Discussion of Intense Tropical Cyclones

[mrbagyo]

The lowest landbase barometric pressure reading for Typhoon Rammasun was 899.2 hpa! It was recorded in Qixhou Island Station.

Just 7.2 hpa shy of Labor Day Hurricanes 892 hpa.

http://adsabs.harvard.edu/abs/2016EGUGA..1813654C

[1900hurricane]

I had seen that number thrown around a couple of times, but never knew where it came from. Good to see a source for it. That is easily the deepest system I am aware of in the Sout China Sea. Here is an IR BD and visible image of Rammasun '14 at about that time (0532Z July 18).





When I run KZC (p = 899.2 mb, forward speed = 12 kt, r34 = 108 nm/roci = 220 nm, latitude = 19.9ºN, and oci = 1001 mb), I get an expected 1 minute maximum sustained wind of about 155 kt. ~165 kt can be obtained if CMA's estimated 888 mb is used instead, although I do not know what went into making that estimate.

[euro6208]

155 knots? That's insane. The SCS has probrably never seen such an intensity or has it before? Has there ever been a TC with a similiar intensity during and after post recon?

[euro6208]

The lowest landbase barometric pressure reading for Typhoon Rammasun was 899.2 hpa! It was recorded in Qixhou Island Station.

Just 7.2 hpa shy of Labor Day Hurricanes 892 hpa.

Rammasun joins a ton of parade typhoons peaking at sub 900 in history! Due to dvorak, it's the strongest pressure confirmed since STY Flo's measured 891 mb in 1990.

Too bad.

. It is evident that Rammasun's eyewall did not pass across Qizhou Island directly, so the actual MSLP should be lower than 899.2hPa. By applying wind-pressure relationship, it is reckoned that the reasonable MSLP and peak wind of Rammasun should be 888hPa and 70-76m/s

[1900hurricane]

NHC and CPHC are certainly looking at the SFMR readings with a more skeptical eye this season, especially in the presence of comparable flight level winds. CPHC and NHC waited an additional mission to upgrade Lane to a category 5 for this reason.

 https://twitter.com/firebomb56/status/1032129359895658496

[Chris90]

NHC and CPHC are certainly looking at the SFMR readings with a more skeptical eye this season, especially in the presence of comparable flight level winds. CPHC and NHC waited an additional mission to upgrade Lane to a category 5 for this reason.

I'm glad you started a discussion on this over here in this thread, I think this is a interesting topic for everyone to discuss/debate.

My amateur thoughts on this topic:

I'm not quite sure why they believe so strongly that the SFMR has a high bias at Cat 5 winds. Pro-met Alyono mentioned in the Lane thread that the HRD scientists who maintain the SFMR do not agree with the NHC scientists who believe the SFMR is running too hot. I know the SFMR algorithm had some changes made back in 2015, but from what I read, it was mainly for a high bias in depressions/tropical storms. Apparently rain inflation was more of a problem at lower wind speeds, which makes sense to me, as the instrument basically measures the brightness temperature, so heavy rainfall is going to inflate the reading to a certain level regardless of wind speed, so it makes sense to make adjustments to account for this. In my mind, and maybe I'm wrong, there comes a point where the wind will generate a strong enough return on brightness temperatures that rain won't be able to inflate the readings by all that much the same way it would at lower wind speeds.

Irma was the storm that they specifically singled out in her TCR that made them question the SFMR and think there was a high bias. I would understand where they are coming from if there was a big discrepancy in data, but one thing last season gave us was a variety of SFMR readings. I would be really questioning it as well if there was a big jump in data points, like if the SFMR was returning 145kts readings and then making big jumps to 160kts. With Harvey, Maria, and Irma though, we got a variety of data points over a large spectrum of winds. Between the 3 we got multiple returns in the 110,120,130,140, and 150 kt range, with Irma producing 2 160kt returns as the highest intensity measured last year.
Irma alone provided a wide variety of returns over the spectrum of winds due to multiple recon missions while she was intensifying. I know there were more SFMR readings than what I'm pulling up off the top of my head, but I know she produced a 147,152,154, and the 2 160 kt readings via SFMR. I would be more inclined to believe a high bias if there were holes in the data, such as Irma producing returns in the 140-145 kt range and then jumping to 155-160, with no returns between 145-155.

