1. Seasonal Climate Forecast October – December 2015 Issued: September 17, 2015 A cooperative product between the Oregon Department of Agriculture (ODA), and the Oregon Department of Forestry (ODF). Contact: ODF Meteorologist Pete Parsons at 503-945-7448 or peter.gj.parsons@oregon.gov Get related Seasonal Climate Forecast information at: http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx A cooperative product between the Oregon Department of Agriculture (ODA), and the Oregon Department of Forestry (ODF). Contact: ODF Meteorologist Pete Parsons at 503-945-7448 or peter.gj.parsons@oregon.gov Get related Seasonal Climate Forecast information at: http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx

2. El Niño Southern Oscillation (ENSO) Current Status and Forecast The Climate Prediction Center (CPC) has issued an El Niño Advisory. Equatorial Pacific Ocean SSTs have continued to warm and have entered the moderate El Niño range. The Climate Prediction Center (CPC) has issued an El Niño Advisory. Equatorial Pacific Ocean SSTs have continued to warm and have entered the moderate El Niño range. The Oceanic Niño Index (ONI) for the June-August period was +1.2°C. The CPC thresholds for a weak, moderate, and strong El Niño are +0.5°C, +1.0°C, and +1.5°C respectively. The Oceanic Niño Index (ONI) for the June-August period was +1.2°C. The CPC thresholds for a weak, moderate, and strong El Niño are +0.5°C, +1.0°C, and +1.5°C respectively. CPC forecaster consensus unanimously favors El Niño becoming strong and peaking this late-fall/early-winter. CPC forecaster consensus unanimously favors El Niño becoming strong and peaking this late-fall/early-winter. http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

3. Forecast Method Notes… The top analog years (1987; 1991; 2004) all had a strengthening El Niño, in the fall and winter, following a winter with positive ONI anomalies (like the 2014-15 period). The top analog years (1987; 1991; 2004) all had a strengthening El Niño, in the fall and winter, following a winter with positive ONI anomalies (like the 2014-15 period). All three of the above years were weighted equally to generate the forecast graphics. All three of the above years were weighted equally to generate the forecast graphics. This forecast is based solely on historical weather data and does not utilize dynamic modeling (see Forecasting Methods). This forecast is based solely on historical weather data and does not utilize dynamic modeling (see Forecasting Methods).Forecasting MethodsForecasting Methods

4. Forecast Notes of Interest… 2015 has proven to be quite rare, in terms of Pacific Ocean SSTs. The corresponding weather patterns have been “extreme,” with Oregon experiencing record or near-record warm and dry conditions since last winter. 2015 has proven to be quite rare, in terms of Pacific Ocean SSTs. The corresponding weather patterns have been “extreme,” with Oregon experiencing record or near-record warm and dry conditions since last winter. SST records, going back to 1950, show only one other year (1987) with an ONI for the June-July-August period of +1.0 or greater (like this year) following a winter with positive ONIs (like last winter). SST records, going back to 1950, show only one other year (1987) with an ONI for the June-July-August period of +1.0 or greater (like this year) following a winter with positive ONIs (like last winter). El Niño is expected to peak late this fall or early winter, at strong intensity, which favors a continuation of warmer and drier-than-average weather and below-average mountain snow. El Niño is expected to peak late this fall or early winter, at strong intensity, which favors a continuation of warmer and drier-than-average weather and below-average mountain snow.

5. Pacific Ocean Animated (in PowerPoint only) SSTs (top) / Anomalies (bottom) Courtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/gsstanim.shtmlCourtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/gsstanim.shtmlhttp://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/gsstanim.shtml Well above average SSTs extend across much of the Gulf of Alaska and the tropical Pacific Ocean.

6. Tropical Pacific Ocean El Niño has strengthened into the “moderate” range... Courtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstweek_c.gifCourtesy: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstweek_c.gifhttp://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_update/sstweek_c.gif SSTs are well above average across most of the tropical Pacific Ocean

7. ENSO-neutral Tropical Pacific Ocean El Niño La Niña (2003-04; 1990-91; 1986-87) Weak El Niño “Modoki” last winter El Niño is strengthening...

