Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EST Thu Nov 17 2022 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS The December-January-February (DJF) 2022-2023 temperature outlook depicts elevated odds of below normal temperatures over the northern U.S., stretching from the Pacific Northwest to parts of the western Great Lakes. Below normal temperatures are also favored for the Alaska Panhandle and southeastern parts of Alaska. Above normal temperatures are more likely over the Southwestern U.S., stretching across the southern U.S. and into the Northeast. The highest probabilities for above normal temperatures are found over the Gulf Coast States. Over Alaska, above normal temperatures are most likely over the northwestern parts of the state. The DJF 2022-2023 precipitation outlook favors above normal precipitation over the Pacific Northwest through parts of the Northern Plains, as well as over the Great Lakes and Ohio and Tennessee Valley regions. Elevated odds of below normal precipitation are favored over the southern third of the U.S., with the highest probabilities over parts of southeastern New Mexico and southern Texas, as well as parts of the Gulf Coast States. Over Alaska, a tilt toward above normal precipitation is favored over western Alaska, while enhanced probabilities of below normal precipitation are favored over parts of the South Coast. Areas depicted in white and labeled “Equal-Chances” or “EC” are regions where climate signals are weak and so there are equal odds for either above-, near- or below-normal seasonal mean temperatures and total precipitation amounts. Equatorial sea surface temperatures (SSTs) are below average across most of the Pacific Ocean and La Niña conditions are present. The La Niña state is expected to continue through DJF 2022-2023 (76% chance) followed by a transition to ENSO-neutral in February-April (FMA) 2023 (57% chance). 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 A La Niña advisory remains in effect and the tropical Pacific atmosphere is consistent with La Niña. Below average SST anomalies persisted across the equatorial Pacific and strengthened in the east-central tropical Pacific in the beginning of November. Recent observed SST anomalies in the NINO3.4 region reached -1.0 degrees Celsius. Subsurface temperature anomalies (averaged from 180-100W and 0-300 meters) decreased rapidly in mid-June 2022 from positive to negative and have remained negative. During the last two months, negative subsurface temperature anomalies persisted near the surface and at depth in the eastern and east-central Pacific, while positive subsurface temperature anomalies have mostly persisted, at depth, in the western and central Pacific Ocean. These cooler than average temperatures support continuation of La Niña conditions through winter 2022-2023, but chances gradually decrease with a 57% chance of transitioning to ENSO-neutral in FMA 2023. A renewed Madden Julian Oscillation (MJO) signal is forecast for the upcoming few weeks and there is good agreement among dynamical models favoring a more coherent MJO continuing to propagate eastward to the western Pacific. However, forecasts of the progression of the MJO are uncertain and, if the MJO propagates eastward, we expect that MJO activity may only impact very early parts of DJF 2022-2023. Therefore, La Niña remains the primary driver of winter 2022-2023 temperature and precipitation outlooks. SST anomalies along the northwestern coast of Alaska are warmer than normal, while SSTs in the Gulf of Alaska and along the west coast are below average, a shift from mostly warmer than average SST anomalies throughout October. Off the west coast of the U.S., SST anomalies are neutral, with a small region of below normal SST anomalies near southern California, and above normal SST anomalies near northern California. Following mixed positive and negative SST anomalies along the East Coast in October, SSTs are now warmer than average, particularly along the coast of New England. PROGNOSTIC DISCUSSION OF SST FORECASTS The CPC NINO3.4 consolidation forecast shows SST anomalies near -1.0 degrees Celsius in DJF 2022-2023, with the Constructed Analogue (CA) predicting SST anomalies less than -1.0 degrees Celsius and the North American Multi-Model Ensemble (NMME) slightly below -0.5 degrees Celsius. Tools agree on a transition to ENSO neutral in FMA 2023. The International Research Institute for Climate and Society (IRI) / Climate Prediction Center (CPC) plume average of forecasts for the Niño-3.4 SST region from the last month depicts a 76% chance of La Niña during the Northern Hemisphere winter (December-February) 2022-23 and gradually decreasing odds of La Niña with a transition to ENSO-neutral favored in FMA 2023 (57% chance). ENSO neutral then becomes the most favored category and this continues through June-August (JJA) 2023. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS Dynamical model forecasts from the NMME and Copernicus (C3S) multi-model ensemble systems are used for the first six leads when they are available as was the objective, historical skill weighted consolidation, that combines both dynamical and statistical forecast tools. Potential typical impacts known to be associated with La Niña winters are utilized in preparation of the outlook via common techniques that include composite analysis (including consecutive La Niña events) and regressions anchored to Niño 3.4 SST in both diagnostic and prognostic terms. La Niña impacts were considered through the FMA 2023 forecast lead consistent with the expected La Niña evolution. Statistical guidance such as the global SST based Constructed Analog (CA), experimental Calibration, Bridging, and Merging (CBaM) guidance, and long term temperature and precipitation trends played a role in many of the outlook seasons. Objective, historical skill-based consolidation tools contribute to the outlook and include the ENSO/OCN and the complete suite of statistical/dynamical tool combinations. Coastal SSTs also are considered, especially at the early leads. PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2022 