83rd Annual

Tuesday, 11 February 2003
A method for integrated satellite reconnaissance fix accuracy
Roger T. Edson, Anteon Corporation and University of Guam, Mangilao, Guam; and M. A. Lander
Poster PDF (181.0 kB)
Since the 1950s aircraft reconnaissance has been the main stay of tropical cyclone (TC) warning (fix) support for the National Hurricane Center (NHC) in the Caribbean/Gulf of Mexico and Western Atlantic and in the western North Pacific up until 1987 for the Joint Typhoon Warning Center (JTWC). Although aircraft were not always available to support every TC warning, depending upon basin and distance from where the aircraft were based, aircraft reconnaissance were typically tasked to meet the time frames for an ‘on time’, every-other 6-hourly warning (typically ½ hour prior, to 1 hour after the synoptic time warning position). For other warning times and for all other tropical cyclone warning centers, the satellite has been the primary source for TC reconnaissance and warning support. Typically similar to that set by aircraft tasking, satellite “fix” positions were expected to meet the same ‘on-time’ criteria. Prior to global-wide access to the geostationary satellite, dependency upon polar orbiting satellites did not always fit these time frames and warning positions were often considered to be ‘extrapolated’ or estimated with accuracies in excess of 60-100nm for the supported warning position. For on-time fixes, a position code number (PCN) was developed to provide guidance for position accuracy to the warning. A PCN was given depending upon the structure of the TC (eye, well developed, and poorly developed) and the gridding of the imagery. PCN accuracies were typically between 25 and 60nm (90% standard vector deviation). The original PCN development in the mid-70s was primarily for polar orbiting visual and infrared imagery. Over time, geostationary imagery and animated geostationary imagery adapted to these same PCN procedures, although current statistics show that positioning techniques have improved considerably. Now, a new type of polar orbiting data has become available. Microwave imagery and scatterometer data which can see through the thick obscuring upper cloud decks to the low level cloud circulations below have come into routine use within the TC warning system. Unfortunately, these data are often treated as only supporting imagery because they don’t meet the ‘on-time’ criteria. In these cases, less detailed infrared or visual imagery may often be used to reflect the accuracy of the warning position even though far greater information is known. This paper suggests a methodology to try to tie in these new data sources to best reflect the forecaster’s knowledge at warning time. Using the closest ‘on-time’ reconnaissance platform available as a baseline, a method is shown to ‘increase’ the accuracy of the warning with the best available reconnaissance data over the preceding interval. In this manner, knowledge is gained (or loss) depending upon the quality of the particular platform, time difference from other qualifying data, and the consistency of successive data that may increase a forecaster’s confidence. Various examples and suggested warning accuracies will be presented.

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