Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for July through September 2018 (JAS), various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), the Week 3-4 outlooks from CPC, dynamical models at the seasonal time scale, the 384-hour total precipitation forecasts from several runs of the GFS and the Canadian Model, climatology for the JAS season, and initial conditions.

Thanks to the northward transport of subtropical moisture and associated rains from the western Caribbean Sea across the eastern CONUS several weeks ago, all areas of drought were wiped out over the Northeast and Southeast regions. There are a few areas of abnormal dryness (D0), however, one over New York and New England, and two in Alabama. The abnormal dryness in the Northeast is consistent with steadily deteriorating conditions. As precipitation forecasts beyond Week-1 favor below normal or Equal Chances (EC), this area appears ripe for drought development. However, given the high climatic variability of the region, and the possibility of this area being affected by a tropical cyclone during JAS, confidence is tempered. For the Southeast, precipitation forecasts for the next few weeks favor relatively wet conditions, with EC indicated at the 30-day and 90-day time scales.

Forecast confidence for the Northeast and Southeast is low to moderate.


The primary drought area in the Midwestern United States is focused over northern Missouri and southeastern Iowa. According to the Advanced Hydrologic Prediction Service (AHPS), Percent of Normal Precipitation (PNP) during the last 30 days depicts values within this region between 25-50 percent, with a few localized areas even lower than that. During this same observation period, the Applied Climate Information System (ACIS) Departure from Normal Temperatures (DNT) ranged from 6-8 degrees F above normal. The additional precipitation that would generally be needed to bring the Palmer Drought Index to -0.5, the amount needed to end the drought, is on the order of 3-9 inches. The North American Land Data Assimilation System (NLDAS) depicts low soil moisture in this region as well, with deficits ranging from 2-5 inches (top one-meter, or root zone). In order to obtain early guidance regarding possible flash droughts, an experimental potential flash drought development tool is currently being tested at CPC. This tool focuses only on evaporation-driven events at this time, and does not yet incorporate forecast information, just past conditions. Interestingly, this tool points toward northern Missouri as a possible "hotspot" ripe for flash drought development, or for rapid deterioration of conditions if some drought is already present. However, if the Weather Prediction Center's (WPC) Week-1 precipitation outlook is correct, this region can expect to receive anywhere from 3-7 inches of rain. This is due to a predicted meandering baroclinic zone across this general area, with several waves of surface low pressure sliding along it, and back-to-back 500-hPa troughs. Though the precipitation forecast for the early portion of this drought outlook period appears clear-cut, there remains significant uncertainty regarding this situation throughout the balance of the summer. When rainfall predictions for all time scales are considered cumulatively, there is no strong tilt in the odds for either above or below normal rainfall. Complicating the issue further is the fact that the JAS season is a time of high water demand for crops as they continue to grow, and rainfall amounts need to outpace this demand for water to produce healthy crop yields.

Forecast confidence for the Midwest is low to moderate.


In the South, prolonged severe to exceptional drought (D2 to D4 on the U.S. Drought Monitor) has dominated western portions of both Oklahoma and Texas, and moderate to severe drought (D1 to D2) is currently indicated over most of South Texas and the Arklatex. Thirty-day AHPS PNPs range from 10-50 percent across these harder hit areas of the South. ACIS DNTs for the same period range from 2-8 degrees F above normal, with the largest positive temperature anomalies located farthest away from the Gulf Coast. The additional precipitation needed to bring the PDI to -0.5 ranges from 6-12 inches over much of this area. NLDAS soil moisture anomalies (root zone) show anywhere from 1 to locally as much as 5 inches below normal as of June 13th. Two general areas of improvement and/or removal are indicated on the map; one over portions of Oklahoma and Arkansas (due to the previously mentioned baroclinc zone), and the other in southern and eastern Texas, due to the influx of tropical moisture at this time. In-between these two projected rainfall regions (Arklatex region and north-central Texas), where a rainfall minimum is predicted, drought is likely to either persist or develop.