8. ENSO-neutral El Niño El Niño has strengthened into the moderate range El Niño Tropical Pacific Ocean (2003-04; 1990-91; 1986-87) La Niña Weak El Niño “Modoki” last winter. Weak Moderate Strong

9. Average North Pacific Ocean Warm Cool (2003-04; 1990-91; 1986-87) Last Winter Had The Highest PDO Values Since 1997 PDO dropped in August but is still well above average

10. Model forecasts favor ENSO-neutral conditions through spring 2014; followed by El Niño development. ENSO Predictive Models El Niño is predicted to become strong this fall and winter… “Base” Graphic Courtesy: http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/“Base” Graphic Courtesy: http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ La Niña El Niño ENSO-neutral

12. Chart Updates A time-series graphical comparison of “PDO” values was recently added. A time-series graphical comparison of “PDO” values was recently added. Predicted upper-air patterns and anomalies have also been added to help explain the reasons for the corresponding temperature and precipitation forecasts. Predicted upper-air patterns and anomalies have also been added to help explain the reasons for the corresponding temperature and precipitation forecasts. Precipitation forecasts have changed from “departure from average” (in inches) to “percent of average” (with 100% being average). Precipitation forecasts have changed from “departure from average” (in inches) to “percent of average” (with 100% being average). The color palettes have been updated for both the temperature and precipitation anomaly graphics. The color palettes have been updated for both the temperature and precipitation anomaly graphics.

13. October 2015 Forecast Mean Upper-Air PatternUpper-Air Anomalies Stronger than average upper-level ridging is likely over the NW US. Stronger than average upper-level ridging is likely over the NW US. Early-autumn storms will have a tendency to “split,” as they move onshore, with much of their energy directed north, into Canada, and south, into California. Early-autumn storms will have a tendency to “split,” as they move onshore, with much of their energy directed north, into Canada, and south, into California.

14. October 2015 Forecast TemperaturesPrecipitation Analog years suggest a continuation of generally mild and dry weather. Analog years suggest a continuation of generally mild and dry weather. This “El Niño-driven” climate signal typically becomes more evident in the fall and winter months. This “El Niño-driven” climate signal typically becomes more evident in the fall and winter months. Northern zones will likely see the driest conditions (relative to average). Northern zones will likely see the driest conditions (relative to average).

15. November 2015 Forecast Mean Upper-Air PatternUpper-Air Anomalies Anomalous upper-level ridging is predicted to be centered over extreme SW Canada, which would weaken approaching fall storms. Anomalous upper-level ridging is predicted to be centered over extreme SW Canada, which would weaken approaching fall storms. A “split-flow” jet stream pattern will likely direct considerable storm energy south of Oregon, into California. A “split-flow” jet stream pattern will likely direct considerable storm energy south of Oregon, into California.

16. November 2015 Forecast TemperaturesPrecipitation No major change - continued generally warmer and drier than average. No major change - continued generally warmer and drier than average. It is possible that the number of days with rain/snow will be near average but with decreased precipitation totals. It is possible that the number of days with rain/snow will be near average but with decreased precipitation totals. The likelihood of valley fog episodes is elevated. The likelihood of valley fog episodes is elevated.

17. December 2015 Forecast Mean Upper-Air PatternUpper-Air Anomalies Upper-level ridging is likely to be stronger than average over the NW US and SW Canada, with an enhanced jet stream over California. Upper-level ridging is likely to be stronger than average over the NW US and SW Canada, with an enhanced jet stream over California. A “split-flow” jet stream is likely, which would bring weaker and less frequent storms, relative to average, onto the Oregon coast. A “split-flow” jet stream is likely, which would bring weaker and less frequent storms, relative to average, onto the Oregon coast.

