Tropical cyclone occurrences were near average during the 1999/2000 season. During the middle months of 1999 the moderate La Niña phase which had persisted through 1998 showed signs of decline. However by November 1999 the Southern Oscillation Index had returned to strong positive values and remained positive throughout the cyclone season. A cool seasurface temperature anomaly pattern, typical of La Niña, dominated the equatorial central and eastern Pacific for the season. Broadscale tropical convection was generally suppressed over the central and western Pacific near the equator and above average in the tropical Indian Ocean and throughout the maritime continent and South Pacific convergence zone region. Four major active phases of the 30 to 60-day intraseasonal oscillation were identified.
Paterson et al. (Fri,) studied this question.