INTERPRETATION
DISCUSSION
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Regional and Mesoscale Meteorology Team Cooperative Institute for Research in the Atmosphere (CIRA) Colorado State University Fort Collins, Colorado |
March 20, 2002
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On 8 Mar 2002 a large, Canadian high pressure region dropped south along
the Front Range of the Rocky Mountains bringing with it a bitterly cold
arctic air mass. By late in the day, temperatures (deg F) in the high teens
and low 20s had replaced spring-like 70s and 80s as far south as Oklahoma.
Stratiform cloudiness on visible and IR
10.7 µm satellite imagery marked the leading edge of the cold
air. The RUC 00-h forecast of surface temperatures
under-forecast the speed of the advancing cold front.
Visible imagery |
IR 10.7 µm imagery |
RUC 00-h forecast of surface temperatures |
Click on images to start loops.
Warm air advection in the clear air ahead of a deepening surface low
in southeast Colorado intensified a baroclinic zone south of the arctic
front in Kansas and eastern Colorado. This low moved into northwestern
Oklahoma by 00:00 UTC. The rapidly rising temperatures resulted in a southeast-northwest
oriented baroclinic boundary ahead of the arctic front. By mid-afternoon,
this boundary stretched from southwest Kansas into east-central Colorado.
Visible
imagery shows cumulus developing in the vicinity of the pre-frontal
boundary, with development towards the southeast through the day. The convergence
on the easternmost portion of this boundary was sufficient to play a role
in thunderstorm initiation over central Kansas around 23:30 UTC.
IR 3.9 µm imagery |
IR 3.9 µm imagery shows the cold front
move southward through the High Plains. The front was moving south at
approximately 38 kt (20 m/s, computed computed from sequential satellite
imagery). The cold air traversed the entire north-south length of western
Oklahoma in four hours. As a point of interest, note that the southern
end of the squall line marks the leading edge of the cold air. It is also
important to note that infrared imagery (channel 2 or 4) may be best for
tracking the motion of the front, since daylight hours are short at this
time of year.