#Drought news: In #CO and #Wy (and much of the SW) the #monsoon has been rather disappointing. 2- and 3-month SPIs are negative (dry), and precipitation shortages are common

Click on a thumbnail graphic below to view a gallery of drought data from the US Drought Monitor.

Click here to go to the US Drought Monitor website. Here’s an excerpt for the areas around and including Colorado:

This Week’s Drought Summary

The highlight of the week was intense and destructive Hurricane Dorian, with sustained winds of 185 mph and a central pressure as low as 911 mbs. Fortunately for the U.S. (as of Sep. 4), Dorian never made landfall along the Southeastern coast; however, while a Category 5 hurricane, it stalled over the northern Bahamas, devastating the islands of Great Abaco and Grand Bahama. For the most part, Florida dodged a Dorian disaster as the hurricane remained stalled over the northern Bahamas, slowly weakened, and finally drifted northward by the period’s end. Some rain bands from Dorian dropped 1-4 inches along Florida’s east coast. Puerto Rico also missed a direct hit from Dorian as it was strengthening into a hurricane to its east, although scattered convection did bring the island some welcome rain. Elsewhere, a series of cold fronts dropped southeastward out of Canada, bringing subnormal temperatures to most of the Nation east of the Rockies, and helping to prevent Hurricane Dorian from tracking westward and making landfall in Florida. The fronts brought light to moderate rain to the northern Plains, upper Midwest, Great Lakes region, and Northeast, while clusters of storms dumped occasionally moderate to heavy (2-6 inches) rains on parts of the south-central Great Plains, lower Missouri Valley, and Southeast. The Southwest monsoon made a partial comeback, bringing light showers to portions of southern Arizona, most of New Mexico, and southwestern Texas, but overall has been a disappointment. The Far West, with high pressure in control, was mostly dry and warm. Light to moderate showers fell along southern coastal Alaska, but it was not enough for any improvement. Meanwhile, increased rainfall across southern sections of the Big Island aided vegetative growth and diminished deficits, thus improvement was shown…

High Plains

Most of the High Plains experienced relatively dry and cool weather, but fortunately the few areas with dryness or drought (northern North Dakota and southwestern Kansas) received well-placed light to moderate rains. In North Dakota, a thunderstorm complex moved across the northern and eastern portions of the state on Day7, dropping 1-3 inches of rain over the D0-D2 area and effectively reducing dryness and drought by 1-category. 60- and 90-day precipitation anomalies were now close to zero, with only longer-term (6-months) deficits still lingering. In southwestern Kansas, 1-2.5 inches of rain fell across the eastern half of the D0-D1 areas, greatly reducing its coverage. In north-central Montana, although precipitation was light (<0.25”) this week, the past several weeks brought light to moderate amounts, and after reassessing conditions at 60- and 90-days, D0 was removed as most indices were normal or moist. In Colorado and Wyoming (and much of the Southwest), after a wet and cold winter and spring, the summer monsoon has been rather disappointing. 2- and 3-month SPIs are negative (dry), and precipitation shortages are common. With this week’s unseasonable warmth, D0(Abnormally Dry) was added across a large portion of the Southwest (see below) to depict the poor summer rains…

West

In the Southwest, the gradual winding down of the southwest monsoon usually occurs in late September. So far, the 2019 southwest monsoon has been mostly disappointing, with parts of Arizona and the Four Corners region experiencing their driest summer on record mostly due to the notable lack of monsoon rainfall. Hot and dry weather occurred this week, although some rains (0.5-2 inches) fell on southeastern Arizona and most of New Mexico. Across most of the region, SPIs are less than -1 at the 30-, 60-, and 90-day time scales. While the longer-term SPIs show better numbers, the short-term stresses are outweighing the long-term values. Evaporative demand has been greater than normal, and even though water supplies are still in good shape, reservoir levels are dropping quicker than usual for this time of year, and stream flows have declined. Therefore, with August SPEIs less than -1.5, 3-month (JJA) precipitation in the lower tenth percentile, little or no rain this week, and 1-week EDDI at D2 or worse, a large area of D0 was added to reflect this short-term dryness. In southwest Colorado and southeast Utah, D1 was added to depict areas that have reported record low JJA rainfall. In Arizona, D0 was expanded across southeastern sections while D1 slightly increased in central areas in response to low SPIs and increased 90-day deficits. For example, Flagstaff, AZ has only received 1.15” of rain since June 15 (driest on record) when 6.10” should have fallen by now, and several nearby stations (Prescott, Heber, Payson, Winslow) have also measured near-record low monsoon totals…

South

While northeastern, southwestern, and southeastern Texas, most of Oklahoma, and northwestern Louisiana received widespread light to moderate rains (1 to 3 inches, locally to 6 inches), little or no rain fell on the Oklahoma Panhandle, southern and central Texas, northeastern Louisiana, and most of Arkansas, Mississippi, and Tennessee. Accordingly, a 1-category short-term deterioration was made in southern and central Texas, but improvement occurred in portions of central Oklahoma and northeastern Texas, including a 2-category improvement (D1 to nothing) where 3-6 inches of rain fell in the latter area. 7-day averaged USGS stream flows dipped below the tenth percentile (much below normal) in south-central Texas where D2 and D3 expanded. Although it was dry in Arkansas, Mississippi, and Tennessee, prior surplus rainfall has left the soil moisture in good shape for now. An exception was in extreme southeastern Tennessee where D0 and D1 increased…

Looking Ahead

During the next 5 days (September 5-9, 2019), Hurricane Dorian will turn north, then northeastward and make a close pass (or landfall) along the Carolina coasts before accelerating quickly off the Northeast coast and into the northern Atlantic Ocean. Heavy rains, gusty winds, and high waves will pound the Carolina coasts, possibly dropping up to 15 inches of rain on coastal sections of South and North Carolina. Elsewhere, an active Southwest monsoon should drop scattered showers across the Four Corners region, while an active northern jet stream should bring light to moderate precipitation to the Pacific Northwest, northern Rockies and Plains, western Corn Belt, and upper Midwest. Little or no rain is expected in California and southern Nevada, the southern half of the Plains, lower Mississippi, Tennessee, and eastern Ohio Valleys, eastern Great Lakes region, and central Appalachians. Temperatures should average above-normal across the southern two-thirds of the Nation and Northwest, and subnormal from the northern Plains eastward to the Northeast.

The CPC 6-10 day outlook (September 10-14, 2019) favors above-normal odds for precipitation in the Southwest, across the northern third of the U.S., and most of Alaska, with diminished rain chances in the Southeast. Above-normal temperatures are expected east of the Rockies, except for subnormal readings favored in New England. West of the Rockies, below normal temperatures are likely in the Intermountain West. Alaska should continue to experience above-normal temperatures.

US Drought Monitor one week change map ending September 3, 2019.

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