Highlight: Wet soil moisture regime in Central U.S. suggests more above normal precipitation for spring/early summer.
Fig. 1: A fantastic amount of the U.S. is observing near record to record soil moisture. Indicated are the soil moisture rankings from the 1895-2019 climatology.
Discussion: Soil moisture rankings based on 1895-2019 climatology are amazingly soaking wet with record or near record values across much of the Central and East U.S. (Fig. 1). Dry zones in the West are constricting. The super wet regime has been enhanced the past 90 days by a prevailing upper air pattern featuring a West Coast trough and upper ridge over the Bahamas (Fig. 2). On average, low-to-mid level flow in the atmosphere has been from warmer-than-normal ocean surfaces of the Southeast Pacific and Western North Atlantic basins. During the past month the upper trough in the West has strengthened while the ridge amplifies on the East Coast further strengthening dynamics to generation excessive precipitation.
Fig. 2: The 500 MB anomalies depict the average upper air pattern generating U.S. climate the past 90 days.
Despite the very wet soil moisture signature across the Southeast and East U.S. the February trend has been much drier (Fig. 3) as the upper ridge pattern has amplified blocking incoming super wet weather from the west (until yesterday). Note the dramatic wet change during February in California. The seasonal change emphasizes wetter conditions in the Missouri Valley and drier conditions in the Mid-Atlantic and western Gulf of Mexico region (Fig. 4).
Fig. 3: U.S. soil moisture ranking on Nov. 25, 2018.
Fig. 4: U.S. soil moisture ranking on Nov. 25, 2018.
The (limited) NCEP CAS soil moisture forecast indicates the wet soils across the Central U.S. continue through springtime (Fig. 5). The eastern wet signature may fade but does not end. California enters springtime with wet soils and eliminated drought.
The GFDL forecast model indicates an upper ridge pattern will form over warm SSTA regions in the northeast Pacific and off the U.S. East Coast plus over an emerging dry/drought zone in Mexico. In-between the ridge areas low pressure spawns a wet pattern across the Great Plains (Fig. 6).
Fig. 5: NCEP CAS soil moisture anomaly forecast for the U.S. for the end of March and end of May.
Fig. 6: The GFDL precipitation rate anomaly forecast for APR/MAY/JUN 2019.
In California where another intense storm is taking place the next 2 days the percent of snowfall water equivalent is escalating rapidly and extends across the Great Basin (Fig. 7). Interior Northwest drought was expected to develop this winter/early spring season but that forecast is now in doubt. The Southern Rockies are drier than expected.
Fig. 7: The % of normal snow water equivalent for the West U.S.