California and National Drought Summary for June 2, 2015
Summary
A series of cold fronts moving southeastward out of the Canadian Prairies brought additional moderate to heavy (more than 2 inches) rains to the water-logged southern and central Plains, including most of Kansas, Oklahoma, and Texas, along with beneficial moisture to the northern Plains and Midwest, early in the period. Based upon estimated monthly state rainfall totals, May 2015 was the wettest month ever in Texas (8.81 inches) and Oklahoma (14.27 inches), incredibly ending the region’s long-term drought within 4-6 weeks (but causing widespread flooding). Over the weekend as a strong cold front finally pushed eastward, the southern half of the Plains finally cleared out while much of the Southeast, mid-Atlantic, and New England reported welcome showers and thunderstorms which ended the unseasonable warmth and eased short-term dryness. Dry conditions and increasing temperatures returned to the Southwest after an unseasonably cool and wet May that led to unexpected green-up of ranges and pastures in parts of southern and eastern California, Nevada, and western Arizona but did nothing to ease the long-term drought, and most-likely added extra fuel for late summer and early fall wildfires once the vegetation dies off. Light showers were enough to keep the Pacific Northwest at status-quo, while a very warm and record dry May (after a wet April), along with little to no spring snowpack, was enough to expand D0 along the southeastern Panhandle of Alaska. Continued subnormal rains across eastern Puerto Rico and low stream flows justified expansion of D0 and D1, and the addition of D2.Great Plains
The incredible southern Plains drought relief continued this week, although the weekly rainfall amounts “decreased” from copious to heavy, and clear skies finally prevailed later in the period. Still, more than 2 inches of rain fell on parts of the Dakotas, western Nebraska, western and eastern Kansas, eastern Oklahoma, and most of Texas except for the Panhandle and southwest. The week’s heaviest rains fell around the Dallas-Ft. Worth region, with locally up to 8 inches. Based upon estimated monthly state averages, May 2015 was the wettest month ever for Texas (8.81 inches) and Oklahoma (14.27 inches), breaking both the former state monthly records by several inches. This has alleviated long-term drought within 4-6 weeks, but unfortunately produced widespread severe flooding. Monitored Texas water supply reservoirs were 83.4% full on June 3, whereas 6-months ago they were at 62.5% full. A few reservoirs in the Panhandle and west-central Texas were still below normal (where D0 and one small D1 area was kept), but nearly every reservoir in the eastern half of the state was close to capacity. With the continued moisture, decreasing or eliminated long-term deficits, and increasing short-term surpluses, 1-category improvements were made across much of Texas, Oklahoma, western and southern Kansas, southeastern Colorado, eastern South Dakota, and northeastern and southwestern North Dakota. Where lighter rains fell (north-central Oklahoma, south-central Kansas, eastern Nebraska, and south-central South Dakota), conditions were maintained. D0 was slightly expanded in northwestern North Dakota (Mountrail County) where long-term dryness still lingered.Hawaii, Alaska, and Puerto Rico
In Hawaii, daily light showers on the windward sides of the islands provided between 1-3 inches of rain for the week, with lesser 7-day amounts (under an inch) on the leeward sides. The moisture was enough to prevent any deterioration but not enough for improvement, thus no changes were made this week.In Alaska, after a very wet April, record May dryness and above-normal monthly temperatures enveloped southeastern sections of the state, with many panhandle stations (e.g. Sitka, Juneau, Petersburg, Wrangell, Ketchikan, Annette Island) measuring less than an inch of May precipitation with normal precipitation ranging from 4-9 inches. May temperatures were also 3 to 5 degrees F above normal, and with a lack of mountain snowpack for spring runoff (a mild winter produced more rain than snow), D0 was added as a watch for possible drought development if June rains fail to materialize.
In Puerto Rico, another week with light rains (less than 0.5 inches) in southern and eastern areas completed a dry May where under 25% of normal precipitation (deficits of 4-8 inches) fell on southeastern sections. With subnormal April rainfall also occurring in the eastern half of Puerto Rico, and USGS 7-, 14-, and 28-day average stream flows dropping to near- or record low flows, D2 was introduced in the eastern interior including Caguas, Gurabo, Juncos, Las Piedras, and San Lorenzo municipalities, with a D1 westward expansion into Naranjito, Comerio, Barranquitas, and Aibonito.
