MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (KAMMURI) WARNING NR 03// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 17W (KAMMURI), LOCATED APPROXIMATELY 498 NM SOUTHEAST OF IWO TO, HAS TRACKED WESTWARD AT 02 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A 242203Z SSMIS PASS AND A PARTIAL 250005Z ASCAT PASS. THE BEST TRACK POSITION HAS BEEN RELOCATED APPROXIMATELY 90 NM TO THE SOUTHWEST OF THE PREVIOUS ESTIMATE BASED ON THE CLARIFYING MICROWAVE IMAGERY AND ASCAT DATA. THE CURRENT INTENSITY OF 30 KNOTS IS CONSISTENT WITH DVORAK T-NUMBER ESTIMATES FROM PGTW AND KNES AND PERIPHERAL WINDS EVIDENT IN THE AFOREMENTIONED ASCAT PASS. TD 17W IS TRACKING VERY SLOWLY WESTWARD ALONG THE SOUTHERN PERIPHERY OF A DEVELOPING SUBTROPICAL STEERING RIDGE TO THE NORTH. THE BROAD LOW-LEVEL CIRCULATION CENTER (LLCC) IS DEVOID OF CENTRAL DEEP CONVECTION DUE TO SUBSIDENCE ALOFT INDUCED BY A NEARBY UPPER-LEVEL TROUGH. STRONG UPPER-LEVEL DIFFLUENCE AND CONVERGENT LOW-LEVEL FLOW ARE FUELING SUSTAINED DEEP CONVECTION WELL TO THE NORTHEAST OF THE CIRCULATION CENTER. 3. FORECAST REASONING. A. FORECAST TRACK SPEEDS IN THE TAU 72 TO TAU 96 PERIOD HAVE DECREASED FROM THE PREVIOUS WARNING DUE TO A SLOWER ANTICIPATED RECURVATURE INTO THE MID-LATITUDE WESTERLIES. AS A RESULT, EXTRATROPICAL TRANSITION IS NOT EXPECTED TO BEGIN UNTIL AFTER TAU 72. OTHERWISE, THERE ARE NO SIGNIFICANT CHANGES IN THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 17W IS EXPECTED TO MOVE NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE DEVELOPING STEERING RIDGE THROUGH TAU 72. THERE IS SOME UNCERTAINTY IN THE TRACK AMONG CONSENSUS MODELS. A WESTWARD GROUPING CONSISTING OF THE JAPANESE GLOBAL MODEL AND ENSEMBLE, NAVGEM, GFDN, AND ECMWF DEPICTS A MORE CONTINUOUS STEERING RIDGE AND, CONSEQUENTLY, A TRACK FARTHER TO THE WEST FOLLOWED BY A SLOWER AND SHARPER RECURVATURE. THE POLEWARD GROUPING CONSISTING OF HWRF, UKMET, GFS, AND THE GFS ENSEMBLE SHOW THE RIDGE BREAKING DOWN EARLY AND THE SYSTEM TRACKING NORTH-NORTHWESTWARD THROUGH TAU 72 FOLLOWED BY A BROADER RECURVATURE. THE CURRENT FORECAST FAVORS THE WESTWARD GROUPING THROUGH TAU 72 BASED ON ANALYSIS OF THE DEVELOPING STEERING RIDGE AND ITS ORIENTATION. THE SYSTEM WILL INTENSIFY SLOWLY OVER THE NEXT 24 TO 36 HOURS AS TROUGHING ALOFT SUPPRESSES CENTRAL CONVECTION. THEREAFTER, AS THE UPPER-LEVEL TROUGH FILLS AND UPPER- LEVEL OUTFLOW IS ENHANCED AROUND THE RIDGE PERIPHERY, STEADIER INTENSIFICATION IS ANTICIPATED. MARGINAL OCEAN HEAT CONTENT IS EXPECTED TO LIMIT THE PEAK INTENSITY TO AROUND 75 KNOTS AT TAU 72. C. IN THE EXTENDED PERIOD, TD 17W IS EXPECTED TO ROUND THE SUBTROPICAL RIDGE AXIS AND UNDERGO EXTRATROPICAL TRANSITION AS IT ACCELERATES INTO THE MID-LATITUDE WESTERLIES. THERE IS SOME UNCERTAINTY REGARDING WHERE AND HOW QUICKLY THE SYSTEM WILL RECURVE DUE TO SPREAD IN THE MODEL GUIDANCE DISCUSSED EARLIER. THE CURRENT FORECAST IS GENERALLY CONSISTENT WITH THE SLOW AND SHARPER RECURVATURE DEPICTED IN THE WESTWARD MODEL GROUPING, AND LIES WEST OF THE MULTI-MODEL CONSENSUS. GIVEN THE MODEL UNCERTAINTY, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN