Record Warm World’s el-Nino

Record Warm World’s ‘Weird’ 2015 El Nino Sees Westerly Gales, Growing Kelvin Wave

Robertscribbler,

12 March, 2015

“The 2015 El Nino is finally here, but it’s weak, weird and late,” said Mike Halpert, deputy director of the Climate Prediction Center last week.

And the current El Nino is certainly an odd bird. According to reports from NOAA and theNational Weather Service, the center of highest sea surface temperatures for the El Nino this year is offset westward — coming closer to the date line than it typically does. This is a weird heat disposition for El Nino which is, at least, a mid ocean event and often pushes warming well across the Pacific to South American shores.

(Pacific sea surface temperature anomaly [SSTA]. Note the hot water pools off both Australia and North America. These zones are joined by a vast blanket of warmer than average waters arranged diagonally across the Pacific from SW to NE. This disposition includes the warm anomaly along the Equator which is hot enough to reach weak El Nino status. But the disposition of sea surface temperatures throughout the Pacific, with highest equatorial anomalies near the date line and warmer spikes near Australia and the North American West Coast is unusual. SSTA graphic provided by Earth Nullschool. Data Source: Global Forecast System Model and NCEP.)

It’s also late in coming, as typical El Ninos have tended to arrive in full form during late fall or early winter. A Christmas-time warming of waters off the West Coast of South America was a traditional call-sign for El Nino and one that resulted in its name — which is Spanish for “The Christ Child.” Late winter and early spring are more typical times for the formation of deeper warmer water that may trigger an El Nino later in the year but often do not herald a fully-developed event (see What is El Nino? for more related information).

Lastly, the El Nino is currently rather weak — barely meeting a requirement for El Nino from NOAA and still not reaching the threshold that Australia’s Bureau of Meteorology applies.

But despite all this relative oddity, the 2015 El Nino is here. And it appears to be growing.

Intense West Wind Back-burst Coincident with Powerful Cyclone Formation

For earlier this week strong westerly winds began to roar against the typical flow of the trades along the Equator. The west wind back-bursts (WWB) push warmer West Pacific waters eastward and downward, enhancing the sea surface temperature anomaly spikes that fuel El Nino.

(Very strong West Wind Back-Burst hosting 85 kph 10 minute west wind at 7.45 South Latitude on early March 11. Image source: Earth Nullschool.)

As of early Wednesday, March 11, these west winds had formed a gale force wall stretching just past the date line from about 5 North Latitude to 10 South Latitude. 

A gale driven by parallel cyclones — a weaker system to the north (Bavi) and the newly gathering Pam,which may challenge south Pacific records as the strongest storm ever to form in that region. In the above graphic we see a related ten minute sustained WWB of a rather extraordinary 85 kilometers per hour (about 50 mph) along the 7.45 degree South Latitude line.

Strengthening Kelvin Wave in a Record Warm World

Just before the formation of these strong westerlies, sub-surface temperatures also began to spike. A warm Kelvin wave that had already started its run beneath the sea surface, as of March 4, was beginning to show signs of strengthening well in advance of the added shove coming from the vigorous WWB shown above.

(A new Monster Kelvin wave? Sub surface temperature anomalies are again entering the far above normal range for the Equatorial Pacific. Image source: Climate Prediction Center.)

Peak temperatures in the wave as of a week ago had hit more than +6 C above average. A heat signature that is starting to look, more and more, like the very powerful Kelvin Wave of early 2014 that belched so much warmth into the atmosphere and likely contributed to both the current strongly positive PDO as well as 2014’s new record high temperatures.

An event that top ocean and atmospheric scientists Kevin Trenberth and Axel Timmerman attribute to signalling a possible start to much more rapid atmospheric temperature increases.

If this is the case, then what we may be seeing is a slow start to an El Nino that could be much stronger and longer than expected. Last year’s intense Kelvin Wave may have simply been preparation for a slowly building event in conjunction with what was, during December, a record broader warming of the Pacific called positive Pacific Decadal Oscillation (PDO). Some model runs, especially those at Australia’s BoM, appear to have picked up this track.

For this reason, our ‘weird’ El Nino and equally weird and warm Pacific bear close watching.

Links:

El Nino Finally Here, But it’s Weak, Weird, and Late

NOAA

National Weather Service

What is El Nino?

NOAA’s ONI Index

BoM ENSO Wrap-up

Earth Nullschool

Global Forecast System Model

NCEP

Pam at Category 5 Strength

Warming Pacific Drives Global Temperatures

Bad Climate Outcomes

2015 El Nino to Bring Back-to-Back Hottest Years on Record?

Hat tip to Phil

Hat tip to Wili