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.


111 thoughts on “Hurricane expert Maue: extrapolating scale, #Irma could be a “Category 6”

  1. 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

    • 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.

  2. 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?

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

      • “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.

    • 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 –

      • 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.

    • 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.

      • 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.


  3. 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.


      • 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.

      • 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,

      • “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.

    • 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.)

      • jorge
        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

    • 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.

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

    • 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.”

      • 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.

  5. =======
    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.

    • 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.

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

  6. 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.

      • 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?

  7. 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.

  8. 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….


  9. “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.

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

  11. 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?

      • 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.

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

      • 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.

  13. 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.

  14. 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.

      • 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.

  15. 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.

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

  17. 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:


  18. 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

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

  20. 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.

  21. 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.

  22. 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

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