Atlantic Hurricanes: Reanalyzed

[HurricaneJosh]

Situation: Hurricane Hugo makes landfall at Mechanicsville, SC at 12:00 am EDT, 09/22/1989.

Argument by some mets: Hugo managed to clear cut pine forests 20-25 miles inland. Some of the trees were uprooted and literally blown away from the site they had stood. Because of this, there is a strong argument that Hugo may have been a Category Five at landfall. Tree damage to some of the area was worse that in Tatum, SC, where two F-4 tornadoes crossed paths within 10 minutes of each other 5 years prior.

Discuss.

Hey, Hugo.

It's an interesting idea, but I personally don't buy it-- for a couple of reasons:

Pressure-Wind Relationship

A fast-and-dirty calculation, using the Atlantic reanalysis methodology:

The Brown p/w relationship yields 126 kt for a strengthening 934-mb hurricane between 25N and 35N. Other factors: the large RMW would "penalize" the wind speed 5-10 kt, whereas the brisk (but not extremely fast) motion might add 5 kt. (No, you don't add 20 kt because the cyclone was moving at 20 kt-- doesn't work that way. ) So, let's say there's a net penalty of 5 kt. That yields 121 kt-- which is perfectly in line with HURDAT.

Chris Landsea's p/w relationship yields a less-generous ~114 kt as the starting value-- prior to the "rewards-and-penalties" phase.

Now, I'm not suggesting that these calculations are the end-all: they're just guidance to use when there aren't enough surface obs to work with (as in this case). But they're a good starting point.

Storm Surge

The 22-ft surge was impressive, but doesn't surprise me. The cyclone was very strong and very large-- so 22 ft is within the range of what one would expect.

Winds in Charleston

Granted, being just a hair left of the center, Charleston was not in the right-front quad and should not have gotten the max winds.

That having been said, the city was in the inner core and the eye, and I feel if Hugo were a Cat 5, Charleston would have had much, much stronger winds-- not the highest winds in the cyclone, but much higher than they were. Based on reliable surface obs and damage, I feel the city saw max winds in the Cat-2 range-- probably in exposed waterfront locations-- with much of the rest of the city getting Cat-1 winds.

(Before anyone freaks out about this, please note that true Cat-1 winds (sustained at 65-80 kt) raking a city's downtown area is a rare and impressive event; it doesn't actually happen that often.)

[Ed Lizard]

(Before anyone freaks out about this, please note that true Cat-1 winds (sustained at 65-80 kt) raking a city's downtown area is a rare and impressive event; it doesn't actually happen that often.)

Hobby Airport was the only official reporting station in the city of Houston to report sustained hurricane force winds, and that was only 65 knots. Peak gust was only 80.

But all the fun and excitement in the city, with Cat 1 winds. One reason why that TWC 'Day After Tomorrow' NYC Cat 4 seems so interesting, even if so unlikely.

Big building with Cat 1 winds, just imagine a Cat 3 or Cat 4...

[Hugo]

Hobby Airport was the only official reporting station in the city of Houston to report sustained hurricane force winds, and that was only 65 knots. Peak gust was only 80.

But all the fun and excitement in the city, with Cat 1 winds. One reason why that TWC 'Day After Tomorrow' NYC Cat 4 seems so interesting, even if so unlikely.

Big building with Cat 1 winds, just imagine a Cat 3 or Cat 4...

It Could Happen Tomorrow.

[Ed Lizard]

It Could Happen Tomorrow.

Databuoy at Ambrose Light has an SST of 3.8º.

No Cat 4 for NYC tomorrow.

But if I got my disaster titles confused, well, that too.

[Hugo]

Databuoy at Ambrose Light has an SST of 3.8º.

No Cat 4 for NYC tomorrow.

But if I got my disaster titles confused, well, that too.

The name of the show is It Could Happen Tomorrow.

[Hugo]

So how about Hurricane Hugo? Cat 4? Cat 5?

[Ed Lizard]

The name of the show is It Could Happen Tomorrow.

But if I got my disaster titles confused, well, that too.

I knew what you were saying, but I couldn't help myself. I just had to look up that buoy SST. I had to.

[wxmx]

I lean towards a 4. Hugo is a rather modern 'cane, where many of the current tools were available back then (relatively modern radar, satellite, aircraft, etc). There have many upgrades in reanalysis post season, but they are usually more in the 5-10 kt range...not 20kt. Looking at radar and satellite Hugo lacks the perfect symmetry around the eye that cat 5s usually bear upon.

[Normandy]

There is no chance Hugo was a category 5. Just because it knocked over pine trees doesn't mean squat. Pine trees are some of the weakest of trees to begin with. And Charleston seeing Cat 1 conditions in the eyewall? Chetumal saw stronger winds and it was outside of the core of Dean on the weak side.

[Hugo]

There is no chance Hugo was a category 5. Just because it knocked over pine trees doesn't mean squat. Pine trees are some of the weakest of trees to begin with. And Charleston seeing Cat 1 conditions in the eyewall? Chetumal saw stronger winds and it was outside of the core of Dean on the weak side.

