CLICK ON THE IMAGERIES BELOW TO GET THEM ENLARGED
JTWC IS ISSUING 6 HOURLY WARNINGS AND 3 HOURLY SATELLITE BULLETINS ON 17W,20W AND 21W. 3 HOURLY SATELLITE BULLETINS ARE ISSUED ON 01C
WDPN31 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 28.4N 124.2E
INITIAL INTENSITY: 80 KTS
GEOGRAPHIC REFERENCE: 245 NM NORTHEAST OF TAIPEI, TAIWAN
MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
SIGNIFICANT WAVE HEIGHT: 30 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
17W (SAUDEL) TRANSITING WEST-NORTHWESTWARD TOWARD ZHEJIANG PROVINCE,
CHINA. DESPITE MARGINALLY UNFAVORABLE ENVIRONMENTAL CONDITIONS,
PRIMARILY DRIVEN BY MODERATE NORTHEASTERLY VERTICAL WIND SHEAR (VWS)
AND SIGNIFICANT DRY AIR INTRUSION, THE VORTEX HAS MANAGED TO REMAIN
STRUCTURALLY COHERENT. FOLLOWING A BRIEF PERIOD OF CONVECTIVE EYE-
FILL, THE CYCLONE HAS RE-ESTABLISHED A BANDING EYE FEATURE, INDICATING
SUSTAINED INTENSITY. WARM SEA SURFACE TEMPERATURES (SST) OF 28-29 C
AND GOOD EQUATORWARD OUTFLOW OFFSET THE OTHERWISE DEGRADING
THERMODYNAMIC ENVIRONMENT. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE UTILIZING VISIBLE SATELLITE IMAGERY, LENDING TO A TIGHT
CONSENSUS OF AGENCY POSITION FIXES. THE INITIAL INTENSITY OF 80 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF OBJECTIVE
AND SUBJECTIVE AIDS LISTED BELOW.
INITIAL WIND RADII BASIS: 270111Z METOP-C ASCAT AND 270109Z METOP-C
UHR ASCAT DATA
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHWEST
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T4.5 - 77 KTS
RJTD: T5.0 - 90 KTS
RCTP: T4.0 - 65 KTS
KNES: T4.5 - 77 KTS
CIMSS SATCON: 93 KTS AT 270444Z
CIMSS ADT: 90 KTS AT 270540Z
CIMSS AIDT: 76 KTS AT 270600Z
CIMSS D-MINT: 84 KTS AT 270530Z
CIMSS D-PRINT: 80 KTS AT 270600Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 15-20 KTS
SST: 28-29 CELSIUS
OUTFLOW: MODERATE EQUATORWARD
OTHER FACTORS: DRY AIR ENTRAINMENT AND PERSISTENT NORTHEASTERLY
VERTICAL WIND SHEAR
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TY 17W IS FORECAST TO CONTINUE TRACKING WEST-
SOUTHWESTWARD TOWARD LANDFALL OVER EAST-CENTRAL CHINA, LIKELY NEAR THE
CITY OF TAIZHOU. AN INCREASINGLY HOSTILE ENVIRONMENT, DRIVEN PRIMARILY
BY ESCALATING VWS AND PERSISTENT MID-LEVEL DRY-AIR ENTRAINMENT, WILL
RESULT IN GRADUAL WEAKENING PRIOR TO LANDFALL. AFTER THE STR ANCHORED
TO THE NORTHEAST STEERS THE SYSTEM OVER LAND, TERMINAL WEAKENING WILL
PROGRESS AT A MUCH FASTER RATE, ACCELERATED BY THE FRICTIONAL EFFECTS
OF ROUGH LAND INTERACTION. THE SYSTEM IS EXPECTED TO WEAKEN
SIGNIFICANTLY BY TAU 48 AS THE VORTEX TRAVERSES HIGHER TERRAIN, WITH
COMPLETE DISSIPATION PROJECTED TO OCCUR AT OR PRIOR TO TAU 60.
MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS EXCELLENT
AGREEMENT, AS ALL AVAILABLE DYNAMIC MODELS RESOLVE A SIMILAR LANDFALL
TIMELINE AND GEOGRAPHIC LOCATION, FOLLOWED BY A SUBSEQUENT
SOUTHWESTWARD VEER OVER LAND. AS SUCH, THE OFFICIAL JTWC TRACK
FORECAST IS POSITIONED WITH HIGH CONFIDENCE, SUPPORTED BY A NARROW 70
NM CROSS-TRACK SPREAD AT THE END OF THE FORECAST PERIOD. THE INTENSITY
FORECAST IS ALSO ASSESSED WITH HIGH CONFIDENCE. WHILE ALL AVAILABLE
MODEL GUIDANCE SOLUTIONS INDICATE RAPID DECAY THROUGH TAU 36, THE
TEMPORAL TIMELINE OF COMPLETE DISSIPATION RANGES NARROWLY BETWEEN TAU
48 AND TAU 60. THE OFFICIAL JTWC INTENSITY FORECAST IS HEDGED BETWEEN
THE GUIDANCE OF HAFS AND DETERMINISTIC GFS, ALIGNING CLOSELY WITH THE
MULTI-MODEL CONSENSUS.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
INTENSITY 00-72 HR: HIGH//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 28.4N 124.2E
INITIAL INTENSITY: 80 KTS
GEOGRAPHIC REFERENCE: 245 NM NORTHEAST OF TAIPEI, TAIWAN
MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
SIGNIFICANT WAVE HEIGHT: 30 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
17W (SAUDEL) TRANSITING WEST-NORTHWESTWARD TOWARD ZHEJIANG PROVINCE,
CHINA. DESPITE MARGINALLY UNFAVORABLE ENVIRONMENTAL CONDITIONS,
PRIMARILY DRIVEN BY MODERATE NORTHEASTERLY VERTICAL WIND SHEAR (VWS)
AND SIGNIFICANT DRY AIR INTRUSION, THE VORTEX HAS MANAGED TO REMAIN
STRUCTURALLY COHERENT. FOLLOWING A BRIEF PERIOD OF CONVECTIVE EYE-
FILL, THE CYCLONE HAS RE-ESTABLISHED A BANDING EYE FEATURE, INDICATING
SUSTAINED INTENSITY. WARM SEA SURFACE TEMPERATURES (SST) OF 28-29 C
AND GOOD EQUATORWARD OUTFLOW OFFSET THE OTHERWISE DEGRADING
THERMODYNAMIC ENVIRONMENT. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE UTILIZING VISIBLE SATELLITE IMAGERY, LENDING TO A TIGHT
CONSENSUS OF AGENCY POSITION FIXES. THE INITIAL INTENSITY OF 80 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION OF OBJECTIVE
AND SUBJECTIVE AIDS LISTED BELOW.
INITIAL WIND RADII BASIS: 270111Z METOP-C ASCAT AND 270109Z METOP-C
UHR ASCAT DATA
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHWEST
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T4.5 - 77 KTS
RJTD: T5.0 - 90 KTS
RCTP: T4.0 - 65 KTS
KNES: T4.5 - 77 KTS
CIMSS SATCON: 93 KTS AT 270444Z
CIMSS ADT: 90 KTS AT 270540Z
CIMSS AIDT: 76 KTS AT 270600Z
CIMSS D-MINT: 84 KTS AT 270530Z
CIMSS D-PRINT: 80 KTS AT 270600Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 15-20 KTS
SST: 28-29 CELSIUS
OUTFLOW: MODERATE EQUATORWARD
OTHER FACTORS: DRY AIR ENTRAINMENT AND PERSISTENT NORTHEASTERLY
VERTICAL WIND SHEAR
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TY 17W IS FORECAST TO CONTINUE TRACKING WEST-
SOUTHWESTWARD TOWARD LANDFALL OVER EAST-CENTRAL CHINA, LIKELY NEAR THE
CITY OF TAIZHOU. AN INCREASINGLY HOSTILE ENVIRONMENT, DRIVEN PRIMARILY
BY ESCALATING VWS AND PERSISTENT MID-LEVEL DRY-AIR ENTRAINMENT, WILL
RESULT IN GRADUAL WEAKENING PRIOR TO LANDFALL. AFTER THE STR ANCHORED
TO THE NORTHEAST STEERS THE SYSTEM OVER LAND, TERMINAL WEAKENING WILL
PROGRESS AT A MUCH FASTER RATE, ACCELERATED BY THE FRICTIONAL EFFECTS
OF ROUGH LAND INTERACTION. THE SYSTEM IS EXPECTED TO WEAKEN
SIGNIFICANTLY BY TAU 48 AS THE VORTEX TRAVERSES HIGHER TERRAIN, WITH
COMPLETE DISSIPATION PROJECTED TO OCCUR AT OR PRIOR TO TAU 60.
MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS EXCELLENT
AGREEMENT, AS ALL AVAILABLE DYNAMIC MODELS RESOLVE A SIMILAR LANDFALL
TIMELINE AND GEOGRAPHIC LOCATION, FOLLOWED BY A SUBSEQUENT
SOUTHWESTWARD VEER OVER LAND. AS SUCH, THE OFFICIAL JTWC TRACK
FORECAST IS POSITIONED WITH HIGH CONFIDENCE, SUPPORTED BY A NARROW 70
NM CROSS-TRACK SPREAD AT THE END OF THE FORECAST PERIOD. THE INTENSITY
FORECAST IS ALSO ASSESSED WITH HIGH CONFIDENCE. WHILE ALL AVAILABLE
MODEL GUIDANCE SOLUTIONS INDICATE RAPID DECAY THROUGH TAU 36, THE
TEMPORAL TIMELINE OF COMPLETE DISSIPATION RANGES NARROWLY BETWEEN TAU
48 AND TAU 60. THE OFFICIAL JTWC INTENSITY FORECAST IS HEDGED BETWEEN
THE GUIDANCE OF HAFS AND DETERMINISTIC GFS, ALIGNING CLOSELY WITH THE
MULTI-MODEL CONSENSUS.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
INTENSITY 00-72 HR: HIGH//
NNNN
TPPN10 PGTW 270851
A. TYPHOON 17W (SAUDEL)
B. 27/0830Z
C. 28.35N
D. 123.85E
E. THREE/GK2A
F. T4.0/4.5/S0.0/24HRS STT: W0.5/03HRS
G. IR/EIR/VIS/MSI
H. REMARKS: 15A/PBO TIGHTLY CURVED BNDG/ANMTN. LLCC EMBEDDED IN LG
YIELDS A DT OF 4.5. MET AND PT YIELD 4.0. DBO PT.
I. ADDITIONAL POSITIONS: NONE
LINDGREN
A. TYPHOON 17W (SAUDEL)
B. 27/0830Z
C. 28.35N
D. 123.85E
E. THREE/GK2A
F. T4.0/4.5/S0.0/24HRS STT: W0.5/03HRS
G. IR/EIR/VIS/MSI
H. REMARKS: 15A/PBO TIGHTLY CURVED BNDG/ANMTN. LLCC EMBEDDED IN LG
YIELDS A DT OF 4.5. MET AND PT YIELD 4.0. DBO PT.
I. ADDITIONAL POSITIONS: NONE
LINDGREN
Platform: RCM-1 Acquisition Date: 2026-08-26 09:31:16 UTC
Platform: RCM-1
Acquisition Date: 2026-08-26 09:31:16 UTC
Storm Name: WP172026 / SAUDEL
Storm ID: WP17
Storm Center Longitude: 126.205
Storm Center Latitude: 28.498
Incidence Angle (Degrees): 28.686
Quadrant 1 NE VMax (kts): 91.08
Quadrant 2 SE VMax (kts): 79.14
Quadrant 3 SW VMax (kts): 79.34
Quadrant 4 NW VMax (kts): 92.34
RMax (nmi): 21.00 - 24.00
Acquisition Date: 2026-08-26 09:31:16 UTC
Storm Name: WP172026 / SAUDEL
Storm ID: WP17
Storm Center Longitude: 126.205
Storm Center Latitude: 28.498
Incidence Angle (Degrees): 28.686
Quadrant 1 NE VMax (kts): 91.08
Quadrant 2 SE VMax (kts): 79.14
Quadrant 3 SW VMax (kts): 79.34
Quadrant 4 NW VMax (kts): 92.34
RMax (nmi): 21.00 - 24.00
WDPN33 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (TWENTY) WARNING NR
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 16.7N 162.3E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 291 NM WEST-SOUTHWEST OF WAKE ISLAND
MOVEMENT PAST 6 HOURS: EASTWARD AT 09 KTS
SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 20W WITH A HIGHLY COMPACT PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH BUILDING DEEP CONVECTION SLIGHTLY
OFFSET TO THE NORTH OF THE CENTER. A 270218Z AMSR2 89 GHZ MICROWAVE
IMAGE REVEALED EXPOSED LOW-LEVEL CLOUDS TIGHTLY WRAPPING INTO THE
COMPACT CORE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE AMSR2 IMAGE AND ANIMATED MSI. THE INITIAL INTENSITY OF
35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
DVORAK FIXES AND CIMSS INTENSITY ESTIMATES LISTED BELOW. THE AGENCY
DVORAK FIXES OF T2.0 ARE ESTIMATED TO BE SLIGHTLY UNDERESTIMATING
THE INTENSITY DUE TO THE SMALL SIZE OF THE SYSTEM. ENVIRONMENTAL
ANALYSIS INDICATES THAT 20W IS NOW IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT, LOW (10-15 KTS)
VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A NEAR EQUATORIAL
RIDGE (NER) POSITIONED TO THE SOUTH
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T1.5 - 25 KTS
KNES: T2.0 - 30 KTS
PHFO: T2.0 - 30 KTS
CIMSS SATCON: 37 KTS AT 270440Z
CIMSS ADT: 34 KTS AT 270540Z
CIMSS AIDT: 38 KTS AT 270540Z
CIMSS D-PRINT: 27 KTS AT 270540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE POLEWARD
OTHER FACTORS: BINARY INTERACTION WITH TROPICAL STORM 21W (ETAU)
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: EXTENDED THE FORECAST TO 96 HOURS AND
NOW CALLS FOR SUBTROPICAL TRANSITION RATHER THAN DISSIPATION OVER
WATER. ALSO, THE TRACK IS FURTHER EAST THAN THE PREVIOUS FORECAST.
