Highlight: U.S. drought shifts into the southern states, East Brazil/northeast Argentina drought emerges, La Nina rains ease Australian drought while Black Sea dryness is likely to persist.
Fig. 1: The NOAA/CPC soil moisture ranking percentile valid October 2020 with Climate Impact Company annotated 3-month trend.
October 2020 global soil moisture trend: North America observed widespread drying trend of soul moisture during late summer to mid-autumn (Fig. 1). Included is a dangerous widespread drought intensification in the West U.S. induced by a persistent upper level high-pressure ridge climate pattern. The same upper ridge dried-out Western Canada. Dryness persists across south and east portions of Canada and northeast Canada dryness intensified. Alaska also observed a strong dry trend through late summer to mid-autumn. A total of 28 tropical cyclones in the North Atlantic basin ties the all-time record set in 2005 and contributed to wet soil trend across the southeast quadrant of the U.S.
In South America the central Brazil to Paraguay and Southeast Brazil drought intensified. Dryness across northwestern South America was steady. The Chilean drought has re-intensified as waters off the coast cooled related to the strengthening La Nina. Central to southern Argentina wet soil conditions strengthened the past 3 months.
In Europe soil moisture conditions were unchanged except for a wetter trend in Eastern Europe to Northwest Russia. The Black Sea to Caspian Sea regional drought intensified the past 3 months. Worst drought conditions are centered over the Russia winter wheat crop in Southwest Russia. Central to northeast Russia soil moisture also trended drier the past 3 months.
Japan soil moisture dried-out to near normal otherwise most of East Asia including China and South/North Vietnam to Thailand turned wetter the past 3 months. Much of Southern Asia maintained wet soil moisture except a drier zone in northern India. Australian dryness persists despite the wet influence normally produced by La Nina. A wetter trend was noted in central Australia.
October 2020 global SSTA: The global SSTA pattern contributing to the soil moisture regime and 3-month trend is lead by a developing La Nina in the eastern equatorial Pacific Ocean (Fig. 2). The 30-day SSTA trend identifies La Nina as moderate and trending toward a strong event. Interestingly, the normal “horseshoe” cool SSTA pattern accompanying stronger La Nina events is not complete. Waters off the west coast of South America have cooled (contributing to the resurgent Chilean drought) but in the northeast Pacific the semi-permanent “warm blob” present much of the time since 2013 persists. The IOD pattern is neutral. Waters south of the polar ice cap are warmer than normal and have contributed to above normal early season snows in some northern latitudes. North America had their snowiest October on record as cold air in the northern latitudes flowed across the relative warm ocean surface. The western North Atlantic SSTA pattern stayed warm sustaining late season tropical cyclone activity.
Fig. 2: The 30-day global SSTA analysis valid for October identifies a strengthening La Nina, neutral IOD and persistent warmth in the northeast Pacific while the southeast Pacific turns cooler.
The 3-month (through FEB-2021) global soil moisture projection: The La Nina climate weighs heavily on the global soil moisture outlook valid through February 2021 (Fig. 3). The southern U.S. transitions into a drought pattern as spring 2021 approaches. Northwest States plus the Ohio Valley (and vicinity) turn stormy over the winter season increasing soil moisture for these regions. Central Canada continues to trend drier.
In South America the La Nina climate brings drier conditions to central and eastern Brazil causing drought concerns for this region. Paraguay is forecast wetter than normal but forecast confidence for this region (where drought is occurring) is low. Dryness is also forecast to spread across northeast Argentina and is maintained in Chile.
Western Europe is stormy for the winter season ahead and Northwest Russia is snowy. The Black Sea region remains mostly dry as drought continues. China trends much drier plus South-central Asia.
La Nina brings drought-ending rains to northwest and east portions of Australia. Southwest Australian drought may continue.
Fig. 3: The NOAA/CPC soil moisture ranking percentile valid October 2020 with Climate Impact Company annotated 3-month forecast.