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<br />
<br />few hundred kilometers to the east. The
<br />slow-moving cool front that led the Ca-
<br />nadian air mass was located almost
<br />700 km to the south in northeastern New
<br />Mexico and northern Texas (Fig. 5), In
<br />northeastern Colorado and southeastern
<br />Wyoming, anticyclonic flow from the
<br />Canadian air mass produced northeast-
<br />erly to southeasterly winds of 25-8 m S-1
<br />over the high plains, This synoptic pat-
<br />tern is also similar to those observed for
<br />the RC and BT storms (Maddox et al,
<br />1978), with one important exception: the
<br />surface front in the case of the FCL storm
<br />was located much farther south of the
<br />flood area than were the fronts associated
<br />with the RC and BT cases,
<br />
<br />c, Soundings
<br />The nearest sounding to FCL was
<br />taken by the NWS at Denver (DNR, 85 km
<br />south-southeast of FCL) at 1800 MDT
<br />on 28 July (Fig, 6), In an attempt to infer
<br />conditions closer to FCL, we have in-
<br />cluded a vertical profile of temperature
<br />and wind transmitted via the Aircraft Communication
<br />Addressing and Reporting System (Benjamin et al,
<br />1991), The 14 wind and temperature measurements
<br />that compose the ACARS sounding were taken within
<br />:t1 h of 1800 MDT and within a circle defmed by FCL
<br />at the center and DNR at the perimeter; this ensured
<br />that the aircraft data were at least as near to the flooded
<br />area as was the sonde launch site, The ACARS sound-
<br />ing is broadly consistent with the DNR sounding, with
<br />a few exceptions, Lower temperatures from 400 to
<br />500 hPa in the ACARS sounding may reflect aircraft
<br />penetrations of clouds, Further, the ACARS winds
<br />were much stronger than the sonde winds from 300 to
<br />400 hPa, perhaps because of mesoscale variability and
<br />local storms,
<br />The third sounding in Fig, 6 depicts the mean ver-
<br />tical temperature profile of the atmosphere overlying
<br />the tropical western Pacific warm pool as calculated
<br />from soundings made within the intensive flux array
<br />during the intensive observing period of the Tropical
<br />Ocean and Global Atmosphere Coupled Ocean-At-
<br />mosphere Response Experiment (TOGA COARE),
<br />The remarkable similarity between the TOGA
<br />COARE sounding and those from near FCL attests to
<br />the tropical nature of the environment that fostered the
<br />flash flood,
<br />
<br />FIG, 4, 500-hPa analysis for 1800 MDT 28 July 1997 (0000 UTC 29 July 1997),
<br />Isalines of geopotential height (solid) are contoured at an interval of 30 m,
<br />Isothenns (dashed) are contoured at an interval of 20C, Shaded regions indicate
<br />dewpoint depressions ~ 60C.
<br />
<br />of the Rockies in Colorado and Wyoming (e,g" 1800
<br />MDT 28 July 1997; Fig. 5), Dewpoints were 160_
<br />l80C (61-{i40F) along the foothills and 180-200C a
<br />
<br />",
<br />
<br />r~-----'.-_. '-,
<br />
<br />
<br />- -, '- -,"- ;~~~~...\ - -' "
<br />
<br />",
<br />
<br />,_____n___.
<br />
<br />FIG. 5. Schema of synoptic and mesoscale features for 28 July
<br />1997, Two large Xs represent the locations of a 500,hPa vorticity
<br />maximum. Closed solid contours indicate pertinent regions of
<br />cloud top colder than -20oC for I-h intervals between 0600 and
<br />1800 MDT. The wide shaded line shows the northwestern edge
<br />ofsurfacedewpoints> 15.50C (60oF). Wind harhs areforthe sur,
<br />face; short barbs are 2.5 m S-l, long barbs are 5 m S.I, Synoptic
<br />fronts are indicated by solid lines; mesoscale boundaries by bro-
<br />ken lines with pairs of dots, Times are (a) 0600, (b) 1200, (c) 1800,
<br />and (d) 2400 MDT,
<br />
<br />196
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<br />"
<br />
<br />Vol, 80, No.2, February 1999
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