Discussion of Intense Tropical Cyclones

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1900hurricane
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Re: Intense Tropical Cyclone Discussion

#341 Postby 1900hurricane » Sat Jan 26, 2019 3:36 pm

supercane4867 wrote:The problem with Muifa is that it started to weaken just after rapidly intensified, which did not sustain the impressive satellite presentation long enough as typical 150kt+ storms do.
It's clearly at least a low end Cat.5, but I won't go too far beyond that.

I'd also like to present Cyclone Olaf of 2005. It's basically a SPAC version of Dianmu with the most perfect structure ever observed in southern hemisphere besides Monica. The cyclone undergone a phase of rapid intensification under extreme favorable conditions consisting of 31°C SSTs with low shear and strong diffluence aloft. MODIS imagery indicate the eye is well over 20°C and is surrounded by insanely cold CDO. A barometric pressure of 931mb was recorded on an island of American Samoa when Olaf passed more than 25km to its east after significantly weakened. It's possible the central pressure went as low as 900mb at the time and we can only imagine how low it could have been near peak intensity.

http://i.imgur.com/zyQ7Wuq.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/2/21/Cyclone_Olaf_16_feb_2005_0110Z.jpg/933px-Cyclone_Olaf_16_feb_2005_0110Z.jpg

Since I can quickly implement the Schloemer Equation via Python, I used it with Olaf '05, and the results are pretty eye opening. Using a 18.52 km (10 nm) RMW that I've estimated using microwave imagery (below) and spitballing a very low 1000 mb outermost closed isobar (just an educated guess since I don't have access to reanalysis data with the government shutdown) along with the measured 931 mb pressure estimated at 25 km from the center of Olaf, I end up getting Tip type pressure estimates. Even if Olaf passed a little closer and the RMW just touched the observation side, that's still good for an 890 mb pressure estimate. A developing outer eyewall may have affected the pressure gradient a little, but I don't think that would have resulted in a pressure above 900 mb.

Image

Image

 https://twitter.com/1900hurricane/status/1089391885225996288


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Re: Discussion of Intense Tropical Cyclones

#342 Postby Ptarmigan » Sun Feb 10, 2019 3:52 pm

Some of these South Pacific tropical cyclones are very intense and on par with West Pacific.

The South Pacific often gets overlooked.
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Re: Discussion of Intense Tropical Cyclones

#343 Postby NotoSans » Fri Apr 19, 2019 11:31 pm

It is worth noting that in Michael's report, NHC utilised the GBVTD technique to compute actual wind velocities from radar data (see last para in p 4 of the TCR). The same technique had been used by JMA to conduct a re-analysis of Haiyan's intensity: https://journals.ametsoc.org/doi/pdf/10 ... -17-0120.1
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Re: Discussion of Intense Tropical Cyclones

#344 Postby CrazyC83 » Sat Apr 20, 2019 1:38 am

NotoSans wrote:It is worth noting that in Michael's report, NHC utilised the GBVTD technique to compute actual wind velocities from radar data (see last para in p 4 of the TCR). The same technique had been used by JMA to conduct a re-analysis of Haiyan's intensity: https://journals.ametsoc.org/doi/pdf/10 ... -17-0120.1


Interesting they also estimate the pressure at 906 mb, which would be incredibly high for an intensity in the 175-190 kt range, and would be even higher than the Schloemer equation estimate of the pressure at landfall on Leyte, which is around 895-900 mb (which was likely after some weakening).
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Re: Discussion of Intense Tropical Cyclones

#345 Postby Ptarmigan » Mon May 06, 2019 9:47 pm

CrazyC83 wrote:
NotoSans wrote:It is worth noting that in Michael's report, NHC utilised the GBVTD technique to compute actual wind velocities from radar data (see last para in p 4 of the TCR). The same technique had been used by JMA to conduct a re-analysis of Haiyan's intensity: https://journals.ametsoc.org/doi/pdf/10 ... -17-0120.1


Interesting they also estimate the pressure at 906 mb, which would be incredibly high for an intensity in the 175-190 kt range, and would be even higher than the Schloemer equation estimate of the pressure at landfall on Leyte, which is around 895-900 mb (which was likely after some weakening).


I would be curious about the ambient pressure Haiyan was in at the time.
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Re: Discussion of Intense Tropical Cyclones

#346 Postby BYG Jacob » Tue May 07, 2019 5:24 am

Ptarmigan wrote:
CrazyC83 wrote:
NotoSans wrote:It is worth noting that in Michael's report, NHC utilised the GBVTD technique to compute actual wind velocities from radar data (see last para in p 4 of the TCR). The same technique had been used by JMA to conduct a re-analysis of Haiyan's intensity: https://journals.ametsoc.org/doi/pdf/10 ... -17-0120.1


Interesting they also estimate the pressure at 906 mb, which would be incredibly high for an intensity in the 175-190 kt range, and would be even higher than the Schloemer equation estimate of the pressure at landfall on Leyte, which is around 895-900 mb (which was likely after some weakening).


I would be curious about the ambient pressure Haiyan was in at the time.

1012 or so iirc. Haiyian was getting shoved due west basically the whole time.
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Re: Discussion of Intense Tropical Cyclones

#347 Postby 1900hurricane » Tue May 07, 2019 3:30 pm

BYG Jacob wrote:
Ptarmigan wrote:
CrazyC83 wrote:
Interesting they also estimate the pressure at 906 mb, which would be incredibly high for an intensity in the 175-190 kt range, and would be even higher than the Schloemer equation estimate of the pressure at landfall on Leyte, which is around 895-900 mb (which was likely after some weakening).


I would be curious about the ambient pressure Haiyan was in at the time.

1012 or so iirc. Haiyian was getting shoved due west basically the whole time.

The outermost closed isobar (OCI) for Haiyan was actually somewhere between 1000-1008 mb. Low surface pressures and heights aloft due to some combination of MJO/Kelvin/Equatorial Rossby is just as responsible for Haiyan's brisk motion as subtropical ridging to its north. It was this gradient region between the two that Haiyan traversed.
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Re: Discussion of Intense Tropical Cyclones

#348 Postby 1900hurricane » Mon Jun 10, 2019 1:55 pm

Just wanted to take a moment to post about the updated IBTrACS page hosted by UNC Asheville. The dataset is constantly updated with finalized tropical cyclone information from all major agencies and some other older datasets dating back as early as 1842!. For systems with geostationary imagery available, 3 hr IR imagery is also provided by HURSAT in a modified color Dvorak scale, which makes one to one comparisons of tropical cyclones about as close as it gets! Just as an example, here's the Patricia '15/Nuri '14 comparison I had on the first page. When available, data includes Vmax, Pmin, wind radii, ROCI, and more!

ImageImage

Image
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