N.B. If our claim is correct that Equatorial Kelvin Waves (EKWs) are being generated by the interaction between maxima in the lunar atmospheric/oceanic tides with minima in the diurnal sea-level pressure variations in the tropics (please read):
then this post implies that the lunar tides must play a crucial role in initiating the Westerly Wind Bursts (WWBs) in the western equatorial Pacific ocean that are directly responsible for weakening the easterly equatorial trade winds that help trigger El Nino events.
If you visit Kyle MacRitchie's excellent blog site on Tropical waves at:
he states that convectively decoupled Equatorial Kelvin Waves (EKWs) can have outflows from their convection zones that cause Equatorial Rossby Wave (ERWs) trains to develop in their wake.
He indicates that these ERWs aren't as strong as those created by MJOs since EKWs generally move from west-to-east along the Earth' equator at 3 to 4 times rate of Madden Julian Oscillations (MJOs).
In addition, MacRitchie states that Kelvin waves provide favorable conditions for the development of Tropical Cyclones i.e. intense convection, low-level vorticity (in the form of trailing ERWs), vertical shear, and mid-level moisture.
I light of this, we present a report on the passage of a convectively-decoupled Kelvin Wave across the Equatorial Pacific Ocean, over the last several days, that has set off a series of weak tropical storms and possibly one Hurricane.
The following plot shows the location of MJOs in the equatorial regions of the Indo-Pacific (as represented by the MJO phase - vertical axis) for times between May 15th and September 15th, 2019 (horizontal axis).
This plot showed that the most recent MJO event:
a) started off the east coast of equatorial Africa (MJO Phase 1) around the 17th of August,
b) reached the region on the Equator between the Philippines and New Guinea (MJO phase 5), around about the 4th -- 5th of September, where it started producing Westerly Wind Bursts (WWBs) to the north of Papua New Guinea.
c) generated a convectively decoupled Kelvin wave, most likely around September 8th, that began moving out across the equatorial Pacific Ocean at a speed of roughly 1350 km/day, reaching the coast of South America roughly 9 -- 10 days later.
The following weather map shows that the passage of the convectively decoupled Kelvin wave (between September 8th to 17th) generated at least 5 weak topical tropical storms and possibly one hurricane, straddling the Earth's equator at roughly 15 degrees north latitude.
The following plots show that:
1) the MJO event produces WWBs in the western equatorial Pacific ocean between the 8th and 11th of September.
2) the convectively de-coupled EKW that emerges from the MJO event (sometime after September 8th) starts to move across the equatorial Pacific ocean leaving a series of weak tropical storms in its wake (starting on September 13th), straddling the Earth's equator at roughly 15 degrees North latitude.
3) the cumulative westerly wind flows that are produced on the southern sides of this string of tropical storms effectively eliminates the easterly equatorial trade winds as far east as the mid-Pacific ocean, at 160 degrees West longitude (N.B. the red vertical line on the Equator marks the most easterly longitude of the stalled trade winds for that date).
All it would take is a series of vigorous EKWs like this one to trigger a major El Nino event, showing that the lunar atmospheric/oceanic tides must play a role in initiating these significant climate events.
I keep watching, and don't see enough energy in the ocean for any real Nino Kelvin Wave. Not for a few years now. Here in NZ the resultant Modokis have different warm water current results than I have been used to in recent decades.ReplyDelete
The Quiet Sun Effect seems to be mounting too, as Mlynczak (and Corbyn of course) predicted..... Spring here and getting colder, but too soon to draw conclusions. Brett Keane
My posts refers to the atmospheric Kelvin waves not the oceanic ones.
The (last northern) winter of 2018/19 produced an equatorial Pacific Ocean that was primed for an El Nino event but the atmosphere wasn’t ready to play along (i.e. there was no overturning of the atmospheric Walker circulation). Hence,it ended up with a weak El Nino Modoki.
We might see the reverse situation this (coming) northern winter (2019/20) with the atmosphere being primed for an El Nino event but the surface waters of the equatorial Pacific Ocean not be ready to play along (i.e. not enough warm water in the Pacific warm pool to power a full-blown El Nino event).
El Nino events are mechanism for cooling the Earth's atmospheric/oceanic system and so you might expect that they would become more frequent if a solar driven cooling regime starts to driving our climate.