Hurricane expert Maue: extrapolating scale, #Irma could be a "Category 6"

Dr. Ryan Maue said this morning:

Hurricane is still intensifying. Now up to 155-knots (180 mph) Extrapolating Saffir-Simpson scale, 158-knots would be Category 6.

NWS says: (bold mine)

Hurricane Irma Discussion Number 26

NWS National Hurricane Center Miami FL AL112017

1100 AM AST Tue Sep 05 2017

Irma is an extremely impressive hurricane in both infrared and visible satellite images. Experimental GOES-16 one-minute visible satellite pictures show a distinct 25-30 n mi wide eye with several mesovortices rotating within with eye. The aircraft have not sampled the northeastern eyewall where the strongest winds were measured shortly before 1200 UTC this morning, but the Air Force plane will be entering the eye in that quadrant momentarily. A peak SFMR wind of 154 kt was reported, with a few others of 149-150 kt. Based on these data the initial intensity is set at 155 kt for this advisory. This makes Irma the strongest hurricane in the Atlantic basin outside of the Caribbean Sea and Gulf of Mexico in the NHC records.


newest oldest most voted
Notify of

Dr Overpeck must feel like two Christmases have come at once.

The change in weather is much more impressive than the change in climate. Stay safe all in the path of the hurricane.


What change in climate?
Hurricanes can change the weather? Who knew?

Crispin in Waterloo but really in Ulaanbaatar

What are experts (real ones) saying about the influence of the high pressure cells on the NA continent, in terms of steering the storm?
The early route to the coast seems to be getting settled, but it could wander all over the place after that.


…and probably will
It’s going to start reacting to land as soon as it gets to PR…then DR/Haiti…then Cuba
…Has a very small eye….spins faster…..which they call stronger

Mark from the Midwest

Yeah, I was thinking the same thing, very high pressure over the mid continental U.S. and a strong front, could steer and / or take the top off of this. It looks like the high just east of Denver is getting pretty strong, something in the 1030 range.
Hoping that’s what happens, this is just too nasty a storm.


Could the “measured intensity” be merely an artifact of our improved capability to measure the previously immeasurable and our record keeping?
BTW I still have a big issue with calling meters squared per seconds squared, energy. It seems to me that a mass component is missing. If the mass of the air assumed to be identical, why take it out?


Most definitely.

John M

Gyres come to mind as they carry some of the fuel for surface events with amazing transport (mass). Your point is fascinating!

John M

“Intensity” is a fascinating issue. All reports you’ll find relate to a top down look at a hurricane. None display a 3D relationship – atmospheric conditions in relation to sea surface conditions caused by gyre transport etc..
Hurricanes are reported (hopefully not modeled) in 2D.

Tom - the non climate scientist

Rocketscientist – “Could the “measured intensity” be merely an artifact of our improved capability to measure the previously immeasurable and our record keeping?”
Most likely yes –

John M

Rabbit Hole comes to mind.
What aspects are currently “false” given little to no oversight?

John M

What aspects are “True” given …

I don’t think the wind speed and the pressure reported in Irma’s #26 public advisory are consistent with each other: 931 millibars, 180 MPH.


Interesting point, Donald. Let’s have some comment on this.

The 26a public advisory has another combination of pressure and wind speed that I don’t believe: 926 millibars and 185 MPH.


For comparison, Typhoon Tips’ record-breaking low pressure of 870 mbar allegedly yielded wind speed of only 160 mph.
Eastern Pacific Hurricane Patricia, by contrast, registered 872 mbar, but one minute sustained winds of 215 mph.
Wilma hit 882 mbar, but with only 185 mph winds.
Cyclone Gay was 930 mbar and 145 mph, while 2001 India was 932 and 135 mph.
The stated winds for Irma seem too high for her pressure.

The relationship between pressure and maximum possible wind is affected by the storm’s size (lower wind in larger storms such as Tip), latitude (farther from the equator means more downward effect on wind speed by the storm’s size), and surrounding/prevailing pressure (generally about the same from one Cat-5 storm to another).


My rule of thumb – for the UK, and adjacent waters – is 920 millibars – will give Beaufort 12: – a Hurricane.
We rarely indeed get beyond about 920 mb, so I have no predictive guesses for, say, 900 mb.

The 27 forecast discussion for Irma said there were a couple of 160 knot SFMR winds (measurements or indications). Flight level winds were not mentioned, so I don’t know if they are consistent with 160 knot (185 MPH) surface wind. SFMR is stepped spectrum microwave radiometer, and it is used to determine surface winds when a hurricane is over water. Pressure was 926 millibars, same as with the 26a advisory.

