I am an oceangoing person in Socal.

This El Nino phenomena is caused by something called Bjerknes feedback. There is a recurring atmospheric 'wave' of relaxed and enhanced trade winds, called the Madden-Julien oscillation (the MJO) that travels slowly west to east across the planet with a period of approximately 60 days. The "active" phase of the MJO usually comes with a burst of westerly (west-to-east) winds in the west pacific. Those slow down the normally easterly (east-to-west) trades a bit. Some years, those easterly trades are slowed down a bit more than usual; this causes the heated up water in the western pacific to 'escape containment': deep warm water moves west to east, in a Kelvin wave. A strong series of these Kelvin waves can cause a mass of deep warm water to build in the eastern pacific. Upwelling there now brings warm water to the surface, instead of cold water, which means the air above the east pacific gets hotter, which means it rises -- low pressure -- which causes the trades to slacken further (-> the air moves relatively in a westerly direction to take up this low pressure), which causes another, stronger Kelvin wave, and so on and so on. This is Bjerknes feedback; it causes El Nino.

These Kelvin waves stop when they hit South America and split: half moves S->N along the N hemi coast, half moves N->S along the S hemi coast. Warm water is less dense than cool water, so there's a big mass of warm water near the coast. This lower density warm water wants to go 'downhill', offshore. Due to Earth's rotation, it's turned right as it travels (since it's in the Northern hemisphere), and then right again, back towards the coast, which balances against the offshore push. The net effect is a consistent mass of warm water held up against the land, and a consistent S->N current along the shore.

When the water is anomalously warm enough, when the El Nino is severe enough, this effect grows to be very large. In San Diego right now the real tide is around 1-1.5ft higher than the "standard" reading from a tide chart. Dive visibility has been incredible, the best on record, since the warm upwelling is drawing from nutrient poor water. Water temps have been incredible. Water temp is 73 degrees in San Diego right now, normally this time of year I'm in a 3/2 fullsuit. Tropical moisture has been off the charts. At a couple points this year, SoCal was the hottest and most humid place in all the USA. The consistency and count of south swells, including waves from tropical storms, has been absolutely insane. Weird currents everywhere, sandbars in crazy spots. Fog, weird bird action. My neighbor's beautiful 50ft tall Monterey pine was singed by this heat, turned brown from the pine beetle, and is probably going to die. I am buying sandbags for the house and big surfboards for this upcoming winter season. It's all just very very strange, I have never seen weather like this ever in my life. Never ever. And I still have decades to go. We'll see this winter, how bad the storms get...