intense than 915 mb, as well, since its central pressure comes from a ship report in the eyewall, far from the centre of the eye (and, on a probabilistic basis, the ship likely missed the peak, as well); I would not be surprised if it was sub-900.

In terms of damaging hurricanes, a Swiss Re insurance report indicated the Great Miami Hurricane of 1926 would be costlier than Katrina and Harvey (the current record-holders for costliest Atlantic hurricanes) if it struck today, and indeed the top of this "Cost adjusted for wealth normalisation" list is crowded out by various monstrous hurricanes of old, such as the Galveston Hurricane of 1900 (which also supersedes Katrina and Harvey), the Galveston Hurricane of 1915, the New England Hurricane of 1938, the Pinar del Rio Hurricane of 1944, the Lake Okeechobee Hurricane of 1928, and Hurricane Donna. As for latitude, there were quite a few Category 5 hurricanes in rather easterly and northerly positions in the Atlantic during the last AMO+ phase, as well, such as the aforesaid 1938 Hurricane, and 1961's Hurricane Esther.

But I agree that Michael's "record" is likely to fall fairly soon; a Category 5 hurricane in the subtropics around 30N is clearly a fairly common phenomenon, at least on the sorts of timescales we're talking about.

Re. Cat 5 into New England, I wanted to add (but ran out of time last post) that the reason a Category 5 is so much unlikelier relative to the already extremely difficult-to-achieve (everything has to be perfect) Category 4 scenario, aside from the sharp drop-off in SSTs, is that as the storms move north they start to interact with the jet stream/trough to the west (which is what's causing the northward turn and acceleration). The storm gains extratropical characteristics which include the pressure gradient decreasing, the windfield expanding and spreading out; this interaction with the trough is absolutely necessary to bring a major hurricane to New England, because (as we saw in 1938 with the shortwave trough) the baroclinic interaction briefly (before shear from the trough typically tears it apart) gives it an "unnatural" pump to intensity, and accelerates the storm so fast that the winds on the right quadrant are "unnaturally" enhanced (that is to say, a storm with the same central pressure would have considerably lower speeds if it was moving more slowly) and allows the hurricane to maintain intensity over waters otherwise too cold to support such an intensity.

This is why major hurricanes near the East Coast look so "ugly" compared to major hurricanes in the Gulf of Mexico or Caribbean; they are beginning to undergo extratropical transition and take on that characteristic hybrid comma shape, the convection develops predominantly on the west and north side because the jet stream/trough/front is creating a favourable environment for lift ahead, and the eye is ragged or filled. They are typically quite sheared, as well. In other words, these are mostly storms that, if they were magically transplanted to the Gulf of Mexico and were moving more slowly, would likely be Category 2 hurricanes, or such; the higher windspeed is an "artificial" phenomenon resulting from the interaction with a trough or other non-tropical low, both in terms of insane forward speed of the cyclone and baroclinic effects of transitioning. The very same processes that, if "the stars align" perfectly, allow a Category 3 or 4 hurricane to reach New England would yield the very same structure that, dynamically, simply does not create the tight pressure gradient, structural symmetry and cyclonic depth that yields Category 5 intensity; based on land observations, Hurricane Carol was probably the most "purely tropical" of New England's recorded major hurricanes, and it was a marginal Category 3. So far as we can tell, a Category 5 hurricane has to be a purely tropical system; this isn't to say they can't benefit from baroclinic effects (indeed interaction with troughs likely underpinned Patricia's explosive intensification and similarly rapid weakening as it recurved, ditto Michael's and operationally Category 4 Opal's), but they can't be hybrid systems, or well on their way to becoming so, as New England hurricanes are.

For a few satellite references of the kind of structure I'm talking about, see marginal Category 3 Bob in 1991 (https://upload.wikimedia.org/wikipedia/ ... _1230Z.png), Category 2 (peaked at 5) Isabel in 2003 (https://upload.wikimedia.org/wikipedia/ ... _1555Z.jpg), Category 3 (peaked at 4) Edouard in 1996 (https://d3i71xaburhd42.cloudfront.net/8 ... ure3-1.png), Category 2 (peaked at 4) Floyd in 1999 (https://projects.ncsu.edu/atmos_collabo ... oyd.ir.jpg), and Category 4 Ella on the last page.

