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Explanation of Digital TRaP Formats

NOAA/NESDIS has made the TRaP output available to users via anonymous ftp in three formats: McIDAS area file, text file and gif file. McIDAS users can easily display the data while users of the text format can develop the means to view the data on their own systems.

The text file will have the following format where east longitudes are positive and west longitudes are negative:

Line 1: BB##YYYY MMDDHH StormName

BB - Basin
AL Atlantic
EP East Pacific
CP - Central Pacific
WP - Northwest Pacific
NI - North Indian (includes Bay of Bengal and Arabian Sea)
EI - Southeast Indian (between 90 deg E and 130 deg E)
WI - Southwest Indian (west of 90 deg E)
NT - Northern Territory (between 130E and 142 deg E)
SW - Southwest Pacific (between 142E and 160 deg E)
SE - Southeast Pacific (north of 25S and east of 160E)
OT - Southeast Pacific (south of 25S and east of 160 deg E)
## Storm number taken from forecast bulletin; otherwise 99 if not available
YYYY The calendar year the storm occurred
MMDDHH Current month day and forecast hour
StormName - The name of the storm

GGLON - The number of grid points in the longitudinal direction
SSLON - The resolution (in degrees) of the rainfall grid in the longitudinal direction
LONL - The longitude of the lower left hand corner of the rainfall grid
LONR - The longitude of the upper right hand corner of the rainfall grid
GGLAT - The number of grid points in the latitudinal direction
SSLAT - The resolution (in degrees) of the rainfall grid in the latitudinal direction
LATL - The latitude of the lower left hand corner of the rainfall grid
LATR - The latitude of the upper right hand corner of the rainfall grid

Line 3-7: LON LAT TIME
The future forecasted storm track positions.

Line 8-n: LON LAT RAIN
LON/LAT - is the position in longitude/latitude of the rainfall calculated
RAIN - amount of rainfall in inches

Note: Line 8 through line n contains a sorted list of longitude/latitude points. The longitude/latitude points cover a square area and are listed from the lower left corner of the rainfall grid to the top right corner.

Two sample text files, two sample McIDAS area files and two sample gif files can now be accessed through the following site:

By way of example, file names have the following form:
.....2007CLIFF.WTPS01.NFFN.050000.AMSU.04042155.24.GIF (link)
.....2007CLIFF.WTPS01.NFFN.050000.AMSU.04042155.24.Z (link)
.....2007CLIFF.WTPS01.NFFN.050000.AMSU.04042155.txt.Z (link)

With the exception of the gif image, the files are compressed as indicated by the ".Z" at the end of the file names. Text files are indicated by ".txt." Files not containing the ".txt" are McIDAS area files. PC users can use WinZip to uncompress/unzip the files, which will launch automatically after clicking on a compressed file. In Linux/Unix, in the directory where the file is located, type uncompress <file_name> as in the following example:

uncompress 2007CLIFF.WTPS01.NFFN.050000.AMSU.04042155.24.txt.Z

Interpreting the file name is somewhat challenging.


Year   WMO Header  Bulletin Time  Rain Rate Time    
  |         |            |           |
      |           |            |            |
 Storm Name      RSMC  Microwave Sensor  Rainfall Total (24 hour total in this case)

The storm name could be a number (e.g. ONE) or an alphanumeric (e.g. 28S) if the system is only of tropical depression intensity. The RSMC indicates whose forecast was used to generate the TRaP and the bulletin time, in the form of DDHHMM, indicates which specific bulletin was used to generate it. The microwave sensor will be AMSU or TRMM. The rain rate time is in the form of MMDDHHMM and is the time the sensor was actually over the storm. The rainfall totals are available in four 6-hour increments and a 24 hour cumulative total. The rainfall totals will be 00 (for 0-6 hour totals), 06 (for 6-12 hour totals), 12 (for 12-18 hour totals), 18 (for 18-24 hour totals) and 24 (for the 24 hour cumulative total).