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<br />. , <br /> <br />., <br /> <br />II. Meteorological review of the orographic impacts of the Denver Cyclone on Cherry <br />Creek basin storms. $8,750 <br /> <br />Importance factor: Defines the role of the topographically induced Denver Cyclone in PMP <br />storm placement over the Cherry Creek basin through historic storm analyses. <br /> <br />The NWS Site Specific PMP storm was placed in the center of the Cherry Creek basin <br />based on the most stressing location concept as described in HMR51/52 and based on <br />analyses of 53 eastern storm complexes. However, the Denver Cyclone feature plays a <br />major role in the development, intensification and movement of thunderstorm systems <br />across the length of the Cherry Creek basin. This task addresses this role quantitatively. <br /> <br />The existence of the topographically-induced gyre called the Denver Cyclone has been discussed <br />in meteorological literature since the mid-1980s by Ed Szoke of NOAA's Forecast Systems <br />Laboratory in Boulder, Colorado. A physical and dynamical model of the Denver Cyclone has <br />been created to anticipate its location In the boundary layer during periods of strong, persistent <br />southeast to southerly winds flowing along and over the Palmer Divide. Rappolt, 1996 described <br />the impact of the Denver cyclone on the occurrence of both severe weather and iocally heavy <br />rainfall relative to the location of the Denver Cyclone within the six county, Denver, Colorado <br />metro area. These two areas of study provide a viabie basis for defining the role of the Denver <br />Cyclone in producing thunderstorm rainfall in the Cherry Creek basin. <br /> <br />This task will quantify and identify the boundary layer conditions under which the Denver Cyclone <br />forms and produces, suppresses or enhances thunderstorm rainfall within the Cherry Creek basin <br />based on a review of the studies n:oted above. It will rely on an analysis of the identified work and <br />the existing radar/storm arch.iveofimportant storm. rainfall events developed during the period of <br />1985-2001 within the UDFCD Flash Flood Prediction Program to quantify the impacts of the <br />Denver Cyclone. <br /> <br />Specifically, this task wili iocate the Denver Cyclone relative to the formation and movement of <br />locally heavy thunderstorms in the Cherry Creek basin and the related low-level wind, moisture <br />and temperature structure as measured by the ERL PROFS and UDFCD Mesonets. Storm <br />motion and location will be compared to the ERL model anticipation of the location and potential <br />storm motion based on the location of the Denver Cyclone. <br /> <br />Several smaller tasks will be accomplished.to complete this task: <br /> <br />1. Review of the existing literature describing the Denver Cyclone and an analysis of the <br />results relative to defining the impacts of the Denver" Cyclone of Palmer Divide and <br />Cherry Creek basin storm and rainfall development. <br /> <br />2. Visit to ERL in Boulder to interact with Ed Szoke about the application of the existing ERL <br />Denver Cyclone boundary layer model to the Cherry Creek PMP study and a <br />quantification of the conditions under which the DC forms and is maintained. <br /> <br />3. Review of the existing F2P2 radar data archive for the identification of storms that either <br />fonn over or cross the Cherry Creek basin. A detailing of the storm formation and <br />movement and the related existence or impacts of the Denver Cyclone will be noted. <br /> <br />4. A report detailing the results will be prepared. <br /> <br />HDR can develop the Denver Cyclone analyses for a lump sum amount of $8,750 in 30 <br />days from notice to proceed. ' <br />