I don't know about sustained, but the highest wind gust in Charleston (left eyewall) was 137.

Edit: Sustained on the barrier islands just out from downtown were 100-120.

[HurricaneJosh]

I don't know about sustained, but the highest wind gust in Charleston (left eyewall) was 137.

Edit: Sustained on the barrier islands just out from downtown were 100-120.

The highest official readings from the Charleston area were:

Charleston City: 76 kt G 94

Charleston WSO: 68 kt G 85

Mt. Pleasant: 71 kt G 83

I can't find any higher official readings from in and around the city.

By the way, I think these are respectable readings-- nothing to sneeze at.

[Hugo]

The highest official readings from the Charleston area were:

Charleston City: 76 kt G 94

Charleston WSO: 68 kt G 85

Mt. Pleasant: 71 kt G 83

I can't find any higher official readings from in and around the city.

By the way, I think these are respectable readings-- nothing to sneeze at.

NWS Charleston recorded 137 at the naval base. I'm assuming they mean the naval complex, which is across the river from downtown and would have been left of the storm. Now if they mean the naval weapons base, it's considerably farther inland, so I'm assuming they mean the former.

[HurricaneJosh]

NWS Charleston recorded 137 at the naval base. I'm assuming they mean the naval complex, which is across the river from downtown and would have been left of the storm. Now if they mean the naval weapons base, it's considerably farther inland, so I'm assuming they mean the former.

Not to challenge you, but can you send me a link to verify the reading? I'm super-into data quality when I'm doing research-- I'm a bit of a stickler in this area-- and I hadn't previously heard of this reading.

By the way, a 119-kt gust wouldn't be that out of line with my belief that Charleston had max sustained winds in the Cat-2 range.

[Hugo]

Not to challenge you, but can you send me a link to verify the reading? I'm super-into data quality when I'm doing research-- I'm a bit of a stickler in this area-- and I hadn't previously heard of this reading.

http://www.erh.noaa....ents/hugo.shtml

Go down to meteorological stats.

(credit: NOAA's National Weather Service)

Charleston, SC (Naval Station) - 137

Charleston, SC (Downtown-Custom House) - 108

North Charleston, SC (Airport) - 98

When we talk about "Charleston" we have to keep in mind that Charleston is a river city slightly inland. Along the barrier islands and coast, you can see the 110-120 gust estimates left of the center. That large bubble of 120+ right of the center is, of course, an estimate as there were no official readings that I'm aware of anywhere near that area. That whole area is Francis Marion National Forest.

[kwt]

I'd have to think it would be a 4, a strong 4 I'd have thought but certainly not a 5...I suspect most who are calling for a 5 are weenies who want to claim the east coast has had a 5 strike them...

Also as people have said, 65-80kts is very impressive for a downtown area, London UK had something close to that (averaged 60-63kts) and got 80-90kt gusts and it left a real mess...so people should never under-estimate how damaging even cat-1 winds are.

[HurricaneJosh]

http://www.erh.noaa....ents/hugo.shtml

Go down to meteorological stats.

(credit: NOAA's National Weather Service)

Charleston, SC (Naval Station) - 137

Charleston, SC (Downtown-Custom House) - 108

North Charleston, SC (Airport) - 98

When we talk about "Charleston" we have to keep in mind that Charleston is a river city slightly inland. Along the barrier islands and coast, you can see the 110-120 gust estimates left of the center. That large bubble of 120+ right of the center is, of course, an estimate as there were no official readings that I'm aware of anywhere near that area. That whole area is Francis Marion National Forest.

Thanks. The Custom House and Airport readings are accounted for in my list (I used kt, but they're the same). The Naval reading puzzles me, as it's not in the official Preliminary Report from the NHC. I'm gong to research that one.

I'd have to think it would be a 4, a strong 4 I'd have thought but certainly not a 5...I suspect most who are calling for a 5 are weenies who want to claim the east coast has had a 5 strike them...

Also as people have said, 65-80kts is very impressive for a downtown area, London UK had something close to that (averaged 60-63kts) and got 80-90kt gusts and it left a real mess...so people should never under-estimate how damaging even cat-1 winds are.

Agreed. By the way, when did London have winds like that?

[am19psu]

Agreed. By the way, when did London have winds like that?

It happens more often then you'd think. I can't forecast them at all, but my company issues damaging wind forecasts for our European clients.

[kwt]

October 1987 Josh, you can read more here:

http://www.dandantheweatherman.com/Bereklauw/Octstorm.html

Highest UK wind was gust was 100kts, highest gusts full stop was 117kts.

Was a very impressive storm, pretty much a standard storm but on steriods.

