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Monday, November 2, 2009

NINO3.4 SST Anomalies Make A Surge

I’ve moved to WordPress.  This post can now be found at NINO3.4 SST Anomalies Make A Surge
NINO3.4 SST Anomalies have reached 1.5 deg C for the week centered on October 28, 2009.
NINO3.4 SST Anomalies


OI.v2 SST data is available through the NOAA NOMADS website:


John said...

Hi Bob -

I was looking at the lastest Nino graph, and it seems like that very warm pocket is moving east and to the surface - will that possibly result in a significant jump in the anomaly, perhaps pushing this Nino into "significant" territory?


Certainly not looking for a hard prediction, which I know you don't give (for good reason), but I'm more curious what happens to the anomaly if this warm pocket does indeed move east and to the surface.

It does look like there is a cold pocket it will run into, but I'm not sure what effect that will have.

Thanks as always.

Bob Tisdale said...

John: As you'll note in the link you provided, there are a couple of small pools of warm water anomalies in the 5-6 deg range in the most recent cross section. Those anomalies would warm the surface accordingly, if they make it there. They may dissipate or intensify.

Also on the page, scroll down to the Equatorial Temperature cross section. Note how the thermocline is flattening as the warm water moves east. During the 1997/98 El Nino, there was so much warm water in the east that the thermocline there was deeper than in the west; it inverted. For a normal traditional El Nino it only flattens. Just something elso to keep an eye on.

John said...

Thanks for the explanation.

I also noted via the OI v2 website that, excluding the tropics, both Northern and Southern Hemispheres have falling anomalies.

Are those the "seasonal" effects you were talking about?

Also, I seen your many posts on the redistrubitive process of Nino heat, especially during the "significant" Ninos (i.e. the video in "Recharging the PWP Part 1")

During a traditional Nino like this, does the warm water circulate outside of the tropics? Basically, I'm curious if once this Nino dissipates will the warm water sloshing back west effect the now lower anomalies outside the tropics.

Bob Tisdale said...

John: The seasonal effects are easily seen in the Global SST anomaly animation.
Notice how the elevated anomalies cycle between the hemispheres, peaking during the late summer for both.

You wrote, "During a traditional Nino like this, does the warm water circulate outside of the tropics?"

During traditional El Nino events, as the warm water from Pacific Warm Pool sloshes to the east along the equator, some of it is carried from the tropics by the Coriolis effect. Also, during the La Nina phase, the warm water is carried back to the west by the North and South Equatorial Currents. Some follows the gyres and works its way into the mid latitudes. It's visible in the SSH animation of the video "The Lingering Effects of the 1997/98 El Nino".
About 1:15 into the video, I stop the animation and point it out.

You asked, "...will the warm water sloshing back west effect the now lower anomalies outside the tropics."

We'll have to watch and see.

Sven Hagström said...

Hi Bob.

I did notes one thing that I had not noted before. Seeing your graph it struck me that there is some order in how El Ninos rise and fall. If the El Nino starts from La Nina it takes about 12 month to reach maximum and then 6 month to get back to where we started. This is for when the weekly SST reached above 1 deg.

I took your graph and made some modifications to it. If you draw a line from 1991 just before the rise to when we are at the same level in 1992. You see that it was about 18 month. Same thing 1992 to 1994 and 1994 to 1995. Then we have the big El Nino of 1998. But start the 18 month line from Jan 1997 to June 1998. Then we entered a La Nina episode. But from Jan 2002 to June 2003 we had a smaller El Nino spike. And finally we had Jan 2006 to about Aug 2008 I little bit longer than 18 month but close.

So this latest El Nino episode. If this 18 month cycle for an El Nino spike is anything to go by we should peak around December 2009 / January 2010 or even February 2010. But we should fall rapidly to where we started in January 2009 and be there around July 2010. Then I think we have a big La Nina episode ahead of us.

/Sven Hagström

Bob Tisdale said...

Sven: Thanks for the analysis on timing. But then on occasion there is the unusual El Nino that lasts longer than the others, like the 1986/87/88 El Nino.

Also, here's another oddity: if we look at the monthly NINO3.4 data since 1981, note the saw-tooth pattern on the minimums of the La Ninas. I marked up a graph here:

Curious. You could try to do the same thing with the maximums, but it gets confusing.


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