Climate Prediction Center-EL NINO HAS ARRIVED
Posted by
Adrian on 7/9/2009, 3:33 pm
Synopsis: El Nino conditions will continue to develop and are expected to last through the Northern Hemisphere Winter 2009-2010.
During June 2009, conditions across the equatorial Pacific Ocean transitioned from ENSO-neutral to El Nino conditions. Sea surface temperature (SST) anomalies continued to increase, with the latest weekly departures exceeding +1.0C along a narrow band in the eastern equatorial Pacific (Fig. 1). All of the weekly SST indices increased steadily during June and now range from +0.6C to +0.9C (Fig. 2). Subsurface oceanic heat content anomalies (average temperatures in the upper 300m of the ocean, Fig. 3) also increased as the thermocline continued to deepen (Fig. 4). Consistent with the oceanic evolution, the low-level equatorial trade winds were weaker-than-average across much of the Pacific basin, and convection became increasingly suppressed over Indonesia. This coupling of the ocean and atmosphere indicates the development of El Nino conditions.
Model forecasts of SST anomalies for the Nino-3.4 region (Fig. 5) reflect a growing consensus for the continued development of El Nino (+0.5C or greater in the Nino-3.4 region). However, the spread of the models indicates disagreement over the eventual strength of El Nino (+0.5C to +2.0C). Current conditions and recent trends favor the continued development of a weak-to-moderate strength El Nino into the Northern Hemisphere Fall 2009, with further strengthening possible thereafter.
Expected El Nino impacts during July-September 2009 include enhanced precipitation over the central and west-central Pacific Ocean, along with the continuation of drier than average conditions over Indonesia. Temperature and precipitation impacts over the United States are typically weak during the Northern Hemisphere Summer and early Fall, and generally strengthen during the late Fall and Winter. El Nino can help to suppress Atlantic hurricane activity by increasing the vertical wind shear over the Caribbean Sea and tropical Atlantic Ocean. The NOAA Atlantic Seasonal Hurricane Outlook issued in May (will be updated on Aug. 6th) indicates the highest probabilities for a near-average season.
July update-http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html
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Climate Prediction Center-EL NINO HAS ARRIVED - Adrian, 7/9/2009, 3:33 pm Post A Reply
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