Executive Summary: The North America season 1-4 ahead climate forecast is valid through meteorological spring 2024 is re-issued. The forecast is based on a constructed analog heavily considering regional SSTA patterns such as ENSO and warm/cool pools of water in the middle latitudes. Forecast highlights include another hotter than normal summer for most of the U.S. except the northwestern Gulf States where wet weather suppresses anomalous heat risk. The Canadian Prairies, North-central U.S. and parts of the Ohio Valley are drier than normal during summer as drought expansion is a concern. Next autumn season brings wet risk in the Gulf States while areas to the north including the Mid-south U.S. and North-central States stay on the dry side. Drought is possible for a fairly significant portion of the Central U.S. Winter 2023-24 is mild again especially for Southern Canada and the East U.S. El Nino-induced wet bias adheres to the Gulf States next winter and spring. Methodology: All climate forecasts are based on a constructed analog. The constructed analog heavily weighs BOTH the sea surface temperature anomaly (SSTA) patterns in the tropics such as ENSO and the middle/poleward oceans including marine heat waves. Warm season forecasts include the influence of soil moisture regimes while cold season forecasts which are within 1-2 months range apply the influence of projected snow cover. Given unique ocean climate characteristics and their influence on climate during the past 10 years, an optimum climate normal (OCN) is also heavily considered. Finally, a season-4 forecast is added to the format. The latest Climate Impact Company season 1-4 outlook is valid through meteorological spring 2024. Fig. 1: Global SSTA forecast valid for June 2023 by the International Multi-model Ensemble (IMME). Fig. 2: Global SSTA forecast valid for October 2023 by the International Multi-model Ensemble (IMME). Climate: The outlook is somewhat reliant on the global SSTA projection for the immediate short-term (June) and longer-term (October) based on the availability of the International Multi-model Ensemble (IMME). Constructed analog El Nino southern oscillation (ENSO), Pacific decadal oscillation (PDO), and Atlantic multi-decadal oscillation (AMO) forecasts are relied upon for outlooks into early 2024. The short-term forecast for June (Fig. 1) indicates a sprawling El Nino, developing positive phase Indian Ocean dipole (+IOD), marine heat waves (MHW) northeast of Hawaii and off the northwest coast of Africa plus unusually warm SSTA in the main development region (MDR) for hurricanes in the outer tropical North Atlantic. The North Atlantic warm hole (NAWH) is also indicated south of Greenland. The outlook is a general guide and not used verbatim. The El Nino forecast is likely overdone as westward warming of the equatorial East Pacific to the Dateline is slower. Theorized is 2015-like eastward shift of the MHW northeast of Hawaii to the North America West Coast to stop in the cool water inflow from the California Current toward the east-central tropical Pacific allowing waters to warm to the Dateline to cause the stronger El Nino as forecast by IMME. Climate Impact Company indicates that process is slow, delayed, or may not happen. Additionally, the NAWH pattern in the North Atlantic is biased farther westward toward the Southeast Canada/Northeast U.S. coastline. By October, IMME projects a stronger El Nino but without the MHW northeast of Hawaii reaching the North America West Coast (Fig. 2). Consequently, the intensity of El Nino indicated by IMME is likely much too strong. Note the warmth of the North Atlantic basin just after peak activity of the hurricane season likely to prolong active tropics into late year. As usual the open oceans south of the polar ice cap warm for late warm season. The soil moisture regime across North America features drought in the central Great Plains which recently is expanding eastward (Fig. 3). Strong drought resides across Western Canada and the Canadian Prairies. Drought patterns are generally supportive of an anomalous high pressure and increased heat risk during the summer season. Developing El Nino eventually eases drought risk, but timing is uncertain. Finally, OCN is applied to the forecast. This condition is warranted due to the evolution of influence on climate by regions of warm and cool SSTA in the middle/northern latitude oceans during the past 10 years. Fig. 3: North America soil moisture anomalies and where drought is located. JUN/JUL/AUG 2023: Confidence is ABOVE AVERAGE that the U.S. summer 2023 season is hotter than normal. Not everywhere observes anomalous heat. The wet zone forecast for the northwest Gulf States suppresses heat risk while dryness across the Canadian Prairies, North-central U.S., and parts of the Ohio Valley enhances anomalous hot risk. New England is also “sneaky” hot and dry. Fig. 4-5: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for JUN/JUL/AUG 2023. SEP/OCT/NOV 2023: Much of the U.S. is warmer and drier than normal next autumn. Dryness continues in the North-central U.S. and adds the Midwest and Interior Northeast States. Most of these dry zones are warmer than normal. Wet weather near the Gulf Coast suppresses anomalous warm risk in that region. The West U.S. observes a warmer than normal autumn. Fig. 6-7: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for SEP/OCT/NOV 2023. DEC/JAN/FEB 2023-24: Meteorological winter 2023-24 is warmer than normal across Southern Canada and most of the eastern half of the U.S. A typical mild bias for winter caused by El Nino. Stormy weather attacks the Coastal Northwest States and the Gulf region with a near miss for the New England States. The Northern U.S. precipitation regime is near or below normal. Fig. 8-9: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for DEC/JAN/FEB 2023-24. MAR/APR/MAY 2024: Next meteorological spring stays warmer than normal due to El Nino for the Northern U.S. and Western Canada and much of the U.S. East Coast. Also typical of springtime El Nino climate, the southern states centered on Texas are very wet while areas to the north including the Midwest States to New England and coastal Northwest are drier than normal. Fig. 10-11: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for MAR/APR/MAY 2024.  

