Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#41 Postby Vince_and_Grace_fan » Fri Nov 04, 2016 2:25 am

Hi everybody!
I am a meteorology student in Hungary, and I interested in tropical cyclones, particulary that occur near Europe, and also the tropical-like systems over the Mediteranean Sea.
I wrote a brief summary from this cyclone on my Wunderground blog: https://www.wunderground.com/blog/Zivip ... ranean-sea
This is of course not official, just my opinion. But I think, this cyclone became a real tropical storm for a short time, and also was subtropical before it.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#42 Postby Hypercane_Kyle » Fri Nov 04, 2016 9:52 pm

So I'm really confused as to what these cyclones are classified as. Are they officially considered tropical cyclones? Why aren't there advisories for them?
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My posts are my own personal opinion, defer to the National Hurricane Center (NHC) and other NOAA products for decision making during hurricane season.

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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#43 Postby DanieleItalyRm » Sat Nov 05, 2016 8:27 am

Vince_and_Grace_fan wrote:Hi everybody!
I am a meteorology student in Hungary, and I interested in tropical cyclones, particulary that occur near Europe, and also the tropical-like systems over the Mediteranean Sea.
I wrote a brief summary from this cyclone on my Wunderground blog: https://www.wunderground.com/blog/Zivip ... ranean-sea
This is of course not official, just my opinion. But I think, this cyclone became a real tropical storm for a short time, and also was subtropical before it.



I agree with your analysis. I'm glad we scored the same path of 90M.
90M has developed over more warm water than TCAlex developed in January 2016 . Advice this study for who still believes in old meteorological concepts:

" Revisiting the 26.5°C Sea Surface Temperature Threshold for Tropical Cyclone Development, 2014".


A high sea surface temperature is generally accepted to be one of the necessary ingredients for tropical cyclone development, indicative of the potential for surface heat and moisture fluxes capable of fueling a self-sustaining circulation. Although the minimum 26.5°C threshold for tropical cyclogenesis has become a mainstay in research and education, the fact that a nonnegligible fraction of storm formation events (about 5%) occur over cooler waters casts some doubt on the robustness of this estimate. Tropical cyclogenesis over subthreshold sea surface temperatures is associated with low tropopause heights, indicative of the presence of a cold trough aloft. To focus on this type of development environment, the applicability of the 26.5°C threshold is investigated for tropical transitions from baroclinic precursor disturbances in all basins between 1989 and 2013. Although the threshold performs well in the majority of cases without appreciable environmental baroclinicity, the potential for development is underestimated by up to 27% for systems undergoing tropical transition. An alternative criterion of a maximum 22.5°C difference between the tropopause-level and 850-hPa equivalent potential temperatures (defined as the coupling index) is proposed for this class of development. When combined with the standard 26.5°C sea surface temperature threshold for precursor-free environments, error rates are reduced to 3%–6% for all development types. The addition of this physically relevant representation of the deep-tropospheric state to the ingredients-based conceptual model for tropical cyclogenesis improves the representation of the important tropical transition-based subset of development events.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#44 Postby AJC3 » Sun Nov 06, 2016 9:31 pm

DanieleItalyRm wrote:
Vince_and_Grace_fan wrote:Hi everybody!
I am a meteorology student in Hungary, and I interested in tropical cyclones, particulary that occur near Europe, and also the tropical-like systems over the Mediteranean Sea.
I wrote a brief summary from this cyclone on my Wunderground blog: https://www.wunderground.com/blog/Zivip ... ranean-sea
This is of course not official, just my opinion. But I think, this cyclone became a real tropical storm for a short time, and also was subtropical before it.


I agree with your analysis. I'm glad we scored the same path of 90M.
90M has developed over more warm water than TCAlex developed in January 2016 . Advice this study for who still believes in old meteorological concepts:

" Revisiting the 26.5°C Sea Surface Temperature Threshold for Tropical Cyclone Development, 2014".

