A hot end to the summer along with a generally suppressed convective regime resulted in numerous areas of drought development across the southern Plains, Midwest and Southeast, while spotty convection brought some relief to the areas where rainfall occurred. Larger regions of degradation spread across the Four Corners states.
In contrast, above-median precipitation brought drought relief to parts of the Pacific Northwest, Northern Rockies, and Northern Plains.
The October-December period typically offers an opportunity for soil moisture recharge as evapotranspiration rates decline. The window for monsoonal moisture across the Southwest closes, while the West Coast wet season begins to ramp up. Climatological precipitation drops off rapidly across the central U.S. and the extreme Southeast, while remaining fairly steady across the eastern Corn Belt and Northeast.
With no ENSO forcing anticipated during the next several months, the CPC monthly and seasonal outlooks were based primarily on a consensus of the dynamical and statistical model guidance as well as long term temperature and precipitation trends.
Hot, mostly dry weather is anticipated to continue for the next several weeks across much of the East, increasing the potential for rapid expansion of short-term drought from southeastern Pennsylvania and southern New Jersey southward to the Florida Peninsula.
Longer range forecasts show enhanced chances for above-median precipitation across the south- and mid-Atlantic states, which would ease drought conditions that do develop. Therefore, drought development favored to persist through the end of December is indicated on this outlook extending from eastern Alabama through the central Appalachians.
Further west, drought persistence is favored for much of the Southwest and southern Plains as climatological precipitation declines, with slow expansion possible across central Texas. Above-median precipitation favored in both short and long term guidance favors drought relief for southern Arizona, while near-term impacts from the remnants of Tropical Storm Imelda favor widespread reduction of drought across eastern Texas, southeastern Oklahoma, and the lower Mississippi River Valley.
The continuation of enhanced moisture into the Northwest followed by the onset of the wet season favors a continuation of drought reduction, while a wet end to September followed by the Autumn recharge season may bring relief to the Midwest and Great Lakes states.
Across Alaska, drought relief is anticipated along and east of the Kenai Peninsula, while enhanced tropical moisture favors gradual drought reduction for Hawaii ahead of the main wet season. Drought persistence is favored for Puerto Rico, but uncertainty is high as the Atlantic tropical cyclone season continues.
Forecast confidence is low for the Southeast Region.
- A regime of widely scattered summer convection and above-normal temperatures prompted numerous changes to drought conditions across the Southeast region, with drought relief across parts of central and southern Alabama and Georgia combining with new drought development along the Piedmont and southern Appalachians.
- Heavy rainfall from Hurricane Dorian reduced drought conditions along the coastline of the Carolinas.
- 60-day observed percent of normal precipitation values indicate that a region encompassing most of Virginia, the western Carolinas and Tennessee southward through much of Florida has rapidly dried out over the past two months, and correspondingly there has been a substantial increase in D0 coverage on the latest drought monitor.
- Mostly dry conditions are favored for much of the Southeast over the next 7 days, with near to below-normal rainfall anticipated to continue in Week-2. Combined with persistently high temperatures, these conditions favor the potential for a late-season flash drought in the Southeast.
- The persistence of any potentially developing drought through the end of December is highly uncertain, particularly along the Atlantic Seaboard and Piedmont, where the monthly and seasonal outlooks favor above-median precipitation and the potential for additional tropical cyclone activity remains. Therefore, drought development indicated on this outlook is limited to a region extending from the Chattahoochee River Basin northeastward into the central Appalachians, although early in the period the drought conditions could potentially be more widespread.
- Given the anticipated dryness early in the period offset by the enhanced chances for above later in the fall, persistence of existing drought areas is maintained for the small D1 areas extending from North Florida through southern Virginia.
Forecast confidence is moderate for the Midwestern Region.
- In the Midwest Region, below-normal temperatures and above-median precipitation across the upper Mississippi River Valley contrasted sharply with recent heat and dryness in the central Corn Belt. Correspondingly, while drought conditions eased over the northern areas, rapid expansion of drought and abnormal dryness was observed along the Ohio River Valley.
- During the next 7 days, widespread heavy rainfall (2-5 inches), partly associated with the remnants of Tropical Storm Imelda, is forecast to overspread Missouri, Iowa, and Illinois, with 1-3 inches favored across the Great Lakes region.
- Lighter accumulations are forecast south of the Ohio River, which may allow drought conditions to continue expanding in the short term.
