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cycloneye wrote:This transition from El Nino to La Nina with Neutral being there only for a short period is not seen often.
A significant burst of west wind is interrupting the La Nina onslaught and this is a sign that the MJO is alive and kicking. Forecasted pressures in the SOI determination area are reversing later this week, but something significant is moving through there and its effect on the tropics may be something to deal with in a couple of weeks.
Joe B
Aquawind wrote:I am glad to see the La Nina coming fast. I wouldn't call it a fly in the ointment but a flea works..lol I know I know..it only takes one.
P.K. wrote:I don't think it is quite right to say it has reached the La Nina threshold. It has to average -0.5C or lower (-0.8C or lower for the BoM) over a period of 3 months rather than just one week.
And KWT,here it is.I dont believe ENSO will swing like that in reallity.
La Niña likely by July
El Niño rapidly dissipated in May, with sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", falling to 0.50°C below average by June 14, according to NOAA.. The Australian Bureau of Meteorology is reporting that this number was 0.31°C below average (as of June 13.) Since La Niña conditions are defined as occurring when this number reaches 0.50°C below average, we are right at the threshold of a La Niña. NOAA's Climate Prediction Center has issued a La Niña watch, and it is likely that a full-fledged La Niña will emerge by July. Ten of the 23 El Niño models (updated as of May 19) are predicting La Niña conditions for hurricane season. However, as NOAA's Climate Prediction Center commented in their June 3 advisory, a number of the more reliable models are now calling for La Niña to develop this summer. They comment, "there is an increasing confidence in these colder model forecasts, which is supported by recent observations that show cooling trends in the Pacific Ocean and signs of coupling with the atmospheric circulation."
It is interesting to note that the last time we had a strong El Niño event, in 1998, El Niño collapsed dramatically in May, and a strong La Niña event developed by hurricane season. History appears to be repeating itself, and the emergence of La Niña will likely occur by July. The demise of El Niño, coupled with sea surface temperatures in the tropical Atlantic that are currently at record levels, suggest that a much more active Atlantic hurricane season that usual likely in 2010. The 1998 Atlantic hurricane season was about 40% above average in activity, with 14 named storms, 10 hurricanes, and 3 intense hurricanes. The season was relatively late-starting, with only one named storm occurring before August 20.
ENSO Update
17 June 2010
Summary
Following the dissipation of the 2009/10 El Niño in early May 2010, ENSO-neutral conditions were observed. However, borderline La Niña conditions have just recently appeared in mid-June. For the June-August season in progress, there is an approximately 58% probability for developing La Niña conditions, and a 41% probability for maintaining neutral ENSO conditions. Probabilities for La Niña conditions increase to approximately 62% from the August-October season through the remainder of 2010.
General Discussion
By mid-June, the NINO3.4 SST anomaly index decreased to values near the borderline of weak La Niña levels. Since early March zonal wind anomalies in the equatorial Pacific have assumed near-average to slightly stronger than average easterlies, while subsurface heat content rapidly decreased through average to now well below-average levels as cooler than average subsurface sea temperatures occupied the central and east-central tropical Pacific.
Out of a large set of dynamical and statistical prediction models, 61% indicate development of La Niña conditions during the upcoming July-August-September season, while 39% indicate maintenance of ENSO-neutral conditions. Overall, based on model predictions and current observations of the ocean surface and subsurface, for the coming August-October season and throughout the remainder of 2010 the probability for La Niña conditions is estimated at 62%, and for ENSO-neutral conditions approximately 37%. Probabilities for a return to El Niño conditions are negligible through early northern spring 2011.
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