Executive Summary: The North America season 1-3 ahead climate forecast is valid for meteorological summer and autumn 2023 and adding winter 2023-24. Highlights include increasing risk of an upper-level ridge over central North America during summer 2023 as the Central U.S. forecast trends hotter/drier. Most of the U.S. is warmer than normal during summer. The central/southwest Great Plains to Texas drought may expand northeastward during summer before a wet autumn suppresses the dryness. The Texas drought erodes. Next winter looks cold in the Central U.S. and stormy for the East States. Winter 2023-24 could be interesting as an El Nino Southwest U.S. trough develops and combines with a blocking high pressure area over Greenland causing more widespread cold and storminess. Climate: The North America season 1-3 ahead climate forecast is based on projected regional sea surface temperature anomaly (SSTA) regimes such as El Nino southern oscillation (ENSO), Pacific decadal oscillation (PDO), Atlantic multi-decadal oscillation (AMO), and marine heat waves plus current soil moisture analysis and trend. The ENSO forecast into 2024 anticipates El Nino. The last El Nino was observed in 2018-19 and was relatively weak. The last full-throttle El Nino occurred in 2015-16 and rivaled the 1997-98 and 1982-83 El Nino episodes as the strongest on record. Currently, dynamic models are projecting a strong El Nino for the second half of 2023 similar in intensity to the historic 2015-16, 1997-98, and 1982-83 warm ENSO events (Fig. 1). However, statistical models (based on analogs), favor a weaker El Nino (Fig. 2). Climate diagnostics reveal a steady trend toward a stronger El Nino as the northwest coast of South America is prohibitively warm and the equatorial subsurface East Pacific is warming sharply. However, the new presence and influence of the northeast Pacific marine heat wave (MHW) is a governing force on ENSO especially if a 2015-16 El Nino is to form (Fig. 3). The 2013-2023 semi-permanent northeast Pacific MHW budged westward and away from the North America West Coast the past 3-6 months allowing the waters off the West Coast to cool during the 2022-23 cold season and the cool SSTA regime remains in-place (Fig. 4). For El Nino to develop as strongly as indicated by the C3S/ECM projection for August 2023 (Fig. 5), the MHW will need to shift eastward back to the North America West Coast. The C3S/ECM (dynamic) model does not indicate that scenario as of JUL/AUG/SEP 2023. Consequently, El Nino 2023 will develop but not as strongly as dynamic models indicate but more intense than the weaker analog solutions. Fig. 1-2: The NCEP CFS V2, similar to other ENSO forecasts, is forecasting an intense El Nino for the second half of 2023. Meanwhile, analog forecasts such as the Climate Impact Company constructed analog indicate weaker El Nino. Fig. 3-4: The last strong El Nino was in 2015 when the northeast Pacific coastal region was also very warm (left). Currently, the coastal Northeast Pacific is cool and the California Ocean Current circling southwestward to the south of Hawaii is blocking western progress of El Nino warm waters off the northwest coast of South America. Fig. 5: The C3S/ECM global SSTA forecast for JUL/AUG/SEP 2023 keeps the MHW off the Northeast Pacific coast suggesting the El Nino forecast may be too strong. The North Atlantic is quite warm except for the North Atlantic warm hole (NAWH) south of Greenland. The northeast quadrant of the North Pacific contains the MHW and the much cooler regime off the West Coast which is a classic cool phase. The -PDO regime is entering a 4th consecutive year. The CS3/ECM global SSTA forecast indicates the -PDO regime weakens but does not end during Q2/2023. A transition to a weak warm phase for the 2023-24 cool season is likely. Normally, PDO and ENSO phase run parallel. A stronger El Nino requires PDO shift into the warm phase. An aggressive warmer than normal forecast for the North Atlantic basin is projected by the CS3/ECM model. The warm SSTA involves both the North Atlantic basin and deep tropics. Forecast confidence is increasing on expectations of a moderate (or stronger) warm phase of both the AMO and tropical North Atlantic (TNA) patterns. The TNA index calculates SSTA in the ocean region east of the Caribbean Sea to the northwest coast of Africa also known as the main development region (MDR) for hurricanes. Climate Impact Company indicates a weaker El Nino forecast (compared to dynamic models) for tropical cyclone season and combined with a vigorously warm North Atlantic SSTA regime, the seasonal forecast of 12 storms, 7 hurricanes, and 3 intense hurricane is a little stronger than El Nino climatology. Since 2013-14, the MHW pattern in the northeast Pacific Ocean has not only been dominant but also having a consistent influence on climate by producing a semi-permanent upper-level high-pressure ridge oscillating from the North America West Coast or offshore in-between Hawaii and Alaska. This feature will continue through next winter having (great) influence on the western North America climate pattern with residual downstream effects. Similarly, the accelerated ice and snow melt in the northern Atlantic including the Greenland ice sheet