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> 2017-2018 La Niņa watch, Forecasts and Discussions, long range.
grace
post Nov 13 2017, 07:58 PM
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QUOTE(ClicheVortex2014 @ Nov 9 2017, 05:48 PM) *
October 2010 500mb pattern vs October 2017 is just about as opposite as you can get... LOL. Love it. I hope future generations will appreciate (either as comedy or sympathetically) the struggle we go through today trying to figure this out





You're not kidding.

I looked at every Nina year (even -ENSO, -0.2 or better) October & found nothing close. You will not find a matching October since 1979 for sure. I haven't looked before then because of climo, but wouldn't hurt. Now if you expand it to maybe mid-Sept to mid-Nov you might but I haven't looked
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ClicheVortex2014
post Nov 14 2017, 04:59 PM
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Nina looking quite healthy. A lot of cold water in the east ready to spread westward. Wonder how low region 3.4 will go.





This post has been edited by ClicheVortex2014: Nov 14 2017, 05:03 PM


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90°: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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ClicheVortex2014
post Nov 14 2017, 05:54 PM
Post #323




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QUOTE(ClicheVortex2014 @ Nov 8 2017, 07:01 PM) *
Right. The placement is similar to what we saw last year. But here, I was responding to Grace who found a bunch of east-based Ninas of varying intensity. I was saying I'd like to look at the OLR of those years, and in a case such as that where you have a bunch of ENSO events of the same base but varying intensity, the position of the greatest OLR anomalies (which should be similar amongst them all if they all behaved as expected (e.g., east-based Nina -> east-based forcing)) is more important than the magnitude of OLR anomalies (which depend upon the strength of the Nina, which was not a part of the selection of ENSO events).

In other words, I still stand by my post regarding the forcing this year behaving like last year so far. The magnitude of the OLR does appear to be a bit weaker but the greatest anomalies are located around the same latitude.

Side point:
What's interesting is, although OLR has been weaker this year, MEI is stronger than last year. The value for AUG-SEP 2017 was -0.449, compared to -0.091 AUG-SEP 2016. Additionally, JUL-AUG 2017 to AUG-SEP 2017 featured a bigger drop (0.027 to -0.449) than JUL-AUG 2016 to AUG-SEP 2016 (0.186 to -0.091).

Regarding MEI... latest bimonthly numbers are in.

September/October 2017: -0.551 (up from -0.449)
September/October 2016: -0.363 (up from -0.091)

It's kind of an unfair comparison because this Nina is so much different from last year. Not only regarding the location of the Nina, but also the fact that we were almost 2 weeks past peak at this time last year. It looks like this Nina still has a solid 15-30+ days left until the Nina starts dying out.

NOAA has MEI ranks. Their definition:
QUOTE
How can one interpret these ranks? Given that there are 67-68 numbers in each column, the lowest
number (1) would denote the strongest La Nina case for that bimonthly season, while the highest
number (67 or 68) would indicate the strongest El Nino case. For instance, in December-January
(DECJAN), the strongest La Nina was recorded in 1974, while the strongest El Nino occurred in 1983.

If we use percentiles (say, the lower and upper 30%iles) to define La Nina and El Nino, respectively, MEI ranks from 1-21
denote strong to weak La Nina conditions,
while 47-67 (48-68) denote weak to strong El Nino conditions. If one uses the quintile definition for (moderate or stronger) ENSO events, MEI ranks from 1-14
would denote La Nina, while 54-67 (55-68) would denote El Nino. Finally, the comparison figures on this
website refer to strong ENSO events, such as might be defined by the top 7 (upper decile)
ranks, such as 1-7 for La Nina, and 61-67 (62-68) for El Nino.


In other words, focusing on Nina... you have a La Nina according to MEI if the rank is between 1-21. You have a moderate Nina if it's between 7-14. You have a strong Nina between 1-7.

September/October 2017 rank is 19.
August/September 2017 rank was 21.
September/October 2016 rank was 24. This was the lowest it got during the entire event.

https://www.esrl.noaa.gov/psd/enso/mei/rank.html


--------------------
Meteorology undergrad at Ohio University

Historic weather events in the Ohio Valley:
- The 1974 Super Outbreak (read more)
- The 2012 "Super" Derecho
- The Great Blizzard of 1978
- ILN Severe Weather Climatology

2017 Weather for Cincinnati

Days >90°: 11 (Last: 9/24/17)
Marginal risks: 18 (Last: 8/11/17)
Slight risks: 14 (Last: 8/22/17)
Enhanced risks: 7 (Last: 11/5/17)
Moderate risks: 0 (Last: 6/22/16)
High risks: 0 (Last: 11/17/13)

Realtime Weather on Campus: http://www.phy.ohiou.edu/~scalia/state_street/upload.png
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StL weatherjunki...
post Nov 16 2017, 11:25 AM
Post #324




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It's been a while since I brought up the 1999-2000 analog on here, but I'm sticking to my guns (i.e. similarities 2 years after a major El Nino event, particularly given ongoing moderate La Nina forcing) until I see a reason not to. A while back I mentioned what I though to be a ~1 month delay in the 2017 vs 1999 observed patterns and I'm going to continue with that rationale.

September 1999:
Attached File  Sept_1999_500mb.gif ( 15.7K ) Number of downloads: 1


October 2017:
Attached File  Oct_2017_500mb.gif ( 15.38K ) Number of downloads: 1


Yup, there are differences but I am arguing that the similarities are more noteworthy. For example, the banana ridge extending from Japan to the Pac NW / Gulf of Alaska. Additionally, note the weak troughing over the central US and potent ridging across the Northeast/Southeast Canada. If this were a good analog then October 1999 should give a good clue of November 2017:

October 1999:
Attached File  Oct_1999_500mb.gif ( 15.58K ) Number of downloads: 1


Early November 2017:
Attached File  Early_Nov_2017.gif ( 16.99K ) Number of downloads: 1


Current 8-10 day Euro forecast:
Attached File  11_16_00z_ECM.gif ( 141.88K ) Number of downloads: 0


Looks like general troughing over the Gulf of Alaska, ridging over the 4-corners/southern plains, and troughing over SE Canada are a reasonable match. Clearly there are differences in magnitude of ridging near the Bering Sea/North Atlantic as well as the precise locations of trough/ridge axes, but I'm curious how it will look by the end of the month.


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All model guidance is just that, guidance. It is the responsibility of the forecaster to take that information, make it better, and to appropriately communicate the forecast to the users.

Fervent supporter of the idea to make GFS output beyond hour 168 proprietary! Anyone wanting to post/share/tweet/etc GFS output beyond day 7 should have 1) a limited set of graphics available with the option to 2) contribute a nominal fee to get a full suite of products while improving future GFS output. #EURObusinessfor-the-win
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