LOOP                                                                            
ERAS                                                                            
TXT3 ---------------------------------------------------------------             
TXT4       MAKING COMPARISONS WITH PAST/PRESENT MODEL ANALYSES     -             
TXT5 ---------------------------------------------------------------             
4SEC                                                                            
TXT9 -------------------------------------------------------------------------- 
TXTA This menu is intended to allow forecasters to examine the true evolution -
TXTB of fields over the past four forecast periods.  Analysis fields (no      -
TXTC forecasts) are compared for the past 36-h period.  12 and 24-h changes   -
TXTD are computed and displayed from these analyses.                          -
TXTE                                                                          -
TXTF                                 <RETURN>                                 -   
TXTG --------------------------------------------------------------------------
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TEMP GRTN 400
ERAS
TXT4 --------------------------------------------------------------------------                                                          -
TXT5 IN ORDER TO RUN THESE MACROS YOU MUST:                                   -
TXT6                                                                          -
TXT7 1) LOAD THE PAST FOUR GRIDDED FILES ON YOUR WINGRIDDS SESSION.           -
TXT8          When you started WINGRIDDS, you entered a file name, likely     -
TXT9          the most recent file.  If this is the case, load the three (3)  -
TXTA          previous files at this time by using the "OPEN" command.        -
TXTB          (eg. OPEN FIL2 <RETURN>, AP199312.NGM) will load the NGM file   -
TXTC          from 19 April 1993, 1200 UTC in file2.  Once all files have     -
TXTD          been loaded...type "FILS".  A list of files will appear.  The   -
TXTE          most current data should be in file 1, with oldest in file 4.   -
TXTF                                                                          -
TXTG 2) NOTE DIFFERENCES ARE COMPUTED AS OLDEST MINUS NEWEST.                 -
TXTH          All differences are computed as oldest minus newest.  Hence,    -
TXTI          if we wanted to examine the height changes (menu option 1)      -
TXTJ          the difference field shown would be the analysis from 36h ago   -
TXTK          minus the analysis from 24h ago....height rises would be        -
TXTL          positive (eg T-36: 552m - T-24: 560m = +8m).                    -
TXTM                                                                          -
TXTN 3) 12-H CHANGES ARE COMPUTED FOR T-36/T-24, T-24/T-12, and T-12/T-00.    -
TXTO    24-H CHANGES ARE COMPUTED FOR T-36/T-12, and T-24/T-00.               -
TXTP                                                                          -
TXTQ                                    <RETURN>                              -
TXTR                                                                          -
TXTS --------------------------------------------------------------------------
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ERAS
TXT4 --------------------------------------------------------------------                                                          -
TXT5 THE PURPOSE OF THIS MENU IS TO ALLOW FORECASTERS TO EXAMINE ACTUAL -
TXT6 ATMOSPHERIC CHANGES/HISTORY PRIOR TO EVALUATING MODEL FORECASTS.   -
TXT7 --------------------------------------------------------------------
ENDL