I did more followup on the pressure-discrepancy issue: Weather Underground mentioned it. They said two things that I consider relevant: One was a tweet from some professor about pressure gradient, followed by a map of 500 millibar anomalies in sigmas, that I think accounts for at most a few MPH in a storm whose westward movement was not sped up much by the subtropical high having anomaly north of the storm by 1 sigma. Another thing they mentioned was a map of wind potential based on SST, ocean heat content, and thermal profile of the atmosphere, and Irma achieved 185 MPH where its potential was 165 MPH – along with a mention that it’s known that rapidly intensifying hurricanes temporarily overshoot that potential. Since then, Irma’s pressure fell to a level where I consider 180 MPH wind as plausible, and the official wind speed remained at 185 MPH.
And then came forecast discussions (which mention then-current conditions and measurements) after that, for example the #32 forecast discussion. That one mentions factors indicating that Irma has weakened somewhat and is about to weaken somewhat more (although maybe only temporarily). Along with official wind speed unchanged at 185 MPH, due to pressure not having risen much, despite wind speed normally decreasing even with non-rising central pressure during signs of an eyewall replacement cycle, along with a lightning frequency factor that indicates temporary weakening. This is along with a lack of mention of SFMR or flight level winds, which I consider unexpected. And I have never seen this reporting situation with such an intensely probed (or probe-able) intense storm before.


10m SFMR winds are theoretical and maybe undefined under these conditions. Flight level winds are calibrated by comparison to dropsonde measurements at a height of 500m or so, which are then, in turn used to estimate 10m surface winds. 10m sustained winds when the open ocean storm surge may be more than 10m and waves may be more than 10m on top of that under these conditions would mean that these 180 mph winds are blowing under water. I would use the term “estimated 10m wind speed equivalent” or something like that.


The 10m SFMR surface level wind readings are calibrated by comparison to flight level winds.

Some. But my father flew instrumented B-29s off Guam into Pacific typhoons 1948-1950, and even back then in the early days of cyclone research they had pretty solid ideas about storm structure and wind. Saffir-Simspon has been around sonce the 1960s with the classification being windspeeds just outside the eyewall.


Before satellites, the only way to measure the power of a storm was to have a ship sail through it.
The problem was, the captains who didn’t wish to die steered around strong storms.

D. J. Hawkins

Well, the 53rd Weather Reconnaissance Squadron has been flying planes into hurricanes since 1944. Just a tad before satellites.


Mark W
As they still do.
Maybe they won’t die now, maybe, but they will need to fill in a hoist of accident report type paperwork.
So, they look to avoid. Sensibly.
What I told my Masters to do.
Told – now retired. Magic. No further jousting with Southern Railways into London Bridge, and – if you were lucky – home again in the evening.


Speaking abstractly… The almost perfect circular symmetry of IRMA is almost beautiful. Bad – I know – for people and property in her path, but still one purdy hurricane. Given that she hasn’t even begun to touch the even higher temperature/energy caribbean waters, I do wonder how strong she’ll become.
Perhaps the CAT–6 thing isn’t hyperbole.
The days ahead are sure to be interesting.
That much bound kinetic energy just doesn’t fall apart.


There MUST have been such Hurricanes in the past,but we have little records before 1900 to know.


Our ability to measure details such as the speed of the winds at many various points in the hurricane have improved drastically– year by year, decade by decade. As our ability to measure improves, we will set many new records. In this case, it is not necessarily true that the wind speed is higher than it has been ever before, but most likely that we are now able to better detect the maximum wind speed, even when the hurricane is way out in the middle of an ocean.

Probably during the MWP.


We can only speculate about the strength of the storms that took down all those treasure galleons but some of them could have been quite fierce.


garyh845 September 5, 2017 at 8:52 am
Possibly worse in the LIA, due to steeper temperature gradient. The Divine Wind typhoon which sank the Mongol invasion fleet off Japan however was a pretty bad Medieval WP storm.
The 1609 hurricane which marooned by ancestor John Rolfe on Bermuda and inspired Shakespeare’s Tempest might have been a Cat 5.
Note the Great Storm of 1703 during the Maunder Minimum, worst in British history. Also Great Louisiana hurricane of 1722, the Great Gust of 1724 on the Atlantic coast, the Boston storm of 1727 and Great Hurricane of 1752 in SC,

The size of the area of high winds is impressive. I don’t think that I have ever seen such a wide spread of winds at high speed in a hurricane before. …,18.40,1821/loc=-57.936,17.004

“Gilbert was one of the largest tropical cyclones ever observed in the Atlantic basin. At one point, tropical storm force winds measured 800 km (500 mi) in diameter.”
From the link provided by Matthew R Epp.

