Tools used in the U.S. Seasonal Drought Outlook (SDO) included the Climate Prediction Center (CPC) temperature and precipitation outlooks for July through September (JAS) 2019, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), the Week 3-4 outlooks and tools from CPC, dynamical models at the monthly and seasonal time scales, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for the JAS season, and initial conditions such as soil moisture. The oceanic and atmospheric conditions reflect weak El Niño conditions which should continue into the Northern Hemisphere fall 2019.
In the West Region, drought is restricted to parts of the Pacific Northwest, the far northern Intermountain West, with a separate areas in northeasternmost Montana and also western New Mexico. From Washington and northwestern Oregon thru the northern fringes of the Idaho Panhandle and adjacent Montana, drought is forecast to persist, expanding into north-central Oregon, most of Washington, and a larger part of the Idaho Panhandle and adjacent Montana. Generally cooler and wetter than normal conditions are expected through most of the last half of June, But odds significantly favor above-normal temperatures for July-September, with no tilt of the odds in either direction for precipitation. In addition to the temperature forecast, precipitation climatology drives this forecast. Typically, only 5 to 15 percent of yearly precipitation falls during July-September, making it difficult for any significant precipitation deficits to improve, even with above-normal precipitation. In northeasternmost Montana, July-September leans slightly wet compared to the rest of the year, but seasonably warm to hot weather often mitigates much of the benefit, allowing significant soil and plant moisture loss. June is the wettest month of the year, then normals slowly decline from July through early autumn. Surplus precipitation is expected through the end of June, but neither dry nor wet conditions are favored for July-September while warmer than normal conditions are expected from the last half of June through the forecast period. At this time, it seems unlikely that enough rain will fall early in the period to bring lasting drought relief that would carry through September, and with warmer than normal conditions favored, persistence seems the best forecast in the region. The last vestiges of what was a large and protracted drought in the Four Corners States covers part of western New Mexico. This final remnant should be removed by the end of September. Odds favor above-normal precipitation for July-September as a whole, which is the wettest time of the year here. Confidence, however, is reduced by enhanced chances for warmer-than-normal weather through the period, and a possible late onset to the monsoon season.
In the West region, forecast confidence is high for drought persistence and moderate for drought expansion in the Northwest, moderate for persistence in northeastern Montana, and moderate for removal in western New Mexico.
The drought in northeastern Montana extends eastward through much of the northern tier of North Dakota. Drought is expected to persist through September here, with some expansion possible eastward into northwestern Minnesota. July-September leans slightly wet compared to the rest of the year, with 35 to 40 percent of annual precipitation typically recorded, but seasonably warm to hot weather often mitigates much of the benefit, allowing significant soil and plant moisture loss. June is the wettest month of the year, then normals slowly decline from July through early autumn. Surplus precipitation is expected through the end of June, with more than an inch expected over the next week, but neither dry nor wet conditions are favored for July-September. But even without enhanced chances for subnormal precipitation, the areas east of the current drought region are beginning to feel the effects of abnormally dry weather, and drought is expected to push into the region by the end of September, though with low confidence.
Forecast confidence is moderate for persisting drought and low for expanding drought in the High Plains region.
The southern reaches of Texas have turned dry, with moderate drought developing in a few small patches. Above-normal temperatures are favored throughout the period in this area, already quite hot climatologically. July and August are a bit drier than most other months of the year, which decreases the chances for significant beneficial precipitation during these months. September, however, is by far the wettest month of the year, and there's no way to tell how conditions will evolve this far in advance. In addition, heavy precipitation from a tropical system could bring relief even during an otherwise drier-than-normal period. Due to expected conditions and climatology during July and August, persistence and some expansion is forecast; however, September could bring anything from broad relief to rapidly-increasing precipitation deficits, making this a low confidence forecast.
Forecast confidence is low in the South region.
In the Midwest region, drought is forecast to expand into northwestern Minnesota, though with low confidence (see the High Plains region discussion for more details). Drought is the last thing most other areas in the Midwest are worried about, with surplus precipitation and flooding their primary concerns. There is no drought in the region currently, and outside northwesternmost Minnesota, development seems unlikely
Forecast confidence is low in northwestern Minnesota, and high for most other parts of the Midwest Region.
Drought had broadly expanded through much of Georgia and the South Atlantic coast until this past week, when heavy rains brought relief to many of the areas of short-term development. Continued surplus precipitation is expected in most of the current drought areas through the last half of June, But odds favor neither precipitation extreme for July-September. Still, the El Niño, though week, would correlate to at least periods of surplus precipitation, likely improving or removing drought in most areas. The central Carolina coast is the exception, with persistence expected there. Short-term precipitation looks less robust than in areas farther south, and the weak El Niño correlation with wet weather does not extend this far north. A tropical system, however, could squelch drought even if the rest of July-September is drier than normal, and this reduces confidence.
Forecast confidence is low for the Southeast Region.
The Northeast region has remained drought-free since early November, and development is unlikely through the end of September.
Forecast confidence is moderate to high for the Northeast Region.
Drought has intensified in the southern Alaska Panhandle, with areas of severe to extreme drought developing this past month. June-August is a relatively dry time of the year in the region, with precipitation typically on the increase in September. Given this and the intensity and duration of the drought here, persistence seems likely.
Forecast confidence is high for Alaska.
July-September is expected to be wetter than normal across much of Hawaii. Drought conditions, however, are limited to the leeward parts of the islands, where this is a dry time of year. This climatology makes even above-normal rainfall unlikely to bring significant relief.
Forecast confidence is moderate to high for Hawaii.
Drought coverage slowly increased across Puerto Rico this past month, and some dynamic models significantly favor drier than normal weather through September, as do conditions historically observed during El Niño episodes. But conidence is reduced by the potential for tropical systems, which can remove drought conditions, even during a generally drier-than-normal three-month period.
Forecast confidence is moderate for Puerto Rico.
Forecaster: Rich Tinker
Next Seasonal Drought Outlook issued: July 18, 2019 at 8:30 AM EDT