FLOOD01363

• County: Statewide
• Title: Colorado High Plains Thunderstorm Systems - A Descriptive Radar-Synoptic Climatology
• Date: 6/1/1974
• Prepared By: CSU
• Floodplain - Doc Type: Educational/Technical/Reference Information

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4.0 Conclusion

In conclusion a simple but useful SkewT -LogP based quantitative convective
precipitation potential (QCP2) technique was described as an aid in flash flood
prediction. The technique related the depth of the updraft that is warmer than OC or the
updraft warm layer (UWL) to the precipitation efficiency and potential of the
thunderstorm based on the formation of warm coalescence rain mechanisms. The peak
60 minute rainfall potential was related by an equation to the surface to 500mb
precipitable water index and a regional warm layer value.

In general the QCP2 notes the enhanced ability of thunderstorm updrafts to process
more than twice the estimated PWI in a one hour period when the warm layer of the
updraft equals or exceeds 1.5 kIn a t elevations above 3,500 feet, 2.5 kIn at elevations
below 3,500 feet and 3.5 kIn when the surface dew points exceed 70F.

The QCP2 calculation technique could be adapted for use in the NWS SHARP
program and initialized hourly on ASOS or local mesonet observations. In data rich
observation areas such as the Oklahoma Mesonet statewide QCP2 could be easily
obtained for use in the issuance of flash flood predictions and for use by River Forecast
Center products based on QPF. The author has had some additional success in using
the QCP2 to "atmosphere-truth" the Z-R relationship in the WSR-88D to assist in
the preparation of radar-precipitation mapping products.

The QCP2 technique has been used successfully by the author over the past 14 years in
the Denver F2P2 on an almost daily basis for the issuance of a variety of heavy
precipitation products in support of the Denver emergency response community, The
technique requires the user to possess both predictive and analytic skills which can
be applied in a stressful operational environment. Yet it is simple enough to easily
be assimilated into most forecast routines and provide reliable assistance to crucial
decision-making during flash flooding situations.

Clearly the thunderstorm and flash flooding QPF is one of the most vexing forecast
problems facing the operational meteorologist. It is hoped that the QCP2 technique will
prove to be"a reliable asset during flash flood forecast situations to the forecaster until
more sophisticated techniques and tools can be provided by the research and operational
communities.

Acknowledgements: The author apologizes for the late submittal of this manwcript Effective time useage is a
problem he is addressing. Special thanks are due to Dennis Sims of the old GRD Weather Center, Ron Kelly of the
old Henz Kelly & Associates and Bryan Rappolt and Frank RobItaille of Henz Meteorological Services for the
effective contributions they made in assisting the author in the refmement of the QCP2 technique and the effective
operational application of QCP2 in the Denver P2P2 for the past 14 yean;.

References

Henz. J.F., 1993: Operationally Predictable Updraft Characteristics of Heavy Precipitation Producing Thunderstorms, 847.849.
Preprints of the 16th Conference on Severe Local Stonos, October 1993. St.Louis. Missouri. American Meteorological Society.

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