- The CPC 8-14 day outlook indicates a similar distribution of precipitation, while the monthly and seasonal outlooks maintain equal chances for below-, near-, and above-median precipitation.
- Based on the short term forecasts, drought reduction is favored for eastern Iowa through Michigan and Ohio, while persistence is favored along and south of the Ohio River. Drought development is favored for parts of Kentucky, and while further expansion is possible early in the outlook period, the potential for soil moisture recharge later in the fall may limit the duration of drought conditions.
Forecast confidence is high for eastern Texas and the lower Mississippi Valley, moderate for the Southern Plains, and low for the Tennessee Valley.
- Drought depictions over the last month changed substantially across Texas, with small areas of improvement interspersed with widespread development and expansion across the central portions of the state. Eastern Texas had the most widespread degradation, with many regions north and west of Houston going from drought-free to severe drought (D2) in the last 4 weeks.
- Tropical Storm Imelda made landfall along the northeastern coast of Texas on 17 September, and the remnants of this tropical cyclone are expected to continue producing widespread heavy rainfall across eastern Texas and southeastern Oklahoma. Accumulations near or greater than 10 inches are possible in the vicinity of Houston.
- Due to this extreme near-term event, widespread immediate drought reduction is favored across eastern Texas, southeastern Oklahoma, and northern Louisiana.
- Across the remainder of the Southern Plains, climatological precipitation drops steadily over the next three months, limiting the window for improvement.
- The CPC 8-14 day outlook shows slightly enhanced chances for above-median rainfall across Texas, while the monthly and seasonal guidance maintain equal chances or even favor below-median precipitation.
- Given the lack of a clear wet signal in October, drought persistence is favored across the remainder of the Southern Plains, and enhanced chances for above-normal temperatures favor slight expansion of drought across south-central Texas.
- Elsewhere, drought development is possible across eastern Tennessee, due to the same factors discussed above for the Southeast Region.
Forecast confidence is high for the northern half of the Western Region, and moderate for the southern half.
- A north-south contrast was also observed across the Western Region, with above-normal precipitation observed across the northern tier and a very quiet Southwest Monsoon season.
- The abundant Northwest moisture ate away at drought conditions across Washington, Oregon, and the northern Rockies, while widespread drought development occurred across the Desert Southwest.
- Climatological precipitation ramps up across the Pacific Northwest during OND, while the monsoon season ends for the Southwest.
- Therefore, despite both the short and long term guidance favoring above-median precipitation for the Southwest, the chances for substantial improvements are limited. Drought persistence is the most likely outcome for most of the region, but short-term moisture across southern Arizona may yield some improvement.
- Across the Northwest, widespread heavy precipitation is favored in the short term, and a wet pattern is anticipated to persist through October. Therefore, continued drought improvement is favored.
- The seasonal outlook does indicate enhanced chances for below-median precipitation across Oregon, but the remaining D1 along the Willamette River is likely to be ameliorated early in the period.
Forecast confidence is low to moderate for the Northeast Region.
- Outside of a small area of moderate drought in southern West Virginia, the Northeast region remains drought free.
- Abnormal dryness (D0) has expanded northward into much of West Virginia, Maryland, Delaware, southeastern Pennsylvania, and southern New Jersey, however, due to recent warmth and dryness.
- The pattern of above-normal temperatures and suppressed rainfall is favored to continue through the end of September, which increases the potential for rapid short-term drought development.
- Beyond this period, the CPC October and OND outlooks both favor enhanced odds for above-median precipitation across the mid-Atlantic along and east of the ridge-and-valley Appalachians, and as evapotranspiration rates decrease, conditions become more favorable for soil moisture recharge. Therefore, while drought development during the OND period is likely across southern portions of the Northeast region, much of it may be alleviated by the end of December.
- Expansion of drought is favored for southern West Virginia, where the monthly and seasonal guidance maintain equal chances for below-, near-, and above-median precipitation.
Forecast confidence is moderate for Alaska and Hawaii, and low for Puerto Rico.
- Climatological precipitation decreases across Alaska during OND, but enhanced precipitation favored during October increases the chances for drought improvements along and east of the Kenai Peninsula.
- For Hawaii, OND falls before the wettest time of year, but model guidance strongly favors a wet pattern over the next several weeks. Therefore, drought reductions are the most likely outcome.
- Drought remains across southern Puerto Rico, with model guidance generally depicting suppressed Caribbean convection outside of any potential tropical cyclone activity. Therefore, drought persistence is indicated, but uncertainty is high as the hurricane season continues.