Was Ivan a Category 4?

[tallywx]

Something I've been wondering for a while (and maybe Derek or others have some insight into this) is whether 1996 Fran was a category 3 at landfall. Nothing whatsoever seems to support the claim.

Frying Pan Shoals tower offshore, which caught the northern eyewall, only reported sustained winds of 79 knots at an elevation of 80 feet (where winds are higher than the standard 30 feet). The storm landfalled at 954 mb, which is not very low. Also, the storm was weakening. Recon. at landfall reported a maximum flight level wind of 107 knots a distant 76 km northeast of the center. Assuming an generous 85% reduction (appropriate for a weakening storm where convection was sparse where this report was taken) yields 90 knots.

If a weakening Opal or Ivan at 942 mb were marginal cat 3, I don't see how Fran could qualify as well.

More wind reports. Wilmington airport, which also caught the northern eyewall, only got a peak sustained wind of 58 knots. Tropical storm force.

Plus, the radar and sat. presentations of the storm were awful, much worse than Ivan, Opal, or even cat 2 Frances had at landfall:

[Derek Ortt]

90% reduction was likely still appropriate for Fran. There seemed to be enough convection near the core at landfall. 90% of 107KT yields 96.7KT, a very marginal cat 3. The maximum winds; however, were NOT in the eye wall, but in streaks about 50 miles NE of the eye wall, which is where the strongest recon winds were reported, likely in a very small area

There was something funny about the radar of Fran as that was just when the new dopplers were installed and long range mode wasn't widely used, as it is today. It had a problem seeing the back eye wall (when Opal was at peak intensity, radar showed only half of the hurricane.

[Matt-hurricanewatcher]

Derek, I think that there is a smaller differents when its on the beach then a mile or two inland. So at 200 feet the winds could be 30 mph higher at 200 feet. So 120 mph at the surface=150 mph at 200 feet. But right on the coast/Beach or over the ocean that differents would be alot less different. Like At 200 feet 150 mph...Then you got at the surface mapybe a 5 to 10 mph decrease.

[Anonymous]

Here is another thought--hurricanes spawn numerous tornadoes upon lanfall. Maybe some of this extreme cat4 damage was actually caused by hurricane spawned tornadoes! This tonado damage could have very well been obscurred by the enormous cat 2 hurricane damage and could have been confused as hurricane damage but the hurricane damage will continue and hide the tornados.

[Matt-hurricanewatcher]

One more quastion how can a Sail boat be 200 feet in the air?

[HurricaneBill]

One more quastion how can a Sail boat be 200 feet in the air?

They don't call them sailboats for nothin!

[tallywx]

One more quastion how can a Sail boat be 200 feet in the air?

When it's descending from 300 feet, of course.

[Anonymous]

I doubt it. Ivan was 120 mph with a 140 mph wave and surge impact.

[AussieMark]

my point is, this phenomenon has been documented in the forms of mini-swirls.

so many past hurricanes had miniswirls.

Andrew did

I think Celia did. The following was in the Celia prelim report

Celia was a unique hurricane meteorologically in that most of the damage occurred in conjunction with explosive tornado-like winds that developed in the left semicircle. As Celia moved across the northern edge of Corpus Christi Bay the damage which occurred to the city of Corpus Christi to the south appeared to have resulted almost entirely from a few high energy bursts of west winds, all occurring in the course of about 15 minutes. The highest sustained winds were apparently no more than 120-130 mph. However, gust speeds locally reached values of 160 mph. Even to the right of the storm center the heaviest damage appeared to have occurred from south or southeast of the center.

The highly damaging gusts in Celia provided streaky damage. Viewed from a helicopter, a succession of long streaks of heavy damage were apparent as small packets of high energy winds radially spaced from north to south at intervals of a mile or more and raked across the City from west to east. In discussion with town's people and airport personnel these bursts of high energy wind occurred all across the City apparently within the space of about 15 minutes. Individual descriptions from various sectors of the town were similar and described the situation in somewhat this way.

---Mark---

[weatherwindow]

ALhurricane.....can you describe the core collapse process? would it result is something akin to a downburst?...or more cyclonic like fujita's phenomena in andrew?.....thank you for the info........rich

[dhweather]

One more quastion how can a Sail boat be 200 feet in the air?

When it's descending from 300 feet, of course.

Or ascending to 300 feet.

[vbhoutex]

Derek, are you suggesting that these streak winds are not indicative of the winds in a hurricane? I understand that they would be different than the sustained winds. I can imagine them being sustained as it is defined for a one minute average. Should they not be considered if they are documented? I'm trying to understand your thinking on these winds.

[dhweather]

Well, this debate is one of interest.

I've seen the damage from Ivan first hand, and it's really, really bad.
I've got a lot of respect for Derek, after all he is a pro met and he brings
up many valid points. The most important one is that people don't get
the full brunt of a storm (say a cat 3), and then discount the next cat 3
that comes along, citing the "last cat 3 was nothing". Those folks end
up calling 911 during landfall pleading for others to help them, or
even worse, they don't make it. So yes, Derek has some good points
with that.

