Note: This product is published by the Oregon Department of Agriculture (ODA), in cooperation with the Oregon Department of Forestry (ODF). Contact: Pete Parsons, ODF Meteorologist ODA Production support from Diana Walker and Andy Zimmerman Note: This product is published by the Oregon Department of Agriculture (ODA), in cooperation with the Oregon Department of Forestry (ODF). Contact: Pete Parsons, ODF Meteorologist ODA Production support from Diana Walker and Andy Zimmerman Seasonal Climate Forecast Verification January – March 2015 Issued: April 19, 2015

Format and Purpose: A side-by-side comparison of the “Seasonal Climate Forecast” vs. what (Actually Occurred) is done for both the 1-month & 3-month forecasts. A side-by-side comparison of the “Seasonal Climate Forecast” vs. what (Actually Occurred) is done for both the 1-month & 3-month forecasts. To assess the utility of this forecast and form a basis for “adjustments” to the forecast method*. To assess the utility of this forecast and form a basis for “adjustments” to the forecast method*. Some recent forecast “adjustments” have dramatically impacted forecast accuracy (next slide). Some recent forecast “adjustments” have dramatically impacted forecast accuracy (next slide). Note: long-term averages are used. Note: long-term averages are used. * See “Forecasting Methods…” at:

Verification Updates: This forecast method has greatest skill during El Niño (warm) or La Niña (cold) events. ENSO-neutral winters are more varied and usually have more “extreme” weather events. This forecast method has greatest skill during El Niño (warm) or La Niña (cold) events. ENSO-neutral winters are more varied and usually have more “extreme” weather events. A return to the “cool phase” of the Pacific Decadal Oscillation (PDO) occurred no later than 2007, but the real- time value of the PDO index (warm or cool) appears to be the more-dominant factor for this type of analog work. A return to the “cool phase” of the Pacific Decadal Oscillation (PDO) occurred no later than 2007, but the real- time value of the PDO index (warm or cool) appears to be the more-dominant factor for this type of analog work. Only “cool phase” PDO years were used to create the forecasts issued this past autumn. However, the real-time PDO index is highly positive, which may help to explain this winter’s significant increase in forecast error. Only “cool phase” PDO years were used to create the forecasts issued this past autumn. However, the real-time PDO index is highly positive, which may help to explain this winter’s significant increase in forecast error. Current forecasts consider years in both warm and cool phases of the PDO, which should decrease this error. Current forecasts consider years in both warm and cool phases of the PDO, which should decrease this error.

January 2015 (Forecast Issued December 18, 2014) Actual Temperatures Data courtesy of the National Climatic Data Center (NCDC) Forecast Temperatures

January 2015 (Forecast Issued December 18, 2014) Forecast Precipitation Actual Precipitation Data courtesy of the National Climatic Data Center (NCDC)

January 2015 (Forecast Issued December 18, 2014)/(Actual) Extreme variation among the analog years, ranging from very cold and wet (1969) to very mild and dry (2010)…lowered forecast confidence… Extreme variation among the analog years, ranging from very cold and wet (1969) to very mild and dry (2010)…lowered forecast confidence… The “extreme” 1969 analog skewed the forecast graphic colder and wetter than average, but mild and drier-than-average conditions would be more typical with El Niño. (Typical of a Modoki El Niño (occurs when the tropical SST warming is confined mainly to the west-central Pacific Ocean), conditions were much warmer and drier than average statewide.) The “extreme” 1969 analog skewed the forecast graphic colder and wetter than average, but mild and drier-than-average conditions would be more typical with El Niño. (Typical of a Modoki El Niño (occurs when the tropical SST warming is confined mainly to the west-central Pacific Ocean), conditions were much warmer and drier than average statewide.) Extreme variation among the analog years, ranging from very cold and wet (1969) to very mild and dry (2010)…lowered forecast confidence… Extreme variation among the analog years, ranging from very cold and wet (1969) to very mild and dry (2010)…lowered forecast confidence… The “extreme” 1969 analog skewed the forecast graphic colder and wetter than average, but mild and drier-than-average conditions would be more typical with El Niño. (Typical of a Modoki El Niño (occurs when the tropical SST warming is confined mainly to the west-central Pacific Ocean), conditions were much warmer and drier than average statewide.) The “extreme” 1969 analog skewed the forecast graphic colder and wetter than average, but mild and drier-than-average conditions would be more typical with El Niño. (Typical of a Modoki El Niño (occurs when the tropical SST warming is confined mainly to the west-central Pacific Ocean), conditions were much warmer and drier than average statewide.)

