FLOOD01375

• County: Larimer
• Title: Mesoscale and Radar Observations of the Fort Collins Flash Flood of 28 July 1997
• Date: 2/1/1999
• Prepared By: American Meteorological Society
• Floodplain - Doc Type: Flood Documentation Report

b

t.o~;"';:~/^
~ T-~r
W'
'000'"

400+

400~

t

iL2 I d
'tl~Q~ 2lSNY
~_~RE!~~ur-__17 ~ 410'\"

y
T
t

400+

t
1

FIG. 7. Hourly mesoscale analyses for 1800-2100 MDT 28 July 1997 (0000-0300 UTe 29 July 1997). Surface streamlines are in
solid arrows. Wind barbs plotted as in Fig. 6; temperature and dewpoints in oc. Mesoscale boundaries arc indicated as in Fig. S.
Regions of radar reflectivity;;' 35 dBZ are shaded: (a) 1800 (0000), (b) 1900 (0100), (e) 2000 (0200), and (d) 2100 MDT (0300 UTe),

shown in Fig, 7a, Generally east-to,southeaster]y flow
prevailed over the Front Range, except in the vicinity
of Denver, where a Denver cyclone was evident. This
cyclonic circulation commonly develops when soulh-
easterly flow impinges on the Palmer Lake Divide
(Szoke et aL 1984; Blanchard and Howard 1986;
Brady and Szoke] 989), Its foOllation has been attrib-

uted to a variety of mechanisms (see Davis 1997 for
a review), This convergence associated with the
Denver Cyclone (e,g" Wilczak and Christian 1990)
appears to have played a role in initiating a bow echo
in the Denver area after 1800 MDT, which then moved
onto the plains at 8 m S-1 over the next 3 h (Figs, 7a-
d), However, the bow echo was also coincident with

198

Vol, 80, No, 2, February 1999