A high sea surface temperature is generally accepted to be one of the necessary ingredients for tropical cyclone development, indicative of the potential for surface heat and moisture fluxes capable of fueling a self-sustaining circulation. Although the minimum 26.5°C threshold for tropical cyclogenesis has become a mainstay in research and education, the fact that a nonnegligible fraction of storm formation events (about 5%) occur over cooler waters casts some doubt on the robustness of this estimate. Tropical cyclogenesis over subthreshold sea surface temperatures is associated with low tropopause heights, indicative of the presence of a cold trough aloft. To focus on this type of development environment, the applicability of the 26.5°C threshold is investigated for tropical transitions from baroclinic precursor disturbances in all basins between 1989 and 2013. Although the threshold performs well in the majority of cases without appreciable environmental baroclinicity, the potential for development is underestimated by up to 27% for systems undergoing tropical transition. An alternative criterion of a maximum 22.5°C difference between the tropopause-level and 850-hPa equivalent potential temperatures (defined as the coupling index) is proposed for this class of development. When combined with the standard 26.5°C sea surface temperature threshold for precursor-free environments, error rates are reduced to 3%–6% for all development types. The addition of this physically relevant representation of the deep-tropospheric state to the ingredients-based conceptual model for tropical cyclogenesis improves the representation of the important tropical transition-based subset of development events.


Daniele, my friend...

As always, it is good to see your posts on this subject. You and I have had this same conversation before in the "Xandra" (2014) thread.

viewtopic.php?f=31&t=116987

It's now apparent (or at least it should be apparent) to those who study such things that the 26C threshold only works in a standard or seasonal "MDR-type" barotropic environment. My thoughts there are similarly relevant here, so I will repeat them...

"The traditional low end SST threshold of 26-27C (79-81F) assumes a barotropic atmosphere typical of the deep tropics. Generally, in absence of cold core TUTT cells or troughs that show some reflection down into the mid levels, this type of atmosphere features 500MB temperatures of -4C to -6C. Since instability is a function of temperatures both at the surface and aloft, obviously traditional SST thresholds for TC formation will almost never apply to "medicanes", given their formation north in the range between 30-37N.

I think a decent rule of thumb here might be to look for a temperature difference of no less than 30C between SST/near surface air mass and 500MB when looking at true TC processes (i.e latent heat feedback from convection). In other words, when your SSTs drop to, say...20C, as long as 500MB temps have cooled to at least -10C or lower, and in absence of a significant intrusion of a dry and/or cool (polar) air mass at the time, the local atmosphere, would still support TC formation, at least thermodynamically."

Since your proposal looks at 850MB-tropopause and mine looks at near surface-500MB, I think it would be interesting to compare the two alternative thresholds (or similarly less stringent alternatives) for this subset of developments.

This is a FANTASTIC opportunity for a comprehensive M.S. thesis just waiting to be written!
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#45 Postby DanieleItalyRm » Tue Dec 20, 2016 4:44 am

AJC3 wrote:
Daniele, my friend...

As always, it is good to see your posts on this subject. You and I have had this same conversation before in the "Xandra" (2014) thread.

viewtopic.php?f=31&t=116987

It's now apparent (or at least it should be apparent) to those who study such things that the 26C threshold only works in a standard or seasonal "MDR-type" barotropic environment. My thoughts there are similarly relevant here, so I will repeat them...

"The traditional low end SST threshold of 26-27C (79-81F) assumes a barotropic atmosphere typical of the deep tropics. Generally, in absence of cold core TUTT cells or troughs that show some reflection down into the mid levels, this type of atmosphere features 500MB temperatures of -4C to -6C. Since instability is a function of temperatures both at the surface and aloft, obviously traditional SST thresholds for TC formation will almost never apply to "medicanes", given their formation north in the range between 30-37N.

I think a decent rule of thumb here might be to look for a temperature difference of no less than 30C between SST/near surface air mass and 500MB when looking at true TC processes (i.e latent heat feedback from convection). In other words, when your SSTs drop to, say...20C, as long as 500MB temps have cooled to at least -10C or lower, and in absence of a significant intrusion of a dry and/or cool (polar) air mass at the time, the local atmosphere, would still support TC formation, at least thermodynamically."

Since your proposal looks at 850MB-tropopause and mine looks at near surface-500MB, I think it would be interesting to compare the two alternative thresholds (or similarly less stringent alternatives) for this subset of developments.

This is a FANTASTIC opportunity for a comprehensive M.S. thesis just waiting to be written!


AJC3,
Thank you very much for your reply, which unfortunately I read late. I remember our discussions many years ago. I'm glad that someone begins to understand the dynamics of Medicanes, which are similar to those of the North Atlantic cyclones, as Vince 2005, Grace 2009 or Alex 2016. I think like you; You probably more 'competent than me in physics and dynamic meteorology.

