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<br />The DNR sounding shows very
<br />'"
<br />moist conditions throughout the tro-
<br />posphere, with no lower,tropospheric
<br />inversion or cap above the boundary
<br />layer. Midtropospheric winds were
<br />weak to moderate and southwesterly,
<br />and winds from the surface to 750 hPa
<br />were east to southeasterly, The total pre, '"
<br />cipitable water below 500 hPa at DNR
<br />was 3.4 cm; the July average is ] ,9 cm
<br />and values exceed 2,8 cm only 5% of ,,,
<br />the time, The soundings proximate to
<br />the RC and BT storms cxhibited simi,
<br />larly high values of precipitable water <00
<br />(Maddox et a1. 1978; Caracena et al,
<br />1979),
<br />Table I lists some of the thermo,
<br />dynamic variables calculated from the
<br />DNR sounding, Note that the thermo- "0
<br />dynamic parameters were relatively,,,
<br />insensitive to methods of mixing the
<br />boundary layer and to inclusion of
<br />surface conditions at Fort Collins, A
<br />very shallow isothcrmallayer existed
<br />from near the surface to 810 hPa, The
<br />troposphere was conditionally un-
<br />stable from 810 to 500 hPa and from
<br />460 to 400 hPa, Convective available potential energy
<br />(CAPE) was relatively small at 868 J kg-I (assuming
<br />pseudoadiabatic ascent of a parcel with the mean ther,
<br />modynamic characteristics of the lowest I km of the
<br />sounding), The relatively small negative lifted index
<br />of -2,8 also indicates only a slightly unstable tropo-
<br />sphere, The modest instability of the troposphere prior
<br />
<br />
<br />0000 UTe 29 July 1997
<br />
<br />'CARS {I, wind}
<br />
<br />TOGA COARE mean (T)
<br />
<br />,,"
<br />
<br />,,"
<br />
<br />,-"
<br />
<br />,""
<br />
<br />FIG. 6, Skew. T plot for Denver, CO, at 1800 MDT and for TOGA COARE (see
<br />text). The respective soundings are labeled in the upper left corner of the figure. Wind
<br />barbs are plotted in knots; full wiod barb = 10 kt (5 m s"), half barb = 5 kt (2,5 m So').
<br />
<br />TABLE I. Denver sounding characteristics.
<br />
<br />Precipitable water through 500 hPa
<br />(% climatology)
<br />
<br />3A em (179%)
<br />
<br />I Preci~~ble .:::::~o~gh lOO'bPa
<br />Lifting condensation level (LCL)
<br />
<br />3,8C1l1
<br />
<br />764 hPa
<br />
<br />-
<br />
<br />Environmental aoc level
<br />
<br />570 hPa
<br />
<br />L~E _ ~
<br />
<br />Lifted index
<br />
<br />868 J kg"
<br />
<br />-2.8
<br />
<br />Bulletin of the American Meteorological Society
<br />
<br />-
<br />
<br />-~. _.
<br />
<br />to the FCL flood differs markedly from the highly
<br />unstable profiles of the RC and BT floods, for which
<br />the lifted indices were -7 and -6, respectively
<br />(Maddox et a1. 1978; Caracena et a1. 1979), The small
<br />dewpoint depressions for the FCL storm produced a
<br />low lifting condensation level (LCL) of 764 hPa and
<br />a low level of free convection (LFC) of 690 hPa, The
<br />OOC level in the DNR sounding was located at a height
<br />of approximately 3,6 !an above ground level (AGL)
<br />(570 hPa) ,
<br />
<br />5. Surface mesoanalyses
<br />
<br />Surface streamline mesoanalyses from 1800 to
<br />2100 MDT 28 July 1997 are shown in Figs, 7 a-d, The
<br />analyses are based on National Weather Service, Colo,
<br />rado Agricultural Meteorological, and Colorado De,
<br />partment of Transportation surface stations, Positions
<br />of outflow boundaries are based on radar data and sur-
<br />face observations (e,g" wind shifts, temperature
<br />drops),
<br />For most of the afternoon of 28 July the surface
<br />flow field over northeastern Colorado resembled that
<br />
<br />197
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