There are a couple of notable things this month. First, NINO3.4 region sea surface temperature anomalies, which NOAA uses as its primary metric for determining the strength of an El Niño, are still running a tick ahead of the 1997/98 El Niño. Considering the volume of warm water below the surface of the central and eastern equatorial Pacific, we shouldn’t expect the El Niño to decay anytime soon. See the NOAA animation of subsurface temperature anomalies through September 15 here. In fact, we may expect the NINO1+2 region to warm again.
Second, for the first time in a few months I can report that there appears NOT to have been another westerly wind burst in the western tropical Pacific recently. If Mother Nature wants the El Niño to continue strengthen, she’ll continue to provide westerly wind bursts in the western equatorial Pacific.
ENSO METRIC UPDATES
This post provides an update on the progress of the evolution of the 2015/16 El Niño (assuming one continues into next year) with monthly data through the end of August 2015, and for the weekly data through mid-September. The post is similar in layout to the updates that were part of the 2014/15 El Niño series of posts here. The remainder of the post includes 17 illustrations so it might take a few moments to load on your browser. Please click on the illustrations to enlarge them.
Included are updates of the weekly sea surface temperature anomalies for the four most-often-used NINO regions. Also included are a couple of graphs of the monthly BOM Southern-Oscillation Index (SOI) and the NOAA Multivariate ENSO Index (MEI).
For the comparison graphs we’re using the El Niño evolution years of 1997 and 2014 (a very strong El Niño and the last El Niño) as references for 2015. The 1997/98 El Niño was extremely strong, while the 2014/15 event was extremely weak and intermittent.
Also included in this post are evolution comparisons using warm water volume anomalies and depth-averaged temperature anomalies from the NOAA TOA project website.
Then, we’ll take a look at a number of Hovmoller diagrams comparing the progress so far this year to what happened in both 1997 and 2014.
Last, we’ll compare maps and cross sections (2014 and 2015) from the GODAS website of a number of ENSO-related metrics.
http://wattsupwiththat.com/2015/09/21/september-2015-enso-update-sea-surface-temperatures-continue-to-rise-in-the-central-equatorial-pacific/
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