2 Operational Analysis 

 Depictions 



Evaluation of a particular storm event is typically based upon analysed 

 weather charts. Since the predominant use of the charts is directed toward 

 supporting forecast development, there is a strong constraint on the time avail- 

 able for chart preparation. The charts therefore are based upon meteorological 

 data available at the time the charts are prepared, even though other relevant 

 data may become available later. This process results in charts that may not 

 incorporate all relevant data, which can lead to an incomplete or erroneous 

 depiction of a particular event 



Several investigators (Davis and Emanuel 1988, Sanders 1990, Pauley and 

 Bramer 1992) have noted that the National Meteorological Center's (NMC) 

 limited-area fine mesh (LFM) and Nested Grid Model (NGM) tend to under- 

 forecast rapid maritime cyclogenesis (storm formation), while the LFM model 

 at least is reasonably successful in forecasting rapid continental cyclogensis 

 (Silberberg and Bosart 1982). This behavior suggests that some physical pro- 

 cess is not being well treated by the model in oceanic situations, or poor qual- 

 ity data in the marine environment increase the difficulty of making accurate 

 predictions. Studies by the aforementioned investigators indicate both effects 

 may contiibute to the forecast difficulties. While this report is not concerned 

 with forecasting, the latter contributor (poor quality data) is relevant to the 

 analyzed depiction of maritime storms. 



The source of most analyzed weather data is the National Weather Service 

 (NWS), and it is reasonable to assume that comparisons of storm events wiU 

 be made based upon NWS analyses. In practice, however, it is quite common 

 for oceanic storms, which cause damage or disruption to maritime shipping or 

 coastal communities, to be analyzed in greater detail using reports and data rwt 

 usually included in routine NWS analyses (e.g., Gyakum (1983). Events ana- 

 lyzed in this manner can differ in significant aspects from depictions of the 

 same event prepared in a routine manner. 



Sanders (1990) made a detailed comparison of what he termed research 

 analyses versus both manual and automated NMC operational analyses. The 

 comparison was based on 35 analyses of surface conditions during intensive 

 observation periods (lOP) 1-5 of the experiment on rapidly intensifying 



Chapter 2 Operational Analysis Depictions 



