One objective of the comparison was to determine how well the different 

 analyses depicted the accepted minimum central pressure (936 mb) determined 

 by Sanders. Figure 1 shows the latitudinal profiles of sea level pressure as 

 determined using the different analyses. Some data interpolation and smooth- 

 ing were performed on the hemispheric analysis in the vicinity of the cyclone 

 center. Table 2 contains the values of the minimum sea level pressures 

 derived from the different analyses. The 00-hr NGM analysis, which most 

 closely resembles a typical operational analysis, shows the minimum central 

 pressure of the cyclone at that time to be 10 mb higher (946 mb), and the 

 modified hemispheric analysis 4 mb higher (940 mb), than the Sanders 

 analysis. 



B 



9 

 I/] 



M 



o 



1030 



1020 



1010 



1000 



990 



980 



970 



960 



950 



940 



930 



8 









. Sanders '5^ .yy/ 



Hemispheric '■^Xk/,// 



' 24 h NGM \j 



: 48 h NGM V 



5 80 75 70 65 60 55 50 45 40 35 3 

 Longitude (Degrees West) 



Figure 1. Profiles of sea-level pressure at 41 °N latitude through the cyclone 

 for the hemispheric, Sanders, and 00-hr NGM analyses (from Pau- 

 ley and Bramer (1992)) 



A second objective of the Pauley and Bramer investigation was to estimate 

 the effective spatial resolution of the analyses necessary to reproduce the mini- 

 mum central pressure. This was done by Fourier decomposing the respective 

 pressure profiles in wave number space, then recomposing the profiles with 

 increasingly higher wave components until the original profiles were effec- 

 tively reproduced. Figure 2 shows the sea-level pressure for each analysis as a 

 function of maximum wave number retained. Note that up to about wave 

 number 30 (equivalent wavelength of 1,333 km), all three analyses show 

 equally increasing resolution. The equivalent wavelength here is the circum- 

 ference of the 41-deg latitude circle divided by the wave number. Table 2 

 shows the minimum wave numbers and effective wavelength of each analysis 



Chapter 2 Operational Analysis Depictions 



