ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM Tropical Storm Iselle Discussion Number 14 NWS National Hurricane Center Miami FL EP092026 200 PM PDT Wed Aug 26 2026 Deep convection remains limited this afternoon with Iselle, and its time as a tropical cyclone is limited. The low-level center remains fully exposed as the system deals with dry air and moderate wind shear. A recent scatterometer pass, which showed a peak wind of 34 kt, was helpful in adjusting the wind radii as the system continues to weaken. Subjective and objective satellite intensity estimates also continue to trend downward. Based on the scatterometer data and the deteriorating satellite appearance, the initial intensity is lowered to 35 kt. Iselle is expected to continue moving west-northwestward over the next few days, steered by a mid-level ridge to the north. Increasing wind shear, cooler sea surface temperatures, and a drier air mass will continue to weaken the cyclone. The latest NHC forecast follows these trends and indicates Iselle will likely become a post-tropical cyclone tonight. The post-tropical/remnant low is then expected to gradually spin down and open into a trough in about 2 to 3 days. Very minor adjustments were made to the previous NHC track and intensity forecasts. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 22.7N 124.9W 35 KT 40 MPH 12H 27/0600Z 23.2N 126.2W 35 KT 40 MPH...POST-TROPICAL 24H 27/1800Z 23.9N 127.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 28/0600Z 24.6N 129.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 28/1800Z 25.3N 131.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 29/0600Z...DISSIPATED $$ Forecaster Kelly NNNN

WDPN31 PGTW 262100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 034// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 28.6N 125.3E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 183 NM NORTHWEST OF KADENA AB MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 30 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A STEADILY BUT SLOWLY WEAKENING TYPHOON 17W, WHICH HAS MAINTAINED A 30NM WIDE, RAGGED EYE FEATURE OVER THE PAST SIX HOURS. THE PREVIOUSLY OBSERVED CLOUD-TOP WARMING HAS CEASED WITH THE APPROACH OF DIURNAL MAXIMUM AND SMALL POCKETS OF DEEP CONVECTION ARE REFORMING ALONG THE EASTERN FLANK OF THE EYE. A 261726Z NOAA-20 ATMS 89GHZ MICROWAVE IMAGE REVEALED A LARGE MICROWAVE EYE FEATURE, TILTED WESTWARD WITH REFERENCE TO THE LOWER-LEVEL EYE DUE TO THE PERSISTENT MODERATE EASTERLY SHEAR, AND MODERATE CONVECTIVE ACTIVITY ACROSS THE SOUTHEASTERN FLANK. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 30NM WIDE EYE IN THE EIR AND THE MICROWAVE IMAGE DISCUSSED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON AN AVERAGE OF THE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES NOTED BELOW. ENVIRONMENTAL CONDITIONS ARE MARGINAL, WITH THE WARM SSTS AND MODERATE RADIAL OUTFLOW ALOFT BEING OFFSET BY THE MODERATE TO HIGH EASTERLY SHEAR AND STEADILY DECREASING OHC. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SYSTEM IS POSITIONED TO THE SOUTH OF A WEAKNESS IN THE SUBTROPICAL RIDGE (STR). AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.5 - 77 KTS RJTD: T5.0 - 90 KTS RCTP: T4.5 - 77 KTS KNES: T4.5 - 77 KTS CIMSS SATCON: 84 KTS AT 261728Z CIMSS ADT: 65 KTS AT 261730Z CIMSS AIDT: 71 KTS AT 261730Z CIMSS D-MINT: 86 KTS AT 261729Z CIMSS D-PRINT: 75 KTS AT 261800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: DRY MID-LEVEL AIR TO THE NORTH. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TYPHOON (TY) 17W IS CURRENTLY POSITIONED SOUTH OF A WEAKNESS IN THE STR TO THE NORTH, WHICH HAS RESULTED IN THE SYSTEM SLOWLY DRIFTING NORTHWESTWARD OVER THE PAST 12 HOURS. OVER THE LAST SIX HOURS, THE SYSTEM HAS REACHED ITS SLOWEST FORWARD SPEED, BUT IMPORTANTLY, HAS BEGUN TO TURN WESTWARD AS THE STEERING PATTERN BEGINS TO SHIFT. TY 17W WILL CONTINUE TO TRACK GENERALLY WESTWARD FOR THE NEXT 12 HOURS AT A SLIGHTER FASTER SPEED THAN ITS CURRENTLY TRACKING. THE SYSTEM THEN TURNS MORE SOUTHWESTWARD AS A LARGE STR CENTERED OVER NORTH-CENTRAL CHINA BECOMES THE DOMINANT STEERING INFLUENCE. TY 17W IS FORECAST TO MAKE LANDFALL ALONG THE CHINESE COAST IN SOUTHERN ZHEJIANG PROVINCE BETWEEN TAU 24 AND TAU 36, BEFORE CONTINUING INLAND ALONG A WEST-SOUTHWESTWARD TRACK THROUGH TAU 60. REGARDING INTENSITY, THE SYSTEM IS EXPECTED TO SLOWLY WEAKEN AS IT APPROACHES THE CHINESE COAST DUE TO THE PERSISTENT MODERATE TO HIGH EASTERLY SHEAR AND DRY AIR ENTRAINMENT. ONCE THE SYSTEM MOVES ASHORE, IT WILL RAPIDLY DECAY DUE TO LAND INTERACTION AND FRICTIONAL EFFECTS, ULTIMATELY DISSIPATING OVER SOUTHEASTERN CHINA WITHIN THE NEXT 60 HOURS. MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD THROUGH THE END OF THE FORECAST PERIOD. THE ONE NOTABLE EXCEPTION BEING THE EC-AIFS, WHICH TRACKS THE SYSTEM ON A MUCH MORE SOUTHWARD TRAJECTORY, ENDING THE SYSTEM JUST NORTH OF HONG KONG BY TAU 60. THE JTWC FORECAST IS PLACED…

WDPN33 PGTW 262100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (TWENTY) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.2N 161.0E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 343 NM WEST-SOUTHWEST OF WAKE ISLAND MOVEMENT PAST 6 HOURS: EASTWARD AT 01 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXTREMELY COMPACT AND DISORGANIZED SYSTEM, WITH A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO THE SOUTH OF FLARING DEEP CONVECTION AND ASSOCIATED MID-LEVEL MESOVORTEX. A 261524Z AMSR2 36GHZ IMAGE REVEALED THE COMPACT LLCC EXPOSED ON THE SOUTHERN EDGE OF A WEDGE OF LINEAR CONVECTION EXTENDING NORTHWARD. BASED ON COMPARISON OF THE AMSR2 IMAGERY AND THE EARLIER ASCAT DATA, THE SYSTEM HAS REMAINED QUASI-STATIONARY SINCE 1200Z. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AMSR2 DATA AND ANIMATED MSI. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW. THE ENVIRONMENT IS MARGINALLY FAVORABLE, CHARACTERIZED BY LOW DEEP- LAYER WIND SHEAR, MODERATE POLEWARD OUTFLOW ALOFT, AND WARM SSTS WITH HIGH OHC. THE SYSTEM IS APPROXIMATELY 415NM SOUTHWEST OF INVEST 91W AND UNDERGOING THE INITIAL PHASE OF BINARY INTERACTION. THE TWO SYSTEMS ARE INTER-CONNECTED WITHIN A 1009MB CLOSED OUTER ISOBAR. THE TWO ARE ALSO INTERTWINED ALOFT, WITH 20W POSITIONED IN THE SOUTHWESTERN END OF AN ELONGATED UPPER-LEVEL ANTICYCLONE CENTERED ROUGHLY IN THE VICINITY OF INVEST 91W. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT; WEAK BAND OF LOW-LEVEL SOUTHWESTERLIES ALONG THE NORTHWESTERN PERIPHERY OF A NEAR EQUATORIAL RIDGE (NER) AND BINARY INTERACTION WITH INVEST 91W TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.0 - 25 KTS KNES: T2.0 - 30 KTS PHFO: T2.5 - 35 KTS CIMSS SATCON: 34 KTS AT 261720Z CIMSS ADT: 34 KTS AT 261740Z CIMSS AIDT: 32 KTS AT 261740Z CIMSS D-MINT: 22 KTS AT 261751Z CIMSS D-PRINT: 22 KTS AT 261800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: EXTREMELY COMPACT NATURE OF THE SYSTEM AND THE INFLUENCE OF THE BINARY INTERACTION WITH 91W. 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: TROPICAL DEPRESSION (TD) 20W HAS MOVED LITTLE IN THE PAST SIX HOURS, CURRENTLY TRAPPED IN A WEAK AND COMPETING STEERING ENVIRONMENT. OVER THE NEXT 12 TO 24 HOURS, TD 20W WILL TRACK SLOWLY EASTWARD ALONG THE NORTH SIDE OF THE WEAK NER TO THE SOUTHEAST. AFTER TAU 24, THE NER IS EXPECTED TO RECEDE EQUATORWARD, WHILE A NOSE OF THE STR TO THE NORTHEAST PUSHES SOUTHWARD TO THE EAST OF BOTH 20W AND 91W. THE COMBINATION OF A STRENGTHENING GRADIENT ON THE EASTERN SIDE OF TD 20W AND THE INFLUENCE OF THE BINARY INTERACTION WITH 91W, WILL PUSH TD 20W NORTHWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, THE SYSTEM WILL REMAIN STAGNANT OR INTENSIFY ONLY SLIGHTLY OVER THE COURSE OF THE NEXT 24 HOURS DUE TO THE CONTINUED INFLUENCE OF MODERATE MID-LEVEL SOUTHERLY SHEAR AND A RELATIVELY WEAK OUTFLOW ENVIRONMENT ALOFT. BY TAU 36, AS 91W MOVES RAPIDLY NORTHWARD INTO A BAND OF UNFAVORABLE CONDITIONS ALOFT, 20W WILL HAVE AN OPPORTUNITY TO INTENSIFY MORE RAPIDLY AS IT REMAINS IN A REGION OF LIGHT SHEAR A…