Watching (Closely) Drying Soil Moisture Conditions

Convective Inhibition in the ECMWF Model
06/22/2020, 12:36 pm EDT
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06/25/2020, 8:12 am EDT
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Fig. 1-2: PDSI identifies where wet soils remain (left). Rainfall needed to end developing-to-drought conditions is increasing (right).

U.S. soil moisture: An exceptionally important climate diagnostic…wet soil moisture zones identify areas most susceptible to flooding from summertime rains and also where clouds/showers are most likely to suppress summertime heat. Dry zones do just-the-opposite. They identify areas most susceptible to anomalous heat risk. Right now wet soil moisture areas caused by the 2017-19 wet regime remains over the Midwest and a new area due to 2020 heavy rains is intact in the Mid-South States (Fig. 1). The wet zones are slowly eroding. Meanwhile areas with rainfall deficits are increasing (Fig. 2). The Northeast is becoming a dry zone warranting a drought watch which includes the Ohio Valley. Texas dryness is becoming extreme. From California to Colorado a general dry pattern continues and is (officially) associated with a drought. Dryness remains intact in Washington while Oregon has recently received beneficial rainfall.

Short-term and medium-range U.S. rainfall pattern: Extreme rainfall is likely the next 2 days in Ontario while southern Texas is hit hard with severe storms and (much needed) heavy rainfall (Fig. 3). The next batch of storms with patchy heavy rains surges across the Midwest States mid-to-late week. Wet weather returns to the northern Rockies this weekend. Outside of these primary rainfall zones the pattern is normally wet or dry and soil moisture conditions will trend drier. The 8-14 day forecast favors increasing influence of tropical moisture in the Gulf of Mexico surging north and interacting with short wave energy in the upper atmosphere to cause a thundery Midwest/Mid-south pattern (Fig. 4). The ECM (model) is much drier.

Fig. 3-4: The NOAA/WPC 7-day rainfall forecast (left) and day 8-14 GFS Ensemble rainfall anomaly forecast (right).