Western Pacific Tropical Weather Discussion
The West Pacific has no National Hurricane Center discussion. The equivalent products are issued by the Joint Typhoon Warning Center (JTWC): the basin-wide Significant Tropical Weather Advisory and the prognostic reasoning behind each active warning.
Significant Tropical Weather Advisory (JTWC ABPW10)
Issued: 2026-11-05 09:00:00 UTC
ABPW10 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND SOUTH
PACIFIC OCEANS REISSUED/050900Z-060600ZNOV2026//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/050751ZNOV2026//
AMPN/REF A IS A TROPICAL CYCLONE FINAL WARNING.//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY:
(1) AT 05NOV26 0600Z, TROPICAL STORM 30W (IN-FA) WAS LOCATED
NEAR 29.4N 141.5E, APPROXIMATELY 366 NM SOUTH-SOUTHEAST OF YOKOSUKA,
JAPAN, AND HAD TRACKED NORTHEASTWARD AT 20 KNOTS OVER THE PAST SIX
HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 60 KNOTS
GUSTING TO 75 KNOTS. SEE REF A (WTPN31 PGTW 050900) FOR THE FINAL
WARNING ON THIS SYSTEM.
(2) NO OTHER TROPICAL CYCLONES.
B. TROPICAL DISTURBANCE SUMMARY:
(1) THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED NEAR
16.0N 159.9E IS NOW LOCATED NEAR 15.6N 157.2E, APPROXIMATELY 738 NM
EAST-NORTHEAST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) AND A 042103Z SSMIS F16 91GHZ MICROWAVE PASS DEPICT A POORLY-
ORGANIZED, FULLY EXPOSED WAVE FEATURE, WITH DISORGANIZED FLARING
CONVECTION TO THE NORTH AND EAST OF THE WAVE AXIS. A 042244Z ASCAT-C
PASS, SHOWS A WELL-DEFINED EASTERLY WAVE FEATURE, WITH AN AXIS ALONG
158E, MOVING RAPIDLY WESTWARD WITH ENHANCED WINDS ALONG THE NORTHERN
SEMICIRCLE WHILE LACKING A WESTERLY WIND COMPONENT EQUATORWARD THE
WAVE. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY FAVORABLE
ENVIRONMENT FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (VWS) OF 5-
10 KNOTS, WEAK UPPER-LEVEL OUTFLOW, AND WARM SEA SURFACE TEMPERATURES
(SST) OF 28-29C. GLOBAL DETERMINISTIC AND ENSEMBLE MODELS ARE IN GOOD
AGREEMENT PORTRAYING SLOW CONSOLIDATION INTO A CIRCULATION CENTER,
WHILE 99W SLOWLY TRANSITS WESTWARD, OVER THE NEXT 48 HOURS. MAXIMUM
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 23 KNOTS. MINIMUM SEA
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1010 MB. THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS REMAINS LOW.
(2) NO OTHER SUSPECT AREAS.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY: NONE.
C. SUBTROPICAL SYSTEM SUMMARY: NONE.
3. JUSTIFICATION FOR REISSUE: UPDATED PARA. 1.A.(1) WITH 30W FINAL
WARNING INFORMATION.//
Prognostic Reasoning for Active Systems
Tropical Storm In-Fa — 70 mph (1-minute sustained)
Issued: 2026-11-05 03:00:00 UTC
WDPN31 PGTW 050300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 051// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 28.1N 140.0E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 131 NM WEST-NORTHWEST OF CHICHI JIMA MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 17 KTS SIGNIFICANT WAVE HEIGHT: 31 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE LOW LEVEL CIRCULATION CENTER (LLCC) OF TYPHOON (TY) 30W (IN-FA) BECOMING INCREASINGLY EXPOSED AS THE CENTRAL CONVECTION CONTINUES TO BE SHEARED TO THE EAST. A 042121Z MWI MICROWAVE SUITE REVEALED THAT THE MICROWAVE EYE FEATURE IN THE 37 GHZ IMAGE HAS STRENGTHENED, ONCE AGAIN FULLY CLOSED AND RELATIVELY ALIGNED WITH THE CENTER IN THE 89 GHZ IMAGE. A 042032Z RCM-2 PASS SUPPORTS THIS MARGINALLY IMPROVED CONVECTIVE STRUCTURE WITH A BAND OF ENHANCED WINDS EXPANDING FROM THE NORTHERN SEMICIRCLE AND EXPANSIVE GALE-FORCE WINDS TO THE SOUTHEAST. ENVIRONMENTAL CONDITIONS ARE ASSESSED AS UNFAVORABLE WITH HIGH (35-40 KTS) VERTICAL WIND SHEAR CAUSING DRY AIR ENTRAINMENT, COOL (25-26 C) SEA SURFACE TEMPERATURES (SSTS), AND MODERATE OUTFLOW ALOFT, SUPPRESSED BY AN UPPER-LEVEL TROUGH POSITIONED OVER 30W. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC. REGARDING INTENSITY, THE SAR DATA SUGGESTS AN INTENSITY OF ROUGHLY 90 KTS WHILE AGENCY DVORAK AND CIMSS OBJECTIVE ESTIMATES CONTINUE TO DROP WELL BELOW TYPHOON STRENGTH. CONSIDERING THE KNOWN WEAKNESS OF THE DVORAK METHOD WITH SYSTEMS LACKING CENTRAL CONVECTION AS WELL AS A PREVIOUSLY OBSERVED HIGH BIAS OF RCM SAR DATA AS COMPARED WITH OTHER WIND SPEED DATA AND OBSERVATIONS, THE INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE, AVERAGED BETWEEN THE VARIOUS INPUTS. INITIAL WIND RADII BASIS: 042032Z RCM-2 SAR DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE SOUTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.0 - 65 KTS RCTP: T4.0 - 65 KTS CIMSS ADT: 57 KTS AT 042030Z CIMSS AIDT: 63 KTS AT 042030Z CIMSS D-MINT: 46 KTS AT 050103Z CIMSS D-PRINT: 47 KTS AT 050100Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 30+ KTS SST: 25-26 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: DRY AIR ENTRAINMENT ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 24 HOURS FORECAST DISCUSSION: 30W HAS BEGUN ITS NORTHEASTWARD TURN AS IT IS NOW POLEWARD OF THE AXIS OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHEAST AND ACCELERATES IN TRACK SPEED. THE SYSTEM IS EXPECTED TO CONTINUE DOING SO FOR THE REMAINDER OF THE FORECAST PERIOD. 30W IS FORECAST TO BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 12 AND COMPLETE BY TAU 24 AS IT BECOMES EMBEDDED UNDERNEATH THE UPPER-LEVEL JET AND LOSES TROPICAL CHARACTERISTICS. REGARDING INTENSITY, 30W IS EXPECTED TO STEADILY WEAKEN AS IT CROSSES THE 26 C ISOTHERM IMMINENTLY AND VWS RISES TO OVER 50 KTS BY TAU 24, ENTRAINING FURTHER DRY, COOL AIR INTO THE CORE. HOWEVER, THE WIND FIELD OF 30W IS EXPECTED TO CONTINUE EXPANDING AND 30W IS FORECAST TO COMPLETE ETT WHILE MAINTAINING TYPHOON STRENGTH. MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE EXCEPTION OF GALWEM AS A POLEWARD OUTLIER. EXCLUDING GALWEM, CROSS-TRACK SPREAD IS 50 NM AND ALONG-TRACK SPREAD IS 100 NM AT TAU 24. THE OFFICIAL JTWC FORECAST TRACK IS THUS ASSESSED WITH HIGH CONFIDENCE, IN GOOD AGREEMENT WITH THE TRACK OF THE MULTI-MODEL CONSENSUS AND HEDGING BETWEEN ITS TRACK SPEED AND THE SLIGHTLY FASTER AI CONSENSUS TRACK SPEED. INTENSITY MODEL GUIDANCE CONTINUES TO BE A BIT MORE SPREAD, WITH HAFS-A AND COAMPS-TC PREDICTING INTENSIFICATION OUT TO TAU 12, WHILE THE REMAINDER OF MODELS DEPICT SHARPER WEAKENING. GFS SHOWS RE-INTENSIFICATION AFTER TAU 12, WHILE GOOGLE DEEPMIND, HWRF, AND DECAY-SHIPS ALL PREDICT STEADY WEAKENING THROUGHOUT. WHILE NOT DEPICTED IN THE FORECAST, THERE IS A POSSIBILITY FOR SOME RE-INTENSIFICATION AS IT UNDERGOES ETT AS THE SYSTEM ENTERS AN AREA OF STRONG TEMPERATURE ADVECTION. THE OFFICIAL JTWC INTENSITY FORECAST IS THUS ASSESSED WITH MEDIUM CONFIDENCE, IN GOOD AGREEMENT WITH THE MULTI-MODEL CONSENSUS. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH INTENSITY 00-72 HR: MEDIUM//