Thirtyone
Western Pacific
Tropical Depression · WP312026
18.4°N,
145.8°E
Moving west at 16 mph
Max Winds
35 mph
Pressure
1005 mb
Forecast Points
8
JMA Winds (10-min avg)
30.0 kt
JMA Pressure
1004.0 hPa
JMA (10-min average): tracked, no typhoon number assigned
JTWC Warning #2 06 Nov 12:00 UTC
WTPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL DEPRESSION 31W (THIRTYONE) WARNING NR 002//
RMKS/
1. TROPICAL DEPRESSION 31W (THIRTYONE) WARNING NR 002
01 ACTIVE TROPICAL CYCLONE IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
061200Z --- NEAR 17.9N 147.5E
MOVEMENT PAST SIX HOURS - 270 DEGREES AT 14 KTS
POSITION ACCURATE TO WITHIN 040 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 17.9N 147.5E
---
FORECASTS:
12 HRS, VALID AT:
070000Z --- 18.7N 144.5E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT
010 NM SOUTHEAST QUADRANT
010 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 295 DEG/ 15 KTS
---
24 HRS, VALID AT:
071200Z --- 19.9N 141.7E
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
090 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 295 DEG/ 13 KTS
---
36 HRS, VALID AT:
080000Z --- 21.0N 139.1E
MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 050 KT WINDS - 040 NM NORTHEAST QUADRANT
020 NM SOUTHEAST QUADRANT
020 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 110 NM NORTHEAST QUADRANT
060 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
090 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 290 DEG/ 12 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
081200Z --- 21.8N 136.7E
MAX SUSTAINED WINDS - 070 KT, GUSTS 085 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT
020 NM SOUTHEAST QUADRANT
020 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
030 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
070 NM SOUTHWEST QUADRANT
100 NM NORTHWEST QUADRANT
VECTOR TO 60 HR POSIT: 305 DEG/ 08 KTS
---
60 HRS, VALID AT:
090000Z --- 22.7N 135.2E
MAX SUSTAINED WINDS - 090 KT, GUSTS 110 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
020 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
030 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
090 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 005 DEG/ 04 KTS
---
72 HRS, VALID AT:
091200Z --- 23.5N 135.3E
MAX SUSTAINED WINDS - 100 KT, GUSTS 125 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
030 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT
050 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 080 NM NORTHEAST QUADRANT
080 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
080 NM NORTHWEST QUADRANT
VECTOR TO 96 HR POSIT: 070 DEG/ 09 KTS
---
LONG RANGE OUTLOOK:
---
96 HRS, VALID AT:
101200Z --- 24.7N 139.2E
MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 015 NM NORTHEAST QUADRANT
025 NM SOUTHEAST QUADRANT
025 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT
050 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
050 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT
090 NM SOUTHEAST QUADRANT
100 NM SOUTHWEST QUADRANT
130 NM NORTHWEST QUADRANT
VECTOR TO 120 HR POSIT: 075 DEG/ 13 KTS
---
120 HRS, VALID AT:
111200Z --- 26.2N 144.9E
MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 064 KT WINDS - 040 NM NORTHEAST QUADRANT
045 NM SOUTHEAST QUADRANT
050 NM SOUTHWEST QUADRANT
055 NM NORTHWEST QUADRANT
RADIUS OF 050 KT WINDS - 110 NM NORTHEAST QUADRANT
090 NM SOUTHEAST QUADRANT
080 NM SOUTHWEST QUADRANT
110 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 215 NM NORTHEAST QUADRANT
130 NM SOUTHEAST QUADRANT
115 NM SOUTHWEST QUADRANT
180 NM NORTHWEST QUADRANT
---
REMARKS:
061500Z POSITION NEAR 18.1N 146.7E.
06NOV26. TROPICAL DEPRESSION 31W (THIRTYONE), LOCATED
APPROXIMATELY 293 NM NORTH-NORTHEAST OF ANDERSEN AFB, HAS TRACKED
WESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS.
MINIMUM CENTRAL PRESSURE AT 061200Z IS 1006 MB. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 061200Z IS 13 FEET. NEXT WARNINGS AT
062100Z, 070300Z, 070900Z AND 071500Z.//
NNNN
Forecast Reasoning 06 Nov 15:00 UTC
WDPN31 PGTW 061500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 31W (THIRTYONE) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.9N 147.5E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 293 NM NORTH-NORTHEAST OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WESTWARD AT 14 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED SHORTWAVE INFRARED (SWIR) SATELLITE IMAGERY DEPICTS A VERTICALLY TILTED, ASYMMETRIC SYSTEM, WITH THE MID-LEVEL VORTEX DISPLACED WESTWARD (DOWNSHEAR) OF A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). A 061113Z ASCAT PARTIAL PASS REVEALED A COMPACT LLCC ON THE EDGE OF THE OBSERVATIONAL SWATH, WITH WINDS OF 25-30 KNOTS ON THE NORTHERN FLANK OF THE LLCC, 20-KNOT WINDS BEGINNING TO WRAP AROUND THE WESTERN SEMICIRCLE, AND LIGHTER WINDS ON THE SOUTHERN FLANK. A 061059Z GMI COLOR-ENHANCED 89 GHZ MICROWAVE IMAGE DEPICTED SHALLOW CONVECTIVE BANDING FEATURES WRAPPING INTO A WELL-DEFINED, BUT EXPOSED LLCC LOCATED TO THE EAST OF AN AREA OF DISORGANIZED DEEP CONVECTION, WHICH REMAINS UNABLE TO WRAP UPSHEAR DUE TO MODERATE EASTERLY VERTICAL WIND SHEAR (VWS). UPPER-LEVEL ATMOSPHERIC MOTION VECTORS (AMVS) DEPICT DEEP, STRONG EASTERLY FLOW DIRECTLY OVERLYING TD 31W, THOUGH INITIAL SIGNS OF DIFLUENCE AND A SPLIT IN THE UPSTREAM FLOW PATTERN ARE BEGINNING TO EMERGE IN THE AMV DATA. THE 061200Z UPPER-AIR SOUNDING FROM PGUM INDICATES DEEP EASTERLIES EXTENDING UP TO APPROXIMATELY 400 MB, BEFORE VEERING SHARPLY TO SOUTHWESTERLIES BETWEEN 400 MB AND 350 MB AND RESUMING EASTERLY FLOW ABOVE THAT LAYER, HIGHLIGHTING THE PRIMARY MECHANISM DRIVING THE ENHANCED MID-LEVEL SHEAR. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED LLCC IN THE SWIR IMAGERY AND THE ASCAT DATA. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE ASCAT DATA, CONFIRMING THE OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW. ENVIRONMENTAL CONDITIONS ARE GENERALLY FAVORABLE, CHARACTERIZED BY LOW TO MODERATE DEEP-LAYER SHEAR, HIGH SEA SURFACE TEMPERATURES (SSTS), AND STRONG DIVERGENT OUTFLOW ALOFT, THOUGH TEMPERED BY THE VERTICALLY DECOUPLED VORTEX. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.5 - 25 KTS CIMSS ADT: 28 KTS AT 061130Z CIMSS AIDT: 33 KTS AT 061130Z CIMSS D-MINT: 30 KTS AT 061102Z CIMSS D-PRINT: 30 KTS AT 061130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH 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: OVER THE PAST SIX HOURS, TROPICAL DEPRESSION (TD) 31W HAS TRANSITIONED TO A DUE WESTWARD TRAJECTORY, STEERED BY THE MORE ZONALLY ORIENTED LOWER-LEVEL FLOW AXIS OF THE STR TO THE NORTHEAST DUE TO SHALLOW VORTEX DEPTH. GLOBAL MODELS AGREE THAT OVER THE NEXT 6-12 HOURS, THE RIDGE AXIS WILL AMPLIFY INTO A MORE NORTHWEST-SOUTHEAST ORIENTATION, ALLOWING TD 31W TO RESUME A NORTHWESTWARD TRAJECTORY; HOWEVER, A MORE ZONAL WESTWARD NEAR-TERM TRAJECTORY REMAINS POSSIBLE IF THE VORTEX REMAINS DECOUPLED. TRANSLATIONAL SPEEDS ARE FORECAST TO REMAIN RELATIVELY STABLE THROUGH TAU 24 BEFORE GRADUALLY DECELERATING AS THE STR CENTER PROPAGATES EASTWARD AND THE STEERING GRADIENT RELAXES. AFTER TAU 36, THE PASSAGE OF A MID-LATITUDE SHORTWAVE TROUGH TO THE NORTH WILL BEGIN TO ERODE THE RIDGE, WITH A COL EXPECTED TO DEVELOP SOUTH OF JAPAN. BY TAU 60, TD 31W WILL APPROACH THIS COL AND RAPIDLY DECELERATE AS IT ENTERS THE WEAK STEERING ENVIRONMENT. SIMULTANEOUSLY, A STRONG LOW-LEVEL NORTHEASTERLY COLD SURGE WILL ADVECT OUT OF THE EAST CHINA SEA AND INTO THE PHILIPPINE SEA. BY TAU 72, THE LEADING EDGE OF THE