Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EST Thu Jan 19 2023 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS The February-March-April (FMA) 2023 temperature outlook favors below-normal temperatures across the Pacific Northwest, northern California, portions of the Great Basin, the northern Rockies, and the northern Great Plains. Below-normal temperatures are also favored for southeastern Alaska. Above-normal temperatures are more likely for the southern and eastern contiguous United States (CONUS) along with parts of northwestern Alaska, southwest mainland Alaska, and the Aleutians. The FMA 2023 precipitation outlook depicts elevated probabilities for above-normal precipitation for the Pacific Northwest, northern Rockies, parts of the northern Great Plains, and from the Great Lakes southward to the Tennessee Valley. Below-normal precipitation is favored for southern California, the Southwest, the central to southern Great Plains, the Gulf Coast, and parts of the Southeast. Areas depicted in white and labeled “Equal-Chances” or “EC” are regions where climate signals are weak and so there are equal chances for either above-, near- or below-normal seasonal mean temperatures and total precipitation amounts. 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 Below-average SSTs persisted across the equatorial central and eastern Pacific. Recent observed SST anomalies in the Niño 3.4 region are at -0.7 degrees Celsius (up from -1.0 degrees Celsius one month ago). Subsurface temperature anomalies (averaged from 180-100W and 0-300 meters) remained at near -0.2 degrees Celsius during the last month, continuing to reflect warmer subsurface temperatures than those observed in August to October of 2022. During the last two months, negative subsurface temperature anomalies weakened, but weak anomalies continue to reside near the surface of the central and east-central Pacific Ocean. Positive subsurface temperature anomalies mostly remain at depth in the western and central Pacific Ocean. Some positive anomalies are evident near the surface in the eastern Pacific Ocean. Positive OLR anomalies (suppressed convection and precipitation) continue over the equatorial west-central Pacific with weak negative OLR anomalies (enhanced convection and precipitation) throughout Indonesia and Southeast Asia. The tradewinds have weakened across the central Pacific, with sustained westerly anomalies as far east as 160E during January. Intraseasonal variability may cause a westward shift in the dividing line between westerly and easterly anomalies, but the weakening of La Nina should be accompanied by a slow eastward drift during the outlook period. SST anomalies are positive over the North Pacific and near the Aleutians. Positive SST anomalies, present earlier in the fall along the West Coast, have moderated to near average. Positive SST anomalies persist over the Gulf of Mexico and along the East Coast with the largest anomalies offshore of the Mid-Atlantic and New England. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC SST consolidation forecast for Niño 3.4 depicts decreasing negative anomalies through the spring 2023 as a transition to ENSO-neutral conditions is predicted to occur. The inputs by the consolidation are tightly clustered through AMJ, after which some inputs suggest El Nino conditions and others remain in the ENSO-neutral phase, though on the positive side. The North American Multi-Model Ensemble (NMME) ensemble mean forecast is similar to the CPC consolidation. Based on the latest observations and model forecasts, the CPC official ENSO outlook indicates a 73 percent chance for ENSO-neutral during FMA and a 82 percent chance during MAM. ENSO-neutral conditions are the most likely outcome through JJA, after which El Niño becomes the most likely category. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS The temperature and precipitation outlooks for FMA 2023 were based on dynamical model guidance such as the NMME and statistical tools, including the global SST based Constructed Analog (CA), Canonical Correlation Analysis (CCA), experimental Calibration, Bridging, and Merging (CBaM), relationships to ENSO, and trends. The objective, historical skill weighted consolidation was a major tool used in the outlooks, and that includes the ENSO/OCN tool and a complete suite of statistical and dynamical tool combinations. Although a transition to ENSO-neutral is favored during the early forecast lead times, La Niña composites were used during FMA as the atmospheric response to La Niña is expected to linger through the late winter or early spring. Land surface conditions, including an expectation of dry soil moisture heading into the spring for the central to southern Great Plains and anomalous snowpack across the western CONUS and northern Plains, played a role in the temperature outlooks during the 2023 spring and summer seasons. Long-term climate trends were considered for all leads, but were relied upon more heavily from the summer 2023 through FMA 2024. PROGNOSTIC DISCUSSION OF OUTLOOKS - FMA 2023 TO FMA 2024 TEMPERATURE Elevated probabilities of above-normal temperatures during FMA 2023 are forecast across the southern and eastern CONUS. This favored area of above-normal temperatures is supported by the calibrated NMME, CBaM, and consolidation tool. Probabilities for above-normal temperatures exceed 50 percent across the Southeast and Rio Grande where the consolidation has the strongest warm signal and ENSO correlations are relatively high. Coverage and probabilities for above-normal temperatures across the southern Great Plains are tempered by concerns of Arctic air outbreaks through February and March. Elevated odds for below-normal temperatures from the Pacific Northwest to Northern Great Plains are based on model output, relationships with Nino3.4, and trends. Trends would favor below-normal temperatures across the Central Plains, but low soil-moisture and model forecasts for above normal temperatures increase uncertainty. Snow depths ranging from 100-228 percent of normal slightly favor a colder start to the FMA period across California and parts of the Great Basin. Dynamical and statistical tools support increased probabilities of below-normal temperatures for southeastern Alaska with above-normal temperatures favored for the Aleutians, southwest mainland Alaska, and parts of northern Mainland Alaska. Coastal areas of Alaska, where SSTs are above normal are most likely to experience above-normal temperatures. The temperature outlook for FMA 2023 (compared to the previous month release) contains a slight increase in the odds for below-normal temperatures across the northern Great Plains, Northern California, and parts of the Great Basin. Corresponding to the increased odds for below-normal temperatures across the northern Great Plains, odds for above-normal temperatures are slightly reduced across the central and southern Great Plains. That slight shift toward a colder outlook is carried through MJJ. From MJJ to JAS, odds for above-normal temperatures across the central Rockies, Great Basin, and portions of the Pacific Northwest are increased relative to the prior set of outlooks. From SON onward, the outlooks reflect the statistical consolidation that includes trends, SST-CA, and the anticipated impact of the predicted state of ENSO. EC is forecast for areas of the CONUS where temperatures are expected to be most variable during this three-month period. It should be noted that subseasonal variability related to the MJO and Arctic Oscillation (AO) are expected to influence the circulation pattern and temperatures this winter. PRECIPITATION Dynamical model guidance and statistical tools continue to depict a La Niña related precipitation pattern through FMA 2023. Impacts on the primary storm track and precipitation due to La Niña are forecast to linger even if negative SST anomalies across the equatorial central Pacific begin to weaken. Updated outputs from the guidance listed above resulted in decreased odds for below-normal precipitation across eastern Texas and the Gulf Coast, with increased odds for above-normal precipitation across the Tennessee Valley. Calibrated model guidance also increased uncertainty across portions of central California, so some of that area was changed to EC during FMA. The outlook for Alaska during FMA has not changed. The outlook for MAM was updated to remove the area of enhanced odds for above-normal precipitation across the Northern Rockies as trends and relationships with SSTs no longer favor above-normal precipitation. During AMJ, odds for below-normal precipitation were increased across the Great Basin and the Alaska Panhandle, reflecting the 4 statistical tools and dynamical model guidance (NMME, CBaM). Enhanced odds for above-normal precipitation was also removed from the Southwest during MJJ and JJA, as a shift to El Nino can inhibit the monsoon. From SON 2023 to FMA 2024, the outlooks were adjusted to reflect the latest output of the skill based consolidation, which includes the predicted state of ENSO according to the SST consolidation, trends, CCA, and SST-CA. FORECASTER: Matthew Rosencrans 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 Feb 16 2023 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$