Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu Jul 21 2022 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS The August-September-October (ASO) 2022 temperature outlook predicts elevated probabilities of above-normal seasonal mean temperatures across most of the U.S. The largest probabilities of above-normal temperatures exceed 60 percent for New England and parts of the West. The ASO precipitation outlook predicts elevated probabilities of above-normal precipitation for the East Coast, eastern Gulf Coast, and eastern Mainland Alaska, while below-normal precipitation is more likely across much of the Great Plains, the upper Mississippi Valley, western Great Lakes region, and the northern to central Rockies. Equal chances (EC) are forecast in areas where the likelihood of seasonal mean temperatures or seasonal accumulated precipitation amounts are expected to be similar to climatological probabilities. A La Niña advisory remains in effect and equatorial sea surface temperatures (SSTs) are below average across the central and eastern Pacific Ocean. The tropical Pacific atmosphere is consistent with a La Niña, with enhanced low-level easterly winds and suppressed convection near the Date Line. La Niña is favored to continue through the Northern Hemisphere summer, with a 62% chance in ASO 2022, and probabilities from 56 to 66% chance through the Northern Hemisphere autumn and winter. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS Oceanic and atmospheric observations across the equatorial Pacific are consistent with the persistence of La Niña conditions. The observed weekly SSTs show negative anomalies across most of the central and eastern equatorial Pacific, with the largest negative anomalies of greater than -1 degree C generally near the Date Line and over the far eastern Pacific near the coast of South America. Negative SST anomalies have weakened to near zero near the equator over the eastern Pacific from about 100 to 150 W longitude since early June. Subsurface temperature anomalies remain positive at depths of about 100 to 200 meters to the west of the Date Line, with negative temperature anomalies emerging from the surface to more than 50 meters depth over the central Pacific, as well as the far eastern Pacific. Low-level easterly and upper-level westerly wind anomalies persisted from June into July. Suppressed convection continues near the Date Line, primarily south of the equator, with enhanced convection over parts of the Maritime Continent. Positive SST anomalies remain near the south coast of Alaska and along most of the east coast of the contiguous U.S. (CONUS), potentially influencing local climate conditions. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC SST Consolidation for the Niño 3.4 region indicates a slight decrease in the magnitude of the negative anomalies this summer, followed by increasingly negative anomalies peaking around -1.0 degrees C during the autumn. The spread among ensemble members of the North America Multi-Model Ensemble (NMME) for the Nino 3.4 forecast for autumn ranges from a strong La Niña with anomalies around -1.5 C to near zero anomalies. Niño 3.4 forecasts by statistical tools range from anomalies exceeding -1.5 C for the Constructed Analog (CA) to about 0 C for the Canonical Correlation Analysis (CCA). The NMME maintains a La Niña with negative anomalies averaged for the Niño 3.4 region at or below -0.5 degrees C persisting through JFM 2023. As of early July, the CPC/IRI consensus forecast has increased the probability of a persisting La Niña through the JAS and ASO seasons to over 60 percent, with increasing probabilities of La Niña into autumn and early winter, reaching 66 percent in OND. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS Dynamical model guidance such as the North American Multi-Model Ensemble (NMME) and the Calibration, Bridging, and Merging (CBaM) version of the NMME were used through lead 5. La Niña temperature and precipitation impacts based on regressions on Niño-3.4 SST anomalies were primarily relied upon for seasons from OND 2022 through MAM 2023, as was an ENSO-OCN tool that uses the consolidation forecasts of the Niño-3.4 SST anomalies plus decadal trends to predict temperature and precipitation. The consolidation tool, which combines both the NMME and various statistical tools as inputs, was used through all seasonal leads. At longer leads, from AMJ to ASO 2023, decadal trends represented by the optimum climate normals (OCN) were the primary driver of the climate outlooks. PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2022 TO ASO 2023 TEMPERATURE Above-normal temperatures are favored throughout much of the U.S. during ASO, with probabilities that vary regionally. Driven in part by decadal trends and consistent with dynamical model forecasts from the NMME, above-normal temperatures are strongly favored for much of the western CONUS, along the southern tier, and for the eastern CONUS. Probabilities are moderated for the west coast by potential impacts due to La Niña. Calibrated NMME forecasts and the CBaM NMME forecasts support an area of EC for the Northern Plains. Above-normal temperatures are favored across most of Alaska except for the southern Alaska Panhandle in ASO supported by the consolidation tool. Enhanced probabilities of above-normal temperatures persist in the outlooks across most of the CONUS through autumn into early winter. The potential for greater impacts due to a La Niña alters the temperature forecast pattern in late autumn and through winter into next spring. Areas with an EC forecast expand across the northern tier of the CONUS from the Northwest into the Midwest region. Below normal temperatures are more likely for parts of the Pacific Northwest and northern tier in the DJF 2022-23 through FMA 2023 seasons. Decadal trends primarily favor above-normal temperatures over much of the CONUS and various areas of Alaska for later leads, except for some areas of the central CONUS and parts of Alaska where EC is forecast due to near zero decadal temperature trends. The longer lead outlooks were only slightly modified from previous outlooks for consistency with the consolidation forecast. PRECIPITATION Supported by the precipitation consolidation tool, the ASO seasonal precipitation outlook slightly favors below-normal precipitation for a large area of the central CONUS, extending from parts of the Great Basin and central Rockies into western areas of the Southern Plains and much of the Central Plains, and northeastward across the Upper Mississippi Valley into the western Great Lakes region. Greater probabilities are indicated for parts of the West and the Great Lakes region. Areas of the Southwest monsoon region that are predicted to receive above normal precipitation early in the season are forecast as EC in the ASO seasonal outlook. Above normal precipitation is more likely for eastern areas of Mainland Alaska, the Atlantic Coast, and the eastern Gulf Coast, as indicated in the consolidation tool. Likely below-normal precipitation continues in the seasonal outlooks across much of the central CONUS in SON and shifts to cover the southern tier of the CONUS by the outlook for winter, consistent with the consolidation and La Niña impacts. An area of enhanced probabilities for above-normal precipitation emerges over the Midwest in winter into spring of 2023, related to potential La Niña impacts and consistent with the consolidation. Longer lead outlooks beginning in the spring of 2023 remain consistent with the previous forecast from last month, related primarily to decadal timescale trends, with only slight modifications for consistency with the precipitation consolidation tool. These include areas of enhanced probabilities of above normal precipitation for parts of the central and eastern CONUS, in longer leads. FORECASTER: Dan Collins The Climatic normals are based on conditions between 1991 and 2020, following the World Meterological Organization convention of using the most recent 3 complete decades as the climatic reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals. For a description of of the standard forecast tools - their skill- and the forecast format please see our web page at http://www.cpc.ncep.noaa.gov/products/predictions/long_range/tools.html (Use Lower Case Letters) Information on the formation of skill of the CAS forecasts may be found at: http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Outlook/outlook.shtm l (use lowercase letters) Notes - These climate outlooks are intended for use prior to the start of their valid period. Within any given valid period observations and short and medium range forecasts should be consulted. This set of outlooks will be superseded by the issuance of the new set next month on Aug 18 2022 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$