Tom in Florida

GoatGuy September 5, 2017 at 8:23 am
Yes, a truly beautiful thing, visually. The awesome power of nature on display.


Old phony Chinese curse: “May you live in interesting times.”
(Phony, because the one uttering it is living in the same times you do.)


But possibly a different area – a few miles from the path of – whatever:
the wrath of a Sun-God; the path of an invader; the track of a crop pest.
Others could certainly add to the list.
Smiles, Auto

Roger Knights

Maybe it was a senior citizen speaking to a youngster. Likely.

Wilma was reanalyzed upward to 185 knots, which is Category 7 according to part of the chart in this article. But the National Hurricane Center calls Patricia a Category 5 and does not define any higher categories.

I meant Patricia.


Is it normal practice for NHC to use ‘peak winds’ as ‘sustained winds’ and then add a few knots to create a record hurricane?

David A

My question as well.

No, if anything NHC tends to err on the conservative side. They’ve been criticized on a number of occasions for not upgrading a storm when plenty of armchair stormwatchers were convinced it was stronger. Unlike other atmospheric agencies in the govt, the NHC has actual meteorologists rather than climate “scientists.”

David A

? So then do the satellite projections refer to wind gusts, or one minute sustained winds?


It’s a matter of definition (instantaneous peak winds vs sustained), distribution (taking the highest measurement and using it to represent the most likely speed) and then ADDING 1 knot for good measure to produce a record.
That is NOT good science, IMHO

David A: Wind determinations from satellite readings are maximum 1-minute average. The “official” strength of a storm is the maximum 1-minute-average determined to occur 10 meters above the surface anywhere in the storm. The NHC forecast discussions generally mention what data support this wind speed determination.


Experimental GOES-16 one-minute visible satellite pictures show a distinct 25-30 n mi wide eye with several mesovortices rotating within with eye.
And you can see them for yourself, at MDS sector 5, band 2, on this page:
or direct link (html5 loop):

What other hurricanes have had winds that strong and eyes that big? Winds of 180 MPH or more seem to happen with smaller eyes. Also, the ratio of eye radius to hurricane wind field radius gets smaller as a hurricane intensifies much past the point of having a clear, well defined eye, which tends to be in the Cat-4 range. The figures for Irma when it was first reported at 180 and at 185 MPH seem to me as typical of at least 15 MPH less.


And here comes Jose. And that’s a pretty impressive blob of convective growing in the Gulf.


Just waiting for the “unprecedented” rant from global warming nutters any time soon.


Put enough qualifiers on the statistic to make it worthy of baseball (most RBIs, with a man on 1st base, facing a left handed pitcher, in AM games, on even numbered days, in months with an R, …) and you can concoct almost any “unprecedented” and unlikely to ever recur statistic.
It is meaningless, but sells ad space.

Bruce Cobb

Patience, grasshopper. They have to decide whether to call it “global warming”, or “climate change”, or maybe even something brand-new, like “frankenclimate”.


Extreme climate,

Matthew R Epp

Hurricane Gilbert, 1988
Officially Cat 5
185 mph winds
888 mb
Theoretical cat 7, based on scale above
Hurricane Wilma 2005
Officially Cat 5
173 mph winds
882 mb
Theoretical cat 6, just shy of 7, based on scale above.
Both blasted Mexico’s Yucatan peninsula.
Great site for hurricane info. Irma is big and bad, maybe she makes a theoretical 6. She has to get bigger and badder though to surpass these two.

These current stats from the last NHC bulletin are a little odd:
Gilbert was at 185 MPH @ 888 MB. But then, Wilma’s were 173 MPH at 882.
There was a 885 MB reading for Gilbert – but they discarded it.
I was under the impression that there was a tighter correlation between max sustained wind speeds and central atmospheric pressure, than this seems to indicate.

Depends on the size of the eye. Smaller eye gives higher winds for same eye low pressure.

Sweet Old Bob

Camille ?


Yep, Camille. No landfall windspeed recorded because she broke them. Gust had been measured at 200mph.
And this Cat 6, Cat 7 stuff is BS. When you get to Cat 5, all you have left at landfall are the slabs the homes were on. Does Cat 6 or 7 start destroying matter?

