It is indeed good news but she is going begrudgingly, kicking and screaming.
There are several metrics by which it is measured of which the Southern Oscillation
Index (SOI) is one. The BOM reported the SOI for last month, that is April 2011, as 25.1.
See table here -
http://www.bom.gov.au/climate/current/soihtm1.shtml
See graph here -
http://www.bom.gov.au/climate/current/soi2.shtml
Positive SOI values are usually indicative of La Lina events and 25.1 is very high
by La Nina record standards. By comparison, it was 19.9 in January when the
Brisbane River broke its banks. Originally, meteorologists had been predicting
La Nina would bne gone by April and it seems some of them were scratching
their heads when the SOI was so high in April. Other metrics, however,
indicate that the "La Niņa event is nearing its end, with most indicators
approaching neutral values."
What was significant about the most recent La Nina event was that it was also
in conjunction with a wet Indian Ocean Dipole (IOD) event. The two don't
necessarily work in phase but this time around was one of the rare times they
did, hence the record flooding. The IOD is now neutral.
The girl-child certainly brought her share of death, destruction and misery
this time around during her tantrum.
