California and National Drought Summary for June 9, 2015
Summary
The NCEI (formerly NCDC) May 2015 precipitation total for the contiguous U.S. was the wettest May and month of any month in the 121-years of record keeping. State-wise, it was the wettest May in Texas, Oklahoma, and Colorado, and one of the top 5 wettest Mays in Utah, Kansas, Wyoming, Arkansas, and South Dakota. With those statistics, it is not surprising that nearly all drought from late March has been eliminated in the Plains, Midwest, and central Gulf Coast. In addition, wet spring weather in the Great Basin and Four Corners Region has continued into June, necessitating improvements to parts of these areas. During this week, stalled or slow-moving cold fronts in the north-central Plains and along the southern Atlantic and eastern Gulf Coasts triggered scattered showers and thunderstorms, some locally heavy, in parts of the northern and central Plains, upper Midwest, central Corn Belt, and from the Delmarva Peninsula southward into Florida. During the weekend, moisture from the remnants of eastern Pacific Hurricane Andres was pulled into the Southwest, producing light to moderate showers in central Arizona, southeast Utah, southwest Colorado, and New Mexico. Late in the period, additional moisture from former Pacific Hurricane Blanca streamed northward, poised to generate additional showers in the Southwest, including California. As the slow-moving cold front finally tracked far enough eastward, light to moderate rains fell on the eastern Tennessee Valley, mid-Atlantic, and western New England. Dry weather finally allowed the southern Plains to recover from weeks of copious rains and severe flooding, with mostly dry weather also occurring in the lower Mississippi and western Tennessee Valleys. Mostly dry weather continued in drought areas of Puerto Rico and Hawaii, but decent rains (2 to 8 inches) finally returned to the southeastern Panhandle of Alaska.Great Plains
Moderate to heavy rains were reported across portions of the northern and central Plains, including a band of 4-8 inches in southeastern Nebraska, northeastern Kansas, and northwestern Missouri. Additional improvements were made where the rains (generally more than 2 inches) erased or greatly diminished 60-, 90-, or 180-day deficits, and this encompassed eastern Montana and western North Dakota, southeastern South Dakota and northeastern Nebraska, southwestern and southern Nebraska, small sections of D0 and D1 in western Kansas and the Panhandles of Oklahoma and Texas, and in north-central Oklahoma. In Texas, mostly dry weather aided flood recovery efforts to continue, allowing for a re-assessment of conditions with more stable reservoir levels that required some changes to the D0 areas in west-central Texas. As of June 10, Texas monitored water supply reservoirs stood at 83.6% full, with some reservoirs still less than 40% full in Coke, Tom Green, and Mitchell counties – hence the lingering D0(L) near the San Angelo area. Additional decent rains should be enough for continued improvements in the Dakotas and Nebraska, but longer-term hydrologic drought conditions (e.g. low reservoirs) will require a longer span of surplus rains (inflow) to alleviate.Hawaii, Alaska, and Puerto Rico
In Hawaii, generally light showers (less than 0.5 inches, with a few isolated stations measuring over an inch) fell on the windward sides of the islands, with little or no rain on the leeward sides. On the Big Island, some ranchers reported dryness along the lower elevations of the Kau District, thus D0 was expanded into southeastern sections of the Big Island. In northern sections, FSA received reports of pasture degradation near Puukapu (near Waimea) which forced herd relocation, therefore D1 was extended around Waimea. The rest of the islands stayed at status-quo.In Alaska, welcome and heavy rains finally returned to the southeastern Panhandle, with weekly totals of 2 to 8 inches from the Kenai Peninsula eastward to Ketchikan. This came after a record dry May in the same region, so it will take additional rains to erase the accumulated May deficits (and D0). Farther north, light rains (0.2 to 0.9 inches) maintained conditions across the rest of the state.
In Puerto Rico, although 2 to 6 inches of rain fell on northwestern areas, little or no rain fell on southern and eastern sections of the island where the drought was most pronounced. With major degradations made last week, no changes were done this week, although a continued lack of rain during June would most likely lead to additional deterioration in the upcoming weeks. In San Juan, less than 40% of normal rain has fallen since March 1 (a bit over 5 inches), the third such driest period on record and driest since 1975. In some areas of San Juan, rationing of water is occurring, due in part to both lack of rain and sedimentation problems with the Carraizo Dam.