TO DJF 2023 TEMPERATURE The DJF 2022-2023 temperature outlook favors above-normal temperatures for most of the southern half and the eastern third of the CONUS. The highest odds for above normal temperatures (50 to 60 percent) are over parts of the Gulf Coast States, consistent with agreement among dynamical and statistical tools, as well as expected impacts during La Niña and positive decadal temperature trends. Anomalously high SSTs and decadal trends, along with consistency in dynamical models, tilts odds towards above normal over the Northeast. Above normal temperature probabilities are weaker in DJF 2022-2023 and January-February-March (JFM) 2023 over southern California compared to the previous outlook given weaker signals in tools over the western U.S. Elevated probabilities for below normal temperatures are forecast for the northern contiguous United States (CONUS) over the region stretching from the Pacific Northwest to the Great Lakes in DJF 2022-2023. Some NMME and C3S models favored warmer than normal or EC for parts of the northern CONUS, however, the forecasted below normal temperatures are consistent with La Niña impacts, below normal decadal trends in the north-central CONUS, and an anomalously positive snowpack. Over Alaska, the DJF 2022-2023 depicts enhanced probability of above normal temperatures over northwestern parts of the state, consistent with dynamical model forecasts, decadal trends, and anomalously warm SSTs. Below normal temperatures are favored over southeastern Alaska and the panhandle, given strong consistency among available tools. Though some tools, such as NMME, favored warming stretching to the southwestern coast of Alaska, EC is favored due to anomalously cold SSTs along the southeast coast. The area of below normal probabilities along the northern CONUS and over southeastern Alaska is expected to persist through JFM 2023 consistent with the forecast La Niña, and coverage gradually decreases and probabilities weaken through March-April-May (MAM) 2023 as ENSO neutral becomes the favored state in the Tropical Pacific. Though ENSO neutral is forecast with a 57% probability in FMA 2023, CFSv2 forecasts of SST anomalies remain weakly cold through at least MAM 2023, and we expect some lingering persistence of the atmosphere related to La Niña. Similarly, above normal temperature probabilities over the southern and eastern CONUS and northwestern Alaska are maintained, though expand spatially over CONUS, through MAM 2023. Above normal temperature probabilities are prevalent over CONUS beginning in April-May-June (AMJ) 2023 and expand through September-October-November (SON) 2023, given dynamical and statistical tools that agree on enhanced above normal probabilities, as well as ENSO/OCN and other consolidation forecast tools for which long term temperature trends contribute significantly at times in various regions beyond lead 6. Over Alaska, the tilt toward above normal temperatures over northwestern Alaska shifts southward in May-June-July (MJJ) 2023 following dynamical models, and above normal probabilities expand across the state by August-September-October (ASO) 2023 before decreasing spatially through the end of the forecast period (DJF 2023-2024), consistent with statistical forecast tools. PRECIPITATION The DJF 2022-2023 precipitation outlook depicts increased probabilities for above-normal seasonal precipitation over the west coast of Alaska, the Pacific Northwest, northern Rockies, and portions of the Great Lakes, and Ohio and Tennessee Valley regions. Enhanced probabilities of above-normal precipitation in the Pacific Northwest are largely based on composite analysis of La Niña winters, as are enhanced precipitation over the Great Lakes and Ohio/Tennessee Valley, however, elevated chance of Lake Effect snow over the Great Lakes also adds to enhanced above normal probabilities over the Great Lakes. NMME, CFSv2, and decadal trends support a slight tilt toward above normal probabilities over parts of North Dakota and Minnesota, which is expected to persist through JFM 2023. Drier than normal conditions are most likely for south-central Alaska and along the southern tier of the CONUS in DJF 2022-2023, also consistent with expected La Niña impacts in DJF. The highest probability of below-normal precipitation (50%) is depicted over parts of the Southwest and Texas, as well as parts of Georgia and Florida, consistent with dynamical model guidance favoring enhanced probability of below-normal precipitation in these regions, and enhanced probabilities of above normal temperatures over the Gulf Coast States. Though NMME and C3S were slightly drier this month over the state of California, EC is favored over northern parts of the state due to comparatively low hindcast skill over Northern California as well as tendency toward storminess over northern California in winter months. Similarly to the temperature outlooks, probabilities remain strong through JFM 2023 given the La Niña forecast, and are forecast to persist through MAM 2023 though the areas of favored above normal precipitation decrease spatially as Tropical Pacific SSTs transition to neutral. The favored area of below normal precipitation remains steady across the southern tier of the U.S. through FMA 2023 before decreasing to the Southwest in MAM 2023. This is consistent with dynamical model and statistical tools through MAM 2023, as well as expected La Niña impacts through the winter and transition seasons. Uncertainty increases in AMJ 2023 through the end of the forecast period, particularly as we rely more heavily on ENSO/OCN and other statistical consolidation forecast tools based on trends beginning in MJJ 2023. As such, larger areas of EC are forecast over the CONUS. This remaining set of outlooks are primarily based on the forecast consolidation of statistical guidance and long term precipitation trends and remain similar to the forecasts issued in October. FORECASTER: Johnna Infanti 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 Dec 15 2022 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$