Atlantic storms added in post-analysis (and maybe some that were missed)

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Atlantic storms added in post-analysis (and maybe some that were missed)

#1 Postby Hurricanehink » Sun Jan 24, 2016 5:26 pm

This is the first in a series of topics that have interested me for a long time, and I thought I would wait for the off-season to hear the tropical community's thoughts on them. For this topic, I thought I would start with those pesky storms that weren't caught operationally. For many borderline storms, I often see "it might get added off-season", and I even saw that before Alex got classified this year. I thought it would be good to start a general discussion topic on these rare storms, and see why they weren't classified in real time and why they were added later. There is a relatively small data set, so I will work with what I got. I only went back to 1990.

December 2013 Subtropical Storm
In real time, the NHC did monitor it in tropical weather outlooks, first mentioning it on 12/4, and estimating a peak 30% chance for formation on 12/5. The odds were not higher due to expected high wind shear. In post-analysis, the storm was classified on 12/5, based on proof that it was non-frontal and had a warm core.

September 2011 Tropical Storm
The NHC first mentioned the storm on 9/1 and only estimated a 10% chance for formation. Within hours, the NHC issued a STWO and gave the classic line "ONLY A SLIGHT INCREASE IN THE ORGANIZATION OF THIS SYSTEM COULD RESULT IN THE FORMATION OF A TROPICAL STORM." It was at its peak organization on 9/2 while accelerating to the northeast south of Halifax, warranting a 60% chance of formation, but the storm didn't organize much more. In post-analysis, the storm formed on 9/1, and NHC confirmed later that they planned on issuing advisories a few times, but the intermittent convection and possibly frontal nature caused them to hold off.

July 2006 Tropical Storm
The NHC first mentioned the system on July 16, which eventually split into two. The western system became Tropical Storm Beryl, which threatened the east coast of the United States. The unnamed storm "SHOWS SOME SIGNS OF ORGANIZATION BUT IS MOVING NORTHEASTWARD OVER COOLER WATERS SO SIGNIFICANT TROPICAL DEVELOPMENT OF THIS SYSTEM IS NOT ANTICIPATED." The NHC thought it was non-tropical and frontal at the time, which they later re-assessed due to a Advanced Microwave Sounding Unit (not available at the time) pass that indicated a warm core and no frontal characteristics.

October 2005 Subtropical Storm
The NHC did not mention this storm in any tropical weather outlooks, which was near the Azores. In the tropical weather discussion, NHC stated "A SURFACE TROUGH EXTENDS FROM 19N43W THROUGH THE 1010 MB LOW NEAR 22N41.5W NE OUT OF THE REGION NEAR 32N36W." That was the closest the storm got to being mentioned. The NHC thought it was non-tropical, but, like the 2006 system, a subsequent Advanced Microwave Sounding Unit and reanalyzing frontal data indicated the storm was a subtropical storm.

October 2000 Subtropical Storm
As I don't have access to the tropical weather outlooks, I'll have to go with what's in the TCR. The NHC said they treated it as a non-tropical storm operationally, although recon data on 10/27 confirmed it was a subtropical storm. Of note: NHC had not used the "subtropical" classification operationally since 1992.

June 1997 Subtropical Storm
As with many of the others, it was classified as extratropical at the time, but recon confirmed the tight circulation and winds necessary to warrant a post-season upgrade.

October 1991 Hurricane
The strongest and most notable of the bunch, this was the "Perfect Storm", which had lashed the east coast for days as a significant nor'easter, only to develop a warm core center after it recurved out to sea. Due to the heavy damage from the nor'easter and the ensuing attention from the media on the cleanup, the NHC opted not to name the storm, even though they acknowledged in real time it met the criteria to be a hurricane, in an attempt to reduce confusion.

In summary, the NHC has a great track record in catching these storms in real time. Ignoring the Perfect Storm (which is an extraordinary precedent), the other six were considered non-tropical at the time, and they didn't know there was a warm core or lack of frontal boundaries. As we know, there is a wide spectrum between tropical and extratropical, and pigeonholing them can be difficult, especially when taking into account media interests, lack of data at the time, and unusual areas/times of formation.

What do you think? Do you think they handle these borderline storms well? Are there any storms the NHC might have missed, and maybe will add in the future? Tropical cyclone warning isn't stuck in a vacuum - analyzing data and assessing storms changes yearly, so it's possible that a storm wouldn't be classified in the 90s or early 2000s but might today.
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#2 Postby Alyono » Sun Jan 24, 2016 8:50 pm

the 1992 hurricane that hit the Mid Atlantic in January is one that may very well be added in reanalysis. Perhaps that was the real hurricane Andrew and Andrew really was Charley (considering the unnamed subtropical storm as well)
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#3 Postby TheAustinMan » Sun Jan 24, 2016 9:07 pm

Alyono wrote:the 1992 hurricane that hit the Mid Atlantic in January is one that may very well be added in reanalysis. Perhaps that was the real hurricane Andrew and Andrew really was Charley (considering the unnamed subtropical storm as well)


There's a report with some observations of the system: http://www.dgs.udel.edu/sites/dgs.udel.edu/files/publications/OFR36.pdf
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#4 Postby terstorm1012 » Wed Jan 27, 2016 8:00 am

I suspect Hurricane Santa from Christmas 1994 will get a second look. Was it just a nasty warm seclusion low, or was it actually tropical at some point? We'll see!
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#5 Postby CrazyC83 » Sun Feb 07, 2016 3:32 pm

I'm thinking reanalysis will find in the late 1960s and 1970s a lot of new tropical storms as early satellite imagery is investigated with a better understanding of how storms behave.

As for that 1992 storm, I believe it will be added into HURDAT2, but as a somewhat weaker storm. The lowest pressure based on analysis of observations was probably around 989mb at landfall just south of the VA/MD border. The highest sustained winds I can find were 46 kt. Given that observations were fairly sparse overall and the sustaining period is unknown, combined that data probably supports a 55 kt intensity at landfall, and there is no evidence that it was any deeper or stronger in the ocean.
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#6 Postby terstorm1012 » Mon Feb 08, 2016 9:35 am

I think there's a chance the storm spinning east of NC has a small subtropical storm embedded in its center---might see that get added too in the future. I'll have to look deeper though, might just be a deep baroclinic storm
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#7 Postby CrazyC83 » Mon Mar 14, 2016 6:16 pm

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I took another look at the January 1992 storm and some thoughts:

* It definitely was extratropical initially, but broke away from the frontal system

* It likely became tropical around 24 hours before landfall - given the eye structure and wind reports, most likely it was more tropical than subtropical (which would increase the 1992 season to 8 storms)

* It intensified slowly before landfall on the Delmarva coast just south of Chincoteague as a strong tropical storm, weakening and dissipating within 11 hours (likely sooner - just after 1800Z although a point at 18Z January 4 is warranted) as it was absorbed by a larger Nor'easter with the energy moving offshore

* Although some speculate it was a hurricane, the highest sustained winds I have found were 46 kt. Given the high gusts and sparse observations, I believe the peak (and landfall) intensity was 55 kt. The lowest recorded pressure (not calm at the time) I could find was 991mb. Hence I believe the pressure at landfall was 989mb, which was also the minimum pressure.

If I drew it on HURDAT2 (note: UNOFFICIAL!), here is what I would have:

AL011992, UNNAMED, 11,
19920102, 1200, , EX, 24.9N, 77.9W, 30, 1010,
19920102, 1800, , EX, 26.1N, 77.6W, 35, 1007,
19920103, 0000, , EX, 27.3N, 77.4W, 35, 1006,
19920103, 0600, , EX, 29.0N, 77.2W, 35, 1004,
19920103, 1200, , TS, 30.5N, 77.2W, 40, 999,
19920103, 1800, , TS, 32.0N, 75.5W, 45, 998,
19920104, 0000, , TS, 33.9N, 74.6W, 45, 995,
19920104, 0600, , TS, 35.8N, 74.0W, 50, 991,
19920104, 1200, , TS, 37.6N, 74.9W, 55, 989,
19920104, 1300, L, TS, 37.8N, 75.5W, 55, 989,
19920104, 1800, , TS, 38.0N, 77.2W, 35, 997,
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#8 Postby Alyono » Mon Mar 14, 2016 7:53 pm

also we had what may have been a strong TS or a hurricane east of New England and Canada when Iniki was making landfall in Kauai

1992 was not as inactive as it seemed. It probably was not all that different from 1959
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#9 Postby terstorm1012 » Wed Mar 16, 2016 7:04 am

I'm not convinced the 1992 storm was fully tropical although I think it was a warm-core system.