This is bringing back memories. Was in Hurricane Gilbert, in Cozumel, MX, in Sept 1988. Irma is presently right about where Gilbert was at it’s max – 888 mb – but Gilbert didn’t reach Cat 5 status until it was well west of Jamaica (where it had laid out extensive damage and loss of life).
I agree with a Cat 6 being added to the scale; however, we have to know that as soon as they do that – it will be like adding the new colors to the rain prediction map – ‘see – it’s all because of AGW/ACC.


I have a lot of family in Florida, most of whom I hope to see again and not flying off to Oz! Who pushed the magic button that caused us to have a very active hurricane season all of a sudden? I have a long list of the usual suspects….


Waiting for Irma
(It is often believed that appearance of this ‘distinguished’ bird adorned with a gown of the feather-light knowledge ‘professes’ impending catastrophe)


“Climate” is the average weather over 30 years, I believe. So before we can talk about climate change the dearth of hurricanes over the last 10 years in that area must enter into the calculations. There is a lot of catching-up.


BBC reports that the current measurements show gusts of wind around 220mph (more than 350km/h). Horrendous.


Are they reporting on storms in the atmosphere of Jupiter?


BBC just repeated the wind gusts for the
‘Great Anthropocene Hurricane’
are at 220mph, the strongest on the record.


Got a dumb question. The sun let loose a CME that is earthbound and should arrive in a day or so.
As I understand it, one of the effects of a CME striking earth involves some heating of the upper atmosphere.
My question is: Would that have a small effect of large storms like Irma?


My first guess would be that the area being heated by a CME is too high up to have any impact on a hurricane.

Look at
It’s a 0 not a O.
They have a disaster prediction App and with reasonable confidence tied solar activity to earthquakes and storm strengths and peoples health. (actual testable predictions) Doesn’t make sense to me but they call the statistics whether right or wrong.

Mike Bromley the Kurd

Gawd, what a blow. And the alarmists WILL holler “toldyaso”, despite the 12 year drought.

And they only make guesses a la: as more the ocean warms as more energy for hurricans is available. BUT this paper shows: It’s the stregth of the trade winds in the MDR and the difference between the SST of the MDR region and the global tropics. The link to AGW is not obvious.

David A

Frank, yes…
“We find that trade wind speed over the Caribbean Sea and the tropical North Atlantic is the environmental field which individually replicates long-term hurricane activity the best. We identify a dropout in hurricane replication centered on the 1940s and show that this is likely due to a decrease in data quality which affects all data sets but Atlantic sea surface temperatures in particular.,


A storm the size of Irma is going to take a lot of that heat out of the Atlantic. Just as Harvey measurably cooled the Gulf for a while.

David: And one more step: What about the difference between the SST of the MDR and the global tropic SST, following the CMIP5- models:
There is no difference in warming! And the trade winds? See this: . All the climate science says: The hurricans will get smaller and smaller with ongoing forcing. The trade winds weaken and the SST-differences weaken too. So see who will take an advantage from Irma! These are not climate scientists because they await lesser and weaker hurricans.


Visible/IR2 Satellite Image (click for loop):

J Mac

Thanks ren!

J Mac



Look at Maue’s twitter feed, he jumps on Kurt Eichenwald over prediction of Irma intensification.


The Great Hurricane of 1780 had 200 MPH+ sustained winds that destroyed stone forts and buildings.


Did they have accurate wind gauges then? Or did someone model it.


The 1780 hurricane blew the bark off tree stumps. Experience from tornadoes suggest that requires wind speeds close to 250 mph.


And what species of tree was this.


Typhoon Tip of 1979 remains the lowest recorded pressure, highest wind speed and largest in size. Super El Nino driven eastern Pacific Hurricane Patricia of 2015 supposedly had higher winds, but our ability to measure them was better in 2015. Tip remains the most intense tropical cyclone on record.

Dick Kahle

I assume that Saffir and Simpson had a logic to the boundaries for the different hurricane categories. Note that the increase from one category to the next is not the same number of knots as Dr. Maue has done. The most consistent pattern I noticed was the percentage increase of the peak wind speed over the lower category. The increases are 16% for Cat 2 over Cat 1 and 19% for the increases of both Cat 3 and Cat 4 over the lower category. Following that pattern would give a peak wind speed of 161 knots for a theoretical Cat 5 and 193 knots for a Cat 6.

