Latest Monthly Assessment -
ENSO conditions currently remain neutral (leaning negative), with the potential for La Niña to develop later in September. During August, drought coverage expanded across the CONUS, mainly in the West. The much below-normal monsoon season and much above-normal temperatures resulted in expansion and intensification in the Desert Southwest and Four Corners Region. The remainder of the western CONUS was dominated by enhanced ridging through much of August, leading to some development in the Central Rockies and Western Plains. Areas east of the Rockies saw a mixture of drought improvement and degradation. Western Iowa and New England saw the most degradation, while most other areas experienced general improvement. An amplified pattern is favored to dominate much of North America during September, with ridging building in the West and mean troughing progressing from the central CONUS into the eastern CONUS during the period. The predicted mean ridging in the West favors above-normal temperatures and below-normal precipitation, favoring drought persistence with some development in the Pacific Northwest, Northern Rockies, and Central Plains. Heavy precipitation is likely during the first week of September, enhancing the likelihood for drought improvement for much of Texas and western Oklahoma. With increasing odds for below-normal precipitation in the latter half of the period, drought persistence is favored for western areas of the Corn Belt. The Ohio Valley and the Northeast are predicted to see some removal and improvement in the first half of September, with above-normal precipitation favored through the Week-2 period. However, some drought will likely still remain for areas experiencing long-term (90 days and beyond) deficits in the Northeast. The Southeast has experienced scattered, persistent rainfall in recent weeks. With the peak of the hurricane season during September, coupled with increased odds for above-normal precipitation throughout the period, no development is likely in this region.
D1 drought (Kodiak Island) and abnormal dryness (D0) developed in portions of Alaska in August. The predicted amplified pattern favors mean southwesterly flow and above-normal precipitation through the first half of September which should be enough to remove D1 on Kodiak Island. In Hawaii, although the western islands have increased odds for above-normal precipitation during the first half of October, a drier airmass is favored for the second half of the month. As such, drought persistence is favored for Hawaii, with some development on the leeward slopes of the Big Island and Kauai. The passage of Isaias in late July and Laura in August eliminated all drought in Puerto Rico, and with the expectation for an active tropical season, no development is expected during September.
Forecaster: Adam Hartman
Next Monthly Outlook issued: September 30, 2020 at 3 PM EDT
Monthly Drought Outlook Discussion