11/30/2021, 6:11 am EST

FINAL U.S. Winter 2021-22 Outlook

The Last Look at The U.S. Winter 2021-22 Outlook Executive Summary: The Climate Impact Company month 1-3 ahead climate forecast valid for meteorological winter is updated. The month of March 2022 is added to the forecast. The outlook is based on a weighted constructed analog. The forecast reveals a warmer revision for the winter season based on a warmer adjustment for the northwest quadrant of the U.S. in January and a potential ferocious warm February in the East and South States. However, despite the warmer revision some important cold is in the forecast. Despite the warm start to December, the constructed analog forecast indicates cold and snowy changes for the northern states the second half of December. Through mid-winter the southern tier is very dry but reverses wet in the Mid-south States/northwest Gulf States mid-to-late winter. Despite a wet start to the cool season, a mostly dry winter is ahead for California. Climate discussion: To approximate a constructed analog to project the month 1-3 ahead most likely U.S. climate pattern, a review of the persistent climate pattern identified by the 90-day and 30-day northern hemisphere upper air pattern (Fig. 1-2) and compared with the November 2021 global SSTA regime (Fig. 3) is reviewed. Two dominant upper air features were causal to the SEP/OCT/NOV 2021 North America climate pattern: 1. The Gulf of Alaska Low (GOA) and 2. The compensating downstream upper ridge over Canada. During the past 90 days, the pattern described has caused heavy precipitation into Southwest Canada while a persistent weak upper trough has caused heavy rains mostly just-offshore the U.S. East Coast. Typical of the modern-day climate, the 90-day temperature anomalies across North America are warmer than normal except for the Southeast U.S. and immediate West Coast. Fig. 1-2: The northern hemisphere 90-day and 30-day upper air pattern. Fig. 3: The November 2021 global SSTA analysis. Shifting forward to the 30-day climate pattern the GOA low-pressure area remains firm and the Canadian high-pressure area extend southwestward to the Great Basin and amplifies and is compensated for by an amplifying upper trough centered on the Mid-Atlantic region. In November the dominant anomalous warm North America climate remained in-place except for a cooler pattern change in the Southeast States while super-wet anomalies remained anchored off the U.S. East Coast and throughout coastal Southwest Canada. Fig. 4-5: The northern hemisphere 90-day and 30-day upper air analog pattern. Fig. 6: The global International Multi-Model Ensemble (IMME) SSTA forecast for January 2022.   The global sea surface temperature anomaly (SSTA) regime, in-part driving the described climate pattern has (most recently) featured a developing La Nina. The La Nina pattern is weak-to-moderate as indicated by ocean indices but atmospheric indices such as southern oscillation index (SOI) and multivariate ENSO index (MEI) identify a fairly strong La Nina climate presence. The Canadian upper-ridge pattern is well-correlated to warm SSTA in Hudson Bay and the northwestern North Atlantic basin while the GOA SSTA pattern has cooled dramatically (coolest since 2012) beneath the persistent upper trough pattern. The constructed analog is based on the emergence of a second La Nina climate within a double La Nina episode prominent in late 2017, 2011 and 2008 (Fig. 4-5). The three double La Nina episodes used to generate a base constructed analog are somewhat unique to the 30-day climatology.  The attendant upper air patterns are similar to 2021 but less amplified. The GOA low-pressure area is displaced slightly eastward and consequently the upper ridge near the Dateline is stronger while across North America the Canadian upper ridge extends to the Southwest U.S. earlier in the SEP/OCT/NOV timeframe and in Canada an upper trough replaces the ridge by November. The constructed analog has the Southeast U.S. trough albeit weaker. The 2021 upper air features are more prominent due to the more distinct (global) SSTA pattern especially the vividly cool GOA and warm North Atlantic. The global SSTA forecast by the International Multi-Model Ensemble (IMME) for the mid-point of northern hemisphere winter indicates La Nina is peaking, the GOA cool SSTA is weaker as the “warm blob” near the Dateline is shifting east and the North Atlantic SSTA remains warm although Hudson Bay and the far northwest North Atlantic SSTA cool-off and should produce some ice (Fig. 6). The analog year most similar to the IMME global SSTA projection for January is more heavily weighted amongst the 3 analog years chosen to produce the most likely projected upper air pattern for winter 2021-22. Analog years (for January) 2018 and 2012 are very close to the early 2022 ENSO forecast while 2009 is too weak. Conversely, the 2021-22 -PDO regime is best represented by 2008-09 and 2011-12. The “warm blob” is a relatively new feature but present in both 2009 and 2012. The 2021-22 anomalous warm North Atlantic as defined by the Atlantic multi-decadal oscillation (AMO) is unprecedented. The JAN-18 AMO pattern was marginally warm while 2009 and 2012 were neutral. The SSTA-driven CIC-CA forecast is driven by various weighting(s) of the SSTA components of the forecast identified in Table 1. The projected upper air pattern for North America based on the weighted CIC-CA forecast indicates a broad Alaska/Canada cold upper trough while the Pacific “warm blob” induced upper ridge pattern shifts eastward (Fig. 7). The warm SSTA in the North Atlantic is well-correlated to an upper ridge pattern. The East Pacific/North Atlantic ridge pattern(s) leave the Central U.S. susceptible to an exceptionally changeable winter climate pattern. The proximity of a cold trough in Northeast Canada leaves the Northeast U.S. susceptible to “sneaky cold” from Quebec. Year (Weight) ENSO PDO Warm Blob AMO 2017-18 (2) X     X 2011-12 (3) X X X   2008-09 (2)   X X    Table 1: The CIC-CA SSTA-driven analog years and their weighting to compute the most likely U.S. month 1-3 ahead climate outlook. Fig. 7: The CIC-CA projection of the most likely upper air pattern across North America for DEC/JAN/FEB 2021-22.   Winter 2021-22 outlook: The Climate Impact Company meteorological winter 2021-22 outlook based on a constructed analog yields anomalous warmth for much of the U.S. and a warmer revision due to less cold in January for the northwest quadrant of the U.S. and a warm February in the East. The precipitation forecast remains dry on the West Coast where drought is likely to re-intensify. Dryness remains in the coastal Southeast/Florida forecast. Fig. 8-9: The Climate Impact Company constructed analog winter 2021-22 temperature and precipitation anomaly outlook.  December 2021 outlook: Despite a warm start, the CIC-CA forecast insists on developing Canadian cold which shifts south likely across snow cover to chill the northern U.S. later in the month. To the south of snow cover, the Southwest and Southeast U.S. are warm. Surprisingly, the West Coast climate shifts drier (given the wet start to the cool season). Expect above normal snowfall from the Great Lakes to New England while the only wet zone is centered on the Mid-south States. Fig. 10-11: The Climate Impact Company constructed analog December 2021 temperature and precipitation anomaly outlook.  January 2022: The eastward shift of the Pacific “warm blob” projected for mid-to-late winter is likely responsible for the warmer revision in the West for mid-winter. Less impressive anomalous warmth remains in the forecast across the northwest Gulf States. The East is close to normal. Of interest is the precipitation pattern featuring a feast or famine signature. Typical La Nina dryness extends across the southern states and includes California during mid-winter. Meanwhile, the Pacific storm track returns to the Coastal Northwest U.S. The Interior Northeast observes a snowy January. Also note a dry mid-winter forecast for the southern Great Plains to the Missouri Valley. Fig. 12-13: The Climate Impact Company constructed analog January 2022 temperature and precipitation anomaly outlook.  February 2022: The outlook is very similar to the previous forecast. Indicated is a big warm-up in the East (and South) to finish meteorological winter 2021-22. An arctic air presence is observed across Montana and the northwestern Great Plains. The West is changeable and averages near normal for the month although parts of the Northwest U.S. are cold. An interesting part of the forecast is the insistence on the CIC-CA forecast of a wet pattern change in previously dry zones in the Mid-south States to the Northwest Gulf States. Meanwhile, the strong dry signature common during winter 2021-22 shifts to the East Coast and Florida and persists across California and the coastal Northwest. Fig. 14-15: The Climate Impact Company constructed analog February 2022 temperature and precipitation anomaly outlook.  March 2021: The early meteorological spring forecast remains overwhelmingly warm. The West Coast forecast also remains cold and wet with heavy mountain snows. In the Mid-south States to the northwest Gulf region a wet pattern remains in-place. Dryness is most profound in New England and Florida while 4 Corners and vicinity is also drier than normal. Fig. 16-17: The Climate Impact Company constructed analog March 2022 temperature and precipitation anomaly outlook.  DEC/JAN/FEB 2021-22 HDD at a glance: The updated DEC/JAN/FEB 2021-22 U.S. HDD anomaly forecast is adjusted warmer mainly due to a warm February (in the East) and less cold northwest quadrant of the U.S. during January. Fig. 18: The Climate Impact Company constructed analog HDD anomalies for DEC/JAN/FEB 2021-22.   
11/29/2021, 5:13 am EST

