Double eyewall structure revealed in hurricane #Matthew

From hurricane expert Dr. Philip Klotzbach (successor to Dr. Bill Gray) comes this interesting image from the 85 Ghz satellite microwave sounder, courtesy of the Naval Research Lab in Monterery.

He notes:

Recent microwave imagery pass shows the current double eyewall structure of Hurricane #Matthew

I downloaded the full resolution image:



More on eyewall replacement cycle here. Some notable language:


After the secondary eyewall totally surrounds the inner eyewall, it begins to affect the tropical cyclone dynamics. Hurricanes are fueled by the high ocean temperature. Sea surface temperatures immediately underneath a tropical cyclone can be several degrees cooler than those at the periphery of a storm, and therefore cyclones are dependent upon receiving the energy from the ocean from the inward spiraling winds. When an outer eyewall is formed, the moisture and angular momentum necessary for the maintenance of the inner eyewall is now being used to sustain the outer eyewall, causing the inner eye to weaken and dissipate leaving the tropical cyclone with one eye that is larger in diameter than the previous eye.

A microwave pass of Cyclone Phailin revealing the moat between the inner and outer eyewalls.

In the moat region between the inner and outer eyewall, observations by dropsondes have shown high temperatures and dewpoint depressions. The eyewall contracts because of inertial instability.[23] Contraction of the eyewall occurs if the area of convection occurs outside the radius of maximum winds. After the outer eyewall forms, subsidence increases rapidly in the moat region.[24]

Once the inner eyewall dissipates, the storm weakens; the central pressure increases and the maximum sustained windspeed decreases. Rapid changes in the intensity of tropical cyclones is a typical characteristic of eyewall replacement cycles.[24] Compared to the processes involved with the formation of the secondary eyewall, the death of the inner eyewall is fairly well understood.

Some tropical cyclones with extremely large outer eyewalls do not experience the contraction of the outer eye and subsequent dissipation of the inner eye. Typhoon Winnie (1997) developed an outer eyewall with a diameter of 200 kilometres (120 mi) that did not dissipate until it reached the shoreline.[25] The time required for the eyewall to collapse is inversely related to the diameter of the eyewall which is mostly because inward directed wind decreases asymptotically to zero with distance from the radius of maximum winds, but also due to the distance required to collapse the eyewall.[23]

Throughout the entire vertical layer of the moat, there is dry descending air. The dynamics of the moat region are similar to the eye, while the outer eyewall takes on the dynamics of the primary eyewall. The vertical structure of the eye has two layers. The largest layer is that from the top of the tropopause to a capping layer around 700 hPa which is described by descending warm air. Below the capping layer, the air is moist and has convection with the presence of stratocumulus clouds. The moat gradually takes on the characteristics of the eye, upon which the inner eyewall can only dissipate in strength as the majority of the inflow is now being used to maintain the outer eyewall. The inner eye is eventually evaporated as it is warmed by the surrounding dry air in the moat and eye. Models and observations show that once the outer eyewall completely surrounds the inner eye, it takes less than 12 hours for the complete dissipation of the inner eyewall. The inner eyewall feeds mostly upon the moist air in the lower portion of the eye before evaporating.[13]



92 thoughts on “Double eyewall structure revealed in hurricane #Matthew

  1. “…hurricane expert Dr. Philip Klotzbach (successor to Dr. Bill Gray)…”
    This seems to be the same gentleman who, just 2 days ago, was apparently suggesting that “Hurricane data from 1851 suggests Matthew landfall on east coast of Florida is a longshot”?
    It looks pretty much nailed-on now. Godspeed to all in Florida East. (I have an elderly aunt on vacation there from Toronto at the moment.)

    • The tangent path will be far less damaging than a direct hit. Though the amount of coast affected will be much longer.

      • You are wrong…I think the damage will be very widespread instead of limited to a small area.

      • Crossing the coast at 90 degrees means the storm dissipates much more quickly. The last thing you want is the storm to maintain strength and rake a long stretch of (built up) coastline.

      • Worry about it running up the barrier islands, piling water into the inlets, and it has to go somewhere while being driven south by the winds. As well as long times under the effects. But, it just did wobble in the last view hours, so it looks like the path is going to not hit much south of Melbourne. One can hope. This storm has the earmarks of being the most expensive ever if it coast hugs.

    • Is it considered “landfall” if the eye never crosses the coast? So far that hasn’t happened (as of 2am EDT).

  2. While the dual eyewall is interesting, what I found the most heartening was this line:

    The time required for the eyewall to collapse is inversely related to the diameter of the eyewall which is mostly because inward directed wind decreases asymptotically to zero with distance from the radius of maximum winds, but also due to the distance required to collapse the eyewall.

    That is science. Sadly it is also 30+ years old. But we need more like it.

    • But the example he gave of Winnie, which had a large eyewall that persisted until landfall, seems to contradict this inverse relationship.

  3. This is good news – eyewall replacement. Weather Underground radar plot shows it turning to the northeast at the moment.