Other than the old weather charts I found on some archive site, is there any other available data?
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#10 Postby CrazyC83 » Wed Mar 16, 2016 2:07 pm

terstorm1012 wrote:I'm not convinced the 1992 storm was fully tropical although I think it was a warm-core system.

Other than the old weather charts I found on some archive site, is there any other available data?


I've only seen a few reports from the individual states, which were connected via the Wikipedia page. The weather maps were helpful - at 1200Z January 3 (when I have it becoming a TS) it was breaking away from the front, and at 1200Z January 4 well removed.
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#11 Postby tatertawt24 » Wed Mar 16, 2016 10:08 pm

Weird. I've never heard anything about the 1992 Delmarva storm until now. It's like no one knows about it lol. It's weird; you'd think anything that actually made landfall in Virginia would be remembered. And it was organizing as opposed to weakening, which is even more rare around here. It looked good too (for around here, at least).

Image

Not bad.
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#12 Postby terstorm1012 » Thu Mar 17, 2016 11:57 am

it probably wasn't remembered by anyone but the interested because it didn't dump any snow. The air mass around it was pretty warm for that time in January, at least according to the old weekly weather charts.
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Re: Atlantic storms added in post-analysis (and maybe some that were missed)

#13 Postby CrazyC83 » Sat Mar 18, 2017 10:55 pm

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

I also took a look at the December 1994 storm:

* When it formed on December 21, it had a weak (possibly faux) frontal structure. It was cut off from the jet stream though.

* It was definitely non-frontal on December 22 and warm core. Hence, it belongs in HURDAT as a TC there. I estimate the time of tropical cyclogenesis to be 0000Z December 22.

* Although another cyclone developed near the Carolinas on December 23, this storm remained sufficiently detached - and was non-frontal. As it was not embedded in the jet stream, a tropical classification remains appropriate.

* The weather map at 1200Z December 24 shows the front and jet stream catching up to it, and overtaking the storm shortly thereafter. Hence, I estimate it becomes extratropical once again at 1800Z December 24 as it goes for a loop off the coast.

* The lowest pressure was analyzed through other documents as 970mb. As far as I know, Recon never flew into the system. Hence I have accepted 970 as the minimum pressure.

* It rapidly weakens on December 25 and dissipates at 0000Z December 26.

* Assessing a peak intensity is very difficult - land data supported an intensity of about 55-60 kt (but that was after peak) but there aren't any ship obs that I could find, and standard P-W relationships are useless in the high latitudes with large storms, as we saw with Sandy. Normally the pressure of 970mb would support an intensity of about 90 kt, but obviously a much lower intensity applies here. With significant uncertainty, I set it at 70 kt, resulting in a category 1 hurricane at its peak.

If I drew up a (totally unofficial) best track:

AL131994, UNNAMED, 20,
19941221, 0000, , EX, 24.2N, 85.0W, 30, 1007,
19941221, 0600, , EX, 24.4N, 84.8W, 30, 1006,
19941221, 1200, , EX, 24.9N, 83.9W, 30, 1006,
19941221, 1800, , EX, 25.6N, 81.0W, 35, 1003,
19941222, 0000, , TS, 26.3N, 78.2W, 40, 1000,
19941222, 0600, , TS, 27.1N, 76.7W, 45, 996,
19941222, 1200, , TS, 28.6N, 75.5W, 50, 993,
19941222, 1800, , TS, 30.3N, 74.0W, 55, 989,
19941223, 0000, , TS, 32.2N, 72.8W, 60, 985,
19941223, 0600, , TS, 33.9N, 71.8W, 60, 982,
19941223, 1200, , HU, 35.6N, 71.0W, 65, 977,
19941223, 1800, , HU, 36.9N, 70.2W, 70, 972,
19941224, 0000, , HU, 38.7N, 70.6W, 70, 970,
19941224, 0600, , HU, 39.8N, 71.1W, 65, 973,
19941224, 1200, , TS, 40.2N, 71.8W, 60, 978,
19941224, 1800, , EX, 39.4N, 73.0W, 60, 981,
19941225, 0000, , EX, 38.0N, 74.2W, 55, 986,
19941225, 0600, , EX, 36.7N, 72.8W, 50, 988,
19941225, 1200, , EX, 37.4N, 71.2W, 40, 992,
19941225, 1800, , EX, 38.0N, 69.8W, 35, 994,
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