Monday, June 08, 2015

Early Summer El Nino Update

More geeky weather talk ahead >>>

The newest updated from the MEI (Multivariate Index) website run by Klaus Wolter shows a significant increase over the last month of +0.61 to +1.57 as of April/May which rates the El Nino in the strong category using a ranking method.  If we look at the top April/May rankings according to Mr. Wolter then then take away the El Nino events that were weakening as of April/May, we are left with the 5 years below. ALL OF THESE YEARS STAYED AT EL NINO LEVELS THROUGH THE END OF THE YEAR.

One important note: Only 1998, 1993, 1992, 1987 and 1983 had HIGHER MEI levels in April/May. 1987 was a only building El Nino. The rest were fading or close to it.

The El Nino is very apparent in the current sea surface temperature anomaly map in the last week of May.

The 2014 El Nino (although not official using the ONI) was considered weak by many meteorologists including myself.  If you assume a weak El Nino for a time last year, this year's much stronger event would be a 2nd year El Nino. Expanding the possible El Nino matches using the MEI TIME SERIES for "double El Nino events" we found two such events:  Late 1991 through 1993 and 1986/87.  A 2nd year El Nino has the advantage of an ocean already primed from the previous one.

It's not an exact match but comparing these two years to 2014-15 gives us an idea of a possible El Nino outcome.  Remember that this year's El Nino is developing much earlier. Most El Nino's develop in late summer and fall.

By examining the MEI, assuming a building El Nino, a double El Nino event (last year was weak) and a very high April/May MEI, a good match so far is the 1986-87 event.

What were the bi-monthly overlapping sea surface temperature anomalies starting in April through the end of 1987?  Notice the cooler water in the western Pacific near Australia which is necessary for the development of a strong El Nino according to the Australian Bureau of Meteorology.

Watch how the lower temperature areas warm by the end of the year (lower two maps below) and the warmest regions start to cool a bit as the El Nino started to fade by year's end.

How about this year's event?  The water off the coast of Australia (circled in red) is starting to cool comparing April 1st to may 27th but not at the level of the 1986-87 event...yet.

This El Nino continues to strengthen much earlier than other El Ninos. We continue to watch the water temperatures in the western Pacific near Australia as they cool.  How cool will they get? Will the El Nino peak in late Fall then taper off?

Models are strongly hinting at this...

Our summer outlook took much of this into account. Check it out here on my weather blog post from early May. 

BIGGER QUESTION, how will this El Nino impact winter?  Too early to call. More on this in August!