Summary
Trade winds in the central equatorial Pacific have been strongly suppressed during February with the development of three tropical cyclones east of the dateline. Accompanying the reduction in the trades (known as a westerly wind burst - WWB), has been a marked increase in subsurface temperatures near the dateline and a substantial fall in the Southern Oscillation Index (SOI), which was at –17 for the 30 days ending 21st February.
These recent developments have increased the chances of a basin-wide El Niño occurring later this year, as opposed to the more restricted warming which occurred in 2004. The tropical Pacific has now been warmer than average for most of the past three years (including during the 2002/03 El Niño), and was close to the El Niño threshold during spring and early summer. As autumn is the critical time for El Niño development, any further changes over the coming months will be monitored closely.
Historical data and the latest information indicate that:
The sub-surface warmth in the western Pacific will gradually move to the east, reaching South America in about two to three months (April/May). This movement is called a "Kelvin wave".
Surface temperatures in the eastern to central Pacific are likely to rise in response to the arrival of the Kelvin wave.
Most computer models haven't included the current WWB and its associated strong subsurface warming. The Bureau of Meteorology's POAMA model has included these, and it has the chance of warming above El Niño thresholds at 40 to 50%, which is roughly double the long-term average for this time of year.
The Pacific Ocean is likely to remain warmer than average for the foreseeable future.
March to June is known as the "predictability" barrier and model skill is at its lowest predicting across this span of months.
There remains uncertainty about:
The intensity and duration of the warming in the eastern to central Pacific in response to the Kelvin wave.
Whether any follow-up westerly wind bursts will occur during autumn - if an El Niño event is to occur this year there will almost certainly need to be more WWBs in the next few months, as it is unlikely the current one will be sufficient in itself to trigger an event.
The above is an update from the Australian folks who analize ENSO.
Kelvin wave is moving eastward from the WPAC which moves warmer waters from the dateline area of el nino 4 to el nino 3 and to el nino 1-2 off South America.But let's see if that wave will be sufficient to cause el nino to revive and be a trend towards warm ENSO which can have big implications when hurricane season arrives.
What do the pro mets and the amateour forecasters think about this data from them?