FORECAST DISCUSSION: TS 20W IS FORECAST TO BEGIN TURNING
NORTHEASTWARD WITHIN THE NEXT 24 HOURS AS THE STEERING MECHANISM
TRANSITIONS TO A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHEAST. NEAR TAU 36, THE SYSTEM WILL TRACK MORE NORTHWARD AS IT
TRACKS ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 72. AFTER
TAU 72, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN FROM THE NORTH
AND PICK UP 20W, PULLING IT FURTHER POLEWARD. SUBTROPICAL TRANSITION
IS FORECAST TO COMPLETE AT AROUND TAU 96 AFTER THE VORTEX PASSES THE
26 C SST ISOTHERM AND INTERACTS WITH THE STRONG MID-LATITUDE TROUGH.
HOWEVER, THERE IS A SEPARATE SCENARIO THAT IS STILL POSSIBLE. THE
OTHER SCENARIO IS THAT 20W BECOMES ABSORBED BY THE LARGER 21W TO THE
NORTHEAST. THIS SCENARIO IS MORE LIKELY IF TWO THINGS OCCUR. THE FIRST
BEING THAT 20W WEAKENS CONSIDERABLY OVER THE NEXT 48 HOURS, AND THE
OTHER IS IF THE TRACK SPEEDS OF 21W ARE SLOWER THAN ANTICIPATED.
REGARDING INTENSITY, 20W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU
48 TO A PEAK OF 60 KTS. IF THE SYSTEM IS ABLE TO STABILIZE A CORE OF
CONVECTION, THEN A HIGHER INTENSITY IS POSSIBLE DUE TO THE COMPACT
NATURE OF THE WIND FIELD. AFTER TAU 48, WESTERLY SHEAR AND DRY AIR IS
EXEPCTED TO INCREASE, CAUSING 20W TO WEAKEN AS IT TRACKS NORTHWARD.
MODEL DISCUSSION: MODEL TRACK GUIDANCE CONTINUES TO BE IN POOR
AGREEMENT WITH A CROSS-TRACK SPREAD OF 370 NM AT TAU 72. HOWEVER, A
MORE DISCERNIBLE TRACK DIFFERENCE BETWEEN 20W AND 21W IS MUCH MORE
APPARENT THIS MODEL RUN. THE ONLY TWO TRACKERS THAT JUMP TO 21W ARE
NOW NAVGEM AND GALWEM, MAKING UP THE FAR WESTERN OUTLIERS. ON THE
OTHER HAND, THE EXPERIMENTAL GOOGLE DEEPMIND AND THE GFS ARE THE
EASTERNMOST TRACKERS. THE JTWC TRACK FORECAST IS PLACED CLOSER TO THE
GOOGLE DEEPMIND ENSEMBLE MEAN WITH OVERALL LOW CONFIDENCE. INTENSITY
GUIDANCE IS NOW IN EXTREMELY POOR AGREEMENT WITH MULTIPLE RAPID
INTENSIFICATION (RI) AIDS TRIGGERING THIS MODEL RUN. ADDITIONALLY, THE
COAMPS-TC (GFS-BASED) SHOWS A PEAK INTENSITY OF 105 KTS, WHICH
ACTUALLY ALIGNS WITH THE MULTITUDE OF RI AIDS. SHIPS OUTPUT HAS A 70
PERCENT PROBABILITY OF AN INCREASE OF 55 KTS IN 48 HOURS AS WELL.
HAFS-A AND GOOGLE DEEPMIND SHOWS A PEAK INTENSITY OF 55-60 KTS AND THE
JTWC INTENSITY FORECAST IS PLACED CLOSER TO THIS DEPICTION WITH VERY
LOW CONFIDENCE. THERE COULD BE MAJOR CHANGES TO THE INTENSITY FORECAST
FOR 20W IF RI APPEARS MORE LIKELY THAN NOT.