Midwest and Great Lakes Region
Another week of widespread moderate to heavy showers and thunderstorms provided a fitting end to a wet May in the Midwest. More than 1.5 inches of rain fell on northwestern and southern Minnesota, northern Iowa, central Missouri, most of Wisconsin, Illinois, Michigan, and the northern halves of Indiana and Ohio, allowing for a 1-category improvement across much of the region. The rains effectively eliminated abnormal dryness (D0) in most of Wisconsin, southern Minnesota, Michigan, northern Indiana and Ohio, and central Missouri, and D1 was improved to D0 in northwestern and east-central Minnesota, and in central Wisconsin. Where the weekly totals were lower (less than 1 inch) or short-term deficits initially greater, D0 and D1 remained, and this included northern Minnesota, west-central Illinois, northern and southeastern Indiana, and south-central lower Michigan. Overall Midwest major crop progress (planting and emergence) were close to the 5-year average, and crop and pasture conditions were generally favorable.Southeast
Scattered showers and thunderstorms were a daily occurrence across most of the region during the 7-day period, and after a week’s worth of rainfall, significant totals (more than 2 inches) were measured across most of Arkansas, Louisiana, Mississippi, Alabama, central Tennessee and Kentucky, northern and western Georgia, west-central Florida, western Carolinas, and northern Virginia. In contrast, much lighter amounts (less than 0.5 inches) fell on southeastern Virginia, and eastern sections of the Carolinas, Georgia, and Florida. Since much of the area under D0 was short-term dryness, the moderate to heavy rains were enough to eliminate D0(S) in central Kentucky and Tennessee, northern sections of Alabama and Georgia, central Alabama, and southwestern Georgia. The D0 in central Mississippi was shifted westward to best reflect 3 and 6-month lingering deficits, while a small D0 area remained in east-central Alabama due to 90- and 180-day shortages. With the subnormal rainfall along the southern Atlantic Coast, D0(S) was expanded into southeastern Virginia, the eastern Carolinas, and northeastern Florida. In southern Florida, a slow start to the wet season and subnormal rainfall during the normally dry season (since Oct. 1) has accumulated 8-month deficits of 8-9 inches at West Palm Beach, Miami, and Ft. Lauderdale. Accordingly, D0 and D1 was expanded in southeastern Florida, and D2 was added in central Miami-Dade county.The Northeast
: After a very dry and warm May across much of New England and the mid-Atlantic, along with subnormal precipitation during the spring, the region was primed for abnormal dryness and drought expansion this week; however, a late-week surge of moisture combined with a strong cold front generated widespread showers and thunderstorms across the region, effectively halting the expansion of drought. Greatest weekly amounts were found across the eastern Great Lakes region (3-5 inches), western New England (2-4 inches), and along the Northeast Coast (from Maryland and Delaware northeastward into Maine, 2-5 inches). Interior sections of the Northeast (western West Virginia, central Pennsylvania, central New York, northern and eastern Maine), along with most of Long Island, coastal Connecticut, Rhode Island, and Cape Cod, generally received lesser amounts (0.5-2 inches). Since this was the first decent widespread rainfall event in New England in a while, only the areas with the heaviest rains were improved by one category. As of June 2, instantaneous and daily average USGS stream flows quickly rebounded from near- to record low levels to much above normal, but 7-, 14-, and 28-day average flows were still below the tenth percentile. Before the rains, May 31 USDA topsoil moisture was rated short or very short in Maryland (34%), Delaware (79%), New Jersey (51%), Pennsylvania (43%), New York (34%), Rhode Island (70%), and New Hampshire (51%). Surprisingly, pastures and ranges were rated mostly fair to good across the Northeast on May 31, most-likely due to the cold March and cool April weather and slow spring snow melt into the soils, providing adequate subsoil moisture for vegetation during May’s warmth.The West
Seasonably drier and warmer weather returned to the West after unseasonably cool and unsettled conditions occurred during the first 3 weeks of May. As a result, May recorded above-normal precipitation (except along the Pacific Coast) and well below-normal temperatures (except in the Pacific Northwest). With May precipitation normally low, it didn’t take much rainfall to produce well-above normal percentages (e.g. San Diego, CA obs=2.39”, normal=0.12”). An unusual effect of the cool and wet May weather was a green-up of pasture and range vegetation in southern and eastern California and Nevada where extreme to exception drought is widespread and ongoing. Although California and Nevada pasture and range conditions were rated 35% and 50% good or very good on May 31 by the USDA, no improvements were made to the drought depiction as long-term (4-year drought) hydrologic conditions remained dire. In fact, the green-up of vegetation and sprouting of grasses will most-likely provide extra fuel for wildfires once the vegetation dies off later this summer. To depict the short-term wetness, the impact line between SL and L was drawn where May was wet (L-only) versus May was dry (SL) from central Washington southward into southern California. In western and central San Bernardino County, the May rains missed this desert region, and with conditions similar to areas to the immediate west, D3 was expanded into this county. In southwestern Montana, areas west of the divide did not receive the May rains that east of the divide enjoyed, thus D0 was expanded into this region. In contrast, areas east of the divide and north of Yellowstone saw excess May rains, and D1 and D0 was trimmed away there. Elsewhere, no changes were made as light precipitation across the Northwest and eastern Great Basin was enough to maintain status-quo.Looking Ahead
: For the upcoming 5-day period (June 4-8), decent precipitation should occur across the Great Basin, north-central Rockies, central and northern Plains, most of the Midwest and Great Lakes region, and along most of the southern Atlantic Coast States (from Florida northward into Virginia). Little or no rainfall is expected in the Far West, Southwest, southern third of the Plains, and coastal New England. Temperatures should average above-normal in the Northwest, southern half of the Plains, middle and lower Mississippi, and Ohio Valleys. Elsewhere it should be near or slightly below normal.For the ensuing 5-day period (June 9-13), the CPC 6-10 day outlooks, odds favor above-median precipitation in the Southwest, Great Basin, central Rockies and Plains, eastern third of the Nation, and northern Alaska, with subnormal precipitation likely in the Northwest, northern and southern Plains. Above-normal temperatures are favored in the West, northern Plains, and in the Southeast and along the Eastern Seaboard, with subnormal readings limited to central Alaska.
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)
