Anyone visiting Cabo in the summer of 2014 will recognize that we have been having an extremely hot one!
Summer is usually hot down here in the Baja, but this year we have been baking in the heat and sweltering in the humidity.
Many people feel that this is pointing to an El Niño event.
El Niño: A temperature anomaly
The vast tropical Pacific Ocean receives more sunlight than any other region on Earth. Much of this sunlight is stored in the ocean in the form of heat. Typically, the Pacific trade winds blow from east to west, dragging the warm surface waters westward, where they accumulate into a large, deep pool just east of Indonesia, and northeast of Australia. Meanwhile, the deeper, colder waters in the eastern Pacific are allowed to rise to the surface, creating an east-west temperature gradient along the equator known as the thermocline tilt.
The trade winds tend to lose strength with the onset of springtime in the northern hemisphere. Less water is pushed westward and, consequently, waters in the central and eastern Pacific begin to heat up (usually by several degrees Fahrenheit) and the thermocline tilt diminishes. But the trade winds are usually replenished by the Asian summer monsoon, and the delicate balance of the thermocline tilt is again maintained.
Sometimes, and for reasons not fully understood, the trade winds do not replenish, or even reverse direction to blow from west to east. When this happens, the ocean responds in a several ways. Warm surface waters from the large, warm pool east of Indonesia begin to move eastward. Moreover, the natural spring warming in the central Pacific is allowed to continue and also spread eastward through the summer and fall. Beneath the surface, the thermocline along the equator flattens as the warm waters at the surface effectively act as a 300-foot-deep cap preventing the colder, deeper waters from upwelling. As a result, the large central and eastern Pacific regions warm up (over a period of about 6 months) into an El Niño. On average, these waters warm by 3° to 5°F, but in some places the waters can peak at more than 10°F higher than normal (up from temperatures in the low 70s Fahrenheit, to the high 80s).
In the east, as temperatures increase, the water expands, causing sea levels to rise anywhere from inches to as much as a foot. But in the western Pacific, sea level drops as much of the warm surface water flows eastward.
During the 1982-83 El Niño, this drop in sea level exposed and destroyed upper layers of coral reefs surrounding many western Pacific islands.
The last El Niño event to affect Cabo directly was in 2009 and then temperatures soared through the summer months, lasting well into the fall. As well as the crushing heat, the biggest environmental impact was on the fishing in the area. Striped marlin catches dropped dramatically whilst dorado increased, and Blue marlin were still being found as late as December in good numbers.
For a town that still depends to a great degree on visiting anglers, an El Niño is not good news!
So what is the forecast for this year?
As ever, scientific opinions vary with some, mainly those affiliated with the business community in North America such as Bloomberg, saying that after an initial sharp increase in likelihood the event is now looking much less probable.
However the NOAA, which also provides the fantastic Hurricane Watch service, as of July 17th is saying: “The chance of El Niño is about 70% during the Northern Hemisphere summer and is close to 80% during the fall and early winter.”
We’re clearly not out of the woods yet.
La Niña: the opposite twin
The La Niña event occurs often following an El Niño year and the effect in Los Cabos is pretty much the opposite to that of El Niño: colder summer and fall sea temperatures bringing down the air temperature as a consequence.
Paradoxically, La Niña events make the climate in Los Cabos cooler and more pleasant during summer and fall.
The last La Niña event was 2010 following the 2009 El Niño.