Western U.S. Drought To Expand Into Great Plains. Western Russia Drought Continues.

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Recent helpful research published in the AMS Journal of Climate identifies deep layer soil moisture deficits as a potential catalyst to future drought (and flash drought during the warm season). Northern hemisphere summer has ended BUT there area significant deep layer soil moisture shortages likely to cause Southwest U.S. drought to expand to the central and southern Great Plains. Similarly, emerging deep layer soil moisture anomalies in Southwest/West-central Russia foreshadow intensifying drought ahead.

Highlight: Central/South Great Plains Drought Emerges; Western Russia Drought Continues.

Fig. 1-2: U.S. deep layer (10-200 CM) soil moisture deficits and precipitation rate for 2020 (so far).

U.S. discussion: Drought is currently in-place across the Southwest U.S. including California to the central and southern Rocky Mountains. The drought appears likely to shift east into the Great Plains. According to research published by University of Auburn School of Forestry and Wildlife Sciences oncoming drought and especially flash drought is linked to long-term rainfall deficits which realize in deep layer (10-200 CM) soil moisture deficits. Flash drought is a warm season phenomenon. However, entering the northern hemisphere cool season a LARGE area of deep layer soil moisture deficit has developed from the Upper Midwest and especially the west-central Great Plains southward into Mexico (Fig. 1). The deep layer soil moisture deficit is the result of rainfall shortages across much of this region in 2020 (Fig. 2). During quarter 4 of 2020 the western U.S. drought will expand eastward across much of Kansas, Oklahoma and Texas. Areas to the north (Upper Midwest) are likely to gradually gain La Nina-inspired rain and snow to ease drought risk during winter.

Fig. 3-4: Eastern Europe/Western Russia deep layer (10-200 CM) soil moisture deficits and precipitation rate for 2020 (so far).

Russia discussion: A drought has evolved across Romania, Ukraine, Russia’s Southern District and northward across West-central Russia in recent months. Deep layer soil moisture deficits are notably dry across Ukraine, parts of Southern District and West-central Russia (Fig. 3). A larger area of deep soil moisture deficits is possible due to lack of data in parts of this zone. The precipitation rate so far in 2020 clearly identifies a dry climate for the Black Sea region to West-central Russia certainly including most crop areas (Fig. 4).

The evolution of the Russia/Black Sea drought is mostly recently generated. Earlier this year a gigantic amplified upper ridge pattern crested over Siberia leading to record (100F) north coast of Russia early season heat (Fig. 5). The ridge pattern split during mid-to-late summer with one center emerging over Southwest Russia accelerating the drought condition (Fig. 6). The Siberian and Southwest Russia upper ridge amplified (again) during September (Fig. 7).

Looking ahead note the intense polar vortex in the 30-day analysis. Forecast models indicate the polar region warms into October and the polar vortex weakens ejecting a piece of the attendant energy into Western Europe. Europe looks wet for early October and some of that rain will benefit Ukraine. However, the persistence of the Western Russia ridge is likely to prevail well into early autumn leaving West-central to Southwest and South Russia dry.

Fig. 5-7: Evolution of a strengthening Southwest Russia drought is indicated by following the 180-day, 90-day and 30-day upper air pattern.