Southeastern Pacific devoid of tropical cyclones?

[euro6208]

Such a large area. I can imagine this being equivalent to the West Pacific with cyclones hitting South America with a large area of warm open ocean or is it? Are waters here warm enough to support cyclone development? What is causing no tropical cyclones to develop here? Have any tropical cyclones ever developed in the past?

[AJC3]

There have been cases of the occasional tropical cyclone occurring near or a little east of the Pitcairn Is. (or their LON of roughly 125-130W), however I can't recall there being one as far east as the LON of Easter Island (about 110W).

I suspect the primary reason for this has to do with the preferred location of the SPCZ being well to the west, as well as cooler SSTs and the resultant greater low level atmospheric stability toward the SOAM coast. The west coast of land masses in both hemispheres have cold ocean currents running along them, owing to the differing circulations of their respective semi-permanent oceanic high pressure cells. There may also be shear considerations as well, but I'm just speculating. I would also wager that there would be a better chance for something to form in the SEPAC during strong, perhaps even moderate warm ENSO events.

Here's one case from March 1983, with some full disk sat images included...
http://www.metsoc.org.nz/system/files/j ... revell.pdf

This TC corresponded to the peak MEI value during the monster 1982-83 warm episode...
http://www.esrl.noaa.gov/psd/enso/mei/table.html

[AJC3]

I have a disk which has several POES passes from 2-5 APR 2002 of what I believe may have briefly attained STC or TC status (unofficially) in that same general area. It appears to have formed a couple of hundred miles to the south of the island group (the first image is at 28S 128W) and intensified as it moved SW away from them, before turning back toward the south while becoming a remnant low.

While APR 2002 was not during a warm phase, the MEI values were in the process of rapidly increasing toward the protracted multi-year weak warm to neutral episode that began the following month.

02 APR 0248 UTC


02 APR 1003 UTC


02 APR 1504 UTC


02 APR 2130 UTC


03 APR 0227 UTC


03 APR 0951 UTC


03 APR 1441 UTC


03 APR 2117 UTC


04 APR 0200 UTC


04 APR 0341 UTC


04 APR 0940 UTC


04 APR 1544 UTC


04 APR 2106 UTC


05 APR 0318 UTC


05 APR 0929 UTC

[jaguarjace]

I had a vague memory of a thread for a rare Invest designated near Peru:
http://www.storm2k.org/phpbb2/viewtopic.php?f=59&t=112496
I never got to witness a floater loop of it though.

[Ptarmigan]

Tropical cyclones have developed in the Central South Pacific east as Pitcairn Island. It usually occurs due to El Nino.

There never have been any recorded tropical cyclones affecting the west coast of South America. The reason is the water is very cold from Humboldt Current. The same current responsible for Atacama Desert in Chile. Also, there is wind shear as westerlies generally are stronger as you head further south, which leads to Roaring Forties, where the ocean is rough as you head closer to Antarctica. The lack of landmass is the reason why westerlies are stronger than in the Northern Hemisphere. Ironically, tropical cyclones need landmass as they produce heat and heat the ocean. They also allow Inter Tropical Convergence Zone (ITCZ) to go north or south of equator. Also, landmass of Asia, North America, and Europe weaken westerlies.

However, that part of the Pacific is not free of storms. There are power extratropical storms that hit South America and they are quite nasty. They also produce a lot of wind shear.

[AJC3]

There is another system in the far SEPAC basin being discussed on the SPAC TC group on FB. It's near 28S 104W, and looked a heck of a lot more like a STC yesterday than today. It looks like it has ingested stable air and is weakening as a result. I'll try and grab a few images of it later.

[TheAustinMan]

Image from May 2, 2015.

[CaliforniaResident]

Is the Humboldt current basically a Southern Hemisphere version of the California current?

[Dean_175]

Waters there are too cold to support tropical or subtropical development. There is never an ITCZ in that region, and cool waters from the Humboldt current extend right up to the equator. Very little convection occurs in that region of the Pacific.

It is even less favorable than the South Atlantic. The South Atlantic is at least marginally favorable-with occasional subtropical storms forming off South America, and one observed tropical system with hurricane strength.