[gfsperpendicular]

Very interesting post. Isabel, Edouard, and Floyd all reached their peak intensities well southeast of the east coast, whereas Bob and Ella reached theirs over the gulf stream.

I think those two are the most interesting. Bob reached category 3 status over the gulf stream near the coast, then managed to maintain intensity somewhat while racing up the coast. Ella, on the other hand, reached mid-level Category 4 intensity over the part of the gulf stream that bends away from the coast.

I also notice that the banding seems to be the most asymmetrical feature in those East Coast hurricanes - Bob's core, while certainly not beautiful, still features an embedded eye. One is forced to wonder if removing some of these bands could have expanded his lifestyle. The other noteworthy thing about Bob was his speed of approach, landfalling in Rhode Island just about 12 hours after peak intensity east of NC.

The more extreme version of this scenario is 1954's Hurricane Carol which went from a standstill to blazing in about 12 hours and intensified up until its Long Island landfall. It would've only spent maybe half a day without the gulf stream.

I believe these two hurricanes - Ella and Carol - form the majority of the important part of our hypothetical New England Cat 5. It would be absolutely outrageous, but not completely impossible.

A tropical wave or some other system with a large moisture envelope approaches the Bahamas. In the warm waters there, it develops into a major hurricane, before turning north along the gulf stream. While it turns, it would undergo an ERC to build a much larger eye. This process completes quickly and the core tightens. From here, it begins a path up the East Coast, able to (at least) maintain its intensity.

A ridge builds in over the storm, forcing it to slightly turn NE and continue along the gulf stream. At this moment, the storm resembles Hugo upon its EC approach with a large, well-defined eye and somewhat limited banding. As the storm makes its turn, it undergoes another ERC and quickly becomes annular. This is plausible because as Ella passed this area, she jumped 3 categories while developing an eyewall. Our hypothetical cyclone is moving much more slowly and thus is able to do this at a lower latitude.

The annular cyclone moves over the same area as Ella's rapid intensification, albeit slower, and intensifies to a low-end Category 5. Ella intensified 60 mph over this area, so it's possible that our idealized cyclone could manage 50 or so. It may not be able to bomb out due to its annular characteristics, but rather slowly intensify.

The blocking ridge that has been slowing our cyclone's motion has begun reorienting and strengthening (or maybe a trough suddenly comes into play), pointing roughly NW/SE. But as soon as our storm achieves Cat 5 intensity, it suddenly and violently moves southward. Our cyclone finds itself in a Sandy-esque situation.

Here begins the Carol phase. Similarly, our cyclone rapidly accelerates. Heading NW, it leaves the gulf stream and makes landfall over extreme eastern Massachusetts in 6-8 hours. During this time, it (like Carol) does not weaken appreciably, due to its annular structure, fast forward speed, and a hypothetically near-perfect environment.

This scenario seems to be the most plausible solution, especially since it's a mashup of scenarios that have happened previously. But that still doesn't make it likely. If anything, it demonstrates just how far-fetched this is. Anyways, sorry for the long, rambling post.

TL;DR: Carol '54 + Ella '78. An annular cyclone tracks the gulf stream, gradually intensifying to Cat 5. It sharply turns NW and hits Massachusetts at that intensity.

[Shell Mound]

Maybe prospective “Isaias,” currently emergent from West Africa, will set a record for the earliest Cat-5 landfall in the U.S., including territories such as Puerto Rico. The 1825 hurricane season featured el huracán Santa Ana, one of the most intense July hurricanes on record. The storm, which was probably a CV-type Cat-5, passed over Guadeloupe and then PR on 25–27 July, with a pressure of 27.10 inHg (918 mb!) registered on Guadeloupe, and killed more than 1,300 people in PR alone. The track was very similar to that of el huracán San Ciriaco (1899), el huracán San Felipe Segundo (1928), and Hurricane Maria (2017), given that the eye made landfalls around Pointe-à-Pitre, Guadeloupe, and Humacao/Yabucoa, PR. Given that reliable models, including the CFSv2 and EPS, have been consistently aggressive—even several weeks out, in the case of the CFSv2—with the AEW currently emerging from West Africa, there is certainly reason to be somewhat concerned, given that this would be the “dreaded ‘I’-storm.” Multiple intense landfalls may be possible from the islands of the northeastern Caribbean to the Bahamas and the mainland U.S., possibly in either FL or GA, if the worst-case scenario(s) come to fruition.

