LOOP                                                                            
ERAS                                                                            
TXT3 --------------------------------------------------------------             
TXT4                 ANALYSIS USNIG ISENTROPIC METHODS            -             
TXT5 --------------------------------------------------------------             
4SEC                                                                            
TXT9 -------------------------------------------------------------------------- 
TXTA In order to analyze data using isentropic methods, you must first        -
TXTB create isentropic surfaces.  In the case of moisture return, a good      -
TXTC first guess of an isentropic surface to use for reference is the value   -
TXTD of Theta at the 1000 mb level, along the western Gulf of Mexico for      -
TXTE the forecast time of interest.  I suggest the following procedure:       -                     -
TXTF --------------------------------------------------------------------------
TXTI -----------------------------------
TXTJ NOTE...AN ENTIRE MENU DEDICATED   -
TXTK TO ISENTROPIC METHODS IS GIVEN IN -
TXTL <shift>-F11 and <cntl>-F11.       -
TXTM -----------------------------------
9SEC
9SEC
4SEC
1000
THTA CIN4
TXT5 --------------------------------------------                                                -
TXT6 Pick a value of theta relative to the      -
TXT7 western Gulf for the forecast time of      -
TXT8 interest.  Select this value from the 1000 -
TXT9 mb level.  This doesn't have to be exact,  -
TXTA for example 296K, 300K, +/- 4K is usually  -
TXTB adequate....                               -
TXTC ------------------------------------------ -
9SEC
9SEC
THTA CIN4
TXT5 ------------------------------------------ -
TXT6 FOR EACH FORECAST TIME, 0H - 48H, compute  -
TXT7 the isentropic surface by typing:          -
TXT8                                            -
TXT9           MTHT L01 L02 I                   -
TXTA                                            -
TXTB from the WINGRIDDS command line, where L01 -
TXTC is the lowest isentropic level, L02 is the -
TXTD upper isentropic level, and I the interval.-
TXTE For example:                               -
TXTF           MTHT 296 300 4                   -
TXTG will compute theta surfaces from 296K to   -
TXTH 300K in 4 degree intervals.  If we         -
TXTI wanted the 292, 296, and 300 K surfaces,   -
TXTJ we could type:  MTHT 292 300 4.  Similarly,-
TXTK if we only wanted the 296 level, we could  -
TXTL type: MTHT 296 296 4 (whereby the interval -
TXTM would be ignored since only one surface    -
TXTN could be computed......                    -
TXTO                                            -
TXTP * HIT THE RETURN/ENTER KEY WHEN FINISHED * -
TXTQ --------------------------------------------
ENDL
LOOP
TEMP GRTN 400
TXT5 ----------------------------------------------
TXT6 I would suggest creating the same isentropic -
TXT7 levels for each forecast interval of a       -
TXT8 particular model run.  This may take a few   -
TXT9 minutes...but will likely save you time in   -
TXTA the long run.                                -
TXTB ----------------------------------------------
9SEC
9SEC
TEMP GRTN 400
TXT3 ----------------------------------------------
TXT4 After your isentropic levels are selected,   -
TXT5 they are regarded as if they were their own  -
TXT6 surface (ie...1000, 850 etc.).  To set       -
TXT7 WINGRIDDS to the isentropic level of interest-
TXT8 type I### (eg. I296).  The program will      -
TXT9 remain at that isentropic level until        -
TXTA changed.                                     -
TXTB ----------------------------------------------
9SEC
5SEC
TXTE ----------------------------------------------
TXTF IT IS UNFORTUNATE THAT A MACRO CANNOT BE     -
TXTG WRITTEN TO COMPUTE ISENTROPIC LEVELS FOR     -
TXTH YOU...AS A RESULT, YOU MUST CREATE THEM      -
TXTI INDIVIDUALLY FOLLOWING THE PROCEDURES LISTED -
TXTJ IN THE PREVIOUS PAGES....                    -
TXTK                                              -
TXTL  * TO REPEAT THIS MESSAGE, TYPE 0000. *      -
TXTM ----------------------------------------------
ENDL
