Highlight: Cooler bias West, anomalous heat East for the warm season ahead. East/Southeast dry climate emerges. Polar vortex Western Canada next winter. Executive Summary: The North America season 1-4 ahead forecast valid for meteorological spring 2024 through winter 2024-25 is updated. The forecast is based on combining an El Nino to La Nina transition and the influence of persistent warm SSTA in the middle latitude oceans. Highlights include a cool spring in the West while rain spreads across the Midwest drought area. Summertime is hotter than normal across the eastern 2/3 of the U.S. A dry climate develops in the Southeast and East U.S. while tropical cyclone risk stays mostly offshore. More dryness Interior East next autumn while much of the U.S. remains warmer than normal. Winter 2024-25 finds a polar vortex and attendant arctic chill over Western Canada while the eastern U.S. is mild. Climate discussion: Early-to-middle northern hemisphere winter has produced steady stratospheric warming extending from Siberia to northwest North America. The regime produced two arctic air masses each in Eurasia. The first formed in early December and eventually shifted southeastward into China. The second arctic air mass traveled cross-polar into North America during early-to-middle January. During the period of stratospheric warming, the transient Madden Julian oscillation (MJO) was quiet. However, a surge of the convective phase of the MJO is forecast to shift into the West Pacific tropics during the next 2 weeks igniting an atmospheric river (AR) storm track across the mid-latitude North Pacific and into North America unloading copious precipitation to the West Coast. Latent heat release of the AR regime across North America causes potential record warmth in Canada to the U.S. to start February. El Nino 2023-24 has peaked and based on the subsurface equatorial Pacific trend in which upper ocean heat is diminishing rapidly, the ENSO regime is heading toward weakening El Nino during late winter and early spring. Unique to the 2023-24 El Nino has been the difference in ocean intensity vs. the influence on the atmosphere. The atmospheric reaction has lagged. In fact, one measure of the atmospheric reaction to equatorial East Pacific warming, the southern oscillation index (SOI), has shown a La Nina-like positive phase the past couple weeks. Forecasts of ENSO phase is agreeable to weakening the next several months with neutral phase for mid-year. The recent deceleration of upper ocean heat is impressive and if that cooling continues the NCEP CFS V2 forecast of developing moderate-to-strong La Nina later this year may be correct. Climate Impact Company favors the NCEP CFS V2 forecast and applies a constructed analog through 2025 helping to guide the year-2 ahead outlook. The mid-latitude oceans have developed their own climatology during the past decade whereas sea surface temperature anomaly (SSTA) patterns have consistently produced large areas of oceanic warming. The warm SSTA regions are sometimes referred to as marine heatwaves (MHW). The 10-year climatology, which Climate Impact Company (CIC) refers to as an optimum climate normal (OCN), also features cool SSTA zones such as the North Atlantic warm hole (NAWH) located south of Greenland. The MHW’s are well-correlated to increased high pressure in the upper atmosphere across or downwind the event which can alter the upper air pattern farther downstream. The NAWH plays a similar role whereas upper atmosphere low-pressure troughing forms across or downwind the cool SST region and is compensated for by an upper ridge farther downstream. The oceanic OCN pattern seems to operate somewhat independently from ENSO and is continues and therefore added to the 2024-2025 climate forecast generation process. Climate summary: The primary catalyst to the North America season 1-3 ahead and year-2 ahead climate forecast is decelerating El Nino to neutral ENSO phase the first half of 2024 and evolution of a long-lasting La Nina for later this year lasting through DEC/JAN/FEB 2025-26. An added indicator with equal importance to ENSO is the OCN regime inspired by the recent unique oceanic SSTA regimes in the middle latitudes of the past decade. Forecast methodology: A constructed analog based on past similar ENSO regimes combined with OCN correlated to the atmospheric upper air pattern generates the seasonal forecasts beginning with meteorological spring 2024 and ending with meteorological winter 2025-26. Also considered is soil moisture conditions for the warm season outlooks. ECMWF upper air forecasts through the next 6 months were also considered generating the outlook. MAR/APR/MAY 2024: The meteorological spring 2024 forecast is interesting. The springtime prevailing upper air pattern is an evolving upper-level low pressure area over the Southwest U.S. with a persistent upper ridge across Canada to the Northeast U.S. The trough in the Southwest is well-correlated to the presence of negative phase of the Pacific decadal oscillation (-PDO). The -PDO pattern is present, but some dynamic models are erasing the -PDO during springtime although there is no sign of that development yet. The Southwest U.S. trough means wet weather is ahead for springtime across the East-central U.S. including the Midwest States where NOAA has issued a drought concern. CIC is forecasting wet climate for mid-to-late spring to ease Midwest U.S. drought concern. Drought in the Gulf region should also weaken due to spring rains. The Northeast U.S. is the anomalous warm zone for springtime. The outlook is wetter in the East-central U.S. and cooler in the Southwest States compared to the previous outlook. Fig. 1-2: The Climate Impact Company constructed analog forecast for temperature and precipitation anomalies during MAR/APR/MAY 2024 across North America. JUN/JUL/AUG 2024: During meteorological summer 2024, a developing MHW in the Northeast Pacific is well-correlated with an upper-level high pressure ridge extending to Southwest Canada. An upper low resides in the Continental Divide region, and an upper ridge anchors over the Southeast U.S. The climate result is a hot summer for the eastern 2/3 of the U.S. and all of Canada. The West U.S. is temperate. Beneath the high-pressure dome, the Southeast U.S. is dry. The high-pressure area protects the Southeast U.S. from tropical cyclones which are present in the southwestern Gulf of Mexico and just off the U.S. East Coast. Also note the extremely dry climate forecast in Hawaii. The forecast has similarities to the previous outlook although the Midwest is less wet, and the Southeast dryness is stronger. Fig. 3-4: The Climate Impact Company constructed analog forecast for temperature and precipitation anomalies during JUN/JUL/AUG 2024. SEP/OCT/NOV 2024: Upper trough patterns during meteorological autumn 2024 are located over Newfoundland and British Columbia while in-between, an amplified ridge brings a warm-to-mild season to the eastern 2/3 of the U.S. Dryness continues in the East. Late season tropical events affect the western Gulf of Mexico and Caribbean Sea. The Pacific Northwest coastal region is wetter than normal. Fig. 5-6: The Climate Impact Company constructed analog forecast for temperature and precipitation anomalies during SEP/OCT/NOV 2024. DEC/JAN/FEB 2024-25: The polar vortex returns during meteorological winter 2024-25. The likely strike area is Western Canada. Consequently, the winter season is likely colder than normal featuring arctic air in Alaska and Western Canada. To compensate, the East U.S. is milder than normal. Dry climate persists in the Gulf States and also the Southwest U.S. The Northwest States are wetter than normal, typical of a La Nina winter. Fig. 7-8: The Climate Impact Company constructed analog forecast for temperature and precipitation anomalies during DEC/JAN/FEB 2024-25.