cyclones over the AUantic (ERICA) (Hadlock and Krietzberg 1988). The 

 comparisons were only in terms of the central positions and (minimum surface) 

 pressures of lows occurring during ERICA. Thirty-three of the thirty-five 

 analyses were at 6-hr intervals; the remaining two were at 3-hr intervals. The 

 results of the comparison are summarized in Table 1. Note that all the opera- 

 tional analyses indicated a higher central pressure than Sanders' analyses. 

 While this might be indicative of bias by Sanders toward deeper lows, a com- 

 parison of Sanders' analyses with research analyses independently prepared by 

 G. Forbes showed only a +0.5-mb difference. Moreover, extreme cases of 

 individual analyses showed differences of 20 mb between the operational and 

 Sanders analyses. 



Table 1 



Mean Latitude and Longitude (degrees) and Mean Centrai 



Pressure (mb) for tlie F, Sanders (FS) Analyses.^ 



Series 



Bearing/distance 



Pressure 



N 



GF 



272/31 (69) 



+0.5 (2.5) 



35 



NH 



066/11 (107) 



+0.6 (4.0) 



29 



NA 



063/08(131) 



+2.1 (5.6) 



34 



NGM 



152/34(181) 



+3.4 (3.5) 



17 



MRF 



217/45(179) 



+7.5 (5.7) 



8 



FS Analyses: 37.6N (4.7) 653.7W (7.1) 987 (20) N=35 



^ For the other analyses, mean geographic bearing (degrees) and distance (km) from this 

 position, and mean central-pressure deviation. Values in parentheses are RMS deviations 

 from the mean. From F. Sanders (1990). 



As a more quantitative example of detailed versus operational analyses, a 

 case study is used to examine the depiction of the minimum surface pressure, a 

 commonly used measure of storm intensity. The minimum surface pressure is 

 a useful example because at any given time, it is a unique scalar quantity, and 

 therefore imambiguous. The study is of an extratropical cyclone, during lOP 4 

 of the ERICA (Hadlock and Krietzberg 1988) at 0000 hr Universal Time Coor- 

 dinate (UTQ 5 January 1989. Pauley and Bramer (1992) examine the effects 

 of spatial resolution on depiction of the sea-level pressure profiles along a line 

 of latitude (41 deg N) passing through the storm. They used five analyses, but 

 two were forecast analyses, therefore not relevant to the present discussion. Of 

 the remaining three, one was based upon a detailed hand analysis of Prof. F. 

 Sanders using all available ship, buoy, and reconnaissance aircraft data; the 

 second was the NMC hemispheric analysis based upon operational weather 

 charts; the third was the NGM forecast initialization analysis valid at (XX)0 hr 

 UTC, 5 January 1989. 



Chapter 2 Operational Analysis Depictions 



