SOI drop needs to be watched

['CaneFreak]

Since we are seeing these conflicting numbers from the SOI, could we indeed see a westerly wind burst in the Pacific and still have a La Nina? Absolutely. Why? Because subsurface anamolies are all cool and when you upwell cool water you just get even cooler water at the surface. Again, all great points here. I think this also proves what others are saying about this La Nina not being a strong one. I agree with their statements because of these conflicting signals as well as many others that are showing up in some of the upcoming long range models for the mean 300 mb flow in the Pacific. I think if we get a La Nina this year, it will be relatively weak but I think there is an even greater chance we will see neutral conditions in the Atlantic throughout the peak of hurricane season due to some of the factors listed above and in previous posts.

[cycloneye]

SOI continues to tank as graphic shows.

['CaneFreak]

SOI continues to tank as graphic shows.

We went through the same thing in 2005. There were 10-15 days where the trend went from positive to negative then jumped back up again. Again, look at the big picture. The trend is still towards a positive SOI. It will pick back up soon. Just give it about a week. La Nina conditions are possible, but more likely neutral conditions will ensue from June to at least October.

[hurricanetrack]

It is -29 today. It just keeps getting lower. What will it take to get that number to rise? Anyone? Anyone? Bueller? Bueller?

[AussieMark]

I asked this question on the Australian weather board I use and was told that basically the SOI fluctuates this time of year and really doesn't tell you whats happening.

its usually in the late Autumn-Early summer (i.e for northern hemispshere that is late Spring and early winter) period where you get the impacts of SOI.

['CaneFreak]

This would make sense because interseasonal pressure differences can be observed ANYWHERE...remember the SOI is only based on pressure differences....again...give it a few weeks and it will be back up....again...look at the graph cycloneye posted and you will see that for some reason, this time of year the SOI tends to buckle...it has a lot to do with the low level pattern I believe because they experience a great deal of troughiness down there this time of year. Let me go through some MET classes Mark and I will be able to tell you...

[Coredesat]

The SOI plot is interesting, since it seems that it's on a gradual upward trend overall since October 2006 or so. It might be reasonable to guess that the SOI will rebound based on extrapolation alone (it's low, but it's not as low as it was in February 2005, which was toward the end of a weak El Nino).

['CaneFreak]

http://www.longpaddock.qld.gov.au/Seaso ... SOIValues/

Here's a link that basically supports what I said in previous discussions. Note the statements at the top: "**Daily values are not the SOI but contribute to the calculation of the monthly SOI. Daily values are presented for research purposes only. 30 day (or larger) average SOI values are the key indices for forecast purposes. "

http://www.bom.gov.au/climate/glossary/soi.shtml

Another even more creditable source says: "The SOI is usually computed on a monthly basis, with values over longer periods such a year being sometimes used. Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes."

AGAIN, DON'T LOOK AT THE DAILY SOI!!!!!! LOOK AT THE AVERAGES!!!

[SouthFloridawx]

http://www.longpaddock.qld.gov.au/SeasonalClimateOutlook/SouthernOscillationIndex/30DaySOIValues/

Here's a link that basically supports what I said in previous discussions. Note the statements at the top: "**Daily values are not the SOI but contribute to the calculation of the monthly SOI. Daily values are presented for research purposes only. 30 day (or larger) average SOI values are the key indices for forecast purposes. "

http://www.bom.gov.au/climate/glossary/soi.shtml

Another even more creditable source says: "The SOI is usually computed on a monthly basis, with values over longer periods such a year being sometimes used. Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes."

AGAIN, DON'T LOOK AT THE DAILY SOI!!!!!! LOOK AT THE AVERAGES!!!

I am going to have to agree with you on your posts... if you look at the graph it is in an general upward trend. Looking at the daily values is as Mike said, like wobble watching. Besides... looking at the daily it's already starting to go up. Click on 'Canefreaks first link he provided in my reply.

[cycloneye]

10-Apr-2007 1010.31 1012.00 -29.40 -10.15 -6.25
11-Apr-2007 1011.03 1011.10 -17.70 -10.61 -6.40
12-Apr-2007 1011.60 1010.20 -7.10 -10.63 -6.43
13-Apr-2007 1012.74 1010.45 -0.70 -10.62 -6.31
14-Apr-2007 1013.83 1010.50 6.70 -10.49 -6.02


The SOI has turned up. After tanking at -29.40,it's now positive at +6.70

[boca]

What exactly does the SOI do as far as in relation to hurricane season or EL Nino or La Nina?

[cycloneye]

What exactly does the SOI do as far as in relation to hurricane season or EL Nino or La Nina?

http://www.bom.gov.au/climate/glossary/soi.shtml

SOI going up means La Nina conditions and SOI tanking down means El Nino.You can read at link above all about this important factor.

[WeatherEmperor]

CaneFreak was right afterall. We focused too much on the daily values instead of the averages. A few posts up Luis mentioned that the SOI is now at positive +6.70 which is much higher then it has been in previous days. Lets continue to monitor the averages over the next several weeks.

<RICKY>

[cycloneye]

10-Apr-2007 1010.31 1012.00 -29.40 -10.15 -6.25
11-Apr-2007 1011.03 1011.10 -17.70 -10.61 -6.40
12-Apr-2007 1011.60 1010.20 -7.10 -10.63 -6.43
13-Apr-2007 1012.74 1010.45 -0.70 -10.62 -6.31
14-Apr-2007 1013.83 1010.50 6.70 -10.49 -6.02
15-Apr-2007 1013.44 1009.95 7.90 -10.29 -5.70
16-Apr-2007 1012.49 1009.50 4.30 -10.04 -5.37
17-Apr-2007 1012.29 1009.75 1.00 -10.27 -5.07
18-Apr-2007 1013.44 1010.35 5.00 -10.35 -4.65
19-Apr-2007 1013.23 1012.10 -9.00 -10.65 -4.36


SOI Daily Data

SOI is down again on the daily data.But it's better to look for the 30 or 90 day average to get a more complete picture.

[hurricanetrack]

It is back in toilet city. The 30 day is really getting down there- quite a plummet from where it was just a few weeks ago. Anyone think it means anything significant for the upcoming hurricane season or just a blip on the old radar? As I said in an earlier post, until it remains positive for some time, I am not going to buy in to the whole La Nina stock that is being sold. Gotta see some real evidence of a positive turn around first. April is likely to end quite negative....

[boca]

If 2007 hurricane season ends up like 2006's I'm fine with that. As far as early predictions go with hurricanes I'm not a believer until its here. I think well be neutral this year.

[AussieMark]

In February 2005 there was a monthly average of -30 or so.

So I would not read much into it

[windycity]

I agree ,to look at a couple of weeks doesn't reflect on the whole pichure.Remember folks,we had a period of cold spells which often happen this time of the year.Personally,another 2006 would be great,but we need to prepare .I would hate to see someone read into this post and think this year will be uneventful. Lets remember Andrew,and that year as a whole.

[AussieMark]

This is what BOM said about SOI in the latest update

The SOI on the other hand, has dropped below −10 during April thereby raising concerns about continued dry weather in eastern Australia. However, the SOI often shows increased monthly fluctuations at this time of year, so at this stage there is no longer-term significance in the SOI behaviour. There appears to be little chance of a return to El Niño conditions in 2007, with a continuation of neutral, or a switch to La Niña conditions, the more likely outcomes.