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Volume 22, issue 8 | Copyright
Hydrol. Earth Syst. Sci., 22, 4155-4163, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 07 Aug 2018

Research article | 07 Aug 2018

Convective suppression before and during the United States Northern Great Plains flash drought of 2017

Tobias Gerken1,2, Gabriel T. Bromley1, Benjamin L. Ruddell2, Skylar Williams1, and Paul C. Stoy1 Tobias Gerken et al.
  • 1Montana State University, Department of Land Resources and Environmental Sciences, Bozeman, MT 59717, USA
  • 2Northern Arizona University, School of Informatics, Computing, and Cyber Systems, Flagstaff, AZ 86011, USA

Abstract. Flash droughts tend to be disproportionately destructive because they intensify rapidly and are difficult to prepare for. We demonstrate that the 2017 US Northern Great Plains (NGP) flash drought was preceded by a breakdown of land–atmosphere coupling. Severe drought conditions in the NGP were first identified by drought monitors in late May 2017 and rapidly progressed to exceptional drought in July. The likelihood of convective precipitation in May 2017 in northeastern Montana, however, resembled that of a typical August when rain is unlikely. Based on the lower tropospheric humidity index (HIlow), convective rain was suppressed by the atmosphere on nearly 50% of days during March in NE Montana and central North Dakota, compared to 30% during a normal year. Micrometeorological variables, including potential evapotranspiration (ETp), were neither anomalously high nor low before the onset of drought. Incorporating convective likelihood to drought forecasts would have noted that convective precipitation in the NGP was anomalously unlikely during the early growing season of 2017. It may therefore be useful to do so in regions that rely on convective precipitation.

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Short summary
An unprecedented flash drought took place across parts of the US Northern Great Plains and Canadian Prairie Provinces during the summer of 2017 that in some areas was the worst in recorded history. We show that this drought was preceded by a breakdown of land–atmosphere coupling, reducing the likelihood of convective precipitation. It may be useful to monitor land–atmosphere coupling to track and potentially forecast drought development.
An unprecedented flash drought took place across parts of the US Northern Great Plains and...