18. December 2015 Forecast TemperaturesPrecipitation Expect a continuation of above average temperatures and below average precipitation. Best chance of storminess is early in the month. Expect a continuation of above average temperatures and below average precipitation. Best chance of storminess is early in the month. Snow levels should generally be above average. Higher mountain sites may get near-average snowfall, but deficits are likely elsewhere. Snow levels should generally be above average. Higher mountain sites may get near-average snowfall, but deficits are likely elsewhere.

19. October – December 2015 Forecast Mean Upper-Air PatternUpper-Air Anomalies Strong anomalous upper-level ridging off the southern BC coast and anomalous troughing over southern California. Strong anomalous upper-level ridging off the southern BC coast and anomalous troughing over southern California. Expect a “split-flow” jet stream pattern, with considerable storm energy being directed both to the north and to the south of Oregon. Expect a “split-flow” jet stream pattern, with considerable storm energy being directed both to the north and to the south of Oregon.

20. October – December 2015 Forecast TemperaturesPrecipitation A moderate-to-strong El Niño typically yields warmer and drier-than- average weather for Oregon during the autumn season. A moderate-to-strong El Niño typically yields warmer and drier-than- average weather for Oregon during the autumn season. “Cool” periods are usually brief but can bring an early mountain snowpack. However, winter snowpacks tend to fall short of average. “Cool” periods are usually brief but can bring an early mountain snowpack. However, winter snowpacks tend to fall short of average.

21. Forecast Resources CPC Official US Three-Month Forecasts (Graphics): CPC Official US Three-Month Forecasts (Graphics): h ttp://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=01http://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=01 CPC US 30-Day & 90-Day Forecasts (Discussions): CPC US 30-Day & 90-Day Forecasts (Discussions): http://www.cpc.ncep.noaa.gov/products/predictions/long_range/fxus07.html CPC Weekly & Monthly ENSO Discussions: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory CPC Weekly & Monthly ENSO Discussions: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory Australian Government Weekly Tropical Climate Note: Australian Government Weekly Tropical Climate Note: http://www.bom.gov.au/climate/tropnote/tropnote.shtml Australian Government ENSO Wrap-Up: Australian Government ENSO Wrap-Up: http://www.bom.gov.au/climate/enso IRI ENSO Quick Look: IRI ENSO Quick Look: http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/ ODA Seasonal Climate Forecast Home: ODA Seasonal Climate Forecast Home: http://www.oregon.gov/ODA/programs/NaturalResources/Pages/Weather.aspx

22. Water Supply Information NDMC U.S. Drought Monitor: NDMC U.S. Drought Monitor: http://droughtmonitor.unl.edu/ NIDIS North American Drought Portal: NIDIS North American Drought Portal: http://www.drought.gov/nadm/content/percent-average-precipitation NRCS Snow Water Equivalent Oregon Map: NRCS Snow Water Equivalent Oregon Map: http://www.wcc.nrcs.usda.gov/ftpref/data/water/wcs/gis/maps/or_swepctnormal_update.pdf NRCS Snow Water Equivalent Products: NRCS Snow Water Equivalent Products: http://www.wcc.nrcs.usda.gov/snow/snotel-wereports.html NRCS Weekly Water and Climate Update: NRCS Weekly Water and Climate Update: http://www.wcc.nrcs.usda.gov/cgibin/water/drought/wdr.pl NRCS Western Snowpack Data & Water Supply Forecast: NRCS Western Snowpack Data & Water Supply Forecast: http://www.wcc.nrcs.usda.gov/cgibin/westsnowsummary.pl WRCC WestWideDroughtTracker: WRCC WestWideDroughtTracker: http://www.wrcc.dri.edu/wwdt/

23. Updated Monthly (around the 20 th ) Contact: Pete Parsons, ODF Meteorologist at 503-945-7448 or peter.gj.parsons@oregon.gov ODAProduction support from Diana Walker and Andy Zimmerman ODA Production support from Diana Walker and Andy Zimmerman Contact: Pete Parsons, ODF Meteorologist at 503-945-7448 or peter.gj.parsons@oregon.gov ODAProduction support from Diana Walker and Andy Zimmerman ODA Production support from Diana Walker and Andy Zimmerman Your Feedback is Welcome!