Sorry for my English; Soon, I hope somebody does a correct theory, because all the studies that exist today, compare a Medicanes with a common tropical cyclones surroundings, and this is wrong.
Daniele Bianchino
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#46 Postby Vince_and_Grace_fan » Wed Mar 15, 2017 1:24 pm

Hi folks!
Today I finished my 'Tropical Cyclone Report' from the Mediterranean TS 90M (which got the name Trixie from some European media) that include a synoptical and meteorological part as the NHC's TCRs, and it contain an analysis based on the ECMWF high-resolution re-analysis data too.
The report is available here (if the link doesn't work at first, push an enter): http://zivipotty.hu/trixie.pdf
The animation of the re-analysis maps attainable from the report or from here: https://www.youtube.com/watch?v=w4x_c9wcn9w
I hope you enjoy it, and also the report is professionally correct. :)
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#47 Postby bg1 » Wed Mar 15, 2017 9:14 pm

I skimmed through it, and it looks pretty good! Though the color scale you used on page 11 is very jarring to me; I usually associate red with Category 4-5 hurricanes, not 55-knot tropical storms. (Then again, Trixie probably is the equivalent of a Category 5 in the Atlantic...)
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#48 Postby CrazyC83 » Fri Mar 17, 2017 2:23 pm

Excellent report. Was that ship in the absolute maximum winds? Otherwise I would have set the peak intensity to 60 kt.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#49 Postby Vince_and_Grace_fan » Sun Mar 19, 2017 3:29 am

Thanks!

bg1: The maximal intensity of these cyclones is mostly equivalent with strong tropical storms or rarely Cat 1 hurricanes, so I think that the use of the Saffir-Simpson scale as a color scale is needless. Thus I adjusted the color scale to the wind speed values.

CrazyC83: Yes, the 54 knots ship report on 28 October was the strongest available wind data (if you mean that), but that was maybe a wind gust because it is relatively high compared to the other measurements in the nearby hours, or maybe a strong thunderstorms caused a short wind strengthening. The maximal intensity of the cyclone was perhaps closer to 60 knots than 55, but based on the ASCAT pass map it is not clear. I stayed with 55 knots because the instensity of the convection slowly weakened through the second half of the night although the cyclone's structure became better organized, and the eye-like feature also was short-lived and not fully closed.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#50 Postby bg1 » Sun Mar 19, 2017 7:52 am

Vince_and_Grace_fan wrote:Thanks!

bg1: The maximal intensity of these cyclones is mostly equivalent with strong tropical storms or rarely Cat 1 hurricanes, so I think that the use of the Saffir-Simpson scale as a color scale is needless. Thus I adjusted the color scale to the wind speed values.


That's what I meant by comparing Trixie to a Cat 5. A 55-kt Mediterranean TS would be an impressive feat, as rare as a Cat 4-5 hurricane in the Atlantic.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#51 Postby 1900hurricane » Sun Mar 19, 2017 9:47 am

For some reason, I'm getting a 403 Forbidden error when trying to access the report.
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#52 Postby Vince_and_Grace_fan » Sun Mar 19, 2017 11:23 am

1900hurricane wrote:For some reason, I'm getting a 403 Forbidden error when trying to access the report.


I don't know what could be the problem (sometimes I also can't open the file firtsly, but if I push an enter, then it is okay).
I made a short TCR web page on my website, please try to open from here: http://zivipotty.hu/tcr.html
I also put there my other two reports - from TS Rolf (2011) and STS Qendresa (2014).
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#53 Postby 1900hurricane » Sun Mar 19, 2017 11:52 am

Vince_and_Grace_fan wrote:
1900hurricane wrote:For some reason, I'm getting a 403 Forbidden error when trying to access the report.


I don't know what could be the problem (sometimes I also can't open the file firtsly, but if I push an enter, then it is okay).
I made a short TCR web page on my website, please try to open from here: http://zivipotty.hu/tcr.html
I also put there my other two reports - from TS Rolf (2011) and STS Qendresa (2014).

Got it from there, thanks!
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm) - updated with SWH data

#54 Postby Vince_and_Grace_fan » Sat May 20, 2017 10:29 am

I noticed that Altimeter data have became availeble on the NOAA Ascat page ( https://manati.star.nesdis.noaa.gov/datasets/SGWHData.php ), so I updated Trixie's report (the storm surge part) with it.

Unfortunately the description of this product is unavailable on the website, and I never saw or used it previously, so somebody knows how reliable is this measurement? I mean that the measured wave heights around the cyclone are proportional to the estimated and measured wind speedds?
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Re: MED: 90M/TRIXI (Trixie) - Tropical Storm

#55 Postby AJC3 » Fri Sep 29, 2017 5:24 pm

Kudos on a very impressive and interesting write-up!
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