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MAY 2015


3-9: Tropical Storm Ana formed east of the Carolinas on May 7 and moved inland near Myrtle Beach, SC, around daybreak on May 10. Although Ana was the earliest named storm to make a U.S. landfall in the satellite era, impacts were minimal other than rough surf, gusty winds, and locally heavy showers. Farther west, heavy showers and locally severe thunderstorms hammered the Plains. Weekly rainfall totals in excess of 4 inches were common across Oklahoma and northern Texas, while most areas from central Texas to South Dakota received at least an inch. However, the Plains also endured several rounds of severe thunderstorms, including dozens of tornadoes.

Elsewhere, the West also experienced a pattern change, with cooler weather easing irrigation demands in California and the Desert Southwest. Significant, late week snow accumulated across the parts of the northern Intermountain West and the central Rockies, but scattered showers provided mostly inconsequential relief in drought-stricken California and the Great Basin.

 Early week rainfall was heaviest in the south-central U.S., where Lubbock, TX, weathered its third-wettest day in May behind 4.32 inches on May 23, 1941, and 3.71 inches on May 6, 1949. On May 4, Lubbock’s calendar-day rainfall totaled 3.42 inches. Other daily record amounts for May 4 included 1.87 inches in Salina, KS, and 0.75 inch in Albuquerque, NM. The following day, record setting amounts for May 5 reached 3.84 inches in Austin (Camp

Mabry), TX, and 1.11 inches in Cedar City, UT. For Cedar City, it was the fifth-highest daily total on record during May. Starting on May 6, locally torrential downpours across the central and southern Plains accompanied the year to date’s biggest tornado outbreak. In a 24-hour period on May 6-7, rainfall totaled 6.65 inches in Lincoln, NE. Of Lincoln’s rainfall, 3.77 inches fell on the 7th, representing the wettest May day on record in that location (previously, 3.35 inches on May 5, 2007). Farther south, Oklahoma City, OK, received 7.10 inches on the 6th, marking its highest daily total on record during May (previously, 6.64 inches on May 8, 1993). As many as four dozen tornadoes were spotted on May 6 from southeastern Nebraska to central Texas. Meanwhile, widespread, soaking rain finally arrived on May 6 in South Dakota, where Rapid City (1.61 inches) and Aberdeen (1.24 inches) netted daily-record amounts. Late in the week, another powerful spring storm began to unfold across the West. In Nevada, Elko received 2.0 inches of snow on May 7. On the 8th, Bishop, CA, received its first trace of snow in May since May 13, 1998. Bishop also experienced its fourth-wettest May day, with 0.55 inch falling on May 8. Elsewhere in California on the 8th, Mt. Palomar received an impressive daily record total of 1.65 inches. At week’s end, heavy precipitation and isolated tornadoes returned to the nation’s mid-section, while snow blanketed parts of Wyoming and neighboring states. On May 9, several dozen more tornadoes struck the central and southern Plains. In Nebraska, daily record precipitation totals for the 9th reached 2.91 inches in Scottsbluff and 2.90 inches in Sidney. Official snowfall for May 9-10 totaled 13.0 inches in Rapid City, SD; 5.6 inches in Flagstaff, AZ; 5.3 inches in Cheyenne, WY; and 4.0 inches in Denver, CO. Farther east, Tropical Storm Ana neared the Atlantic Coast at week’s end, with wind gusts clocked to 58 mph (on May 9) at Frying Pan Shoals, just offshore, and 50 mph (early May 10).


