Explaining Argentina Dryness

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Discussion: February 2018 was bone-dry across parts of the wheat/soybean crop areas of northeast Argentina. Operational models are drier-than-normal days 1-7 (Fig. 1) with some marginal rainfall possible days 8-14 (Fig. 2) but rainfall needed to reverse the dryness is not expected AT ALL!

Fig. 1: The GFS operational model percent of normal rainfall for days 1-7.

Fig. 2: The GFS operational model percent of normal rainfall for days 8-14.

The anomalous dry pattern across Argentina is associated with a persistent February 2018 upper ridge pattern (Fig. 3) linked to warm SSTA on either side of subtropical South America (Fig. 4-5). Rainfall caused by a persistent low pressure trough southeast of Brazil occurred across Brazil only.

Fig. 3: The February 500 MB height anomaly analysis identifies the upper ridge pattern causing Argentina dryness.  

Fig. 4-5: The Argentina upper ridge is associated with warm SSTA west of Chile and east of Argentina.