Forecast confidence for the South is moderate.


Across the High Plains region, the AHPS PNP pattern for the past month reveals the drier areas to be eastern South Dakota, southeastern Nebraska, much of Kansas and Colorado, and southwestern Wyoming. The lowest PNP values are located from Colorado into southwestern Wyoming, and scattered parts of Kansas (10-25 percent). For the other areas mentioned, PNPs fell into the 25-75 percent range. ACIS DNTs for the past month ranged from 6-10 degrees F above normal over eastern portions of the region, and 2-6 degrees F above normal over western portions of the region. Most of the High Plains region is anticipated to receive moderate to heavy rain (0.5-4.0 inches, with the greatest amounts forecast in eastern Nebraska) during Week-1, except for North Dakota which lies farther away from the predicted position of the mean baroclinic zone. During Week-2, the situation is reversed with North Dakota having the best chances for above normal rainfall. Beyond Week-2, the rainfall outlooks call for EC in the High Plains region. The heavy rain amounts anticipated early in the drought outlook period favor the removal of drought in southeastern Nebraska, but the lack of a strong wet signal across the Dakotas favors drought persistence.

Forecast confidence for the High Plains region is low to moderate.


The 30-day AHPS PNP pattern is generally consistent with a climatologically dry time of year across the West. This is especially pronounced across most of California, southern Nevada, Utah, and western and northern Arizona, where PNP values range within the lowest quartile of the historical distribution. The remnants of tropical cyclone Bud and an approaching mid-level trough resulted in 0.5-1.5 inches of rain (locally greater) across parts of Arizona and New Mexico during the past week. With the climatological onset of the Southwest summer monsoon only two weeks away, it suggests that the region may be off to a good start. Elsewhere in the West, dry conditions have returned to the Pacific Northwest, with moderate to severe drought (D1 to D2) indicated east of the Oregon Cascades. Drier conditions were noted during the past 30-days across northwestern Montana and northern Idaho. In contrast, large precipitation excesses (30-day PNPs 150%-400% of normal) are indicated over eastern and southeastern Montana. The primary factor to consider for the southern half of the West is the summer monsoon, with the latest projections promoting a robust event this year. When rainfall outlooks for all time scales out to a season in advance are considered, drought improvement is deemed most likely for the Four Corners region. CPC's monthly rainfall outlook for July depicts probabilities of 50%-59% in much of this region, while the seasonal rainfall outlook for JAS predicts 40%-49% probabilities in this same general region though offset slightly north and west of where the highest monthly probabilities are. Though CPC's monthly and seasonal rainfall outlooks depict above normal rainfall extending into much of Nevada and southern California, the probabilities are modestly above climatological odds, and are not expected to result in changing the status of the drought in these two areas. For the northern half of the West, (notably in central and eastern Oregon), most rainfall forecasts favor below normal rainfall, which favors the continuation of drought conditions in that area.

Forecast confidence for the West is moderate (in the Monsoon area) to high (in Oregon).


In Hawaii, most of the rainfall during the past month occurred over the northeast-facing windward slopes, while many leeward areas remained relatively dry. Several brief disruptions in the trades occurred, which allowed land and sea breezes to dominate local conditions. Drought development (D0) is favored during the next several months over the leeward slopes of the archipelago. Only small areas of abnormal dryness (D0) exist near the coast in southern Alaska, where precipitation forecasts at nearly all time ranges call for above normal precipitation. Abnormal dryness (D0) has expanded across much of the southern coast region of Puerto Rico, but with JAS being well within their traditional rainy season, this area of recent dryness is unlikely to last throughout the period.

Forecast confidence for Hawaii, Alaska, and Puerto Rico is moderate.


Forecaster: Anthony Artusa

Next Seasonal Drought Outlook issued: July 19, 2019 at 8:30 AM EDT