    • Nullshool is only showing 110mph winds at 850mb/4700ft and surface winds of 70-80mph. How do they get Cat-4 out of this?

      • It’s not. NDBC staton SPGF1 is recording 65 knots sustained winds at 6pm EST. That’s 20 miles NW of Freeport City. Station SPGF1 is a fixed tower in the open with the anemometer height of 10 meters.
        65 knot sustained winds at 10 meters height is barely a category 1 on Saffir-Simpson scale.

      • But if it weren’t Cat 4 or higher how could the news media predict catastrophe? And the media are ALWAYS right! Just ask them. and they fall all over themselves to be first with the scoop!
        One of the little tidbits I picked up a while back is that the ‘Category’ of the hurricane is officially based on wind speed ON THE GROUND. Then someone mentioned that the only actual measurements of a hurricane over the ocean are from hurricane hunter aircraft actually flying through the storm (C130s). It seems the speeds reported by the aircraft, at altitude, are at least 10 knots higher than the ground wind speed. But the media, in their rush to be ‘first with the worst’ doesn’t even bother to mention this. Thus, what is now a cat 4 is really probably a cat 3 or less [but that wouldn’t be nearly as exciting nor as likely to create the ‘need’ for declarations of emergency and the money that requires].

  4. As of now the well developed “inner eye” is over Freeport and headed almost north. At this rate the inner eye will not landfall in Florida, but some folks may shift the goalpost to this much larger but less defined “outer eye”.

    • If the outer eye carries winds like the inner, that is no goal post shift. Miami is now ‘safe’ but for band squalls because the center is now at their latitude. Fort Lauderdale is projecting Cat 1 winds in another 1.5 hours. The eye will pass in 4-5 hours. The waves crashing over the inner coral reef just a few hundred meters offshore have become truly awesome. Cannot wait to dive it this weekend and see what is different.

      • To look at radar it appears the strong winds are largely from the north near Fort Lauderdale. Is there a concern for beach erosion?

      • Yes. But we just did a $56million beach restoration from Pompano south to mid Fort Lauderdale. Trucked in high quality sand (56000 truckloads). As night fell, was holding up well. The big waves were breaking over the innermost coral reef (of three off Fort Lauderdale), so losing a lot of power before hitting the beach. We will know more in the morning after the eye passes offshore. Should be interesting beachcombing tomorrow. And interesting shallow reef diving on Saturday.

    NASA Bracing for First Hurricane Since Shuttles Retired
    By THE ASSOCIATED PRESSOCT. 6, 2016, 5:49 P.M. E.D.T.
    CAPE CANAVERAL, Fla. — NASA is bracing for its first hurricane without space shuttles to worry about. Now it’s SpaceX and Boeing fretting about hurricane-force wind and equally devastating storm surges.
    Before the shuttle fleet’s retirement in 2011, rollbacks from the launch pads were commonplace during hurricane season at Kennedy Space Center. Now both pads are empty, at least for the time being.
    NASA is modifying Launch Complex 39B for its still-in-development Space Launch System mega-rockets intended for outer-space travel. SpaceX is leasing the other pad, 39A, from where Apollo astronauts departed for the moon and multiple shuttle flights began.
    SpaceX was counting on this historic pad to get its rockets flying again, possibly in November, once modifications were complete. The SpaceX pad at neighboring Cape Canaveral Air Force Station was damaged Sept. 1 when a Falcon rocket exploded during prelaunch testing.
    Boeing, meanwhile, is using a former shuttle hangar to build capsules to fly future space station crews as early as 2018. The building can withstand 105 mph wind — no more.”

  6. Glad I don’t live in Florida, cus if a “hurricane” came thru and then doubled back for a second shot, I might have to reevaluate my life’s choices.

    • Its doubling back, but not as a hurricane, a mere wimpy tropical storm. Summer in South Florida is miserable, but not worse than clearing 2 feet of snow off a long Chicago driveway in January.

      • it may double back— who knows how strong, unless you believe in models.
        which do you prefer ECMWF— ( hint look at its relationship to GCMs)
        Seems to me folks are putting a lot of trust in these models.

      • Had one. A $700 big old Honda electric start tread track. Still took three hours of snow blowing, back into face every other pass depending on wind. And the damn plow trucks would leave a streetwise mess that had to be hand cleared. Maybe 10 feet in by 12 feet wide by (if we were lucky on the first plow pass) and only 3 feet deep. Snowblower useless, all hand shoveled near the street.
        Water drains by gravity. Snow doesn’t. Regards.

      • What with all the reports of clowns roaming around, snow removal might not be the highest priority.
        First things first.

      • 22hp tractor mounted here, as far as road plows…not realy an issue since I also do the road LOL

  7. Thanks for the article Anthony, it is something I was not aware off that could happen, I really hope this happens with this storm it looks awful for Florida and I hope this can be a retrieve for them.

