Highlight: Uncertain forecasts, trend is away from drought (Central/East).
Summary: Summer is approaching and soil moisture forecast confidence is lowering. The issue is whether southwest/central U.S. drought expands toward the Corn Belt which is not well supported by models and where the strong Southwest drought goes during summer? NOAA kills all drought areas except the Southwest. So…uncertainty for drought risk in U.S. for summertime but the trend is away from drought east of the Divide.
Discussion: Wet soil moisture patterns are excessive in the Northwest, Mid-South and East Midwest regions while the Southwest and Kansas plus the far northwest Plains are very dry (Fig. 1). The seasonal soil moisture change indicate the Mid-South and northern California have turned wetter (Fig. 2).
Fig. 1: U.S. daily soil moisture ranking show wet AND dry EXTREMES.
Fig. 2: Seasonal U.S. soil moisture change/trend analysis.
Fig. 3-6: The U.S. CAS soil moisture forecast for the U.S. at the end of May/end of July and end of August/end of October 2018.
The CAS soil moisture forecast model is the older version of operational models but has a tendency to outperform the modern CFS V2 model. The CAS soil moisture forecast maintains the Southwest drought through May (Fig. 3) breaking the intensity a bit by July (Fig. 4) as a wetter monsoon is expected. The CAS outlook lingers dry central Plains to Texas through the late warm season (Fig. 5-6). Note that the eastern 40% of the U,.S. is wet for the middle third of 2018.
NOAA issued their latest seasonal drought outlook today. The outlook BOLDY erases drought in the southwest Great Plains, Southeast U.S. and northwest Great Plains (Fig. 7). A wet scenario in this zone increases support for suppressed heat into early summer. The outlook maintains the Southwest U.S. drought.
Fig. 7: NOAA U.S. seasonal drought outlook is indicated.