WDPN31 PGTW 190900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 07W (SEVEN) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.3N 141.8E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 182 NM WEST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL DEPRESSION 07W WITH DEEP CONVECTION FORMING ALONG THE EASTERN SEMICIRCLE OF A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). A 190619Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALED LOW-LEVEL CLOUDS TIGHTLY WRAPPING INTO THE ASSESSED CENTER, SUPPORTING THE INITIAL POSITION WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND CIMSS INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 07W IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND VERY WARM (30-31 C) SEA SURFACE TEMPERATURES. SOME SLIGHT DRY AIR ENTRAINMENT WITHIN THE WESTERN PERIPHERY IS LIKELY THE CAUSE FOR MINIMAL CONVECTIVE DEVELOPMENT WITHIN THE WESTERN PORTION OF THE CIRCULATION. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF AN ELONGATED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.0 - 25 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 36 KTS AT 190430Z CIMSS ADT: 34 KTS AT 190600Z CIMSS AIDT: 36 KTS AT 190600Z CIMSS D-MINT: 27 KTS AT 190619Z CIMSS D-PRINT: 26 KTS AT 190600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 30-31 CELSIUS OUTFLOW: MODERATE EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 07W IS FORECAST TO TRACK WEST-NORTHWESTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE ELONGATED STR THROUGH TAU 72. NEAR TAU 72, A SEPARATE STR IS EXPECTED TO BUILD OVER THE NORTHERN SOUTH CHINA SEA. THIS WILL CREATE A COMPETING STEERING ENVIRONMENT, WHICH WILL CAUSE 07W TO SLOW DOWN AS IT TURNS POLEWARD THROUGH TAU 120. REGARDING INTENSITY, 07W IS FORECAST TO STEADILY INTENSIFY OVER THE NEXT 24 HOURS AS THE VORTEX BECOMES MORE SYMMETRIC AND VERTICALLY ALIGNED. AFTER TAU 24, A MORE RAPID RATE OF INTENSIFICATION IS EXPECTED AS SHEAR REMAINS LOW AND SEA SURFACE TEMPERATURES REMAIN VERY WARM. RAPID INTENSIFICATION IS EXPLICITLY FORECAST TO OCCUR FROM TAU 24 TO TAU 72 (50 KTS TO 115 KTS). A PEAK INTENSITY IS FORECAST TO OCCUR NEAR TAU 72 AS EASTERLY SHEAR GREATLY INCREASES AFTERWARD. ADDITIONALLY, THE SLOW MOVEMENT SPEED NEAR THE END OF THE FORECAST PERIOD MAY ALLOW FOR THE UPWELLING OF COOLER WATERS, FURTHER SUPPORTING A WEAKENING TREND. MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT ON A WEST-NORTHWESTWARD TRACK THROUGH TAU 72 WITH A 180 NM CROSS-TRACK SPREAD AT TAU 72. AFTER TAU 72, THE GEFS AND UKMET ENSEMBLE MEANS CREATE AN EASTWARD OUTLIER GROUPING. THEY DEPICT THE POLEWARD TURN TO OCCUR NEAR 129E WHILE THE REMAINDER OF GUIDANCE SHOWS THE POLEWARD TURN OCCURRING WEST OF 127E. AS A RESULT, THE CROSS-TRACK SPREAD AT TAU 120 INCREASES TO AROUND 350 NM. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE CONSENSUS THROUGH TAU 72 AND THEN OFFSET TO THE WEST OF CONSENSUS THEREAFTER TO OFFSET THE OUTLIERS. INTENSITY GUIDANCE GENERALLY AGREES ON INTENSIFICATION THROUGH TAU 72 FOLLOWED BY WEAKENING AFTERWARD. HOWEVER, THE PEAK INTENSITY HAS QUITE A LARGE RANGE. THE HAFS-A IS THE MOST AGGRESSIVE MODEL, SHOWING A PEAK INTENSITY OF 145 KTS WHILE DECAY SHIPS IS CLOSER TO 75 KTS. THE JTWC INTENSITY FORECAST IS PLACED NEAR TO THE CONSENSUS THROUGH TAU 60 AND THEN CLOSER TO THE HWRF SUGGESTION THROUGH TAU 120, WHICH SUGGESTS A PEAK INTENSITY OF 125 KTS. THE LARGE RANGE IN PEAK INTENSITIES AND INHERENT UNCERTAINTIES REGARDING RI CAUSES THERE TO BE LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN