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La Niña and The U. S. Winter Outlook

Mike Halpert, Deputy Director Climate Prediction Center / NCEP December, 2011. La Niña and The U. S. Winter Outlook. Outline. Review of 2010-11 Forecasts/Verification Potential Climate Features impacting U. S. Winter 2011-12 U. S. Outlooks. December 2010 - February 2011. Heidke = -16.8

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La Niña and The U. S. Winter Outlook

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  1. Mike Halpert, Deputy Director Climate Prediction Center / NCEP December, 2011 La Niña and The U. S. Winter Outlook

  2. Outline • Review of 2010-11 Forecasts/Verification • Potential Climate Features impacting U. S. Winter • 2011-12 U. S. Outlooks

  3. December 2010 - February 2011 Heidke = -16.8 Coverage = 56% Heidke = 41 Coverage = 57%

  4. NH Winter Arctic Oscillation (AO)

  5. Arctic Oscillation (AO) Positive Arctic Oscillation (left) and negative Arctic Oscillation (right). Source: J. Wallace, University of Washington

  6. NH Winter (monthly) AO

  7. March - May 2011 Heidke = 74 Coverage = 63% Heidke = 45 Coverage = 35%

  8. Outline • Review of 2010-11 Forecasts/Verification • Potential Climate Features impacting U. S. Winter • 2011-12 U. S. Outlooks

  9. Sea Surface Temperature Departures Last 4 weeks

  10. Niño Region SST Departures (oC) Recent Evolution The latest weekly SST departures are: Niño 4 -0.6ºC Niño 3.4 -0.9ºC Niño 3 -1.0ºC Niño 1+2 -0.6ºC

  11. Sub-Surface Temperature Departures (oC) in the Equatorial Pacific • During the last six weeks, positive subsurface temperature anomalies (100-300m) in the western Pacific have shifted slightly eastward, while negative anomalies have been present in the eastern half of the Pacific. • In the recent period, the positive anomalies have persisted in the western half of the Pacific, while the negative anomalies persisted in the eastern Pacific. Time Time Time Longitude Most recent pentad analysis Longitude Longitude

  12. Pacific Niño 3.4 SST Outlook • The majority of ENSO models predict the continuation of La Niña through the Northern Hemisphere winter (Niño-3.4 SST anomalies less than -0.5°C). Figure provided by the International Research Institute (IRI) for Climate and Society (updated 15 November 2011).

  13. SST Outlook: NCEP CFS.v2 Forecast Issued 28 November 2011 The CFS.v2 ensemble mean (black dashed line) predicts La Niña conditions to strengthen and continue through the Northern Hemisphere spring 2012. (not PDF corrected) CFS.v2 is now operational. More information on version 2 is available at http://cfs.ncep.noaa.gov/cfsv2/docs.html

  14. Typical US Temperature, Precipitation and Jet Stream Patterns during La Niña Winters

  15. U.S. Precipitation Departures (mm) and Frequency of Occurrence (%) for La Niña during Dec.-Feb.

  16. U.S. Temperature Departures (°C) and Frequency of Occurrence (%) for La Niña during Dec.-Feb.

  17. Climate Forecast System

  18. Optimal Climate Normal (OCN) • OCN, as it is used as a tool at CPC is, quite simply, a measure of the trend. For a given station and season, the OCN forecast is the difference between the seasonal mean temperature during the last 10 years and the 30 year climatology.

  19. Optimal Climate Normal

  20. Winter 2011-12 Outlook Rationale • La Niña conditions redeveloped across the Pacific during August. • It is expected to persist through the winter. • AO has been and continues to be erratic. Large swings possible in any year (e.g. DJF 2010-11). • Trends (1981-2010 base period): Temperature: slightly negative over South; Precipitation: wet across North, dry across South. • Forecast tilted toward La Niña impacts. • Drought is expected to persist or develop across Florida and Georgia.

  21. Outline • Review of 2010-11 Forecasts/Verification • Potential Climate Features impacting U. S. Winter • 2011-12 U. S. Outlooks

  22. U. S. Seasonal OutlooksDecember 2011 - February 2012 Temperature Precipitation The seasonal outlooks combine the effects of long-term trends, soil moisture, and, when appropriate, the ENSO cycle.

  23. U. S. Drought Outlookvalid through February 2012

  24. U.S. Precipitation Departures (mm) and Frequency of Occurrence (%) for La Niña during Mar. - May

  25. U. S. Seasonal OutlooksMarch - May 2012 Temperature Precipitation The seasonal outlooks combine the effects of long-term trends, soil moisture, and, when appropriate, the ENSO cycle.

  26. Temperature and Precipitation Distribution Extreme Events + http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php Realm of most Common events MEAN Extreme Events - many few # EVENTS

  27. December – February Precipitation and Temperature Distribution Southern GA/Northern FL Strong tilt toward warm and dry Box-Whisker Web Page: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

  28. March-May Precipitation and Temperature Distribution Southern GA/Northern FL Box-Whisker Web Page: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

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