Monitoring Rainfall Shortages Northeast Brazil

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Highlight: The importance of being aware of long-term dryness followed by short-term dryness in the same region during summer.

Fig. 1-2: Awareness of long-term rainfall deficit regions followed by similarly (or worse) dry conditions is the recipe for creating susceptibility for fast-developing drought, flash drought and/or heat waves if the right atmospheric conditions evolve during the summer season.

Discussion: Recent research published in the AMS Journal of Climate by Samjiv Kumar, a professor at Auburn University’s School of Forestry and Wildlife Sciences identified the importance of long-term dryness often reflected in deep soil moisture water deficit followed by short-term dry episodes especially accompanied by anomalous heat can accelerate drought conditions including flash drought. In the absence of reliable deep layer (10-200 CM) soil moisture anomaly data awareness of the long-term (at least 90 days and preferably up to 9 months) rainfall regime as to whether a dry pattern is developing on approach or during summertime requires monitoring especially for a crop region. If a region of dryness is developing and is followed by short-term dryness during summertime anomalous heat is more easily generated and rapidly developing drought can occur. These conditions occurred in the Southeast U.S. late this past summer and early autumn. A new area of interest is northeast Brazil where long-term dryness causing soil moisture deficits is followed by stronger dryness in November. This region is watched closely for any weather patterns where high pressure can cause anomalous heat which more readily will lower soil moisture and potentially cause flash drought.