WDPN31 PGTW 010300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (NIDA) WARNING NR 37// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON (TY) 26W (NIDA), LOCATED APPROXIMATELY 325 NM SOUTH- SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED AND MULTISPECTRAL SATELLITE IMAGERY INDICATE A WEAKENING OF THE OVERALL CONVECTIVE STRUCTURE AS NIDA'S EYE HAS BEEN REPLACED BY TIGHTLY CURVED BANDING. ADDITIONALLY, THE VERY DRY AIR MASS TO THE WEST OF THE SYSTEM CONTINUES TO PERSIST AND PROVIDE A COOLER/DRIER NORTHEASTERLY INFLOW. HOWEVER, INFRARED IMAGERY DOES SHOW PERSISTENT DEEP CONVECTION IN THE WEST-NORTHWESTERN PORTION OF THE SYSTEM AND ANIMATED TOTAL PRECIPITABLE WATER (TPW) PRODUCTS SHOW THE WEDGE OF DRY AIR (30-40 MM) FORMERLY WRAPPING AROUND TY 26W HAS MOISTENED AND IS NO LONGER ISOLATING THE SYSTEM. THE CURRENT POSITION IS BASED ON THE PGTW AND RJTD POSITION FIXES AND THE WESTWARD TRACK OVER THE LAST 12 HOURS IS SUPPORTED BY THE 301644Z TRMM AND 301625Z AMSRE MICROWAVE IMAGES. THE CURRENT INTENSITY IS A COMPILATION OF WEAKENING DVORAK ESTIMATES FROM PGTW (77 KNOTS), RJTD (90 KNOTS), AND KNES (77 KNOTS). 3. FORECAST REASONING. A. THE FORECAST PHILOSOPHY HAS CHANGED SIGNIFICANTLY SINCE THE LAST PROGNOSTIC REASONING BULLETIN. B. THROUGH TAU 48, INCREASING VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT ARE STILL EXPECTED TO CAUSE TY 26W TO WEAKEN. HOWEVER, BY TAU 48 THE MODEL FIELDS NOW A DEPICT A LESS ZONAL MID-LATITUDE PATTERN WITH A DIGGING 500/700 MB TROUGH FORECAST TO LIFT NIDA INTO THE MID-LATITUDES. IN ADDITION, A MUCH-WEAKENED NIDA IS ALSO EXPECTED TO NOW COMPLETE TRANSITION INTO A VERY WEAK BAROCLINIC SYSTEM BY TAU 72. THE TRACK UNCERTAINTY STILL REMAINS HIGH, ESPECIALLY IF THE SYSTEM DISSIPATES FASTER THAN EXPECTED THROUGH TAU 48. IN THE CASE NIDA DISSIPATES, THE SYSTEM WOULD DECOUPLE AND THE LLCC WOULD TRACK SOUTHWESTWARD WITH THE LOW-LEVEL FLOW AS PREVIOUSLY FORECAST. NUMERICAL GUIDANCE HAS COME INTO BETTER AGREEMENT OVER THE LAST 12 HOURS AND NO LONGER SHOWS TWO DISTINCT CLUSTERS. OVERALL, ALL SOLUTIONS, WITH THE EXCEPTION OF GFS, SHOW A TRACK WEST- NORTHWESTWARD THROUGH TAU 48 BEFORE RECURVING NIDA TO THE NORTHEAST. HOWEVER, THE TIMING WITH WHICH THE MODELS TURN THE SYSTEM POLEWARD DOES VARY. THIS FORECAST FAVORS A SOLUTION TO THE WEST OF THE JTWC CONSENSUS WHICH LEANS ON A MORE WESTWARD TRACK THROUGH AT LEAST TAU 36.// NNNN