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 -F11 and -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