  8. I’m getting more and more of a feeling that Matthew will not actually make landfall, just run up the coast creating havoc. The track has been shifting more northerly all day as it seems like the high that was pushing it westwards is weakening a bit earlier than forecast yesterday. I have relatives in West Palm Beach county so I have been watching the wind speed forecasts go down from hurricane to tropical storm as the track has shifted. This time yesterday they we bang on course, but now it looks like they will be spared the worst.
    Not that that makes it any better for Eastern Florida as by staying out to sea there won’t be the weakening associated with moving over land. This is going to be a very expensive weather event, even if it doesn’t actually hit a major city.

  9. Based on this report from the west end of the island just before the eye wall hit, I’m inclined to call b.s. on the Cat 4 rating: (showed approx. 78 mph steady with gusts nearing 90 mph.) Now, a Cat 1, 2, or 3 can kill you just as dead as a Cat 4, so this is not a dismissal of the dangers of the storm–but I can’t help but wonder if we aren’t seeing (again) a case of ‘Saffir-Simpson grade inflation’.

      • SPGF1 last report was 7pm eastern time, 2300 GMT, with sustained winds at 68 knots. The time plot of winds show a rapid peak just about the same time that pressure took a sharp drop. Just a guess that the power failed about that time and the station is off line.
        The NDBC site uses knots when displaying wind speed by default, but I think the raw data is actually stored in meters per second when you look at the archived file.

  10. I think I will stick with my “prediction” from Oct. 3rd. except the outer banks may not feel it, and it looks like it is going to loop around to the south again:
    J. Philip Peterson
    October 3, 2016 at 7:23 pm
    After hitting Haiti and Cuba, I think it will downgrade to a cat 2. But it could strengthen after the Bahamas. I don’t think the eye will cross the US coast. It will dance up the US coastline, but the outer banks could see hurricane force winds. These storms (from past experience) tend to stay just off the Atlantic coast…I hope.
    Just from tracking these storms since the mid 50’s…
    • J. Philip Peterson
    October 3, 2016 at 7:28 pm
    Looks pretty nasty though from the first animation by NOAA – look at all that black stuff…

  11. Right now the eye is about 80 miles directly east of West Palm Beach. The eye would have to take an “extreme” west turn to cross the FL coast. I still hope that it will just hug the coast and that the west side will be much less of a threat for the FL coast. (I hope). Storm surge may still be a problem. We all know that the east side is always the most dangerous side of the storm in the NH.

  12. this is reaching a level of absurdity, 7pm central time tv is “predicting” this will be a category 5 at landfall, while even the sustained winds are now called 130mph the radar shows it moving north and losing its symmetry = further weakening, and likely no landfall at all……….YO nikki haley think 60 hours ago was too soon to tell folks to leave your coastline?????????

    • earthnullschool is showing only 100+/- winds 850mb at the strongest NE corner of the system which is NOT a Cat 4 or 5.

  13. I would much rather warnings are conservative than insufficient. If the core stays offshore further catastrophe may be averted. Hundred dead in the Carribean already.
    East Florida coast is so close to being absolutely smashed by this thing, fingers crossed it doesn’t veer west.

    • Those dead were almost entirely on Haiti, 98. Haiti is a denuded island with almost no forest because they’ve stripped it for fuel (a coal plant would probably help that). Subject to lots of flooding. I flew over the island and made flight stop once and you can see the demarcation btwn Haiti and the Dominican clearly. One side has lush forests the other zilch. I thought the UN machine gun towers on the runway were nice also.

  14. What confuses me is that wind speeds increase with altitude & hurricane hunters fly from 1000 to 10000 feet (so I’ve read) – – how to convert the hurricane hunters wind speed at altitude with wind speed on the ground?

    • There are various means:
      Radiosondes dropped into the eyewall.
      Microwave sounders that measure near-surface wind speed. I posted something about them a few days ago.
      Estimate from the texture of the surface.
      Apply a fairly standard (except when it isn’t) conversion based on the typical change in wind speed with height.

  15. WaPo is still saying the eyewall “will” make landwall at 140 mph and proceed north, devastating coastal FL, despite the growing iffyness of that projection.

  16. Currently @ 11pm EST Cape Canaveral station shows wind speeds a 30-45mph(27-38kts). Which agrees with earthnullschool @ 71kmph currently 11:28EST. NOT Cat 4/5!!!

  17. I was watching the local radar on the continuous coverage here in S. Florida as the double eye formed. It seemed to me that the outer eye really came together as the hurricane moved north past Andros Island. Andros is the largest of the Bahama Islands, with little development, lots of trees and mangroves. I wondered if the island had enough wind resistance to slow a wide band of circulation as Matthew slowly moved past? It just appeared that that’s when it really developed. Any hurricane Meteorologists care to comment?

  18. Central Brevart County was predicted to be the point of minimum distance, perhaps landfall, but just before it got here the storm track jogged east about ten miles, and the eyewall exchange happened. The outer eyewall was still pretty hefty when it hit, the barrier islands look really beat up, but I live about ten miles from the coast and suffered minimum damage. I never lost power, but the main feeder is right in front of the house and FPL spent a ton of money hardening their grid this last year. Reading the article about the eyewall exchange really relaxed my mind after two days of slave labor to get ready. Thanks, Anthony!

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