Yes. The logic is degree of structural damage to buildings.


So, as the buildings get built better the hurricanes get downgraded? That doesn’t seem to be a very robust metric. At least wind speeds and pressures are more objective in attempting to quantify energy.

Check out the Nansen sea ice
Did we just pass maximum?

sorry – minimum

maximum water


Not according to NOAA’s NSIDC:
Tracking 2008 at the moment, at sixth lowest in the dedicated satellite record.


On the other hand NSIDC MASIE which has day-to-day data does suggest we are at minimum or very close to it:


Very odd. The link goes to Sep 4 data but the displayed image is three weeks old. Is there some WordPress cache fiddling involved?

tty September 6, 2017 at 3:47 am
Very odd. The link goes to Sep 4 data but the displayed image is three weeks old. Is there some WordPress cache fiddling involved?

Just click on the graph.

D. J. Hawkins

I’d say wait another week before asking that question again. It may wiggle around for a bit.


Beautiful looking storm, knowing that it’s a giant heat pump pulling gazillions of watts of energy up from the ocean’s surface and dumping it out into the stratosphere through heat of condensation. Alarmists should be applauding these things for removing unwanted surface heat, not vilifying them.

J Mac

At the moment, this is a very symmetrical hurricane, with little energy seemingly dissipated in chaotic turbulence or from high level shear effects.

Gary Pearse

I can better this prediction with one I made in 2013. I am pretty well spot on using the 60yr cycle. I tried to dissuade sceptics from complacency on the drought at the time. I encourage a full read of this:


Gary, that is not prediction. If you have a long enough history of an event and have averages and it falls below average for some time the unless there is a change in the underlying principles then therequest will be a time in which the frequency of the event increases. It is like stating that as we are going down into the valley the path to the next mountain will be up.

Gary Pearse

Actually returning to that thread, there was a lot of discussion about my comment. Some saying making such [predictions] a waste of time. They are worth a read. And maybe someone can make a post going back in Sixty-seventy year jumps to earlier clusters.

Leo Smith

I feel the same depression that accompanied Fukushima: the depression that comes from knowing that this will be spun into the political narrative of the times, whilst the facts are ignored.
Whenever someone says ‘Fukushima disaster’ I say ‘What disaster? No one died’.
But in people’s minds, that’s what it was.


Leo, A number had doses that will lead to early deaths. A number of people drowned as well, many more than the projected to die from the extra radiation dose.


Fascinating to watch but remember it’s based on models. Quote from their site,
a visualization of global weather conditions
forecast by supercomputers
updated every three hours
ocean surface current estimates
updated every five days
ocean surface temperatures and
anomaly from daily average (1981-2011)
updated daily
ocean waves
updated every three hours


with a strong possibility of storm Katia forming at similar distance further ‘east.- south east’

Colin Peterson

Honest question to experts: what will happen if the military drops a large bomb in the middle?? that will raise the mb tremendously and …


My forecast for this hurricane is that it will hit southern Florida hard, but once it moves into north Florida and further north it will weaken quickly. This will most certainly be the case if the [eye] move overland,
Because what looks like that it will be coming to the aid of the SE of USA. ls the fact that the jet stream will be tracking much further to the south then normal. So over the SE the jet stream will be stronger then normal. Which should aid with the [break] up of this hurricane. But l think you can expect a lot of rain getting dumped over the area in the process.


“eye” not “rye” 🙂

Iniki was measured by NASA at 227 MPH at Kokee, Kauai, Hawaii. The reason it is not in the record books is that the anemometer/electronics fell apart. As they did with every other station on Kauai.

Matt G

The Saffir–Simpson scale has categories based on how much damage they cause. Category 5 means total destruction and no matter how higher the winds are, no more damage can be done than total destruction, so for this reason any higher category is pointless.
Saffir–Simpson scale
Wind speeds
≥70 m/s, ≥137 knots, ≥157 mph, ≥252 km/h
58–70 m/s, 113–136 knots, 130–156 mph, 209–251 km/h
50–58 m/s, 96–112 knots, 111–129 mph, 178–208 km/h
43–49 m/s, 83–95 knots, 96–110 mph, 154–177 km/h
33–42 m/s, 64–82 knots, 74–95 mph, 119–153 km/h
Related classifications
Tropical storm
18–32 m/s, 34–63 knots, 39–73 mph, 63–118 km/h
Tropical depression
≤17 m/s, ≤33 knots, ≤38 mph, ≤62 km/h