FWIW the SOI is seriously in the toilet

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hurricanetrack
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FWIW the SOI is seriously in the toilet

#1 Postby hurricanetrack » Sat Aug 05, 2006 11:52 pm

Date: 6 Aug, 2006

Average SOI for last 30 days : -12.17
Average SOI for last 90 days : -9.67
Daily contributor to SOI calculation: -63.97
---------------------------------------------

Monthly Average SOI Values

May: -7.72
Jun: -6.74
Jul: -7.38


Why is this happening? Anyone with any thoughts?
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#2 Postby SouthFloridawx » Sat Aug 05, 2006 11:54 pm

I don't have a good understanding of the SOI could you help me out with that?
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#3 Postby hurricanetrack » Sat Aug 05, 2006 11:56 pm

All I really know is that it is a measure of the SLP pressure Darwin and Tahiti. It seems to indicate how the current ENSO phase is going. A strong and persistent negative SOI apparently is a symptom of El Nino type conditions where as a positive SOI seems to lean towards La Nina. Just another piece to the puzzle.
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#4 Postby Matt-hurricanewatcher » Sun Aug 06, 2006 12:02 am

What was it before the 2002 El nino and 1997 and 1998 El nino. In could this be a sign of a very major El nino like 1982/1983 or 1997/1998 events?
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#5 Postby SouthFloridawx » Sun Aug 06, 2006 12:04 am

hurricanetrack wrote:All I really know is that it is a measure of the SLP pressure Darwin and Tahiti. It seems to indicate how the current ENSO phase is going. A strong and persistent negative SOI apparently is a symptom of El Nino type conditions where as a positive SOI seems to lean towards La Nina. Just another piece to the puzzle.


What kind of a range is it?

What's the average range for an El Nino and what is an average range for an La Nina?
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#6 Postby wxmann_91 » Sun Aug 06, 2006 12:17 am

Wow. I don't know what to say, except, wow...

Negative usually occurs during an El Nino. Postive, La Nina. (Never mind, hurricanetrack already explained it)

The old record for lowest reading in August was around -47, I believe.
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#7 Postby clfenwi » Sun Aug 06, 2006 12:23 am

Noting that there are a few different ways to calculate the SOI, so be careful when looking at values from different sites.

Here's the Australian Bureau of Meteorology table of monthly averages:
http://www.bom.gov.au/climate/current//soihtm1.shtml

along with their explanation of the SOI and how they calculate it:
http://www.bom.gov.au/climate/glossary/soi.shtml

The Climate Diagnostic Center's Klaus Wolter had this comment on the SOI in his monthly ENSO discussion (updated August 4):

"After oscillating between about 0 and +15 since last December, it dropped dramatically in May, down to -10, rebounded slightly to -6 in June, and back down to -9 in July, indicating El Niño-like conditions during the last three months. "

He goes on to say:

"Due to the continued increase in the MEI (+1.24 in the last three months) , I believe that the odds for an El Niño event later this year are much higher than CPC's assessment from last month. In fact, I consider anything but at least weak El Niño conditions unlikely for the remainder of 2006 (as measured by the MEI)."

(MEI stands for Multi-variate ENSO Index)

EDIT: (and since no one has said it, SOI stands for Southern Oscillation Index)

Here's the AMS glossary definition:

Southern Oscillation index—A measure of the state of the Southern Oscillation.
A common index used for this purpose is the sea level pressure at Tahiti minus the sea level pressure at Darwin, Australia, divided by the standard deviation of that quantity. It is closely associated with El Niño and is thus often referred to as ENSO (El Niño–Southern Oscillation).
Last edited by clfenwi on Sun Aug 06, 2006 12:33 am, edited 1 time in total.
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#8 Postby MississippiHurricane » Sun Aug 06, 2006 12:27 am

What in the world is an "SOI" :think:
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#9 Postby wxmann_91 » Sun Aug 06, 2006 12:31 am

A quick lesson on the SOI (Southern Oscillation Index):

Is contained on Post 3 in this thread.
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#10 Postby Matt-hurricanewatcher » Sun Aug 06, 2006 12:34 am

So this could mean that a El nino bigger then 1997/1998 is coming?
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#11 Postby MississippiHurricane » Sun Aug 06, 2006 12:37 am

Thanks just needed to know what the abbrevation meant. :D
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#12 Postby wxmann_91 » Sun Aug 06, 2006 12:44 am

You're welcome Misshurricane. :)

