Tools used in the U.S. Seasonal Drought Outlook (SDO) include the Climate Prediction Center (CPC) seasonal precipitation and temperature outlooks for August-October (ASO), monthly precipitation and temperature outlooks for August, 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, dynamical model output, ASO climatology, and initial conditions such as snowpack and soil moisture. The U.S. Drought Monitor (USDM) valid on July 18 was used for initial conditions. El Niño conditions are present across the equatorial Pacific, and the latest forecasts show this signal strengthening over the next several months with a high likelihood of continuing into the winter.

A below average winter wet season and below-normal precip this year so far leading up to ASO has resulted in deteriorating conditions across the Pacific Northwest and northern portions of the Intermountain West. Long-lead forecast tools favor predominantly above normal temperatures and below normal or equal chances of above, below, and near normal precipitation. As such, drought persistence and additional development of drought is favored across the Pacific Northwest and northern Intermountain West. In the Four Corners region, the North American Monsoon (NAM) circulation appears to be finally establishing itself, although later than it normally does annually. There is some uncertainty among the model guidance with respect to the robustness of the NAM in the short-term. However, long-range forecast tools and guidance suggest an overall weaker NAM circulation than normal during the ASO season. In addition to the record warmth across the Southwest in recent weeks, above normal temperatures are also favored through the end of October, leading to an increased likelihood of drought development across a broad area of the Four Corners, where the recent excessive heat has already resulted in reductions in topsoil moisture. Portions of the central Intermountain West may have continued short-term improvements to long-term drought conditions, residual from the above-normal 2022-2023 winter rainy season, in addition to below normal June temperatures and spotty areas of above normal precipitation over the past 6 months. So despite above normal temperatures being favored and the potential for below-normal precipitation in August, no additional drought development is forecast for the central Great Basin and central Intermountain West by the end of October.

Forecast confidence is high for the Pacific Northwest and northern Intermountain West, moderate for the Four Corners and Desert Southwest, and low for the central Great Basin in the Western region.

Above normal temperatures and near to below normal precipitation are favored over the next couple of weeks across portions of the Northern Plains, increasing the potential for drought degradation and development across some areas. However, with the establishment of the NAM ridge over the Southwest and the associated potential for clusters of rainfall and thunderstorm activity (known as mesoscale convective systems, or MCSs) on its northeast periphery, a wet climatology through at least the first half of the ASO season, improving drought conditions are forecast across the Central and Northern Plains by the end of October, extending into the Middle Mississippi Valley and the western Corn Belt. In addition, ENSO composites favor above normal precipitation and near normal temperatures across much of the central contiguous U.S. (CONUS) during ASO, increasing the potential for improving conditions. In the Northern Plains, short-term drought development is forecast along the Canadian border, where soil moisture percentiles have fallen below the 30th percentile of the historical distribution and above normal temperatures and near to below normal precipitation are favored over the next few weeks. If drought develops it is favored to remain, as long-range temperature and precipitation signals are lacking along the Canadian border

Forecast confidence is moderate for the High Plains region.

Antecedent short and long-term dryness, in addition to favored above normal temperatures through the end of October, favor drought persistence and development across much of southern Texas and southern Louisiana. Elsewhere, antecedent wetness, ENSO composites, the potential for MCS activity, and equal chances of above, below, and near normal precipitation to above normal chances of precipitation over the next one to three months favor drought improvement and removal from for eastern portions of the Southern Plains and the Tennessee Valley.

Forecast confidence is moderate to high for the Southern region.

The first half of the ASO season is a climatologically wetter time of year for much of the Midwest. Additionally, with the NAM ridge beginning to establish itself across the Four Corners region, there is an increased likelihood for MCS activity across the central CONUS, along its northeastern periphery. The seasonal temperature outlook favors equal chances of above, below, and near normal to below normal temperature chances, and the seasonal precipitation outlook favors equal chances of above, below, and near normal to above normal precipitation chances. ENSO composites also indicate wetter signals during ASO when El Nino conditions are present, although potential contributions from El Nino may be lagged a bit, given its recent onset. Across the upper Midwest and northwestern Great Lakes, drought persistence is broadly favored, although there could be localized areas of improvement and degradation throughout ASO.

Forecast confidence is high for the eastern Corn Belt and southern Great Lakes, and moderate elsewhere in the Midwest region.

Drought removal is favored across the Southeast region. Despite warmer than normal conditions being favored through October, ASO is climatologically a wetter time of year across Florida, where moderate to severe drought is ongoing across parts of the western Peninsula. In addition to near to above normal precipitation being favored over the next one to three months, medium-range forecast tools indicate an increased potential for tropical activity across the main development region (MDR) of the Atlantic Ocean, and the western Atlantic. Sea surface temperatures (SSTs) in the Gulf of Mexico and the western Atlantic promote increased moisture availability across the region, increasing the potential for daytime thunderstorm activity, especially early on in the ASO season.

Forecast confidence is high for the Southeast region.

The Northeast has been the beneficiary of several episodes of heavy rainfall over the past month, associated with passing storm systems and a consistent jet stream pattern that has resulted in persistent daytime thunderstorm activity. Despite above normal temperatures favored through the end of October, above normal precipitation chances are also predominantly favored, particularly over the next few weeks. In addition, SSTs in the western Atlantic are running above normal which favors increased moisture along the Eastern Seaboard, and subsequently an increased potential for localized rainfall activity.

Forecast confidence is high for the Northeast region.

Some abnormal dryness has developed over the past one to two months across portions of the southern and eastern Alaska Mainland. However, there have been recent improvements as a result of above-normal rainfall in drier areas in recent weeks. Despite above normal temperatures being favored and weak precipitation signals during ASO, the season is climatologically a wetter time of year, with the mean storm track gradually shifting southward with time toward the month of October. Favoring the wet time of year, no drought development is forecast in Alaska.

Hawaii could see short-term drought removal and/or improvement with the passage of Tropical Storm Calvin on July 19th. However, long-range statistical and dynamical model guidance indicate large probabilities for below normal precipitation across the island chain. Therefore, despite the potential for improvements early on in the ASO season, drought persistence is favored in Hawaii, with the potential for development throughout the islands.

Despite antecedent short-term abnormal dryness and moderate drought in Puerto Rico, long-range precipitation tools favor near to above-normal precipitation through the end of October. In addition, medium-range guidance indicates an increased potential for tropical activity in the central and western Atlantic, which increases chances for additional moisture from potential tropical systems passing through or by the northern Caribbean. Therefore, drought removal is favored for Puerto Rico.

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

Forecaster: Adam Hartman

Next Seasonal Drought Outlook Issued: August 17, 2023 at 8:30 AM EDT