by Peter Sinclair, climatecrocks.com, March 6, 2014
More as this develops. Nobody knowledgeable is calling this for certain, but equally nobody looks forward to the effects of a strong El Nino.
In a bulletin issued this morning, NOAA issued an El Niño Watch predicting a roughly 50% chance for development later this year. An “El Niño” is the abnormal warming of ocean temperatures in the eastern Pacific Ocean along the west coast of South America near Peru and Ecuador. It can have profound influences on weather patterns around the world.
NOAA’s bulletin says “sea surface temperature anomalies have recently increased near the International Date Line” as well as “in the central and east-central equatorial Pacific,” and that “many dynamical models predict El Niño to develop during the summer or fall.”
El Niño conditions are declared when the average sea surface temperatures in the eastern Pacific are at least 0.5°C above average for three consecutive months. These abnormally elevated sea surface temperatures allow for the atmosphere to warm and provide instability, leading to the development of thunderstorm activity.
Despite the predictions and the issuance of an El Niño Watch, NOAA cautions that there is still “considerable uncertainty” in the models as to whether or not an El Niño will actually develop. Discerning weather observers will remember that the last predicted El Niño in 2012 turned out to be a bust.
All in all, NOAA’s current forecast indicates that there is a 50/50 chance for an El Niño to form later this year, and as with any long-range forecast, significant uncertainties exist that warrant careful caution and observation.
The potential El Niño event has been made more likely over the past month due to the intensification of a strong “Westerly Wind Burst” (WWB) along the equatorial Pacific west of the Date Line. As of March 6, 2014, westerly winds that were more than 10 m/s (22 mph) stronger than average had developed between 140°–150° E, just north of New Guinea. These unusually strong westerly winds were acting to push warm water piled up to the east of the Philippines eastwards towards South America.
The “Westerly Wind Burst” was due, in part, to the counter-clockwise circulation of wind around Typhoon Faxai, which became a tropical storm on February 28 near 9° N, 149° E, and later intensified into a Category 1 typhoon. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30–60 days, was also likely involved in amplifying the WWB. In order to keep the momentum of this WWB going and trigger a full-fledged El Niño event, some additional west-to-east push of winds is likely needed during March and April. Some extra push may come from a tropical disturbance (96P) that has developed this week south of the Equator near 13° S, 153° E, to the northeast of Australia.
The clockwise circulation of air around this storm is bringing increased westerly winds to the Equator in the region of the WWB, and the Joint Typhoon Warning Center is giving this disturbance a “medium” chance of developing into a tropical depression or tropical storm by Friday. The GFS and European models predict that this storm will move southwards and bring heavy rain to the Queensland province of Australia over the weekend.Link: http://climatecrocks.com/2014/03/06/noaa-el-nino-watch-for-later-this-year/