#Drought news: Some improvement in Central #Colorado, SW US megadrought

Click here to go to the US Drought Monitor website. Here’s an excerpt:

The current U.S. Drought Monitor period was dry through much of the Midwest and Plains states. Dryness also dominated much of Idaho, the interior regions of Washington and Oregon, much of California and Nevada, and the Southeast. A slow-moving system brought with it soaking rains from eastern Illinois into the Mid-Atlantic. Some areas of the Mid-Atlantic into Virginia and North Carolina recorded over 5 inches of rain with this event. The soils were primed to soak in the moisture and little runoff was observed, as short-term dryness had dominated this area. Eastern Idaho, northwest Wyoming and central Montana all had good rains this week as well as some of central and eastern Arizona, into western New Mexico. Temperatures were cooler than normal over the coastal regions of the Pacific Northwest and into northern California as well as Arizona where the wet conditions were observed. Much of Texas and Louisiana were cooler than normal; below-normal temperatures also extended up the Mississippi River Valley into portions of Kentucky and Tennessee. Warmer than normal temperatures dominated much of the Rocky Mountains, Central and Northern Plains, Upper Midwest, and East Coast. Some departures in eastern Montana were 6-8 degrees above normal…

High Plains and South
Temperatures were warmer than normal over the northern and central Plains while they were cooler than normal over most of Texas, Louisiana and southern portions of Arkansas and Oklahoma. Portions of Nebraska, South Dakota, and North Dakota did pick up some precipitation this week, but the region was generally dry, again helping with fall agricultural activities and crop maturity. Due to the recent patterns, the moderate drought was eliminated from North Dakota, with only a few pockets of lingering D0 remaining. The recent pattern allowed for an assessment of conditions in western South Dakota, where extreme drought was reclassified as severe drought and the extent of severe drought and moderate drought was also reduced. In southwest South Dakota, the recent dryness in the area did allow for the slight expansion of moderate drought and abnormally dry conditions. In Nebraska, the abnormally dry conditions were improved in the western and central portions of the state. Dryness over the last 30-60 days has allowed for abnormally dry conditions to be introduced into southwest Kansas and the Oklahoma and Texas panhandles. In south Texas, moderate drought and D0 were also expanded slightly, and a new pocket of D0 was added along the Gulf Coast. Northeast Texas had more expansion of both moderate drought and D0 conditions this week as a short-term dry pattern continues. Oklahoma had some expansion of severe and moderate drought in the eastern portions of the state, but this may be short-lived as decent rains fell over the expanded area after the data cutoff for the week. Abnormally dry conditions were expanded in eastern Oklahoma, western Arkansas and central Louisiana as well this week…

The new water year started over the West with some rain along the coastal regions of northern California, Oregon, and Washington as well as much of central and eastern Arizona. Areas in eastern Idaho, southwest Montana, and northwest Wyoming also recorded widespread precipitation this week. Temperatures were warmer than normal from the Great Basin into the Rocky Mountains, with departures of 6-8 degrees above normal. Most other areas were normal to cooler than normal along the west coast, with departures there of 2-4 degrees below normal. Improvements were made this week to the moderate drought in southwest Washington and extreme northwest Oregon.

Accordingly, some improvements were also made to the abnormally dry conditions in this area. Abnormally dry conditions also improved in central Colorado, southwest Wyoming and north central Wyoming in response to the most recent wet pattern. An assessment of conditions in northeast Wyoming led to a reduction in severe drought, similar to what was done in the Black Hills of South Dakota. Arizona saw D0 conditions improve in the southeast and northwest portions of the state where the greatest rains fell…

Looking Ahead
Over the next 5-7 days, many across the Southeast and along the eastern seaboard will be watching to see what Hurricane Matthew does. There is a potential for significant rains over drought areas, so it will be watched closely. Precipitation is anticipated over much of the central United States from New Mexico northeastward into the Great Lakes, with some areas projected to receive 2-3 inches of rain. Another storm system will impact the Pacific Northwest, bringing with it heavy rains along the coastal regions of Washington and Oregon. Temperatures during this time remain above normal, with only those areas along the coastal region, where rain is expected, projected to record temperatures near normal or slightly below.

The 6-10 day outlooks show all of the United States and Alaska having above-normal chances of recording temperatures that are above normal; the greatest chances are in the Plains. Precipitation during this time is anticipated to be greatest over the Pacific Northwest. There are higher chances of below-normal precipitation along the East Coast and in the Plains.

A new peer-reviewed report Relative impacts of mitigation, temperature, and precipitation on 21st-century megadrought risk in the American Southwest (Toby R. Ault, Justin S. Mankin, Benjamin Cook, and Jason E. Smerdon) has recently been released by Science Advances. Here’s the abstract:

Megadroughts are comparable in severity to the worst droughts of the 20th century but are of much longer duration. A megadrought in the American Southwest would impose unprecedented stress on the limited water resources of the area, making it critical to evaluate future risks not only under different climate change mitigation scenarios but also for different aspects of regional hydroclimate. We find that changes in the mean hydroclimate state, rather than its variability, determine megadrought risk in the American Southwest. Estimates of megadrought probabilities based on precipitation alone tend to underestimate risk. Furthermore, business-as-usual emissions of greenhouse gases will drive regional warming and drying, regardless of large precipitation uncertainties. We find that regional temperature increases alone push megadrought risk above 70, 90, or 99% by the end of the century, even if precipitation increases moderately, does not change, or decreases, respectively. Although each possibility is supported by some climate model simulations, the latter is the most common outcome for the American Southwest in Coupled Model Intercomparison 5 generation models. An aggressive reduction in global greenhouse gas emissions cuts megadrought risks nearly in half.

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