El Niño latest

Figure 1 – Courtesy of NCOF

The coastal waters off the coast of Chile seem to have cooled down since last month. There were SST anomalies 0f +5°C on the chart for the 18th of March last month (fig 1), but the highest that I can see in the same area is +3°C twenty five days later (fig 2). The experts are saying that an El Niño event still remains a distinct possibility towards the end of this year though.

Figure 2 – Courtesy of NCOF

I’m no expert and don’t pretend to understand why the cold Humboldt current seems to be the controlling mechanism for the upwelling of warmer water off the coast of Chile (fig 3).

Figure 3 – Courtesy of Wikipedia

But this map I found after a little research on the Internet indicate that there are more than just the Humboldt current at play down the coast of South America (fig 4).

Figure 4 – Courtesy of CALEB

I shall of course try to find out and report back, unless one of my readers would like to do it for me.

The Torrey Canyon and the Seven Stones reef

The Sevenstones Lightship (fig 4) is anchored 15 miles (24 km) to the west-northwest of Land’s End, and 7 miles (11 km) east-northeast of the Isles of Scilly (fig 1). According to Wikipedia, there has been a Lightship there since 1841, to warn vessels of the danger of the Seven Stones reef, which over the years has sunk 71 named ships, and possibly another 200 unnamed others. I would like to give you more details about the Seven Stones reef but it’s impossible to get a decent detailed bathymetric map for around the coast of the UK, it seems that although we may have ruled the waves for a long time, we now charge an awful lot for finding just out how deep the waters are around our sceptred Isle, perhaps the Ordnance Survey can take over the Hydrographic Office and free up some of this data, but I digress.

The Seven Stones reef is where the Torrey Canyon came to grief 50 years ago on the 14th of March 1967. The accident happened in daylight, when the ship was still to the southwest of the Lightship, but the reef is almost 15 miles long. The board of inquiry laid the blame on the Captain, who was apparently taking a shortcut to save time getting to Milford Haven (fig 2), maybe if their approach had been at night, he might have spotted the light and avoided the disaster, who knows.

Figure 2

Believe it or not this article started out being about the wave heights this Winter reported by the Sevenstones Lightship! I didn’t at first consciously connect the 50th anniversary of the Torrey Canyon disaster with the Sevenstones Lightship, so here’s what’s left of the original article that I’ve written.

Figure 3

The above chart is of hourly wave heights, as reported by the Sevenstones Lightship from the 1st of December 2016 through this last Winter (fig 3). On top of the hourly scatter graph I’ve overlaid four of this seasons five named storms. The highest reported wave height of 7.4 metres this Winter, occurred during the unnamed or Candlemas low of the 2nd of February. The other named storms align poorly with any of the peaks in the 24 hour moving average of wave heights that I’ve also plotted for Sevenstones though.

Figure 4 – The Sevenstones Lightship

Recent changes in North Atlantic SST

Figure 1

I thought that I would compare changes in the North Atlantic SST by using two charts, one from the 14th March 2017 (fig 2), and one from the 13th of March last year (fig 1). It looks to me that in the last year sea surface temperatures seem to have warmed by 1 or 2°C in many areas where the North Atlantic has influence. The cold pool that has been resident in the central Atlantic for so long, now seems to have shrunk and become less well organised as it once was. Waters around the British Isles and for much of the North and Norwegian Seas have predominantly positive SST anomalies. I have no idea what the current SST setup in the Atlantic might mean for the weather in our part of the world for the rest of this year.

Figure 2

The stage is set for 2017

Figure 1 – courtesy of NOAA/NESDIS

The stage is now set for the New Year of 2017, with ocean temperature anomalies in most of the world’s oceans starting the year in a decidedly positive state, even though the El Niño event of 2015/16 has now finished. Figure 2 for example shows the latest North Atlantic Ocean SST, and the cold anomalies that seem to have been around for so long in the central Atlantic at around 50°N and 40°W are now much reduced in size and squeezed further north. The other thing to notice is the exceptionally warm anomalies of +3°C and +4°C wrapped around three sides of Svalbard in the Arctic Ocean, and to a lesser accent in the Denmark Straits between Iceland and Greenland.

Figure 2 – Courtesy of NCOF

Figure 3 is a detailed look at the SST along the eastern seaboard of North America in more detail, and that never-ending stream of anomalously warm water that’s spilling into the Western Atlantic as if someone’s left the warm tap on and forgot about it.

Figure 3 – Courtesy of NCOF

Don’t mix up these SST anomaly charts with the Gulf Stream (or more accurately with the North Atlantic drift), SST anomalies and ocean currents are not the same thing, but it does look like the Gulf stream has pushed bodily further north, and the cold Labrador current that runs south along the North American coast does seem to be having a torrid time of it maintaining the ‘cold wall’ south of Nova Scotia.

Figure 4 – Courtesy of Encyclopedia Britannica

There are a number of different methods to fix the exact position of the Gulf Stream and they are:

  • The Global Real Time Ocean Forecast System model [RTOFS]
  • The Navy Coastal Ocean Model [NCOM]
  • The Naval Oceanographic Office [NAVO] Gulf Stream analysis.

The position of the north wall of the Gulf Stream is estimated from the 12°C isotherm at 400 meters of the various global ocean models, but the NAVO Gulf Stream north wall is estimated by analysts using satellite AVHRR SST, ship and buoy data. Figure 5 shows the results from the three methods, and as you will notice none of them align with the SST anomalies in figure 3.

Figure 5 – Courtesy of NOAA/OPC

Figure 6 shows the strength of the Gulf Stream at the moment, and it looks pretty healthy, moving along at around 3 knots. The OPC site is not one you may visit that often, but is very useful nonetheless. So we can keep on hold any thoughts of any ‘Day after tomorrow‘ scenario for the time being.

Figure 6 – Courtesy of NOAA/OPC