06/12/2022, 1:09 pm EDT

U.S. Soil Moisture Monthly Outlook

Executive Summary: So where is the combination of atmospheric conditions coupled with soil moisture thirst highest in the U.S. during early June? Underplayed by the NOAA U.S. Drought Monitor is continued evolution of potential rapid transition into drought in the East U.S. particularly the Mid-Atlantic region based on the latest Evaporative Drought Demand Index (EDDI) analysis (Fig. 1). The well-understood Southwest to South-central U.S. drought rolls while the Northwest to North-central U.S. EDDI identifies a wet pattern. Fig. 1: Latest Evaporative Drought Demand Index analysis for the U.S.    Fig. 2-3: The EDDI 90-day and 30-day change analysis. Discussion: The 90-day EDDI change analysis reveals the newest harsh drought area is centered on Texas (Fig. 2). Typical of a La Nina spring, the Northern U.S. soils trend wetter and some zones are especially wet. The 90-day EDDI change identifies a trend toward increasing dryness in the Mid-Atlantic States which, along with Texas remains steady in the 30-day change observations (Fig. 3). The Western U.S. Drought is slightly less extreme entering meteorological summer. Conventional soil moisture analysis reveals a super drought across most of the southwest quadrant of the U.S. and also harsh dryness developing in the Coastal Mid-Atlantic (Fig. 4). So far, in June, recent heavy rains have expanded a widening wet zone in the Mid-south U.S. while sudden dryness is easing the wet soil moisture regime across the North-central U.S. (Fig. 5). Fig. 4-5: Current U.S. soil moisture anomaly rankings and June change (so far). The latest 15-day percent of normal precipitation forecast by ECM ENS (Fig. 6) indicates the potential changeable weather pattern ahead. Dry soil areas invite some wet weather (Arizona) while recently expanding wet soil regions (Mid-south States) turn dry and hot. Forecasts using convectional climate models of soil moisture from NOAA are judged not particularly reliable at this time. Instead, reliance on the Climate Impact Company constricted analog (CIC-CA) forecast is chosen as the best guide for drought potential through mid-to-late summer. The precipitation forecast favors more regions of wet weather versus dry zones (Fig. 7). The wet regions outweighing dry zones forecast implies an active Madden Julian oscillation (MJO) and/or above normal strength North American Monsoon. The Northwest U.S. Coast is wetter than normal defeating drought expansion into this zone from the Interior West. The Southwest States engage a more active than normal wet monsoonal pattern but California should remain seasonably dry as harsh drought in that state continues. In the East, the influence of subtropical and eventually tropical rainfall should reverse the current developing drought trend. The dry zones are confined to the Midwest U.S. centered on Illinois and southward to Louisiana. Contributing to the spread of drought is anomalous heat risk which covers most of the U.S. in the CIC-CA JUL/AUG/SEP 2022 outlook (Fig. 8). The most hostile anomalous hot weather risk is centered on Texas and the southwest Great Plains. This zone is at highest risk of extreme drought during summer 2022 (other than California). The anomalous warmth projected for the Midwest States helps to motivate potential drought for later this summer. The Northeast Corridor is also very warm likely due to high humidity once an anticipated wetter pattern emerges. Conclusion: Climate Impact Company adjusts the constructed analog drought forecast for mid-to-late summer slightly (Fig. 9). The CIC-CA forecast emphasizes Texas/southwest Great Plains drought and is adjusted to extend northward through the central and northern Continental Divide States. The California drought remains although Southwest Drought eases due to monsoon rainfall. Drought risk is likely to extend across Iowa to Illinois mid-to-late summer. The East is projected to shift wetter as drought risk backs off, the coastal Mid-Atlantic last to observe that easing risk. Fig. 6-9: The ECM ENS 15-day percent of normal rainfall forecast indicates a pattern change. The CIC-CA precipitation/temperature and PDSI projection for JUL/AUG/SEP 2022.