Last week I posted on the very active tropical Pacific Ocean with four storms occurring simultaneously. Tropical Cyclone Pam (17P) made a devastating visit to the island nation of Vanuatu as a Category 5 (145 kts or 165 mph) cyclone and has since joined the westerlies after passing near New Zealand as a much weaker system. Currently, the majority of the region has quieted down some, but Tropical Cyclone Nathan (east of Queensland) and Tropical Storm Bavi (West Pacific) are still active, while Tropical Cyclone Olwyn dissipated after making landfall in Western Australia. Jim Kells (OPC) compiled a few animations that show the evolution of all four tropical cyclones starting on 03/08/15. The imagery is courtesy of the MTSAT-2 satellite and we are eagerly anticipating the new Himawari-8 satellite data over the next few months.
So why did it suddenly get so active?
The MJO is currently near or at a record amplification in Phase 7 and as it swung through Phase 6 to 7, a strong westerly wind burst developed near the equator, while there was enhanced upward motion or ventilation at 200 mb. This has also been coupled with a sudden drop in the Southern Oscillation Index (another ENSO indicator).
According to one forecast (above), the Empirical Wave Propagation forecast shows a return of favorable tropical cyclone formation conditions (green shading) appearing in the same region from the end of March into early April (the season typically winds down in the Southern Hemisphere after April).
Finally, notice that this region is where the warmest SSTs reside in the tropical Pacific, along with the strongest warm anomalies. This is typical of a Modoki El Nino where the warmest conditions are in the Nino 3.4 region or near the Dateline. Also notice how the water near the coast of South America is colder than normal. This shows a mixed signal and makes one wonder whether El Nino conditions will be maintained or expand east with time. . .
Thanks for reading!