I would also like to quickly discuss the eyewall dropsondes. I know they started dropping eyewall sondes in 1997 and have been doing it ever since, and since about that time they've been using a factor of .85 on the average over the lowest 150m to estimate surface winds. I think this might be a dated methodology, and with the SFMR going into operation in 2007, I think there's enough data now that someone could do a study on this. I think there's great variation in eyewall wind profiles, and it can't be summarized using a factor of .85. I think a better methodology could possibly be developed factoring in the relationship between the average wind over the lowest 500m and the average wind over the lowest 150m.
I'm going to use Irma again for this example.

A dropsonde dropped in the NE eyewall measured an average of 168 kts in the lowest 500m, and 157kts in the lowest 150m. This to me indicates that the stronger winds were not as effectively translating to the surface at this moment in time. Drop time was 11:24Z on the 5th.

Another dropsonde in the N eyewall launched at 158Z on the 6th measured 165 kts in the lowest 500m, and 163 kts in the lowest 150m, indicating to me that winds were more effectively translating to the surface at this time, based on the fact the relationship between the 500m and 150m averages is much tighter.

The thing to note though is that dropsondes are basically tubes falling through the atmosphere, so they aren't effectively measuring one straight up and down slice. They get launched in one quadrant and rotate into another quadrant by splashdown, sometimes they fall out of the RMW, it's highly situational. But I do think that now we have more tools and data than ever for our use, more studies should be done in the relationship between flight level winds, dropsonde winds, and the SFMR. I think the relationship is highly fluid and it is not a "one size fits all" relationship that can be figured using standard adjustment factors.

[1900hurricane]

There was quite a bit of SFMR discussion in last year's Tropical Cyclone Report thread, particularly beginning around page 6 with the release of the Jose and Irma reports, but this is a very good discussion to bring over here too.

With regards to the change to the SFMR algorithm prior to 2016, it is true that it was made to more accurately estimate winds in lower end storms, but the tweak may have affected the entire spectrum, which may have particularly affected the higher end where there are a fewer number of data points.

 https://twitter.com/pppapin/status/972265251151499265



 https://twitter.com/EricBlake12/status/972271549012201472




In a couple of very intense systems prior to the algorithm change (Megi '10 and Patricia '15), very high SFMR values were recorded, but they never outplayed the flight level winds near peak intensity (although the ratios were much closer while Patricia was intensifying). The only system I can think of prior to the change that had SFMR values exceeding flight level winds was during the aborted mission into Felix '07, and it's not impossible that those SFMR values were corrupted by the graupel and hail that caused the mission to be aborted in the first place (although an RMW dropsonde did support some extreme winds on that same mission). With several of the more recent storms, particularly Irma and Jose, suddenly SFMR values exceeding flight level winds were being thrown out regularly. Just based on this, I can see why the NHC has become more skeptical of some of the higher end values.

Thankfully, studies are being done right now on the topic, but these things take time to complete. Hopefully we can have a better understanding of high level tropical cyclones once some of them are complete however.

[1900hurricane]

I recently was part of a fun and interesting conversation on Twitter with Josh Morgerman of iCyclone, James Reynolds of EarthUncutTV, and fellow Storm2k member Jim Tang (wxmann) discussing the landfall intensity of Typhoon Vera '59. Check it out if you're interested!

 https://twitter.com/1900hurricane/status/1035691320034123776

[NotoSans]

The lowest SLP recorded in Japan during VERA is 929.2 mb, so the landfall pressure is very likely 928 mb. VERA was indeed very large when it made landfall, so the intensity estimated using modern re-analysis technique may not be particularly high, but its extensive wind field is what makes it dangerous.

[NotoSans]

Would also like to make some notes on RAMMASUN. Some meteorology amateurs from China actually visited CMA after RAMMASUN and confirmed the 899.2 mb pressure reading, but a detailed analysis showed that the weather station may have been hit by a mesovortex, as the pressure readings were consistently 8-10 mb higher when the center of the eye passed.

[mrbagyo]

Would also like to make some notes on RAMMASUN. Some meteorology amateurs from China actually visited CMA after RAMMASUN and confirmed the 899.2 mb pressure reading, but a detailed analysis showed that the weather station may have been hit by a mesovortex, as the pressure readings were consistently 8-10 mb higher when the center of the eye passed.

Are you saying that the pressure in Mesovortices could get even lower than the TC's Central pressure (akin to a pressure drop in a tornado - Tim Samaras was able to measure 850 hpa for a brief period - like for just several seconds only when a tornado passed directly over his probe)

[NotoSans]

Would also like to make some notes on RAMMASUN. Some meteorology amateurs from China actually visited CMA after RAMMASUN and confirmed the 899.2 mb pressure reading, but a detailed analysis showed that the weather station may have been hit by a mesovortex, as the pressure readings were consistently 8-10 mb higher when the center of the eye passed.

