Update on the Eastern Pacific Tropics

The North Pacific and North Atlantic appear to be fairly quiet as far as significant ocean storms. However, I wanted to make note of a likely developing tropical cyclone in the Eastern Pacific Basin (east of 140 W longitude). The US National Hurricane Center has pegged it with a 80% chance of development over the next 2 days before it moves northward toward much colder waters after Monday. It should be no threat to land at this time.

Developing tropical cyclone over the Eastern Pacific late-Saturday afternoon. Much cooler waters exist to the north, which can be noted by the thick layer of low clouds (known as “stratocumulus”) to the north of the red circle. These signify a “stable” atmosphere near the surface, not conducive for deep thunderstorm activity which tropical cyclones need to survive.
Saturday afternoon graphic by the National Hurricane Center showing the likely development region for the future tropical system during the next two days.

A couple of other tropical waves are ongoing east of the one mentioned above; one south of mainland Mexico, another offshore Central America. Numerical models indicate the two waves may merge and possibly form a tropical cyclone the second half of next week (after Tuesday). There’s also appears to be a favorable signal for elevated tropical cyclone development in the Eastern Pacific starting mid-week going into early the following week. Details become sketchy that far out of course, beyond the general pattern set up. The active pattern signals forecasters look for are 1) active monsoon trough…the convergence zone for abundant thunderstorm activity from Central America out over the very warm waters of the Eastern Pacific, 2) active Central American Gyre which provides thunderstorm complexes with mild spin as they move from land over open water, and 3) a low wind shear environment over the open ocean for systems to form without disruption. And with more cyclones means greater risk for landfall impacts as were seen with Bud and Carlotta. Waters over the basin continue to be abnormally warm (1-1.5 C/2-3 F above normal generally) relative to mid to late-20th century norms.

Water temperatures up to 28-30 degrees C (82-86 F) over the main development region for the Eastern Pacific Basin.
Water temperatures are running roughly up 1-1.5 C (2-3 F) above normal across the main development region of the Eastern Pacific. This is relative to the 1961-1990 baseline which I reference as global warming has warmed the oceans significantly since the mid to late-1970s.

So something to watch later next week for more significant impacts to either Mexico or the Southwest US for remnant moisture yet again.

–Meteorologist Nick Humphrey