“Where America’s Climate, Weather Ocean and Space Weather Services Begin”

1. El Niño:Where we are, where we may be headed, and what does it mean for the Carolinas & Virginia? Michelle L’Heureux NOAA Climate Prediction Center October 21, 2009 “Where America’s Climate, Weather Ocean and Space Weather Services Begin”

2. El Niño: Where we are “Where America’s Climate, Weather Ocean and Space Weather Services Begin”

3. Where are we now? ENSO Alert System Status: El Nino Advisory* • El Niño is present across the equatorial Pacific Ocean. • Sea surface temperatures (SST) were at least 1.0ºC above-average across parts of the equatorial Pacific Ocean. • Current observations and dynamical model forecasts indicate that El Niño is expected to strengthen and last through the Northern Hemisphere Winter 2009-2010. * El Niño Advisory: Issued when El Niño conditions are observed and expected to continue. 3

4. January Ocean Temperatures (oC) Comparing Normal to El Niño Normal Warm, Wet Equator Cool, Dry Strong El Niño Temperatures Temperature Departures El Niño: an aperiodic warming of the central and eastern equatorial Pacific

5. SST Departures (°C) in the Tropical Pacific During the Last 4 Weeks • During the last 4-weeks, equatorial SSTs were at least 1.0°C above average between 165°E and 140°W and in small areas in the eastern Pacific. The current El Niño began in June.

6. Niño Region SST Departures (oC) Recent Evolution The latest weekly SST departures are: Niño 4 1.2ºC Niño 3.4 0.9ºC Niño 3 0.7ºC Niño 1+2 0.0ºC 6

7. Comparing El Niño’s Comparing Temperatures in the Nino-3.4 region during El Niño

8. El Niño: Where we may be headed “Where America’s Climate, Weather Ocean and Space Weather Services Begin”

9. Pacific Niño 3.4 SST Outlook • Most ENSO models indicate El Niño will continue through the Northern Hemisphere winter 2009-10. • The models disagree on the eventual strength of El Niño (SST anomalies ranging from +0.5°C to greater than +2.0°C), but a majority indicate at least a moderate strength El Niño (greater than +1.0°C) during November-December-January 2009-10. Figure provided by the International Research Institute (IRI) for Climate and Society (updated 15 Oct 2009).

10. Global El Niño Impacts December-February • El Niño impacts are strongest and most extensive in the Northern Hemisphere winter. • Some impacts are positive, some are negative

11. Typical Pattern Changes over the North Pacific and North America El Niño: Pacific jet stream is stronger than average and shifted southward. Flow is more zonal than average from the central Pacific eastward across the U.S. 11

12. El Niño: What does it mean for Carolinas & Virginia “Where America’s Climate, Weather Ocean and Space Weather Services Begin”

13. Precipitation and Temperature Outlooks December 2009 -February 2010 Winter 2009-10 outlooks indicate an increased probability of below-average temperatures for the Carolinas and Virginia. There is also an increased chance of above-median precipitation over the eastern half of S. Carolina.

14. Additional Precipitation Outlooks January-March 2010 February-April 2010 Wetter Wetter As spring 2010 approaches, there is an increasing likelihood of above-median precipitation for the Carolinas and Virginia.

15. Nov – Jan & Feb – Apr Precipitation Distribution (in) for the Eastern Carolinas KEY Upper 1/3 cases 90%tile 67%tile Middle 1/3 cases Median 33%tile Lower 1/3 cases 10%tile Nov-Jan Feb-Apr http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

16. KEY Upper 1/3 cases 90%tile 67%tile Middle 1/3 cases Median 33%tile Lower 1/3 cases 10%tile December- February Precipitation Distribution (inches) Virginia Western Carolinas Eastern Carolinas http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

17. Current Drought Conditions

18. KEY Upper 1/3 cases 90%tile 67%tile Middle 1/3 cases Median 33%tile Lower 1/3 cases 10%tile December- February Temperature Distribution (°F) Virginia Western Carolinas Eastern Carolinas http://www.cpc.ncep.noaa.gov/products/precip/CWlink/ENSO/box_whiskers/index.php

19. (Unofficial) El Niño Snow Composites January-March Anomalies (in) and Frequency of Occurrence (%) December- February Anomalies (in) and Frequency of Occurrence (%) (use at your own risk) There is some suggestion that El Niño may slightly increase the odds for increased snowfall for western parts of North Carolina & Virginia.

20. Summary • The currently weak El Niño is expected to strengthen and last through the Northern Hemisphere winter. • The most likely peak strength of this event is “moderate” (3-month average Niño-3.4 index value between 1°C-1.4°C). • El Niño has global impacts: some are negative, some beneficial. • During the winter 2009-10 (Dec-Feb), El Niño is expected to bring below-average temperatures to Virginia and the Carolinas. There is also an increased probability of above-median precipitation for the eastern half of S. Carolina. • As spring 2010 (Feb-Apr) approaches, the chances of above-average median increases for both of the Carolinas and Virginia [this is dependent on El Niño lasting through FMA].

21. Back-Up Slides “Where America’s Climate, Weather Ocean and Space Weather Services Begin”

22. Sub-Surface Temperature Departures (oC) in the Equatorial Pacific • In the first half of September 2009, temperature anomalies increased in the eastern Pacific due to the downwelling phase of a Kelvin wave. During late September and early October, the upwelling phase of a Kelvin wave reduced the positive anomalies in the eastern Pacific. • The most recent period (below) shows a strengthening of positive anomalies in the central Pacific near 150m depth. Time Most recent pentad analysis Longitude

23. Weekly Heat Content Evolution in the Equatorial Pacific • During September 2008 – January 2009, negative heat content anomalies returned and then strengthened in the central and eastern equatorial Pacific as La Niña conditions redeveloped. • The negative anomalies weakened during January-March 2009, with anomalies becoming positive since late March. • In April 2009, the combined effects of an oceanic Kelvin wave and weaker-than-average easterly trade winds contributed to an increase in the upper-ocean heat content anomalies across the Pacific Ocean. • Since April 2009, heat content anomalies have remained above-average. • Recently, the downwelling phase of a Kelvin wave is evident. Time • Oceanic Kelvin waves have alternating warm and cold phases. The warmphase is indicated by dashed lines. Down-welling and warming occur in the leading portion of a Kelvin wave, and up-welling and cooling occur in the trailing portion. Longitude

24. Tropical OLR and Wind AnomaliesDuring the Last 30 Days Positive OLR anomalies (suppressed convection and precipitation, red shading) were present over Indonesia, Malaysia, and Australia. Negative OLR anomalies (enhanced convection and precipitation, blue shading) were located across the Philippines, Papua New Guinea, and in the western tropical Pacific Ocean. Low-level (850-hPa) equatorial winds were near-average over the central and eastern Pacific. Westerly anomalies were observed in the western Pacific. Upper-level (200-hPa) equatorial winds were near-average across much of the Pacific.

25. ONI (oC): Evolution since 1950 The most recent ONI value (July – September 2009) is +0.8oC. El Niño neutral La Niña