Are you saying that the pressure in Mesovortices could get even lower than the TC's Central pressure (akin to a pressure drop in a tornado - Tim Samaras was able to measure 850 hpa for a brief period - like for just several seconds only when a tornado passed directly over his probe)

This is exactly what happened during one of Hugo’89 recon mission IIRC.

[Ptarmigan]

The lowest SLP recorded in Japan during VERA is 929.2 mb, so the landfall pressure is very likely 928 mb. VERA was indeed very large when it made landfall, so the intensity estimated using modern re-analysis technique may not be particularly high, but its extensive wind field is what makes it dangerous.

Re-Analysis/Prediction Of Typhoon Vera (1959) Project
https://ams.confex.com/ams/pdfpapers/16 ... 168250.pdf

It has what Vera would of looked like on satellite. Hurricane Katrina had central pressure of 920 millibars when it made the first landfall on Southeast Louisiana. It had 125 mph or 200 km/h wind. Katrina was large when it made landfall on Louisiana and Mississippi.

[CrazyC83]

Would also like to make some notes on RAMMASUN. Some meteorology amateurs from China actually visited CMA after RAMMASUN and confirmed the 899.2 mb pressure reading, but a detailed analysis showed that the weather station may have been hit by a mesovortex, as the pressure readings were consistently 8-10 mb higher when the center of the eye passed.

That would suggest an actual pressure around 905 mb?

[supercane4867]

The lowest SLP recorded in Japan during VERA is 929.2 mb, so the landfall pressure is very likely 928 mb. VERA was indeed very large when it made landfall, so the intensity estimated using modern re-analysis technique may not be particularly high, but its extensive wind field is what makes it dangerous.

Re-Analysis/Prediction Of Typhoon Vera (1959) Project
https://ams.confex.com/ams/pdfpapers/16 ... 168250.pdf

It has what Vera would of looked like on satellite. Hurricane Katrina had central pressure of 920 millibars when it made the first landfall on Southeast Louisiana. It had 125 mph or 200 km/h wind. Katrina was large when it made landfall on Louisiana and Mississippi.

It's almost impossible to get a CAT5 landfall on Japanese mainland. I belive the northernmost CAT5 landfall record was set by Camille just north of 30N. In fact it's much harder for a TC to maintain such intensity at that latitude anywhere near land in the WPAC due to its geographic environment.

[SconnieCane]

It's almost impossible to get a CAT5 landfall on Japanese mainland. I belive the northernmost CAT5 landfall record was set by Camille just north of 30N. In fact it's much harder for a TC to maintain such intensity at that latitude anywhere near land in the WPAC due to its geographic environment.

...and Camille's landfall intensity is now, at least unofficially, disputed. When I first started following TCs in the mid-'90s, it was taken as gospel that Labor Day and Camille were the only C5s to made landfall in the CONUS in the 20th century, and Andrew had been a high-end 4. Now the roles between the latter two have been flipped, although Camille's U.S. landfall intensity has not been officially downgraded, Max Hagen makes many good points in that post.

FWIW although I have no qualifications as a meteorologist, as a total weather geek I am always in the "bigger, stronger, more epic" camp when it comes to intensity of storms, so I started reading that post thinking he was full of it but by the end he had actually convinced me.

*Camille may still qualify as the northern most Cat 5 occurrence, at least in the Atlantic basin, although Katrina and Rita would be close. I don't know enough about WPAC TC history to comment on that basin.

[supercane4867]

It's almost impossible to get a CAT5 landfall on Japanese mainland. I belive the northernmost CAT5 landfall record was set by Camille just north of 30N. In fact it's much harder for a TC to maintain such intensity at that latitude anywhere near land in the WPAC due to its geographic environment.

...and Camille's landfall intensity is now, at least unofficially, disputed. When I first started following TCs in the mid-'90s, it was taken as gospel that Labor Day and Camille were the only C5s to made landfall in the CONUS in the 20th century, and Andrew had been a high-end 4. Now the roles between the latter two have been flipped, although Camille's U.S. landfall intensity has not been officially downgraded, Max Hagen makes many good points in that post.

FWIW although I have no qualifications as a meteorologist, as a total weather geek I am always in the "bigger, stronger, more epic" camp when it comes to intensity of storms, so I started reading that post thinking he was full of it but by the end he had actually convinced me.