10-26: Early coast-to-coast storminess reduced drought’s footprint across the nation’s mid-section but triggered lowland flooding from the southeastern Plains and the western Gulf Coast region into the mid-South. Weekly rainfall amounts of 2 to 4 inches or more were common from the upper Midwest to Texas. Totals in excess of 4 inches were widespread from southern Texas into the mid-South and southeastern Plains. Farther east, however, only light showers, if any, dampened the eastern one-third of the U.S. In the Northeast, where little rain has fallen during the spring, another mostly dry week. Meanwhile, cool, wet weather in the upper Midwest contrasted with warm conditions in the Ohio Valley. The Western showers boosted topsoil moisture and reduced irrigation requirements. Beneficial precipitation dampened parts of California, but failed to dent the Far West’s serious hydrological drought. Snow lingered early in the week across the north-central U.S., where May 9-10 totals included 13.6 inches in East Rapid City, SD, and 4.0 inches in Denver, CO. For East Rapid City, it was the second-greatest May snowfall behind a 14.6-inch total on May 3-4, 1905. Elsewhere in South Dakota, daily record precipitation totals for May 10 reached 2.48 inches in Mobridge and 1.88 inches in Huron. Farther east, minimal Tropical Storm Ana moved ashore around daybreak on May 10 near Myrtle Beach, SC. Wilmington, NC, received a daily record rainfall (2.95 inches) on May 10. By May 11, heavy showers stretched from the Midwest to Texas. Record setting rainfall totals for the 11th included 4.24 inches in Longview, TX, and 3.01 inches in N. Little Rock, AR. Several gauging points, including the Red River near DeKalb, TX, and the Poteau River near Panama, OK, climbed to their highest levels since May 1990. The Red River near DeKalb rose 4.51 feet above flood stage on May 13, while the Poteau River near Panama surged 14.54 feet above flood stage on May 12. By mid-week, precipitation developed in the West and lingered in the western Gulf Coast region. In Texas, daily record amounts for May 12 reached 4.56 inches in Corpus Christi and 3.44 inches at Houston’s Hobby Airport. Meanwhile in Washington, May 12-16 rainfall totaled 1.56 inches in Pullman. During the second half of the week, precipitation shifted into California and the Southwest. On the 14th, San Diego, CA, experienced its wettest May day on record, with 1.64 inches (previously, 1.49 inches on May 8,

1977). Elsewhere in southern California, Palomar Mountain received 2.68 inches in a 48-hour period on May 13-15. Phoenix, AZ, also noted its wettest day on record in May, with

0.93 inch falling on the 15th (previously, 0.91 inch on May 4, 1976). At week’s end, heavy precipitation returned to the nation’s mid-section. Record setting totals for May 16 included 2.01 inches in Topeka, KS, and 1.71 inches in St. Joseph, MO. Farther north, daily record amounts for the 16th reached 1.31 inches in Burley, ID, and 0.86 inch in Helena, MT.


17-23…An active weather pattern led to flood intensification across the central and southern Plains, culminating in a holiday weekend deluge. The latest round of heavy rain pushed Oklahoma to its wettest month on record, based on preliminary data, supplanting October 1941. Showery weather extended beyond the Plains, reaching into the lower Mississippi Valley, parts of the upper Midwest, and much of the northern Intermountain West. Meanwhile, By May 23, month-to-date rainfall totals climbed to 18.19 inches in Oklahoma City, OK, and 13.93 inches in Wichita Falls, TX. In both locations, those values represented the highest monthly totals on record. Previously, Oklahoma City’s wettest month had been June 1989, with 14.66 inches, while Wichita Falls’ had been May 1982, with 13.22 inches. Oklahoma City’s total was boosted by a daily record total (3.73 inches) on May 23, part of a broad heavy rain event that led to catastrophic flash flooding in parts of the south-central U.S. In Texas, for example, preliminary data indicated that the Blanco River at Wimberly rose more than 35 feet in less than 8 hours, cresting on May 24 at 27.21 feet above flood stage. The preliminary high-water mark at Wimberly was 6.91 feet above the previous record set on May 28, 1929. Meanwhile, the San Marcos River near Martinsdale, TX, surged more than 51 feet in less than 24 hours on May 23-24, based on initial data. The flooding in Texas was sparked by 24-hour rainfall totals that exceeded 10 inches on May 22-23 in some locations, including Kendalia. Meanwhile in Oklahoma, the second-highest crests on record were reported at gauging locations such as East Cache Creek near Walters (8.77 feet above flood stage on May 25) and Little River near Tecumseh (9.45 feet above flood stage on May 24). Elsewhere, daily record rainfall totals in excess of 4 inches were noted in several locations across the central and southern Plains, South, and upper Midwest. Selected records included 6.24 inches (on May 18) in Vicksburg, MS; 4.18 inches (on May 18) in Shreveport, LA; and 4.01 inches (on May 19) in San Angelo, TX. Earlier, much-needed precipitation had fallen in the north-central U.S., where daily-record totals for May 17 reached 3.21 inches in Mobridge, SD, and 2.60 inches in Fargo, ND. Late season snow fell in parts of the Dakotas, with 2.6 inches measured in Jamestown, ND, on May 17. Aberdeen, SD, reported a trace of snow on both May 17 and 18. Additional snow fell in the northcentral U.S. on May 19, with North Platte, NE (a trace), reporting its third-latest snowfall on record. Farther east, beneficial rain in the Mid-Atlantic region on May 18 led to daily record totals in Baltimore, MD (1.54 inches), and Martinsburg, WV (1.05 inches). Significant precipitation also fell in the Western States, where selected daily-record amounts for May 19 included 2.83 inches in Clayton, NM, and 1.66 inches in Colorado Springs, CO. On May 21, daily-record amounts climbed to 1.14 inches in Redmond, OR, and 0.43 inch in Alturas, CA. Elsewhere in California, Bakersfield closed the week with consecutive daily-record amounts on May 22- 23, totaling 0.42 inch.


