MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (TWENTYSEVEN) WARNING NR 19// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 159 NM WEST OF NAVSTA GUAM, HAS TRACKED NORTHWESTWARD AT 25 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE MAIN CONVECTION HAS SHEARED SOUTHWESTWARD OF A PARTIALLY EXPOSED, BROAD, LOW LEVEL CIRCULATION CENTER (LLCC). A 240206Z 89GHZ GMI MICROWAVE IMAGE CONFIRMS THAT THE DEEP CONVECTION IS SHEARED TO THE SOUTHWEST OF THE LLCC. ADDITIONALLY, A 240031Z METOB-B ASCAT IMAGE REVEALS THE LOW LEVEL CIRCULATION TO BE HIGHLY ELONGATED. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC EVIDENT IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 40 KNOTS IS HEDGED ABOVE MULTI AGENCY DVORAK INTENSITY ESTIMATES RANGING FROM T2.0 TO T2.5 (30-35 KNOTS) FROM RJTD AND PGTW RESPECTIVELY AND IS SUPPORTED BY A SATCON ESTIMATE OF 41 KNOTS. ENVIRONMENTAL ANALYSIS REVEALS THAT THE SYSTEM IS TRACKING THROUGH WARM (31 CELSIUS) SEA SURFACE TEMPERATURES AND IS IN AN AREA OF MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS). TS 27W CURRENTLY HAS GOOD EQUATORWARD OUTFLOW, HOWEVER, THE POLEWARD OUTFLOW IS BEING SUPPRESSED BY SUBSIDENCE FROM A TUTT CELL LOCATED EAST OF GUAM. THE SYSTEM IS TRACKING TO THE NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF A BUILDING SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 27W WILL CONTINUE TO TRACK TO THE NORTHWEST FOR THE NEXT 72 HOURS ALONG THE SOUTHEASTERN PERIPHERY OF THE STR. THE SYSTEM IS FORECAST TO GRADUALLY INTENSIFY AS MARGINALLY FAVORABLE CONDITIONS WILL PERSIST. AROUND TAU 72, THE SYSTEM WILL APPROACH THE RIDGE AXIS AND THE TRACK WILL SHIFT MORE NORTHERLY AS IT BEGINS TO RECURVE. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. AFTER TAU 72, TS 27W WILL PASS THE RIDGE AXIS AND ROUND THE WESTERN EDGE OF THE STR AND ACCELERATE NORTHEASTWARD. THE SYSTEM WILL ALSO BEGIN TO INTERACT WITH AN APPROACHING MID-LATITUDE TROUGH. INCREASED POLEWARD OUTFLOW ASSOCIATED WITH THE MID-LATITUDE TROUGH WILL ALLOW FOR ADDITIONAL INTENSIFICATION, EVENTUALLY REACHING A MAXIMUM OF 80 KNOTS BY THE END OF THE FORECAST PERIOD. NUMERIC MODEL GUIDANCE BEGINS TO SPREAD IN BOTH TRACK DIRECTION AND SPEED AFTER TAU 48 WITH JGSM BEING THE PRINCIPLE OUTLIER, TRACKING THE SYSTEM MUCH FARTHER EAST THAN THE REMAINING CONSENSUS MEMBERS. THE SYSTEM SPEED ALSO VARIES LENDING A HIGH DEGREE OF UNCERTAINTY IN THE SYSTEM SPEED IN THE LATER TAUS. DUE TO THE VARIABILITY IN BOTH TRACK AND SPEED, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN