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Atlantic Tropical Action 2011 - Part IV


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@HurricaneJosh: Wow, thanks for that interesting case study on that unclassified and outlandish cyclone! It was only deemed as having a low chance of tropical cyclone development; so I'm sure that the cherry in September that I mentioned above has a good chance to being added into the database. It's also impressive to see that the 2006 cyclone developed into a 50-MPH tropical storm at 40N latitude; when in reality, it's hard-pressed for a cyclone to maintain its intensity above 35N overall.

You're very welcome. I thought you'd find it very interesting, given how pertinent it was to your question. :)

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One thing that is rather interesting about this developing disturbance is that it seems to have genesis ties with the remnants of Sean more than a week ago! Watch the animation below with the relevant features labeled. Note that the low level vorticity (lightly shaded contours in black) that was originally associated with Sean can be tracked as it becomes entangled in a frontal boundary. However, some of this vorticity detaches on the southern side, and meanders for the next 2-3 days across the open Atlantic. The gradient of colors provided on the map are dynamic tropopause which gives you a sense of the location of the tropopause given a potential temperature value. Warmer colors indicate higher potential temperature which indicates the dynamic tropopause is located higher in the atmosphere. Cooler colors represent lower potential temperature and a lower dynamic tropopause. Keep in mind convection (outside of the occasional overshooting top) cannot exceed the level of the tropopause. This will be important to note later in this post.

Pre-Tammy.gif

Part of the reason why the low level vorticity has been able to maintain itself is the influence of upper level features. Seen in the second figure below is a Potential Vorticity (PV) streamer at 250 hPa. This feature is generated from an anticyclonic wave-breaking event (AWB), which in this case is a fancy term for a ridge that amplifies ahead of an upper level trough to the point that it breaks off from the amplifying flow, which can allow upper level troughs (with increased potential vorticity in the upper levels) to sneak under this large ridge and stall or propagate westward. These are the PV streamers that can hang around and interact with tropical features between 20-30 degrees north this time of the year and are often pre-cursors to subtropical cyclogenesis. In this case, its obvious there has been some pretty direct interaction between a PV streamer and the vorticity that was once associated with Sean. Further interaction from a tropical wave is likely giving this disturbance an added boost of vorticity and precipitable water.

o087qc.gif

This leads us to today. Yet another PV Streamer has taken the place of the old one which had faded away as latent heat release due to convection helped to create more anticyclonic flow over the system. This new PV feature will likely help to induce non-tropical or subtropical cyclogenesis over the next 24 hours. Beyond this period, this system has a shot to make the transition into a tropical entity. The GFS indicates a eastward track south of 30N and a stall beyond the 96 hour period. During this time the system will dancing along the 26 degree SST isotherm, but will likely be able to maintain moderate convection due to colder than normal temperatures aloft, similar to the evolution of Sean more than a week ago. What stuck me as interesting was the Epsilon like track as a series of upper level systems pass by the the north. Note that the DT over the system is fairly low, which means the system will be more resilient to stronger 850-200mb shear, since the outflow layer is also lower, somewhere around 300mb. Lets see how this plays out.

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Interesting reanalysis news:

The cyclone that hit FL on 01 Dec 1925 has been downgraded to a TS in reanalysis-- meaning the latest known 'cane to hit the USA is now Kate 1985, an 85-kt Cat 2 that hit the FL Panhandle on 21 Nov:

http://www.nhc.noaa....estLandfall.pdf

A couple of things about Kate in 1985-it was the latest hurricane to hit the MAINLAND US-Hurricane Iwa hit the state of Hawai'i' on the 23rd of November in 1982 with 80 kt winds. It later joined forces with an El Niño driven ET low to give NoCA a taste of hurricane force winds and heavy snow in UT which continued the setup started in September by remnants of Olivia for the UT floods of 1983. Looking at the video of hurricane Kate, and taking note of the strongest winds reported by coastal stations, I would say that Kate was more of a Cat 1 hit than Cat 2.

Steve

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A couple of things about Kate in 1985-it was the latest hurricane to hit the MAINLAND US-Hurricane Iwa hit the state of Hawai'i' on the 23rd of November in 1982 with 80 kt winds.

Oooooops. Thanks for the correction, Steve. ;)

It later joined forces with an El Niño driven ET low to give NoCA a taste of hurricane force winds and heavy snow in UT which continued the setup started in September by remnants of Olivia for the UT floods of 1983.

Wow-- crazy!

P.S. We can always count on you to know the freaky, post-tropical part of a Pacific cyclone's history-- it's like your special area of expertise. :P

Looking at the video of hurricane Kate, and taking note of the strongest winds reported by coastal stations, I would say that Kate was more of a Cat 1 hit than Cat 2.

Steve

Interesting-- so you think maybe it wasn't quite 85 kt?

Cape San Blas-- which was ~15 n mi right of the center-- recorded 64 kt (1-min) with gusts to 87 kt. That's a pretty solid reading and would seem to suggest it could have been a Cat 2.

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A couple of things about Kate in 1985-it was the latest hurricane to hit the MAINLAND US-Hurricane Iwa hit the state of Hawai'i' on the 23rd of November in 1982 with 80 kt winds.

Oooooops. Thanks for the correction, Steve. ;)

EDIT: Actually... I looked closely at Iwa's track, and it looked like it was a direct hit but not a landfall. The inner core (and right semicircle) passed over Ni'ihau and Kaua'i, but the center apparently remained just offshore.

It later joined forces with an El Niño driven ET low to give NoCA a taste of hurricane force winds and heavy snow in UT which continued the setup started in September by remnants of Olivia for the UT floods of 1983.

Wow-- crazy!