FORECAST CONFIDENCE:
TRACK 00-72 HR: LOW
TRACK 72-120 HR: LOW
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (TWENTY) WARNING NR
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 16.7N 162.3E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 291 NM WEST-SOUTHWEST OF WAKE ISLAND
MOVEMENT PAST 6 HOURS: EASTWARD AT 09 KTS
SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 20W WITH A HIGHLY COMPACT PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH BUILDING DEEP CONVECTION SLIGHTLY
OFFSET TO THE NORTH OF THE CENTER. A 270218Z AMSR2 89 GHZ MICROWAVE
IMAGE REVEALED EXPOSED LOW-LEVEL CLOUDS TIGHTLY WRAPPING INTO THE
COMPACT CORE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE AMSR2 IMAGE AND ANIMATED MSI. THE INITIAL INTENSITY OF
35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
DVORAK FIXES AND CIMSS INTENSITY ESTIMATES LISTED BELOW. THE AGENCY
DVORAK FIXES OF T2.0 ARE ESTIMATED TO BE SLIGHTLY UNDERESTIMATING
THE INTENSITY DUE TO THE SMALL SIZE OF THE SYSTEM. ENVIRONMENTAL
ANALYSIS INDICATES THAT 20W IS NOW IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT, LOW (10-15 KTS)
VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA SURFACE TEMPERATURES.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A NEAR EQUATORIAL
RIDGE (NER) POSITIONED TO THE SOUTH
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T1.5 - 25 KTS
KNES: T2.0 - 30 KTS
PHFO: T2.0 - 30 KTS
CIMSS SATCON: 37 KTS AT 270440Z
CIMSS ADT: 34 KTS AT 270540Z
CIMSS AIDT: 38 KTS AT 270540Z
CIMSS D-PRINT: 27 KTS AT 270540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE POLEWARD
OTHER FACTORS: BINARY INTERACTION WITH TROPICAL STORM 21W (ETAU)
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: EXTENDED THE FORECAST TO 96 HOURS AND
NOW CALLS FOR SUBTROPICAL TRANSITION RATHER THAN DISSIPATION OVER
WATER. ALSO, THE TRACK IS FURTHER EAST THAN THE PREVIOUS FORECAST.
FORECAST DISCUSSION: TS 20W IS FORECAST TO BEGIN TURNING
NORTHEASTWARD WITHIN THE NEXT 24 HOURS AS THE STEERING MECHANISM
TRANSITIONS TO A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHEAST. NEAR TAU 36, THE SYSTEM WILL TRACK MORE NORTHWARD AS IT
TRACKS ALONG THE WESTERN PERIPHERY OF THE STR THROUGH TAU 72. AFTER
TAU 72, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN FROM THE NORTH
AND PICK UP 20W, PULLING IT FURTHER POLEWARD. SUBTROPICAL TRANSITION
IS FORECAST TO COMPLETE AT AROUND TAU 96 AFTER THE VORTEX PASSES THE
26 C SST ISOTHERM AND INTERACTS WITH THE STRONG MID-LATITUDE TROUGH.
HOWEVER, THERE IS A SEPARATE SCENARIO THAT IS STILL POSSIBLE. THE
OTHER SCENARIO IS THAT 20W BECOMES ABSORBED BY THE LARGER 21W TO THE
NORTHEAST. THIS SCENARIO IS MORE LIKELY IF TWO THINGS OCCUR. THE FIRST
BEING THAT 20W WEAKENS CONSIDERABLY OVER THE NEXT 48 HOURS, AND THE
OTHER IS IF THE TRACK SPEEDS OF 21W ARE SLOWER THAN ANTICIPATED.
REGARDING INTENSITY, 20W IS FORECAST TO STEADILY INTENSIFY THROUGH TAU
48 TO A PEAK OF 60 KTS. IF THE SYSTEM IS ABLE TO STABILIZE A CORE OF
CONVECTION, THEN A HIGHER INTENSITY IS POSSIBLE DUE TO THE COMPACT
NATURE OF THE WIND FIELD. AFTER TAU 48, WESTERLY SHEAR AND DRY AIR IS
EXEPCTED TO INCREASE, CAUSING 20W TO WEAKEN AS IT TRACKS NORTHWARD.
MODEL DISCUSSION: MODEL TRACK GUIDANCE CONTINUES TO BE IN POOR
AGREEMENT WITH A CROSS-TRACK SPREAD OF 370 NM AT TAU 72. HOWEVER, A
MORE DISCERNIBLE TRACK DIFFERENCE BETWEEN 20W AND 21W IS MUCH MORE
APPARENT THIS MODEL RUN. THE ONLY TWO TRACKERS THAT JUMP TO 21W ARE
NOW NAVGEM AND GALWEM, MAKING UP THE FAR WESTERN OUTLIERS. ON THE
OTHER HAND, THE EXPERIMENTAL GOOGLE DEEPMIND AND THE GFS ARE THE
EASTERNMOST TRACKERS. THE JTWC TRACK FORECAST IS PLACED CLOSER TO THE
GOOGLE DEEPMIND ENSEMBLE MEAN WITH OVERALL LOW CONFIDENCE. INTENSITY
GUIDANCE IS NOW IN EXTREMELY POOR AGREEMENT WITH MULTIPLE RAPID
INTENSIFICATION (RI) AIDS TRIGGERING THIS MODEL RUN. ADDITIONALLY, THE
COAMPS-TC (GFS-BASED) SHOWS A PEAK INTENSITY OF 105 KTS, WHICH
ACTUALLY ALIGNS WITH THE MULTITUDE OF RI AIDS. SHIPS OUTPUT HAS A 70
PERCENT PROBABILITY OF AN INCREASE OF 55 KTS IN 48 HOURS AS WELL.