February 2015 (Forecast Issued January 22, 2015) Forecast Temperatures Actual Temperatures Data courtesy of the National Climatic Data Center (NCDC)

February 2015 (Forecast Issued January 22, 2015) Forecast Precipitation Actual Precipitation Data courtesy of the National Climatic Data Center (NCDC)

February 2015 (Forecast Issued January 22, 2015)/(Actual) Mild and dry (relative to average) conditions are expected to continue. (The month was “blow-torch” warm, with all zones more than 5 ºF above average. The eastern zones were the warmest, with the SE zone topping the cake at 7.7 ºF above average.) Mild and dry (relative to average) conditions are expected to continue. (The month was “blow-torch” warm, with all zones more than 5 ºF above average. The eastern zones were the warmest, with the SE zone topping the cake at 7.7 ºF above average.) A transition to a more stormy weather pattern is possible late in the month. (The western US stayed “locked” under an anomalously strong upper-level ridge of high pressure. Mild moisture surges, to start and end the month, kept precipitation totals near average, but mountain snowfall was dismal.) A transition to a more stormy weather pattern is possible late in the month. (The western US stayed “locked” under an anomalously strong upper-level ridge of high pressure. Mild moisture surges, to start and end the month, kept precipitation totals near average, but mountain snowfall was dismal.) Mild and dry (relative to average) conditions are expected to continue. (The month was “blow-torch” warm, with all zones more than 5 ºF above average. The eastern zones were the warmest, with the SE zone topping the cake at 7.7 ºF above average.) Mild and dry (relative to average) conditions are expected to continue. (The month was “blow-torch” warm, with all zones more than 5 ºF above average. The eastern zones were the warmest, with the SE zone topping the cake at 7.7 ºF above average.) A transition to a more stormy weather pattern is possible late in the month. (The western US stayed “locked” under an anomalously strong upper-level ridge of high pressure. Mild moisture surges, to start and end the month, kept precipitation totals near average, but mountain snowfall was dismal.) A transition to a more stormy weather pattern is possible late in the month. (The western US stayed “locked” under an anomalously strong upper-level ridge of high pressure. Mild moisture surges, to start and end the month, kept precipitation totals near average, but mountain snowfall was dismal.)

March 2015 (Forecast Issued February 19, 2015) Forecast Temperatures Actual Temperatures Data courtesy of the National Climatic Data Center (NCDC)

March 2015 (Forecast Issued February 19, 2015) Forecast Precipitation Actual Precipitation Data courtesy of the National Climatic Data Center (NCDC)

March 2015 (Forecast Issued February 19, 2015)/(Actual) Analog years show a transition to cooler and wet weather by the end of the month but not likely in time to break the string of warm and dry weather. (Temperatures were more than 5 ºF above average for all zones. Precipitation was below average statewide. As predicted, there was a transition to much cooler and wet weather at the close of the month.) Analog years show a transition to cooler and wet weather by the end of the month but not likely in time to break the string of warm and dry weather. (Temperatures were more than 5 ºF above average for all zones. Precipitation was below average statewide. As predicted, there was a transition to much cooler and wet weather at the close of the month.)

January – March 2015 (Forecast Issued December 18, 2014) Forecast Temperatures Actual Temperatures Data courtesy of the National Climatic Data Center (NCDC)

January – March 2015 (Forecast Issued December 18, 2014) Forecast Precipitation Actual Precipitation Data courtesy of the National Climatic Data Center (NCDC)

January – March 2015 (Forecast Issued December 18, 2014)/(Actual) Graphic shows colder-than-average but is skewed by an exceptionally cold January 1969 analog… (The observed weather more closely matched the other extreme top analog year, 2010, which was quite mild and much drier than average.) Graphic shows colder-than-average but is skewed by an exceptionally cold January 1969 analog… (The observed weather more closely matched the other extreme top analog year, 2010, which was quite mild and much drier than average.) Warm & dry weather is more typical with El Niño. Analog years favor below average precipitation. (Temperatures were more than 5 ºF above average in all zones and locally near the warmest on record. Precipitation was well-below average statewide with record low mountain snowpacks in some areas.) Warm & dry weather is more typical with El Niño. Analog years favor below average precipitation. (Temperatures were more than 5 ºF above average in all zones and locally near the warmest on record. Precipitation was well-below average statewide with record low mountain snowpacks in some areas.) Graphic shows colder-than-average but is skewed by an exceptionally cold January 1969 analog… (The observed weather more closely matched the other extreme top analog year, 2010, which was quite mild and much drier than average.) Graphic shows colder-than-average but is skewed by an exceptionally cold January 1969 analog… (The observed weather more closely matched the other extreme top analog year, 2010, which was quite mild and much drier than average.) Warm & dry weather is more typical with El Niño. Analog years favor below average precipitation. (Temperatures were more than 5 ºF above average in all zones and locally near the warmest on record. Precipitation was well-below average statewide with record low mountain snowpacks in some areas.) Warm & dry weather is more typical with El Niño. Analog years favor below average precipitation. (Temperatures were more than 5 ºF above average in all zones and locally near the warmest on record. Precipitation was well-below average statewide with record low mountain snowpacks in some areas.)

Pete Parsons, ODF Meteorologist Pete Parsons, ODF Meteorologist Your Feedback is Welcome! Your Feedback is Welcome! Updated Mid-Month