Pressure reading alone proves Camille was certainly an upper-end CAT5 when it made landfall. The lowest pressure recorded on land was 897mb as mentioned in reanalysis. NHC did revise the best track down to 900mb based on that reading. It must take some abnormal structure and size for a TC to be only CAT4 at such pressure. Wilma is the only case in the Atlantic that had CAT4 winds while the pressure was still below 900mb due to EWRing from its extreme pinhole eye. Camille had already completed an EWRC before landfall and was rapidly restrengthening while coming onshore.

[mrbagyo]

Pressure reading alone proves Camille was certainly an upper-end CAT5 when it made landfall. The lowest pressure recorded on land was 897mb as mentioned in reanalysis. NHC did revise the best track down to 900mb based on that reading.

The 900mb was derived from 904mb reading at the eastern edge of the eye. The 897 mb reading (recorded in inHg) was not used since there was no documentation on the accuracy of the barometer and the reading appears to be rounded off only to the nearest 0.5 inch. Still a legit cat 5 landfall though.

[NotoSans]

The lowest SLP recorded in Japan during VERA is 929.2 mb, so the landfall pressure is very likely 928 mb. VERA was indeed very large when it made landfall, so the intensity estimated using modern re-analysis technique may not be particularly high, but its extensive wind field is what makes it dangerous.

Re-Analysis/Prediction Of Typhoon Vera (1959) Project
https://ams.confex.com/ams/pdfpapers/16 ... 168250.pdf

It has what Vera would of looked like on satellite. Hurricane Katrina had central pressure of 920 millibars when it made the first landfall on Southeast Louisiana. It had 125 mph or 200 km/h wind. Katrina was large when it made landfall on Louisiana and Mississippi.

It's almost impossible to get a CAT5 landfall on Japanese mainland. I belive the northernmost CAT5 landfall record was set by Camille just north of 30N. In fact it's much harder for a TC to maintain such intensity at that latitude anywhere near land in the WPAC due to its geographic environment.

A typhoon in 1934 has a minimum SLP of 911.6 mb measured in the Japanese main islands. Although the wind-pressure relationship would be slightly different and this typhoon could be a larger storm, an argument could be made that it made landfall as a category 5. The WPAC unfortunately does not have in-depth re-analysis projects like the ATL though, so we can’t confirm on this.

[EquusStorm]

Oh lordy, Camille landfall intensity debates. Now that's a can of worms.

Not a certified hurricane expert here by any means, but as someone very familiar and experienced with trees and their structure, you do not have whole undamaged stands of Pinus elliotti and Pinus palustris after 220mph wind gusts. You just don't. It is pretty much physically impossible. EF3-strength three second gusts in the 140 to 150 range easily snaps 95% of even thicker Pinus taeda stems, though of course rapid acceleration in tornadic winds is much more likely to snap trees than gradual hurricane acceleration. Category three Ivan caused devastating loss to longleaf and slash pine stands well inland, but the photos I see from Camille directly from the coast where winds were supposedly vastly stronger than Ivan's show mostly standing pines. Andrew's tree and structural damage is trademark CLASSIC category five wind damage, as is Irma's in the Caribbean although tree species distribution there is vastly different. Those two storms were very similar in suggesting extreme winds; however all of the Camille damage I've seen in photos suggests much lower winds (admittedly more significant than Katrina's though) but extreme surge damage.

Camille was a violent monster over the Gulf and its landfall pressure was frightfully low, and I'd say probably only Rita and Katrina come close as being the most impressive northern Gulf hurricane on record, but photos don't lie; unless someone has proof of obliterated pine stands and non-surge related structural damage suggesting winds over 170-180mph, I can't be convinced Camille was as strong as has been long suggested at landfall. Rednecks claiming it has to be because they heard the wind go woosh and their grandpa insisted winds were 220mph without any proof is, scientifically, garbage, more fit to a book on experiences than actual record, and if the article is anything to go by, I'd only trust legit officially recorded winds to estimate landfall intensity. I don't for a minute believe that higher winds weren't recorded because the instruments failed (unless legitimately verified that this happened) if whole stands of pines survived the lashing nearby. If we take unproven anecdotes as intensity facts, then we have to lower the pressure of the 1935 Labor Day cane (which, those who claim the Camille intensity debate is an effort to downplay past storms should realize has been dramatically intensified in recent analysis and was clearly much stronger than Andrew OR Irma) to 880mb, as a barometer thrown into the sea and never recovered supposedly measured this.

Of course maybe tree damage was much more severe right at the core eastern eyewall and I could be wrong... but I kinda doubt it. Very intense hurricane at landfall, perhaps by far strongest in MS history? Absolutely. Possible marginal low end Cat 5? Possible, but available photos make that debatable. High-end 180-190 sustained? Not even a chance given measured and photographed intensity and damage.