HAFS-A AND GOOGLE DEEPMIND SHOWS A PEAK INTENSITY OF 55-60 KTS AND THE
JTWC INTENSITY FORECAST IS PLACED CLOSER TO THIS DEPICTION WITH VERY
LOW CONFIDENCE. THERE COULD BE MAJOR CHANGES TO THE INTENSITY FORECAST
FOR 20W IF RI APPEARS MORE LIKELY THAN NOT.
FORECAST CONFIDENCE:
TRACK 00-72 HR: LOW
TRACK 72-120 HR: LOW
INTENSITY 00-72 HR: LOW
INTENSITY 72-120 HR: LOW//
NNNN
Platform: RCM-2 Acquisition Date: 2026-08-27 07:27:42 UTC
Platform: RCM-2
Acquisition Date: 2026-08-27 07:27:42 UTC
Storm Name: WP202026 / TWENTY
Storm ID: WP20
Storm Center Longitude: 162.712
Storm Center Latitude: 16.972
Incidence Angle (Degrees): 54.510
Quadrant 1 NE VMax (kts): 52.17
Quadrant 2 SE VMax (kts): 46.41
Quadrant 3 SW VMax (kts): 54.86
Quadrant 4 NW VMax (kts): 52.24
RMax (nmi): 8.00 - 14.00
Acquisition Date: 2026-08-27 07:27:42 UTC
Storm Name: WP202026 / TWENTY
Storm ID: WP20
Storm Center Longitude: 162.712
Storm Center Latitude: 16.972
Incidence Angle (Degrees): 54.510
Quadrant 1 NE VMax (kts): 52.17
Quadrant 2 SE VMax (kts): 46.41
Quadrant 3 SW VMax (kts): 54.86
Quadrant 4 NW VMax (kts): 52.24
RMax (nmi): 8.00 - 14.00
WDPN32 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (ETAU) WARNING NR
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 21.2N 168.0E
INITIAL INTENSITY: 40 KTS
GEOGRAPHIC REFERENCE: 139 NM NORTHEAST OF WAKE ISLAND
MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 08 KTS
SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM
21W (ETAU) WITH CURVED CONVECTIVE BANDING ALONG THE EASTERN PORTION OF
A MOSTLY OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). A 270218Z AMSR2
36 GHZ MICROWAVE IMAGE REVEALED THAT THE LOW-LEVEL STRUCTURE HAS
SIGNIFICANTLY IMPROVED OVER THE PAST 6 HOURS, SHOWING A PARTIAL
MICROWAVE EYE FEATURE BEGINNING TO FORM. THE WIND FIELD CONTINUES TO
APPEAR ASYMMETRIC WITH THE STRONGEST WINDS CONFINED TO THE EASTERN
SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON LOW-LEVEL CLOUD TRACING IN THE ANIMATED MSI. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH LOW CONFIDENCE DUE TO AGENCY
DVORAK ESTIMATES SUGGESTING A T2.0 (30 KTS). THE INITIAL INTENSITY IS
SET A BIT HIGHER DUE TO THE STRONG STRUCTURE IN THE AFOREMENTIONED
AMSR2 MICROWAVE IMAGE. ENVIRONMENTAL ANALYSIS INDICATES THAT 21W IS IN
A FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW
ALOFT, LOW (10-15 KTS) WESTERLY VERTICAL WIND SHEAR, AND WARM (29-30C)
SEA SURFACE TEMPERATURES.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T2.0 - 30 KTS
KNES: T2.0 - 30 KTS
PHFO: T2.0 - 30 KTS
CIMSS ADT: 31 KTS AT 270540Z
CIMSS AIDT: 35 KTS AT 270540Z
CIMSS D-PRINT: 34 KTS AT 270540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: MEDIUM
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE
FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 21W (ETAU) IS FORECAST TO TRACK GENERALLY
NORTHWARD, ALONG THE WESTERN PERIPHERY OF THE STR TO THE EAST THROUGH
TAU 72. AFTER TAU 72, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN FROM
THE NORTH, BREAKING DOWN THE RIDGE. THIS WILL CAUSE TRACK SPEEDS TO
SIGNIFICANTLY SLOW THROUGH THE REMAINDER OF THE FORECAST PERIOD.
