‘Cold bias’ removed from Atlantic

From NOAA/NWS technical information notices (TIN) (h/t) to Dr. Ryan Maue and Larry Kummer. It seems the climate models can’t quite zoom in on the short term future of a region of the globe. Literally, they are “all over the map”:

What will the future hold for ENSO? Who knows? These models aren’t in good agreement for the next year. NOAA says they are fixing CFSV2 to “reinitialize” it. Now it looks like cooling ahead in the summer with a bounce in winter:

The PDF referenced below is really quite something to read. Note the before and after the “fix”.

More at WUWT ENSO Forecast Page: http://wattsupwiththat.com/enso-forecast-page/

Here is the technical bulletin describing the change.

Technical Implementation Notice 16-09

National Weather Service Headquarters Washington DC

1205 PM EDT Fri Mar 25 2016

To: Subscribers:

-NOAA Weather Wire Service

-Emergency Managers Weather Information Network

-NOAAPORT

-Other NWS Partners, Users and Employees

From: Tim McClung

Chief Operating Officer

NWS Office of Science and Technology Integration

Subject: Reset of ocean initial conditions in the operational

Climate Forecast System version 2 (CFSv2) to remove

Atlantic Ocean cold bias March 28, 2016

Beginning with the 0600 Coordinated Universal Time (UTC) model run on Monday, March 28, 2016, the National Centers for Environmental Prediction (NCEP) Central Operations will implement a fix to the Global Ocean Data Assimilation system used in the Climate Forecast System (CFSv2). This fix is expected to remove an erroneous cold anomaly in the equatorial and South Atlantic Ocean temperature.

A large temperature cold bias emerged in the ocean initial conditions along the equator in the spring of 2015 and grew to include the South Atlantic in the summer of 2015. These cold biases have translated into cold biases in the same regions in CFSv2 forecasts. The ENSO forecasts from the CFSv2 from December 2015 show unusual behavior, in that the El Nino event does not transition to neutral but rather experiences a double-dip El Nino, which is not realistic. A fix has been tested that re-initialized the ocean initial conditions in the operational CFSv2 from an offline GODAS, which uses a weak relaxation to climatology (the NODC WOD09) to control the noise.

EMC tested this re-initialization strategy for 4 initial months (December 2015 through March 2016). Results can be viewed here:

http://www.nco.ncep.noaa.gov/pmb/changes/downloads/CFSv2_Atlantic_cold_bias_problem.pdf

EMC found that there was no Atlantic cold bias in the initial states as compared to current operational CFSv2. The long lead forecasts evolved from the current El Nino event into neutral or La Nina conditions during the next 9 months in the Nino3.4 SST plumes.

Based on the positive results of the CFSv2 tests and the severity of the cold bias anomaly in the Atlantic Ocean, NCEP will implement this change outside of the normal upgrade process. Users do not need to take any action and will continue receiving data as they do today.

For questions regarding the correction to the CFS GODAS and resulting improvement to the Atlantic cold bias please contact:

Suranjana Saha

NCEP EMC/College Park, Maryland

301-683-3727

Suranjana.Saha@noaa.gov

NWS national TINS are online at: http://www.weather.gov/os/notif.htm

NNNN

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