FWIW the surface SSTA's were already off the charts in August 1997 so don't expect an El Nino of that magnitude.

https://www.fnmoc.navy.mil/products/OTI ... nomaly.gif

Also, LarryWx is an expert on this topic, and he had forecasted in another bb that the SOI would plunge, and that it would be the lowest on Sunday.
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#13 Postby AussieMark » Sun Aug 06, 2006 1:04 am

Matt-hurricanewatcher wrote:So this could mean that a El nino bigger then 1997/1998 is coming?


doubt we would see one that big for a while

that was the biggest one in over 100 years
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longterm patterns

#14 Postby weatherwindow » Sun Aug 06, 2006 8:30 am

Matt-hurricanewatcher wrote:What was it before the 2002 El nino and 1997 and 1998 El nino. In could this be a sign of a very major El nino like 1982/1983 or 1997/1998 events?
....just an observation, matt...grey et al made the observation that during the active phase of the ATC, both the number and duration of enso warm events decline...the obverse also applies, in that, enso cool events tend to be of longer duration and greater frequency....the recent record(95-06) doesnt seem to support these statements. 95- weak el nino trending to borderline la nina thru 96, followed by the mega nino of 97 and a significant la nina thru 98-99. since the dissolution of this last really significant la nina, we have experienced borderline el nino/neutral conditions with marginal nino 2002 and mini la nina oct 05-apr 06. greys observation and hypothesis would seem to call for a trend toward another significant la nina and, of course, this is not supported, in the least, by the current soi trends. comments, questions?
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#15 Postby willjnewton » Sun Aug 06, 2006 9:22 am

Oh NO oh darn is a weak el nino really forming??? I don't think so because I saw on the weatherchannel at weather.com northeast water temperatures that the tropical atlantic is hot with water temperatures, In fact the 80degree water temp mark is approaching as far north as the norfolk va area and the chesapeake bay within bathtub water so are you sure a el nino is really forming???
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#16 Postby WindRunner » Sun Aug 06, 2006 9:41 am

willjnewton wrote:Oh NO oh darn is a weak el nino really forming??? I don't think so because I saw on the weatherchannel at weather.com northeast water temperatures that the tropical atlantic is hot with water temperatures, In fact the 80degree water temp mark is approaching as far north as the norfolk va area and the chesapeake bay within bathtub water so are you sure a el nino is really forming???


El Nino has nothing to do with the Atlantic water temperatures . . . it's the build-up of warmer than normal water on the west coast of South America around the equator.

EDIT: and it looks like I took too long . . . you need to learn some patience, Will.
Last edited by WindRunner on Sun Aug 06, 2006 9:42 am, edited 2 times in total.
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#17 Postby willjnewton » Sun Aug 06, 2006 9:41 am

hello people where are you I just asked a question above
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#18 Postby willjnewton » Sun Aug 06, 2006 9:44 am

well what I am trying to say is will a weak elnino form this year in the eastern pacific and how will that affect the tropics of getting more active???
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#19 Postby Brent » Sun Aug 06, 2006 10:11 am

willjnewton wrote:well what I am trying to say is will a weak elnino form this year in the eastern pacific and how will that affect the tropics of getting more active???


If a weak El Nino does form, it will limit activity later in the season in the Atlantic(in October/November). All predictions still predict an above average year, but nothing on the scale of last year.

Take a deep breath and relax. :)
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#20 Postby Jim Hughes » Sun Aug 06, 2006 10:30 am

Matt-hurricanewatcher wrote:What was it before the 2002 El nino and 1997 and 1998 El nino. In could this be a sign of a very major El nino like 1982/1983 or 1997/1998 events?


The current SOI averages occur when we are basically in an EL Nino or the early to middle stages not the pre stages. Like I have redundantly said. We assume the SST's and SOI must act alike because of a small data base. This does not mean that the atmosphere is not going to exhibit El Nino like conditions just because some people think the SST's must reach + .50 for three straight months. That is ridiculous.

The big thing here is the lower pressure readings at Tahiti. This has basically been missing. It has really been the battle of the high's for the past few months. Remember the SOI is based on the anomaly pressure differences between Tahiti and Darwin. So you can have almost the exact same kind of daily SOI reading, during let's say August 6th 2005 and 2006 but the barometric pressure readings at each place can be totally different between the two years.

So this thing will really take off in my opinion if these lower pressure readings start to consitently show up around Tahiti.
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