Wednesday, 14 October 2015

Update on the el-Nino - 10/13/2015

NASA: Monster El Nino + Climate Change Means ‘Not Normal’ Winter is On the Way

13 October, 2015

Over North America, this winter will definitely not be normal. However, the climatic events of the past decade make ‘normal’ difficult to define.”  — Bill Patzert, climatologist at NASA’s JPL speaking in Earth Observatory today.
It’s official, as of this Monday’s weekly NOAA ENSO report, a still growing 2015 El Nino had taken yet one more step into monster event territory. Hitting a +1.5 C sea surface temperature anomaly in the benchmark Nino 3.4 zone over the period of July through September even as weekly values rocketed to an amazing +2.4 C above average, the 2015 El Nino heightened yet again — making a substantial jump in overall ocean heat content. But according ta recent report out of NASA’s Earth Observatory, it appears we’re just beginning to see the full potential of this thing.

As Big or Bigger in Ocean Heat Content Than 1997-1998

For the 2015 El Nino, an event that NASA scientists are now calling ‘too big to fail,’ appears bound to continue strengthening through late Fall and Early Winter. Growing into a climate and weather wrenching oceanic and atmospheric heavyweight that will significantly impact North American weather patterns during the Winter of 2015-2016. This extreme climate event — which is currently building to an extraordinary ocean heat content anomaly in the Central and Eastern Pacific — is now comparable to the top three strongest El Ninos on record. In other words, and according to NASA: El Niño is strengthening and it looks a lot like the strong event that occurred in 1997–98.”

Sea surface height anomalies
(Sea surface height anomaly graphic provided by NASA shows a pattern very similar to 1997. Positive ocean surface height anomalies, indicated in red above, are the hallmark of an El Nino that is currently ranked among the top three strongest events observed for October. Image source: NASA.)

Ocean surface heights, as seen in the Earth Observatory graphic above, now show a pattern very similar to the monster 1997-1998 El Nino.

In a typical El Nino, Kelvin Waves transfer Equatorial Pacific Ocean heat from west to east which in turn sets off a rise in sea surface heights by thermally expanding the water column throughout the traditional Nino zones. And during the Fall of 2015 what we’re seeing is a big thermal and related ocean surface bulge swelling seas throughout the Eastern and Central Equatorial Pacific. To this point, Earth Observatory notes: “October sea level height anomalies show that 2015 is as big or bigger in heat content than 1997.”

Strong Westerly Wind Burst Lends More Energy to El Nino

Supporting NASA’s conclusions that El Nino intensity during 2015-2016 may hit near or beyond the top of the chart is a recent intensification of westerly winds over the Western Equatorial Pacific. Throughout 2014 and growing into 2015, these westerly wind bursts have fed El Nino by pushing warmer, Western Pacific waters eastward — thus increasing ocean heat content in the El Nino zone to near record levels.
Over the past week, another very strong westerly wind burst was again supplying El Nino with a warm water recharge. By tomorrow, the Global Forecast System model shows not one but four cyclones driving a strong westerly wind pattern from the Philippines all the way to the Date Line:
(Yet one more strong westerly wind burst is providing the already powerful 2015 El Nino with another boost. Note the extensive reverse trade wind pattern stretching all the way to the Date Line. Image source: Earth Nullschool.)

It’s a pretty significant westerly wind pattern — near to par with some of the related weather events (MJO) earlier this year that were among the strongest in the meteorological record. These winds will rise to near gale-force gusts in some regions and provide a dominant fetch from west to east across a 1,500 mile section of Pacific Ocean. According to NASA:
This [weakening of the trades] should strengthen this El Niño. All multi-model averages predict a peak in late fall/early winter. The forecaster consensus unanimously favors a strong El Niño…Overall, there is an approximately 95 percent chance that El Niño will continue through Northern Hemisphere winter 2015–16.”
Not Normal Winter Weather on the Way

A typical powerful El Nino of this kind would tend to drive a very intense train of moisture into the West Coast of the US, make for a cool and very wet winter across the southern US, and drive warmer temperatures and drier conditions across the northern tier. Climatologists, however, are uncertain how interactions between the current powerful El Nino and a globally changing weather pattern set off by a human-forced warming of the atmosphere to 1 C above 1880s levels (or about 1/4th the difference between the 20th Century and the last ice age, but on the side of hot) will interact.
Very warm sea surface temperatures, likely due to both a climate change-forced heating of ocean surface waters and a weakening of the Gulf Stream, off the Eastern Seaboard hint that storms along the US East Coast and particularly for the US Southeast may hit extreme intensity if an El Nino associated trough digs in. Meanwhile extraordinarily intense sea surface temperature anomalies in the range of +2 to near +6 C above average off the US West Coast associated with a ‘hot blob’ that has lingered in this region for many seasons has caused some to question whether California will see the high intensity rainfall events typical of powerful El Ninos during the latter half of the 20th Century.

(Extreme sea surface temperatures off the US West Coast can generate a kind of atmospheric inertia in which high pressure systems tend to develop — deflecting or weakening storms moving across the meridional Pacific northward toward Canada, Alaska and even the Polar region. Alternatively, an El Nino strong enough to over-ride this ocean and atmospheric block is likely to generate some very extreme storms — spurring events possibly exceeding those in the modern climate record. Image source: Earth Nullschool.)

For the US West Coast, the region may be balancing on a razor’s edge. If El Nino is strong enough to overwhelm the atmospheric and ocean inertia generated by the hot blob, storms running into that region could be extremely intense. On the other hand, if the hot blob holds or deflects the moisture stream northward, California may not see a drought-busting delivery of rainfall (See Godzilla El Nino vs the Hot Blob).

[The] elements of our changing climate are too new to say with certainty what the winter will bring.”
A pretty significant statement when one begins to fully take in its meaning — that climate change may be starting to set weather forecasting out of the context of the latter 20th Century. That it’s NASA’s view that aspects of modern weather prediction for El Nino events may have already been set off kilter by ‘elements of our changing climate.’
New Global Temperature Records For 2015 Likely a Lock

But what we do know is that the ocean-to-atmosphere heat back-up generated by what could be a record El Nino, when combined with the enormous added heat forcing provided by human fossil fuel emissions, will almost certainly set new global high temperature records for 2015 and possibly for 2016. This, unfortunately, means that we’ve already started on a dangerous path toward the far more disruptive +1.5 and +2 C above 1880s benchmarks. A range that many scientists associate with a greatly increased risk of hitting climate tipping points.


No comments:

Post a Comment

Note: only a member of this blog may post a comment.