Connecting Regional SSTA With Brazil/Argentina and Australia 15-Day Rainfall Outlooks

Regional SSTA patterns are attached to local weather regimes including Argentina/Brazil and Australia heading into meteorological summer in the southern hemisphere.
11/28/2021, 1:17 pm EST

Emerging -PNA/+NAO Indicates West Warmth Shifts Eastward

ost prominent in today’s medium-range forecast are the reversal in the North Atlantic oscillation/Pacific North America pattern(s) beginning later this week and indicating warmth in the West fades while emerging across the eastern half of the nation. The -PNA pattern should also lead to an increase in rain and snow in California in the extended-range.
11/28/2021, 12:58 pm EST

AG Market Weather/Climate Research: “Warm Blobs” Shaping the Southern Hemisphere Early Summer Climate Pattern

Executive summary: In recent years large areas of warm SSTA commonly referred to as “warm blobs” have emerged as prominent influencers on regional climate. The Northeast Pacific “warm blob” emerging in 2013-14 is the most talked about (and researched) climate influencer but others have emerged. “Warm blobs” are effective climate diagnostics correlating to large regions of semi-permanent high-pressure featuring above normal sunlight and anomalous dry/warm climate. Emergence of “warm blobs” certainly is consistent with the accelerating warming atmosphere of the past decade. To compensate for the “warm blob” to semi-permanent high-pressure ridge areas (in the subtropical and middle latitudes) areas of storm-generating trough(s) are also vividly present. Given the high-amplitude upper air pattern associated with the “warm blob” SSTA pattern slow-moving climate regimes capable of producing harsh conditions such as drought or flooding are generated. In this report, we take a look at the southern hemisphere “warm blobs” and the correlating upper air pattern just ahead of meteorological summer in the southern hemisphere. Discussion: The “warm blob” SSTA regions near and east of New Zealand and east of Argentina are semi-permanent and dominant features in the southern hemisphere SSTA regime (Fig. 1). However, relatively new “warm blobs” have recently emerged off Southwest Africa and in the South Indian Ocean. In fact, ahead of summer, the “warm blobs” off Southwest Africa and particularly in the South Indian Ocean are strengthening most quickly (Fig. 2). The correlating “warm blob” SSTA regions to the upper-level semi-permanent high-pressure ridge areas in the southern hemisphere is striking! The strongest high-pressure ridge areas are across/near the South Indian Ocean and New Zealand “warm blobs” (Fig. 3). High-pressure ridging is also intense to the east of Argentina. Fig. 1:  Daily global SSTA analysis for Nov. 27, 2021 identifying the southern hemisphere “warm blobs” just-ahead of meteorological summer 2021-22. Fig. 2:  Southern hemisphere SSTA changes over the past 30 days. Fig. 3:  The November 2021 semi-permanent high-pressure ridge areas across or near “warm blob” SSTA regions (and compensating upper trough locations). Beneath high-pressure areas sunlight is above normal and a feedback mechanism develops as increased sunlight generates stronger warm SSTA which in-turn maintains/strengthens high-pressure ridging. Often less-discussed is the downstream compensating effects. For instance, note that in-between the South Indian Ocean and New Zealand upper-level ridge areas a compensating upper trough is located over Australia and responsible for bringing drenching rains during late spring. Additionally, just north of the high-pressure region to the east of Argentina a semi-permanent upper trough has generated and responsible (in-part) for bringing significant rains to parts of South America during mid-to-late spring. The ECMWF global SSTA forecast for January 2022 indicates that during mid-summer in the southern hemisphere “warm blobs” will strengthen (Fig. 4). Consequently, attendant semi-permanent high-pressure centers are also likely to intensify. ECMWF upper air forecast for January 2022 projects further amplification of the New Zealand high-pressure ridge which extends eastward across the South Pacific subtropics (Fig. 5). Additionally, the South Atlantic “warm blob” intensification is well-correlated to an amplified high-pressure ridge in that position. Of interest is the compensating upper trough(s) which are weaker during summertime but located over east-central South America and Australia. Presence of the weak upper trough patterns increases risk of wet mid-summer climate most likely for east/north Australia and East Brazil certainly defeating any drought scare but adding to the risk of gully-washer mid-summer flooding rainfall risk. Fig. 4:  ECMWF global SSTA forecast valid January 2022 indicates southern hemisphere “warm blobs” persist. Fig. 5:  ECMWF upper air forecast for January 2022 in the southern hemisphere. Conclusion: La Nina is present and developing and forecast to peak in January 2022. However, ahead of meteorological summer in the southern hemisphere presence of large “warm blob” SSTA regions are likely most prominent in shaping the summer time climate pattern. Included are “warm blob” SSTA regions southwest of Africa, in the South Indian Ocean, near and east of New Zealand and also east of Argentina. Each “warm blob” has strengthened during November and according to ECMWF further intensification is forecast by mid-summer. The “warm blobs” are well-correlated to high-pressure ridge areas also forecast to strengthen across and downwind from each “warm blob” region. To compensate for each high-pressure ridge, weak upper trough(s) capable of producing flooding rainfall are forecast (by ECMWF) over Southern Brazil and Australia for mid-summer. The primary concern for Australia and South America during mid-summer 2022 is risk of gully-washer flooding rainfall which should restrict mid-summer drought risk. Summary: Climate Impact Company continues to stress recent emergence of warm SSTA regions outside of the tropics commonly referred to as “warm blobs” and their influence on the regional (and hemispheric) climate patterns which are as important as the influence of ENSO. The character of climate patterns associated with “Warm blobs” is slow-moving and therefore more impactful.