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I I I I I I I I I I I I I I I I I I .1 The remainder of the diagram is basically unaltered from a standard Skew T, Log P diagram.HMS plots both the 0000 GMf 8I1d the 1200GMf Denver (DEN) soundings on the diagrmn in the conventional manner. The temperature and the dew point for each mandatory and significant level of the sounding are plotted vertically versus pressW'e, The temperature is noted in the solid blaclc line while the dew point is plotted in the dashed black line, The analyses performed using the diagram will now be described. The precipitable water index (PWI) is calculated by estimating the mixing ratio at each of the four levels indicated in the table: 820mb, 750mb, 650mb 8I1d 550mb. This estimated mean mixing ratio for the 100 mb layer surrounding the point is multiplied times the factor opposite the appropriate level. Each layer's contribution is calculated and then added together 8I1d divided by 3.2 to get the estimated PWL In . practice then calculated PWI varies by less than 5% from the NMC calculated PWI and is available much faster. The remainder of the analyses is based on the concept that the undiluted updraft of a strong thunderstorm can be implied by lifting a suitable surface parcer to its level of free convection (LFC) and Its neutral bouyancy point In the case of the sounding shown in Figure I for August 18, 1993 the surface parcel lifted has a surface temperature(A) of85F (29C) and a dew point(B) of 56 F ( 13C). If this parcel is lifted it reaches is LFC at point C at about 3.5 km, From this point vertically the parcel follows the moist adiabst curve to point D and then point E where it intersects the sounding line implying its neutral bouyancy point HMS conducts a very detailed analyses of the lifted parcel thermal trace from point C to point E. First. the thermal deviation of the surface lifted parcel temperature from that of the ambiant atmosphere is noted every 50 mb from point C to point E. This deviation is then divided by the number of 50 mb layers to calculatethe DeIT factor. In the case of the example the DeIT is + 7.8 C which implies the updraft temperature is about 7.8 C warmer than the ambient atmospllFe tluongh the updraft's vertical depth. HMS has found that this indication of the updraft's strength is superior to the standard lifted indices which terminate at 500mb or to the cummulative Convective Available Potential Energy (CAPE) index favored in some models. HMS uses the vertical variation of the DeIT to calculate both the parcel's acceleration and speed. The Del Z factor is used to describe the depth of the updraft by subtracting the lifted parcel's LFC (point C) from its neutral point (point E). In the example's case the DeIZ is 9.2 km which implies the conservative depth of visible cloud from its base to the anvil top. Additionally HMS has found that relationships exist between this depth and the ability of the 'cloud" to produce various forms of lightning and severe weather. Of more importance to this paper is the calculation of the precipitation factor or PF. The PF i. calculated by subtracting the height of the LFC ( Point C) from the height of the point where the updraft cools to OC, in this case at Point D. In the example Point D is at 5.2 km while Point C is at 3.5 km. The difference between the two points i. 1.7 km. In effect this difference i. used to imply.the depth of the cloud'. updraft which is conservatively warmer than OC or that portion of the cloud where coalescence precipitation formation mechanisms should be operative. The remainder of this paper will focus on the relationship ofthi. warm layer depth to the occurrence of heavy convective rainfall. 3.0 The U~. Warm Layer The updraft'. warm layer (UWL) is thought to estimate the portion of the "convective cloud" which is warmer than DC or where it i. reasonable to assume that coalescence precipitation growth processes are present or operative. Warm cloud rainfall is well established as considerably more efficient than mixed or ice phase precipitation growth processes and has been linked to many of the significant f1ash floods of the past ten years. It is believed that the undiluted updraft profile represented by the technique in the previous section may best relate to the most intense rain production portion of the thunderstorm represented by the 5 and 6 level radar echo portion of the storm. In 1981 the author began to measure the presense and influence that warm coalescence rain processes might have on the occurrence of heavy rainfall in the Denver metro area as part of the F2P2 progrmn. The updraft analysis teclutique descibed in the previous section was applied each day and the depth of the warm layer was noted, In each 1981 case of rainfall equalling or exceeding I inch in an hour the depth of tbe warm 'ayer exceeded 1.5 km. In