696 FXUS05 KWBC 151230 PMD90D Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EDT Thu May 15 2025 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS The El Nio Southern Oscillation (ENSO) Alert System Status is currently Not Active as ENSO-neutral conditions are present. ENSO-neutral is favored to persist through summer 2025 with chances reaching 74% during June-August, and remaining above 50% through August-October 2025. ENSO-neutral conditions are thus forecast to be present for much of the Seasonal Outlook leads, and are highly likely for the first lead, June-July-August (JJA) 2025. The JJA 2025 Temperature and Precipitation Outlooks are quite similar to last month's lead 2 forecasts of JJA in terms of overall pattern. The JJA 2025 Temperature Outlook favors above normal temperatures for the entire Contiguous U.S. (CONUS), and probabilities are enhanced over the West, Florida, and the Northeast. The highest probabilities, reaching 70 to 80%, are found over the interior West and southwestern Texas. Over Alaska, slight changes to the forecast from last month include the introduction of Equal Chances (EC) of above, near, and below normal temperatures over parts of the Northern Mainland, and probabilities of above normal temperatures increased to 40 to 50% over the southern coast and 50 to 60% over southeastern Alaska. The JJA 2025 Precipitation Outlook favors a broad region of below normal precipitation stretching from the Northwest coast to the Upper Mississippi Valley, as well as parts of the Central and Southern Plains. Within this area of below normal precipitation, probabilities reach 40 to 50% over much of the northern tier, and 50 to 60% over parts of Montana. Above normal precipitation is favored over the Southeast and along the East Coast to parts of New England, parts of the Southwest (mainly Arizona), and much of Alaska. EC of above, near, and below normal temperatures or precipitation are indicated where there is model and/or tool disagreement, forecast probabilities for each category are similar, and temperatures or precipitation are expected to be close to the climatological distribution. 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 Following the recent period of below average sea surface temperatures (SSTs) in the central Pacific, SSTs have been near average across the central and eastern Pacific Ocean since mid-April. The most recent weekly SST departures in the Nino3.4 region are around 0.1 degrees Celsius (C), with SST departures in the other Nino regions around -0.1 or 0 C. In addition, upper ocean heat anomalies significantly weakened through February and March 2025, making way for the return of near average temperatures in April 2025. The negative subsurface temperature anomalies that had been present in the central and east-central Pacific Ocean have weakened as well, and above average temperatures remain in the western and central Pacific. Overall, these SST departures and state of the equatorial Pacific reflect ENSO neutral conditions. The Madden Julian Oscillation (MJO) is forecast to remain weak over the next few weeks as well, and as such neither the ENSO or MJO teleconnection are strongly considered for early leads. Local SSTs, including above normal SSTs in the Gulf of Alaska, and along the Southeast and East coasts of the CONUS, are considered for early leads where applicable and relevant. Local impacts from soil moisture become more of a player as we shift into the spring. Negative soil moisture anomalies are present over the Southwest, with strong negative anomalies found over much of southwestern and Central Texas. There is a sharp gradient to above normal soil moisture anomalies over northern Texas, parts of the Lower and southern Middle Mississippi Valley, Tennessee Valley, Southeast, and southern Ohio Valley where there has been recent heavy rainfall. Below normal soil moisture is also present over parts of the Central and Northern Plains, Upper Mississippi Valley and the northern parts of the Middle Mississippi and Ohio Valley regions. Given the weakness of ENSO and MJO, the state of anomalous soil moisture is weighted more highly than teleconnections for this Outlook, particularly for the first lead where soil moisture is expected to have more of an impact. PROGNOSTIC DISCUSSION OF SST FORECASTS Though there is some spread amongst models, SST forecasts from the North American Multi-Model Ensemble (NMME) mainly favor ENSO-neutral through JJA. In general, ENSO-neutral is favored to persist through the Northern Hemisphere summer 2025, and chances of ENSO-neutral remain above 50% through August-October (ASO) 2025. Following ASO and into December-February (DJF) 2025, chances of ENSO-neutral are slightly favored over La Nia, and chances of El Nio are least probable comparatively. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS Dynamical model forecasts from the NMME, the Coupled Forecast System Model Version 2 (CFSv2), and the Copernicus (C3S) multi-model ensemble system were used extensively for the first six leads when they are available, as was the objective, historical skill weighted consolidation and Calibration, Bridging, and Merging (CBaM) guidance, that combines both dynamical and statistical forecast information. A consolidation of statistical tools including the ENSO-OCN tool, which represents the combined influence of ENSO (when active) and decadal timescale trends in temperature and precipitation (utilizing the Optimum Climate Normal, OCN) and dynamical models is used for the first six leads. Following this, the ENSO-OCN forecast tool is used more extensively. The presence and forecast of ongoing ENSO-neutral conditions means that longer timescale decadal variability in temperature and precipitation are generally the largest predictable signal for the seasonal forecasts. Decadal variability and trends are determined from the OCN, representing the difference between the most recent 15-year period average seasonal temperature or precipitation and the average for the climatology period, from 1991-2020. PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2025 TO JJA 2026 TEMPERATURE The JJA 2025 Temperature Outlook favors above normal temperatures for the CONUS. Overall the Temperature Outlook for JJA 2025 is similar to last month, though models and tools favored slight warming over e.g. the Northern Plains and Southwestern Texas compared to last month. Any differences over CONUS are minor, and are mainly due to the shorter lead of models and influence from recent rainfall or lack of rainfall on soil moisture which can impact the first season. Given the weak teleconnections from ENSO and MJO, this forecast mainly relies on dynamical and statistical models, a consolidation of these tools, and potential influence from soil moisture. Probabilities for above normal temperatures are enhanced over the West, Southwest, Florida, and New England where there was agreement among dynamical models, including NMME and C3S, and statistical tools that include decadal variability. Probabilities reach 60 to 70% over parts of the interior West where dynamical models showed stronger probabilities, and over southwestern Texas where soil moisture is anomalously low. Probabilities reach 50 to 60% over New England and Florida where coastal SSTs and decadal trends are above normal as well as having good agreement among tools. Probabilities are still above normal but weaker (33-40%) over the Northern Plains and Great Lakes stretching to the northern Gulf states, where model skill is weak (over the northern parts of the region) and where soil moisture is anomalously high (over southern parts of the region). This may lead to a moderation of the above normal temperatures, though likely not enough to tilt probabilities toward below normal. Most of Alaska is at least weakly forecast to be above normal, with much of the state covered with 33 to 40% probabilities of above normal temperatures, though cooler SSTs and a cold signal in NMME, C3S, and CBaM led to favored EC over northern Alaska. In contrast, above normal SSTs, better model agreement, and decadal trends enhance the probability of above normal temperatures over the southern coast and southeastern parts of the state. Above normal temperatures are favored for the CONUS and Alaska through ASO 2025, with higher probabilities over the West and Northeast supported mainly by NMME and C3S forecasts and the presence of decadal trends which tilt odds more strongly toward above normal. While much of the CONUS remains above normal in September-November (SON) 2025 through November-January (NDJ) 2025, EC is indicated over the Northern Plains beginning in SON 2025, which then expands to the West Coast and over the western Great Lakes through NDJ 2026. This area of EC highlights where signals are weaker in forecast tools, mainly the ENSO-OCN tool, and where dynamical models have lower skill and disagreement (through lead 6). During DJF through February-April (FMA) 2026 slightly enhanced probabilities for below-normal temperatures appear in parts of the Northwest owing to the ENSO-OCN tool. The longest lead seasonal outlooks through JJA 2026 are based primarily on signals due to decadal variability as shown by the OCN tool. PRECIPITATION The JJA 2025 Precipitation Outlook is also similar to last month's lead 2 JJA Precipitation Outlook, with some modifications given more recent information and initialization of models and tools. Below normal precipitation is favored from the West Coast to the Great Lakes, with weak below normal probabilities stretching to southwestern Texas. Probabilities are enhanced over parts of Montana mainly due to agreement among models which increased confidence. Above normal precipitation is forecast over Arizona, as models and tools depict a weakening and westward shift of the above normal precipitation compared to last month, and this area of above normal precipitation is maintained through ASO 2025, though with the more westward orientation favored by our tools. The likelihood of an enhanced Southwest Monsoon is weakly increased due to current negative soil moisture anomalies and predicted above-normal temperatures, which tend to be anti-correlated with monsoon precipitation. Above normal precipitation is also favored for the East Coast and much of Alaska for JJA through SON 2025, as well as October-December (OND) 2025 for Alaska, supported by NMME and C3S. In general the pattern of below normal precipitation over parts of the northern CONUS, and above normal precipitation along the East Coast/parts of the East Coast is favored over the through SON 2025. A shift in this spatial pattern is seen beginning in OND 2025 where below normal precipitation becomes more probable over the Southwest, Southeast, and southern parts of the East Coast, and above normal precipitation more probable over the Northern Plains or Northwest and Great Lakes through spring 2026. The shift from above normal precipitation to below normal precipitation over the Southeast from SON 2025 to NDJ 2025 is rapid given climatologies of these seasons as well as weaker chances of an El Nio compared to neutral or La Nia conditions in fall and winter 2025, which leads to more likely below normal precipitation than above normal. Following this, the pattern shifts back to a northern CONUS below normal pattern, which is primarily based on the ENSO-OCN tool, though EC is dominant across the CONUS given uncertainty in longer lead forecasts. Mild probabilities for above normal precipitation are also present over northern and/or western Alaska throughout much of the leads given results from the ENSO-OCN tool, shifting to EC in April-June (AMJ) 2026 when signals become too weak for confidence in precipitation over Alaska. 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 Jun 19 2025 1991-2020 base period means were implemented effective with the May 20, 2021 forecast release. $$