Midwest and Great Lakes Region
More widespread moderate to heavy rains (2 to 5 inches) covered the upper Midwest and middle Mississippi Valley, continuing the wet pattern observed during May. More than 1.5 inches of rain was observed across much of Minnesota, northern Wisconsin, Illinois, and northern Indiana, with locally much higher amounts. These beneficial rains fell on the D0 and D1 areas of Minnesota, Wisconsin, Illinois, and northern Indiana, allowing for continued improvement (1-category) in these states. The exceptions to this occurred where lower totals were measured, namely east-central Minnesota (less than an inch), lower eastern Michigan (less than 0.5 inches), and in the lower Ohio Valley (southern Indiana and Ohio, eastern Kentucky). These areas were left unchanged, except in the lower Ohio Valley where subnormal rains occurred during the past 60-days, leading to growing short-term deficiencies of 3 to 6 inches. Accordingly, D0 was extended northward and eastward to account for these shortages. Overall, the crop, pasture, and moisture conditions in the Midwest generally fared well as of June 7, with Kentucky (15%) and Ohio (12%) reporting the largest percentages of topsoil moisture rated short to very short, according to NASS/USDA.Southeast
Scattered showers and thunderstorms fell on eastern portions of the Southeast, with rainfall totals of 2 to 4 inches reported in eastern Tennessee, southern Virginia, the western and coastal Carolinas, extreme northern and southern Georgia, and parts of central and southern Florida. Little or no precipitation fell on western sections of the Southeast. With deficits accumulated from short-term abnormal dryness, rainfall exceeding 2 inches was generally enough to eliminate the D0(S) in southern Virginia, southwestern North Carolina, western South Carolina, northern edges of the D0 and D1 in southern Georgia, and the western edges of the D0 and D1 in southern Florida. In contrast, no rain fell on north-central Florida (near Tallahassee), adding to the 90-day deficits of 2 to 4 inches; thus D0 was expanded into this area. Elsewhere, light rains in the south-central Appalachians, central Carolinas, and southern sections of Georgia and Florida were enough to maintain conditions but not improve them.The Northeast
After last week’s late period rains, mostly dry and cool weather enveloped the region until another late period rain event from a slow-moving cold front dropped light to moderate totals (1 to 3 inches) on western New England, the mid-Atlantic, and central Appalachians. Slight improvements were made where the amounts were large enough to diminish or erase short- and medium-term deficits, and this included the Finger Lakes region of western New York, south-central Pennsylvania, and northern Maine. Little or no rain fell along coastal New England, but after last week’s rains and ongoing rains occurring after the 12Z Tuesday cutoff, conditions were left unchanged. USGS stream flows somewhat improved in the short-term (1- and 7-day averages), but longer-term values (14- and 28-day averages) still showed flows in the lower tenth percentile mainly in the D1 areas. In contrast to the improvement near the Finger Lakes region, a bit of D0 was extended into Erie and Wyoming counties near Buffalo, NY, after reassessing that area.The West
Moisture from the remnants of Pacific Hurricane Andres triggered showers and thunderstorms in the Four Corners region, including 0.5-3 inches in central and northeastern Arizona, southeastern Utah, southwestern Colorado, and most of New Mexico. Light showers (less than 0.5 inches) also fell on parts of the Great Basin. With much of this region experiencing an unseasonably cool May and wet spring (out to 90-days) after a warm and dry winter, some impacts from this cool and wet weather have been recently observed. SPI values have become “wetter” out to 12- and 24-months in normally semi-arid locales (e.g. Nevada, Utah, Arizona, New Mexico) as have other tools and products. This makes sense as long-term drought is less severe as one moves east from California (and precipitation normally decreases). To represent this, some 1-category improvements were made in areas where the largest totals and 90-day surpluses were located, along with visible impacts. This included central (D1 to D0) and northeastern (D3 to D2) Arizona, southeastern Utah and southwestern Colorado (D1 to D0), northwestern Utah (D3 to D2), northeastern Nevada and south-central Idaho (D2 to D1), and a small area of west-central Nevada (D4 to D3, Pershing County). In the latter area, however, agriculture still depends on irrigation from upstream reservoirs or ground water pumping, and this water source has not improved with the recent rains as Rye Patch reservoir was at 9% of its average storage on May 31. This has resulted in little or no water deliveries and many fallow fields – but based strictly on the area’s current soil moisture, nearly all indicators pointed toward D3. Impacts farther east near Elko were more numerous and included 3-7 inches of May rain and continuing rains into June, widespread thick grass growth, recharge on formerly dry springs, and dirt tanks collecting runoff. Unfortunately, this build-up of vegetation will lead to extra fuel for late summer and fall wildfires if hot and dry weather returns and cures the vegetation. But for now, the recent rains and cool weather have improved pastures and range ratings into good to excellent categories on June 7. This included: California (35%), Nevada (50%), Utah (65%), Colorado (57%), New Mexico (49%), and Arizona (43%), according to USDA/NASS.In contrast, another week of unseasonably warm and dry weather, in addition to a dry spring (and dry and warm winter), has lowered USGS monitored 28-day averaged coastal streams to near- and record lows in California’s Humboldt and Mendocino Counties – that count on spring rains for flow – from D2 to D3. Similarly, along coastal Oregon and Washington, 28-day average USGS streams have also fallen below the tenth percentile, and D1 was expanded to account for the low values. In the Olympic Peninsula of Washington, precipitation deficits have increased out to 60-days, and record low stream flows have surpassed the previous low flows in 2001, including trenching on the Siebert Creek to aid salmon migration. Accordingly, D1 was expanded to include the Olympic Peninsula.
Looking Ahead
For the upcoming 5-day period (June 11-15), moderate to heavy precipitation (1.5 to 4 inches) is expected from the central Rockies and south-central Plains northeastward into western New England. Light to moderate rains are also predicted along the central and eastern Gulf Coast, while unseasonable rains (up to 1.5 inches) are forecast for the Sierra Nevada and Great Basin. Moisture from the remnants of Pacific Hurricane Blanca triggered showers across most of the Southwest (including California) on June 9 and 10. Elsewhere, little or no rain is expected in the Northwest and desert Southwest, with only light totals in the southern Great Plains, Tennessee Valley, and along most of the Atlantic Seaboard (except Florida). 5-day temperatures should average above normal in the Far West, northern Rockies and Plains, Ohio Valley, and mid-Atlantic. Subnormal readings are expected from the Southwest northeastward into the Great Lakes region, with seasonable temperatures elsewhere.For the ensuing 5-day period (June 16-20), the CPC 6-10 day precipitation outlook favors above-median chances in the Nation’s midsection (Plains and Midwest) and Northeast, with sub-median precipitation likely in the Northwest, Southeast, and across southern Alaska. Above normal temperatures are favored in most of the lower 48 States and Alaska, with subnormal readings likely in the Pacific Northwest.
Author(s):
David Miskus, NOAA/NWS/NCEP/CPC
Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.Drought Intensity Categories
D1 ... Moderate DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