P.S. We can always count on you to know the freaky, post-tropical part of a Pacific cyclone's history-- it's like your special area of expertise. :P

Looking at the video of hurricane Kate, and taking note of the strongest winds reported by coastal stations, I would say that Kate was more of a Cat 1 hit than Cat 2.

Steve

Interesting-- so you think maybe it wasn't quite 85 kt?

Cape San Blas-- which was ~15 n mi right of the center-- recorded 64 kt (1-min) with gusts to 87 kt. That's a pretty solid reading and would seem to suggest it could have been a Cat 2. That having been said, the max surge of 11 ft happened at that location, suggesting it was located in the RMW and therefore maybe that location actually did sample the near-max wind. Hard to know. Either way, I can see why you'd doubt it was a Cat 2-- as we now know that a weakening, N-Gulf, late-season hurricane with a central pressure of 967 mb is not exactly going to have the most impressive surface winds.

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If you can't get enough of this subtropical crap, after 99L another system will have a shot early next week near the Bahamas. Woo.

It looks like re- analysis is going to add another un named September storm that was near Bermuda/Nova Scotia...:rolleyes:

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Iwa was HI's worst hurricane hit until Iniki in 1992 I was in Auburn CA for Iwa's ET rampage and that was a wild storm. Winds through the GG and the Altamont Pass and Carqunez Strait were in the 100 mph range with PG&E transmission towers built to withstand 100 mph winds taken out. Severe boomers tore through the Sacramento Valley and the GG bridge was closed to traffic for the first time since 1952. In '52 it was bridge sway alá Galloping Gertie (though not as bad) but in 1982 they were concerned about cars being blown off the bridge after a light pickup truck was blown on its side and pushed to the guard rail by the wind.

I watched some video on Kate taken along the shore of Apalachee Bay and at Cape San Blas and everything seemed consistent appearance and damage wise with Cat 1 winds.

Steve

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Iwa was HI's worst hurricane hit until Iniki in 1992 I was in Auburn CA for Iwa's ET rampage and that was a wild storm. Winds through the GG and the Altamont Pass and Carqunez Strait were in the 100 mph range with PG&E transmission towers built to withstand 100 mph winds taken out. Severe boomers tore through the Sacramento Valley and the GG bridge was closed to traffic for the first time since 1952. In '52 it was bridge sway alá Galloping Gertie (though not as bad) but in 1982 they were concerned about cars being blown off the bridge after a light pickup truck was blown on its side and pushed to the guard rail by the wind.

Wow-- crazy! I had no idea that Iwa wreaked such havoc in the Pac NW. I do remember that that was a wild winter in SoCal, including an F2 tornado that passed very close to Downtown L.A., damaging the roof of the Convention Center, in March 1983!

I watched some video on Kate taken along the shore of Apalachee Bay and at Cape San Blas and everything seemed consistent appearance and damage wise with Cat 1 winds.

Steve

Interesting-- gotcha. I wonder if they might downgrade it in reanalysis. It'll be interesting to see. I wouldn't be surprised.

Apparently Kate did a real number on Tallahassee. The right eyewall passed over the city within a few hours of landfall, when it was still a 'cane.

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Cherry was downgraded to a mandarin as of 1 AM EST. I wonder how much of a time window this subtropical disturbance has to develop into a subtropical cyclone since it is moving into cooler SSTs now.

I'd say there is still time. The frontal system is now starting to occlude, and I think we will see our best chance for subtropical or tropical transformation occur over the next 48-72 hours as the system meanders around 30N 40W. Temperatures there are still hovering at 24-25 degrees Celsius, and given the colder upper atmosphere, that will likely be sufficient enough for moderate convective development.

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Iwa was mostly a NoCA/CenCA event rather than up into WA and thereabouts-it slammed due east into UT with major valley blizzard conditions there. Yes, 1982-83 was an industrial grade winter for the West and Southwest though not so much for the NW. Curiously, the 1981-82 Winter was pretty robust in the Bay Area as well. One could easily argue that the 82-83 Niño was the Mother of all Niños rather than 97-98 certainly its impact in AZ was stronger than 97-98.

Steve

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Ah, Hurricane Iwa! Was just over 5 years old while vacationing in Kauai with my parents back then. Did some massive damage to the island and idiots kept knocking on our hotel door during the storm to take the bus to the airport. That hurricane sparked my interest in weather from that point forward. Never knew it did more damage after it went extratropical though. Crazy stuff!

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As part of its routine post-season review, the National Hurricane Center occasionally identifies a previously undesignated tropical or subtropical cyclone. The NHC re-analysis of 2011 has concluded that a short-lived low that passed between Bermuda and Nova Scotia from 31 August to 3 September briefly had sufficient tropical characteristics to be considered a tropical storm. With this addition, the total numbers of storms, hurricanes, and major hurricanes for 2011 (so far) are 19, 7, and 3, respectively. A complete report on this system is in preparation and should be available on the NHC web page by 30 November.

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As part of its routine post-season review, the National Hurricane Center occasionally identifies a previously undesignated tropical or subtropical cyclone. The NHC re-analysis of 2011 has concluded that a short-lived low that passed between Bermuda and Nova Scotia from 31 August to 3 September briefly had sufficient tropical characteristics to be considered a tropical storm. With this addition, the total numbers of storms, hurricanes, and major hurricanes for 2011 (so far) are 19, 7, and 3, respectively. A complete report on this system is in preparation and should be available on the NHC web page by 30 November.

Way to pad the numbers! Haha...jk, it was another accurate and useful outlook by NOAA this year.

The number of TS was very concerning and took away some from the overall "thrill"...but otherwise pretty solid quality in this basin.

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