[HurricaneJosh]

News for total reanalysis nerds only:

The committee went through and adjusted some of the previously completed work for the period 1851-1930. This involved slight reductions to the landfall intensities of some important American hurricanes:

Indianola 1886 - 130 kt (down from 135 kt)

Galveston 1900 - 120 kt (down from 125 kt)

Tampa Bay 1921 - 100 kt (down from 105 kt)

None of these changes are too significant-- none affect the storm's categories-- although it means the Indianola storm is no longer the strongest know cyclone to hit the USA before Labor Day 1935. Its revised estimated max winds now tie it with Last Island (LA) 1856 and FL Keys 1919.

I wrote to Chris Landsea, asking why the changes were made. I'm curious to know if 1) new things were discovered about these systems, or 2) there've been tweaks to the reanalysis methodology.

By the way, Great Miami 1926 and Lake Okeechobee 1928 remain unchanged at 125 kt.

Like I said, total nerd news. I don't expect any responses.

[Floydbuster]

News for total reanalysis nerds only:

The committee went through and adjusted some of the previously completed work for the period 1851-1930. This involved slight reductions to the landfall intensities of some important American hurricanes:

Indianola 1886 - 130 kt (down from 135 kt)

Galveston 1900 - 120 kt (down from 125 kt)

Tampa Bay 1921 - 100 kt (down from 105 kt)

None of these changes are too significant-- none affect the storm's categories-- although it means the Indianola storm is no longer the strongest know cyclone to hit the USA before Labor Day 1935. Its revised estimated max winds now tie it with Last Island (LA) 1856 and FL Keys 1919.

I wrote to Chris Landsea, asking why the changes were made. I'm curious to know if 1) new things were discovered about these systems, or 2) there've been tweaks to the reanalysis methodology.

By the way, Great Miami 1926 and Lake Okeechobee 1928 remain unchanged at 125 kt.

Like I said, total nerd news. I don't expect any responses.

I'm interested to see why the change from 135 kt to 130 kt with Indianola. Afterall, it had a tighter wind field with a 925 mb pressure. 1900 is no surprise, as we saw with Rita, Katrina and Ike it's possible that if that occurred today it could've been a Category 2 or 3 upon landfall and still had the devastating surge.

[Normandy]

They are analyzing the 1900 as a 4 though, not a 2 or 3. What do they base that re-analysis on? Pressure reading?

[HurricaneJosh]

I'm interested to see why the change from 135 kt to 130 kt with Indianola. Afterall, it had a tighter wind field with a 925 mb pressure. 1900 is no surprise, as we saw with Rita, Katrina and Ike it's possible that if that occurred today it could've been a Category 2 or 3 upon landfall and still had the devastating surge.

Yep, I think they're realizing more and more that surge is not heavily dependent on a certain wind speed at the *exact* moment of landfall. This having been said, the Galveston storm was analyzed to be a Cat 4 based on multiple factors, and it seems like a reasonable conclusion.

They are analyzing the 1900 as a 4 though, not a 2 or 3. What do they base that re-analysis on? Pressure reading?

God, no! I wish it were that simple, but as we've learned especially over the last decade or so, central pressure is only one of many factors. The reanalysis folks are like detectives, and they piece together several items of evidence to try to reconstruct what happened. The main factors they use are estimated central pressure, intensity trend, latitude, translational speed, and RMW-- not to mention that reliable surface obs (wind and surge) and the exact location of those obs factor heavily into the analysis.

[Ginx snewx]

Cold stove league talk already?

[HurricaneJosh]

Cold stove league talk already?

No, this is a year-round topic of interest to me. I actually find it as interesting as chasing.

[Ed Lizard]

Cold stove league talk already?

hyades

[HurricaneJosh]

Please keep the thread on topic. Thx.

[aslkahuna]

Josh, you and I have both been in bona fide Cat 1 and 2 hurricanes (or typhoons) and I agree that a 65-80 kt sustained wind hurricane in a large city would be a hair and hell raising experience given how the winds would swirl around between buildings at street level not to mention that they would significantly stronger up in the high rises.

Steve

[HurricaneJosh]

Josh, you and I have both been in bona fide Cat 1 and 2 hurricanes (or typhoons) and I agree that a 65-80 kt sustained wind hurricane in a large city would be a hair and hell raising experience given how the winds would swirl around between buildings at street level not to mention that they would significantly stronger up in the high rises.

Steve

Thanks, Steve-- and thank for reiterating this important point.

I think even informed people (including amateur wx enthusiasts and chasers) tend to grossly overestimate the winds they experience in hurricanes, sometimes by as much as 100%-- no joke. I've seen videos where the chaser describes the wind as "110 mph" whereas it looked like 50 or 60 kt to me. I've had friends tell me they experienced sustained hurricane winds when the HRD analysis shows winds in their area were no more than 40 kt. I remember a couple of years ago you made a post about how when a hurricane comes ashore, the coverage of true hurricane winds (1-min/10-m winds of 64 kt) is much smaller than most people realize, and-- as you said-- the places that actually get a true sustained 64-kt wind get really get raked. That post of yours stuck with me and I so agree with it.