has caused a cool pool of water to persist in the Labrador Sea to south of Greenland where the North Atlantic warm hole (NAWH) exists. Since 2013-14, the NAWH pattern has forced a semi-permanent upper trough across this region compensated for by persistent upper-level high-pressure ridge areas in eastern North America and Europe. The NAWH pattern is responsible for milder winters in East North America and Europe during the past 10 years (Fig. 6). and increases risk of stronger hurricanes in the western North Atlantic basin as the NAWH regime blocks the Gulf Stream forcing the piling of warm water off the U.S. East Coast. The NAWH regime continues through next winter. Finally, having a significant influence on the warm season climate, is the tendency for high-pressure ridging to form across or downwind of a large drought area while low pressure suppressing summer heat risk is generally present across wet soil moisture regions. In the U.S., a major drought has evolved across the central and southern Great Plains to Texas and Florida plus the Mid-Atlantic region (Fig. 7). The trend of soil moisture as mid-spring approaches is drier in the drought areas mentioned except wetter in Florida and coastal Texas (Fig. 8). After a wet winter season in California and the end of long-term drought, the recent soil moisture trend is drier as the wet soil regime in that region is likely to weaken heading into summer. The key zones are the central and southern Great Plains plus the Mid-Atlantic region as a heat enhancer for summertime ahead if the drought remains intact. Fig. 6: A dominant feature causing North America and Europe climate during 2014-22 (and continuing in 2023) is presence of the marine heat wave in the northeast Pacific and North Atlantic warm hole and the influence on the upper air pattern. Fig. 7-8: Current U.S. soil moisture anomalies and the change in April (so far). Forecast methodology: The climate diagnostics discussed generate the season 1-3 ahead climate forecast for North America. In review, the influence of an evolving El Nino, slowly weakening cool PDO, strengthening AMO, and persistent northeast Pacific MHW and NAWH south of Greenland are each heavily weighted to produce a constructed analog. The soil moisture regime is considered for the warm season (only). The prevailing upper air forecast: The Climate Impact Company constructed analog (CIC-CA) forecast projects an upper-level high-pressure ridge centered over central North America for summer 2023 (Fig. 9). As a result, the North-central U.S. trend is drier and warmer. The primary influence of the ridge is to trend the U.S. hotter for meteorological summer. Unusual for the 10-year climatology is presence of an upper trough north of Hawaii as projected for autumn 2023 (Fig. 10). The upper ridge associated with the northeast Pacific marine heat wave shifts north and over Alaska. Downstream from the upper ridge extending along the North America West Coast is an upper trough in the East-central U.S. which produces shear to prevent hurricanes from roaming the northern half of the Gulf of Mexico. The upper air pattern projected for winter 2023-24 features the classic El Nino low latitude trough across the Southwest U.S. coupled with blocking high pressure over Greenland (Fig. 11) implying a potentially stormy winter ahead with copious snow. Fig. 9-11: The Climate Impact Company upper air forecast for meteorological summer and autumn 2023 plus winter 2023-24. JUN/JUL/AUG 2023: The meteorological summer forecast trend is hotter and drier in the U.S. Corn Belt. The West U.S. to Texas remain hotter than normal. The Northeast remains very warm and humid for summer 2023. The precipitation outlook manages to stay wet in the Mid-Atlantic to New England stretch and much of the Gulf region especially near the coast. The upper air projection indicates much of the Gulf Coast rain is synoptic scale and not tropical cyclone oriented. The central Great Plains drought entering the summer season persists and may yield hotter than forecast results in that region and vicinity. Fig. 12-13: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for JUN/JUL/AUG 2023.  SEP/OCT/NOV 2023: The West/Southwest and East remain warmer than normal for the autumn forecast. However, a cooler trend projects for the Great Plains. Any emerging drought expansion concerns due to a drier and hotter trend for the North-central/Midwest U.S. during summer erodes during a wet autumn. The wet trend is evident for the northwest quadrant of the Gulf States to the interior Mid-Atlantic region. Most wet weather is synoptic oriented and not due to tropical cyclone activity. Fig. 14-15: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for SEP/OCT/NOV 2023.  DEC/JAN/FEB 2023-24: The winter 2023-24 outlook looks interesting with an upper trough across the Southwest U.S. and a blocking ridge over Greenland. The forecast indicates a moderately chilly winter across the Great Plains to the Northwest States while the Southeast is warm. The Southwest States may be cooler/wetter than indicated. A stormy winter in the East but favoring more rain than snow. Fig. 16-17: The Climate Impact Company upper air/temperature/precipitation anomaly climate forecast for DEC/JAN/FEB 2023-24.