I also believe the damage from Ivan warrants looking back into it.
If we did it for Andrew, why not Ivan? Both were very damaging systems.

My personal belief for Ivan is this:

Ivan was a strong cat three six hours out, but weakening due to strong
30 KT westerlies. Ivan was likely a weak cat 3 at landfall. The surge
damage can be attributed to ocean physics and dynamics. Things that
happen in the atmosphere happen in the ocean, just much slower.
While Ivan's structure was reacting to the shear, the ocean did not
nearly as fast, hence we had a surge more like a strong 3 or weak 4.

[MGC]

Ivan was still a cat 4 the afternoon before landfall if I recall. Ivan was also a large hurricane and large hurricanes produce large surges. TS Isadore was a large hurricane before its encounter with the Yucatan and still retained a large circulation as a TS when it hit La. Isadore produced a respectable surge here on the Mississippi coast, larger that some hurricanes that hit La in a similar fashion. Large storms produce large surges and dhweather is correct IMO about the ocean being slow to calm. Ivan was weakening rapidly due to shear and dry air entrainment. Weak Cat 3 when he crossed the Alabama coast......MGC

[vbhoutex]

I don't think anyone will argue the Weak 4 as far as the storm surge is concerned. As stated the surge would react much slower than the windfield would. What is being discussed, at least by some of us is the fact that in some places damage seems to be indicative of CAT3 wind strength.

[Derek Ortt]

typically, the streak winds are not considered to be representative of the storm, but due to mesoscale factors, much like the 111KT gust at Guantanamo during TS Gordon back in 1994, purely due to a thunderstorm downdraft

Andrew was re-examined primarily due to poor science at the time and new research clearly indicated than 80% did not apply

Of interest, Hugo may be raied from 120 to 125KT as FL winds at 700mb were 141KT at landfall.

Regarding the surge, LIli came in as a borderline cat 1/2 storm, yet the surge was still nearly 12 feet. It does not have a chance to decrease

[rtd2]

I doubt it. Ivan was 120 mph with a 140 mph wave and surge impact.

Agreed as I said earlier Theres no doubt the tidal surge was that of a strong cat 4 its just the winds had reduced to cat 3...

[Brent]

Ivan was still a cat 4 the afternoon before landfall if I recall. Ivan was also a large hurricane and large hurricanes produce large surges. TS Isadore was a large hurricane before its encounter with the Yucatan and still retained a large circulation as a TS when it hit La. Isadore produced a respectable surge here on the Mississippi coast, larger that some hurricanes that hit La in a similar fashion. Large storms produce large surges and dhweather is correct IMO about the ocean being slow to calm. Ivan was weakening rapidly due to shear and dry air entrainment. Weak Cat 3 when he crossed the Alabama coast......MGC

He was actually a Weak Cat 4(135 mph) until RIGHT at landfall. The landfall advisory(2am CDT) he was at 130(borderline 3/4).

AT 2 AM CDT...0700Z...THE LARGE EYE OF HURRICANE IVAN WAS CENTERED
NEAR LATITUDE 30.2 NORTH...LONGITUDE 87.8 WEST...VERY NEAR THE
ALABAMA COASTLINE.

IVAN IS MOVING SLIGHTLY EAST OF DUE NORTH NEAR 13 MPH...AND THIS
MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS. ON THE
FORECAST TRACK...THE CORE OF THE HURRICANE WILL BE ON THE COAST
SHORTLY.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 130 MPH...WITH HIGHER
GUSTS. A GRADUAL WEAKENING SHOULD CONTINUE AS THE HURRICANE MOVES
INLAND. OCCUPANTS OF HIGH-RISE BUILDINGS WITHIN THE HURRICANE
WARNING AREA CAN EXPECT HIGHER WINDS THAN THOSE EXPERIENCED AT THE
SURFACE...ABOUT ONE SAFFIR-SIMPSON CATEGORY HIGHER AT THE TOP OF A
30-STORY BUILDING. HURRICANE FORCE WINDS COULD SPREAD INLAND UP TO
ABOUT 150 MILES NEAR THE PATH OF THE CENTER.

[rolltide]

After the storm you could clearly see where the streak winds occured. The easiest way to see it was by looking at the trees. You would see an area where there was light tree damage (no trees down and few broken limbs) and then suddenly you would run into an area about 100 yards wide where almost all trees were blown down are severely damaged. This happened one street over from my house. We had no trees down on our short street (just a bunch of broken limbs) but one street over had about half the trees uprooted or broken off half way up. (and these were large oak tress) This happened all over town. I would love to see a detailed study of this like they did in Homestead after Andrew.

Keith

[ALhurricane]

That was the main point of my post... Research is ongoing to completely understand what happened in Ivan. My topic was not declartive statement, although some may of took it that way. Nobody is saying Ivan was a 4 at this point, but research continues. Ivan may very well have been a 3, but I do not appreciate being labeled somebody who is trying to hype it as otherwise.