[Shell Mound]

Maybe prospective “Isaias,” currently emergent from West Africa, will set a record for the earliest Cat-5 landfall in the U.S., including territories such as Puerto Rico. The 1825 hurricane season featured el huracán Santa Ana, one of the most intense July hurricanes on record. The storm, which was probably a CV-type Cat-5, passed over Guadeloupe and then PR on 25–27 July, with a pressure of 27.10 inHg (918 mb!) registered on Guadeloupe, and killed more than 1,300 people in PR alone. The track was very similar to that of el huracán San Ciriaco (1899), el huracán San Felipe Segundo (1928), and Hurricane Maria (2017), given that the eye made landfalls around Pointe-à-Pitre, Guadeloupe, and Humacao/Yabucoa, PR. Given that reliable models, including the CFSv2 and EPS, have been consistently aggressive—even several weeks out, in the case of the CFSv2—with the AEW currently emerging from West Africa, there is certainly reason to be somewhat concerned, given that this would be the “dreaded ‘I’-storm.” Multiple intense landfalls may be possible from the islands of the northeastern Caribbean to the Bahamas and the mainland U.S., possibly in either FL or GA, if the worst-case scenario(s) come to fruition.

I have a nagging feeling that Isaias could be the “counter-Dorian”: similar (or perhaps a bit greater) in intensity, but striking the U.S. at its peak—and doing so in short order, like the four known Cat-5 hits since 1900: Labor Day ‘35, Camille ‘69, Andrew ‘92, and Michael ‘18 being only tropical storms or minimal hurricanes within two to three days of impact. Maybe Isaias will be similar to Dorian and/or the 1935 hurricane, but with one distinction: while rapidly intensifying up to landfall, it also ends up far larger than any of the four known Cat-5 hits, thereby delivering maximum impact not just in terms of wind, but also, due to fetch, in terms of surge and/or wave (and possibly rainfall, depending on forward speed). I could be wrong, but I have a sinking feeling...

[SconnieCane]

As fascinating it would be to track from a meteorology-nerd standpoint, I doubt the U.S. will in my lifetime see a Cat. 5 landfall from a long-tracking MDR cyclone. All the cards seemed to be stacked for that to happen when the model consensus for Irma shifted from a Matthew-like coast scraper to a bulls-eye on metro SE FL. But as we know, then they kept on shifting west just a little bit more. Enough to scrape it along Cuba for a day or so.

There's just too much that has to go right in terms of conditions (although, by and large SSTs/OHC near the Bahamas/Florida Straits are almost never going to be an issue anymore), track (missing all the GA), timing of EWRCs, etc.

The most likely scenario for a Cat. 5 U.S. landfall has been; and remains, home-grown quick hitters like Michael.

[toad strangler]

As fascinating it would be to track from a meteorology-nerd standpoint, I doubt the U.S. will in my lifetime see a Cat. 5 landfall from a long-tracking MDR cyclone. All the cards seemed to be stacked for that to happen when the model consensus for Irma shifted from a Matthew-like coast scraper to a bulls-eye on metro SE FL. But as we know, then they kept on shifting west just a little bit more. Enough to scrape it along Cuba for a day or so.

There's just too much that has to go right in terms of conditions (although, by and large SSTs/OHC near the Bahamas/Florida Straits are almost never going to be an issue anymore), track (missing all the GA), timing of EWRCs, etc.

The most likely scenario for a Cat. 5 U.S. landfall has been; and remains, home-grown quick hitters like Michael.

Andrew is the longest track Cat 5 to hit the US, but of course, didn't intensify until just days before landfall. That does seem to be the magic ingredient.