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<br />FLOOD REPORT
<br />ARKANSAS RIVER BASI~
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<br />by mechanical lifting (due to the upslope of the terrain) and conver-
<br />gence (due to the low-level pressure pattern), produced phenomenal
<br />rains and calalllitous floods. Plates 2 and 3 showdatly surface and
<br />upper air (SOO millibar) weather maps for the period 13-19 June 1965.
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<br />I'LOOO OF J(lNE 1965
<br />r.0r.ORAOO, K^,'I;S,~S. & NEW \If,nCO
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<br />HiTRODlJCTION
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<br />b. 14JWle.- A layer of moist tropical air (!orn was spread-
<br />lng northward through Texas and along the eastern border of New Mexico
<br />and eastern Colorado. A cold front waS being driven upslope through
<br />northeastern and east-central Colorado early in the day by increasingly
<br />higher pressure developing over the central_plains states. !be air
<br />associated with this front, already moist and unstable, continued to
<br />be pushed upslope over the eastern plains of Colorado. The mechanical
<br />liftin~ plus lower-level convergence in the vicinity of the cold front
<br />WaS further assisted in producing excessively heavy local showers by
<br />colder air in the upper levels (_100 C at 18,000 ft. MSL). The surface
<br />front at this ti~e extended from South Carolina to southeastern Kansas
<br />and northward through central Nebraska to join another front in north-
<br />western South Dakota. This second front extended in a south~sterly
<br />direction fro~ the junctur<! in South Oakota through southeastern
<br />Wyoming, northwestern Colorado, central Utah, and turned southward as
<br />it entered eastern Nevada, thence in a southerly direction to Baja
<br />California. A small squall line extended through Trinidad nnd Pueblo,
<br />Colorado, during the early morning hours. The 5DOlllillibar chart shown
<br />on plate 3 indicates a trough approximately oVer the west coast.
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<br />1. AU1'flORITY.- The final report of the flood of June 1965 is
<br />made in compliance with paraf{raph 172.S20fEM500-1_1. Aflood
<br />emergency (Phase III, Category E flood) on the Arkansas River and
<br />tri~utarics WaS declared on l~ June 1965 in accordance with the pro-
<br />v is ion s of parag raph 1 ~ I ..1 ~ 0 f t~l C ,~1 huq uerque Oi strict's Annex A,
<br />Emergency Flood Control Activities, to E~ 500-1-1. A flood emergency
<br />(~hase 'I, Category B flood) on the Canadian River and tributaries also
<br />Was <1eelared on 16 June 1965. Flood fighting and data collection activ-
<br />ities were commenced under authorities contained in paragraphs 121.343,
<br />122.345, IB2.70, and 182.72 of EM 500-1-1.
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<br />2. SCOPE.- The report covers the Arkansas River and tributaries
<br />in Colorado. the Arkansas River from the Colorado-Kansas State line to
<br />Great Bend, Kansas, and tho Canadian River and tributaries above Conchas
<br />Reservoir in New Mexico. It inCludes a description of the storm and
<br />runoff; extent and magnitude of flooding, flood da~ages, and flood emer_
<br />gency activities by Federal, state, and local governments and organi-
<br />~ations; flood regulation by existing projects and benefits derivod
<br />therefrom, henefits expected to acCrue from authori~ed projects; and
<br />a bibliography. The report also contains supporting data in the form
<br />of tables and plates. Plate I is a general map of the area.
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<br />STORM DESCRIPTION
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<br />c. 15.Tulle.- Movement of the first front continued south-
<br />ward and reached northeastern New Mexico by noon. The inflow of sur-
<br />face moisture increased up to an average of 13 grams per kilogram
<br />through the lower 5,000 feet and thus, enhanced the instability of the
<br />atmosphere. The trough at SOD mho had moved a few hundred miles inland.
<br />d. 16 June.- A slight warming of the upper atmosphere along
<br />with less than normal daytime heating due to considerable cloud cover
<br />decreased the instability temporarily during the daylight hours. Sur_
<br />face temperatures averaged about 10. F COoler than the previous day.
<br />A marked increase in cyclonic flow in the upper atmospheric levels set
<br />the stage for heavy rains during the night of 16-17 June. At about
<br />this time the second front lay in a general north-south alignment along
<br />the Front and Sangre de Cristo Ranges. A squall line developed along
<br />an arc through Trinidad, Colorado,and Cheyenne, Wyoming.
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<br />3. SYNOPTIC SITUATJI)!I.-
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<br />a. G<1r.eroL- The f1ood-prouucing rains of 13-19 June 1%5
<br />were the culmination of a strong and persistent weather pattern which
<br />i,,:ul cxisted over the "este= IJnitedStates fornhout four months. The
<br />.~cneral pattern of t!le upper-level windf1o~' was out of the Gulf of
<br />i\lnska, down the west coast, acrOSS southern California, back up th rough
<br />ArizonllandNewMexico, and over the high plains. This general pllttern
<br />of upper-air circulation was present throughout the storm period and
<br />waS most pronounced on 16-17 June with unseasonably cool air at 20,000
<br />feet. Byl4June,theincreasingsurfacepressuresovertheeentra1
<br />plains, coupled with a low-pressure area centerod over Chihuahua,
<br />"lexico, induced an inf.lew of moist r.ulf air into northeastern New Me~ico
<br />and eastern Colorado. damming it up a~ainst the Rocky Mountains beneath
<br />the cold air aloft. This combination of surface and upper air conditions
<br />rcsultecl in extremely llnstable atmospheric conditions and, reinforced
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<br />e. 17 June.- Drying and some cooling of the upper layers of
<br />the at1llOsphere were noticeable early on the 17th. Thesefactors,accom-
<br />paniedbyincreasedcyclonicflowintheupperlayers,contrihlItedto
<br />increased instability. This system moved northward through Colorado
<br />during the day. Simultaneously, the Jet Stream was present over Colo-
<br />rado.
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