24-30:  A final week of drenching rainfall inundated the southeastern Plains, mid-South, and western Gulf Coast region, culminating in widespread flash flooding and subsequent river flooding. On the central and southern Plains, heavy showers and locally severe thunderstorms continued to threaten the area. As the week progressed, showers began to shift into previously dry areas of the Southeast, although dry conditions persisted along the Atlantic Coast. Meanwhile, significant rain also overspread the Great Lakes region, including Wisconsin and Michigan. Rain also extended eastward through northern New England.

In the wake of relentless May rainfall, the most severe flooding in at least 25 years developed along portions of several mainstream rivers, including the Arkansas, Red, and Trinity Rivers. For example, the highest water levels since early May 1990 were reported along the Arkansas River at Van Buren, AR (11.53 feet above flood stage on May 31), and the Red River near Gainesville, TX (10.75 feet on May 30). Elsewhere in northeastern Texas, the Trinity River near Rosser and Trinidad surged to its highest level since late April 1942. At Trinidad, the Trinity River’s crest (15.20 feet above flood stage) occurred on May 29. Farther upstream, the surface elevation of Lake Lewisville, near Dallas, TX, rose to 537.02 feet on May 31—eclipsing the May 1990 high water mark by nearly 3½ inches. In addition, torrential rain lingered in the western Gulf Coast region, resulting in severe flash flooding.

In Sugar Land, TX, near Houston, the weekly rainfall of 13.82 inches was boosted by a 10.17-inch total on May 25-26. Selected daily record totals in Texas included 5.20 inches (on May 25) at Austin’s Camp Mabry, and 3.30 inches (on May 24) in Brownsville. Heavy rain in other areas of the central and eastern U.S. led to daily record totals for May 26 in locations such as St. Petersburg, FL (2.41 inches); Columbus, GA (1.94 inches); and Wausau, WI (1.84 inches). Early week showers were also heavy in parts of the West, where record-setting totals on May 24 reached 2.83 inches in Buffalo, WY; 1.02 inches in Elko, NV; and 1.01 inches in Jerome, ID. During the second half of the week, a final round of heavy rain crossed the central U.S. before moving into parts of the South, East, and Midwest. On May 28, Burlington, CO, netted a daily record rainfall of 1.07 inches. Two days later, record setting totals for May 30 included 3.68 inches in Laredo, TX; 2.86 inches in Baton Rouge, LA; 2.11 inches in Montpelier, VT; and 2.00 inches in South Bend, IN.


Jim G. Munley, jr.

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