SURGE FLOW WILL IMPINGE UPON TD 31W, WHILE ALOFT THE SYSTEM REMAINS POSITIONED WITHIN THE COL-INDUCED WEAK STEERING PATTERN, INDUCING A GRADUAL POLEWARD DRIFT. CONCURRENTLY, IN THE DEEP-LAYER FLOW PATTERN, AN EXTENSION OF THE STR WILL BIFURCATE INTO A SEPARATE NEAR- EQUATORIAL RIDGE (NER) SOUTHWEST OF GUAM, IMPARTING A WESTERLY DEEP- LAYER STEERING INFLUENCE ON TD 31W. THE COMBINATION OF LOW-LEVEL CONVERGENCE ALONG THE COLD FRONTAL BOUNDARY AND THE DEEP-LAYER WESTERLY STEERING FLOW WILL ACCELERATE TD 31W EAST-NORTHEASTWARD FROM TAU 72 THROUGH TAU 120. REGARDING INTENSITY, AS LONG AS DEEP EASTERLY SHEAR PERSISTS, THE SYSTEM WILL INTENSIFY GRADUALLY AT A CLIMATOLOGICAL RATE OF APPROXIMATELY ONE DVORAK T-NUMBER PER DAY. VERTICAL WIND SHEAR IS FORECAST TO ABATE AROUND TAU 36, WHICH SHOULD FACILITATE RAPID VERTICAL VORTEX ALIGNMENT AND SUBSEQUENT ACCELERATED INTENSIFICATION, THOUGH THE OFFICIAL FORECAST REMAINS JUST BELOW EXPLICIT RAPID INTENSIFICATION (RI) THRESHOLDS. FAVORABLE THERMODYNAMIC AND DYNAMIC CONDITIONS PERSIST THROUGH TAU 72, SUPPORTING A PEAK INTENSITY OF 100 KNOTS, BEFORE RAPIDLY INCREASING MID-LATITUDE WESTERLY SHEAR, DRY AIR ENTRAINMENT, AND DECREASING SSTS INDUCE A SHARP WEAKENING TREND AFTER TAU 96. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 72, WITH SIGNIFICANT TRACK DIVERGENCE EMERGING AT TAU 72. CROSS-TRACK SPREAD IS LOW THROUGH TAU 60, BEFORE RAPIDLY INCREASING TO 210 NM BY TAU 72 AS THE SYSTEM REACHES THE SYNOPTIC INFLECTION POINT, WHERE ALL CONSENSUS MEMBERS AGREE THE SYSTEM WILL RECURVE NORTHEASTWARD. THE GFS IS POSITIONED ON THE SOUTHERN BOUNDARY OF THE GUIDANCE ENVELOPE THROUGH TAU 72, WHILE THE EC-AIFS AND ECMWF RESIDE ON THE NORTHERN BOUNDARY. AFTER TAU 72, CROSS-TRACK SPREAD REMAINS RELATIVELY CONSTRAINED; HOWEVER, ALONG-TRACK SPREAD INCREASES DRAMATICALLY. THE GFS AND NAVGEM DEPICT A VERY SLOW EAST- SOUTHEASTWARD DRIFT AFTER TAU 72, FOLLOWED CLOSELY BY GALWEM. THE ECMWF, GEFS, ECEPS, WINDBORNE EXPERIMENTAL MODEL, AND THE CONSENSUS MEAN ADVECT THE SYSTEM NORTHEASTWARD AT A MODERATE PACE, WHILE THE DATA-DRIVEN AI MODELS, LED BY THE OPERATIONAL GOOGLE DEEPMIND (GDM) AND EC-AIFS, ACCELERATE NORTHEASTWARD AT TRANSLATIONAL SPEEDS EXCEEDING 50 KNOTS. THIS GENERATES AN EXTREME ALONG-TRACK SPREAD EXCEEDING 1,500 NM BETWEEN THE GFS AND EC-AIFS. ENSEMBLE GUIDANCE IS SIMILARLY DISPERSED, DEPICTING SIGNIFICANT INTRA-ENSEMBLE SPREAD EVEN THOUGH THE MAJORITY OF ENSEMBLE MEANS AGREE ON THE SYNOPTIC TRAJECTORY. INDIVIDUAL MEMBERS OF THE EXPERIMENTAL JTWC SUPER ENSEMBLE RANGE IN THEIR TAU 120 POSITIONS FROM NEAR LUZON TO FAR EAST OF JAPAN, SPANNING WELL OVER 1,500 NM. THE OFFICIAL JTWC FORECAST IS PLACED WITH LOW CONFIDENCE NEAR THE GEFS MEAN, ECEPS MEAN, AND WINDBORNE CLUSTER, AND SLIGHTLY SLOWER THAN THE DETERMINISTIC ECMWF. INTENSITY GUIDANCE IS IN GENERALLY GOOD AGREEMENT ON THE OVERALL TIMING AND EVOLUTION OF THE INTENSITY PROFILE, BUT EXHIBITS SIGNIFICANT SPREAD REGARDING PEAK INTENSITY, WHICH RANGES FROM A MINIMUM OF 55 KNOTS (COTC AND SHIPS-NAVGEM) TO A MAXIMUM OF 110 KNOTS (HAFS-A, HWRF, AND CTCX). THE GDM SOLUTION RESIDES CLOSE TO THE CONSENSUS AT 80-90 KNOTS. THE JTWC INTENSITY FORECAST IS PLACED JUST BELOW THE CONSENSUS MEAN THROUGH TAU 48, BLENDS TOWARD THE HWRF PEAK AT TAU 72, AND SUBSEQUENTLY FOLLOWS THE GRADUAL WEAKENING TREND OF THE MESOSCALE DYNAMICAL MODELS AFTER TAU 72. FORECAST CONFIDENCE: TRACK 00-72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN
Source: U.S. Navy/Air Force Joint Typhoon Warning Center (JTWC), via the UCAR Tropical Cyclone Guidance Project. JTWC data is in the public domain. · Updated 2026-11-06 19:55 UTC · JMA analysis: Source: Japan Meteorological Agency (10-minute average winds).