IsabelaWeather wrote:Can someone explain the top left image to me? That graphic makes it look like lows will form in the SW caribbean and move E to NE'ward in the caribbean, is that the proper way to interpret that?
He's strictly talking about the physical connection between SSTAs in the Atlantic and the negative phase of the PMM.
It starts with the bottom right of the image. When high SSTs help hydrostatically lower surface pressure, it means that the warm water from the ocean is causing the air above it to expand and become less dense. This less dense air has a lower pressure than the surrounding air, so it rises and creates an area of low pressure at the surface (fancy way of also saying we're creating convection).
This low pressure in the Atlantic from high SSTs is now creating a strong pressure gradient between the Pacific subtropical high. This helps drive northeasterly winds over the northeastern Pacific, which drives upwelling and wind regime cooling of the sea surface temperatures in that region (or in other words, the Pacific Meridional Mode is negative or cool SSTAs).
These cooler waters act to "choke" El Nino (by decreasing temperature gradient of SSTs) in the central Pacific, and this leads to our east based El Nino.