SUBTROPICAL TRANSITION IS FORECAST TO COMPLETE NEAR TAU 96 AS THE
SYSTEM CROSSES THE 26 C SST ISOTHERM, BECOMES ENGULFED BY DRY AIR, AND
INTERACTS WITH THE STRONG MID-LATITUDE TROUGH. REGARDING INTENSITY,
21W IS FORECAST TO GRADUALLY INTENSIFY THROUGH TAU 36, PRIMARILY DUE
TO THE ROBUST POLEWARD OUTFLOW CHANNEL. SOUTHWESTERLY SHEAR AND DRY
AIR ENTRAINMENT IS EXPECTED TO INCREASE AFTER TAU 36, CAUSING THE
SYSTEM TO WEAKEN THROUGH TAU 96 AS THE SYSTEM CONTINUES TO TRACK
POLEWARD. ADDITIONALLY, OCEAN HEAT CONTENT (OHC) WILL BEGIN TO
SIGNIFICANTLY DROP AFTER TAU 48, FURTHER SUPPORTING THE WEAKENING
TREND.
MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT WITH
THE EXCEPTION OF NAVGEM, WHICH TRACKS THE VORTEX SIGNIFICANTLY FURTHER
WEST THAN THE REMAINDER OF GUIDANCE. DISCOUNTING NAVGEM, CROSS-TRACK
SPREAD AT TAU 72 IS ABOUT 190 NM WITH GFS MAKING UP THE EASTERNMOST
TRACKER. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MODIFIED
CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES
ON SLIGHT INTENSIFICATION THROUGH TAU 36 FOLLOWED BY WEAKENING
THEREAFTER. AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED CLOSE
TO THE CONSENSUS WITH OVERALL MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
TRACK 00-72 HR: MEDIUM
TRACK 72-120 HR: MEDIUM
INTENSITY 00-72 HR: MEDIUM
INTENSITY 72-120 HR: MEDIUM//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (ETAU) WARNING NR
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 21.2N 168.0E
INITIAL INTENSITY: 40 KTS
GEOGRAPHIC REFERENCE: 139 NM NORTHEAST OF WAKE ISLAND
MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 08 KTS
SIGNIFICANT WAVE HEIGHT: 14 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM
21W (ETAU) WITH CURVED CONVECTIVE BANDING ALONG THE EASTERN PORTION OF
A MOSTLY OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). A 270218Z AMSR2
36 GHZ MICROWAVE IMAGE REVEALED THAT THE LOW-LEVEL STRUCTURE HAS
SIGNIFICANTLY IMPROVED OVER THE PAST 6 HOURS, SHOWING A PARTIAL
MICROWAVE EYE FEATURE BEGINNING TO FORM. THE WIND FIELD CONTINUES TO
APPEAR ASYMMETRIC WITH THE STRONGEST WINDS CONFINED TO THE EASTERN
SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON LOW-LEVEL CLOUD TRACING IN THE ANIMATED MSI. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH LOW CONFIDENCE DUE TO AGENCY
DVORAK ESTIMATES SUGGESTING A T2.0 (30 KTS). THE INITIAL INTENSITY IS
SET A BIT HIGHER DUE TO THE STRONG STRUCTURE IN THE AFOREMENTIONED
AMSR2 MICROWAVE IMAGE. ENVIRONMENTAL ANALYSIS INDICATES THAT 21W IS IN
A FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD OUTFLOW
ALOFT, LOW (10-15 KTS) WESTERLY VERTICAL WIND SHEAR, AND WARM (29-30C)
SEA SURFACE TEMPERATURES.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T2.0 - 30 KTS
KNES: T2.0 - 30 KTS
PHFO: T2.0 - 30 KTS
CIMSS ADT: 31 KTS AT 270540Z
CIMSS AIDT: 35 KTS AT 270540Z
CIMSS D-PRINT: 34 KTS AT 270540Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: MEDIUM
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE
FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 21W (ETAU) IS FORECAST TO TRACK GENERALLY
NORTHWARD, ALONG THE WESTERN PERIPHERY OF THE STR TO THE EAST THROUGH
TAU 72. AFTER TAU 72, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN FROM
THE NORTH, BREAKING DOWN THE RIDGE. THIS WILL CAUSE TRACK SPEEDS TO
SIGNIFICANTLY SLOW THROUGH THE REMAINDER OF THE FORECAST PERIOD.
SUBTROPICAL TRANSITION IS FORECAST TO COMPLETE NEAR TAU 96 AS THE
SYSTEM CROSSES THE 26 C SST ISOTHERM, BECOMES ENGULFED BY DRY AIR, AND
INTERACTS WITH THE STRONG MID-LATITUDE TROUGH. REGARDING INTENSITY,
21W IS FORECAST TO GRADUALLY INTENSIFY THROUGH TAU 36, PRIMARILY DUE
TO THE ROBUST POLEWARD OUTFLOW CHANNEL. SOUTHWESTERLY SHEAR AND DRY
AIR ENTRAINMENT IS EXPECTED TO INCREASE AFTER TAU 36, CAUSING THE
SYSTEM TO WEAKEN THROUGH TAU 96 AS THE SYSTEM CONTINUES TO TRACK
POLEWARD. ADDITIONALLY, OCEAN HEAT CONTENT (OHC) WILL BEGIN TO
SIGNIFICANTLY DROP AFTER TAU 48, FURTHER SUPPORTING THE WEAKENING
TREND.
MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT WITH
THE EXCEPTION OF NAVGEM, WHICH TRACKS THE VORTEX SIGNIFICANTLY FURTHER
WEST THAN THE REMAINDER OF GUIDANCE. DISCOUNTING NAVGEM, CROSS-TRACK
SPREAD AT TAU 72 IS ABOUT 190 NM WITH GFS MAKING UP THE EASTERNMOST
TRACKER. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MODIFIED
CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES
ON SLIGHT INTENSIFICATION THROUGH TAU 36 FOLLOWED BY WEAKENING
THEREAFTER. AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED CLOSE
TO THE CONSENSUS WITH OVERALL MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
TRACK 00-72 HR: MEDIUM
TRACK 72-120 HR: MEDIUM
INTENSITY 00-72 HR: MEDIUM
INTENSITY 72-120 HR: MEDIUM//
NNNN
WTPN21 PHNC 270430 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 93E) REISSUED// REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/260430Z AUG 26// AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT.// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 120 NM EITHER SIDE OF A LINE FROM 9.3N 107.3W TO 13.9N 113.3W WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 22 TO 27 KNOTS. METSAT IMAGERY AT 270000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 9.5N 107.5W. THE SYSTEM IS MOVING NORTHWESTWARD AT 04 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 93E) PREVIOUSLY LOCATED NEAR 6.0N 109.0W IS NOW LOCATED NEAR 9.5N 107.5E, APPROXIMATELY 590NM SOUTH-SOUTHEAST OF SOCCORO. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING, ELONGATED LOW LEVEL CIRCULATION (LLC) WITH CONVECTION ALONG ITS NORTHEASTERN PERIPHERY. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS FOR DEVELOPMENT LOW TO MODERATE VERTICAL WIND SHEAR (15-20KTS), WARM SEA SURFACE TEMPERATURES (29-30 C), GLOBAL MODELS ARE IN AGREEMENT THAT INVEST 93E WILL CONTINUE TO DEVELOP OVER THE NEXT 24 TO 36 HOURS AND TAKE A GENERAL WEST-NORTHWESTWARD TRACK. ENSEMBLE MEMBERS ALSO AGREE ON IT TAKING A GENERALLY SIMILAR TRACK AND FOR INVEST 93E TO REACH TROPICAL STORM STRENGTH IN THE NEXT 24 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 22 TO 27 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS HIGH. THIS SUPERSEDES REF A (WTPN21 PGTW 260430) 3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 280500Z.// NNNN
WTPN22 PHNC 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 94E)//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/270300ZAUG2026//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PHNC 270300)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
A 170 NM RADIUS OF 11.6N 134.4W WITHIN THE NEXT 12 TO 24 HOURS.
AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL
CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO
BE 18 TO 23 KNOTS. METSAT IMAGERY AT 270300Z INDICATES THAT A
CIRCULATION CENTER IS LOCATED NEAR 10.9N 135.0W. THE SYSTEM IS
MOVING NORTH-NORTHEASTWARD AT 03 KNOTS.
2. REMARKS: AN AREA OF CONVECTION (INVEST 94E) IS LOCATED NEAR 10.9N
135.0W, APPROXIMATELY 1269NM EAST-SOUTHEAST OF HILO. ENHANCED INFRARED
SATELLITE IMAGERY (EIR) DEPICTS A BROAD LOW-PRESSURE SYSTEM, WITH
WESTERLY WINDS FLOWING INTO THE SOUTHERN EDGE OF THE LOW-LEVEL
CIRCULATION CENTER (LLCC). IT HAS BEEN SLOWLY CONSOLIDATING OVER THE
LAST SEVERAL HOURS. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE
CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (15 KNOTS OR
LESS), UPPER-LEVEL RADIAL OUTFLOW, AND WARM SEA SURFACE TEMPERATURES
(29-30 C). GLOBAL MODELS ARE IN GENERAL CONSENSUS THAT 94E WILL
CONTINUE TO TRACK ANOMALOUSLY EASTWARD, WHILE SLOWLY CONSOLIDATING AND
INTENSIFYING OVER THE NEXT 24 HOURS, BEFORE EVENTUALLY TURNING NORTH-
NORTHWESTWARD OVER THE NEXT 36-48 HOURS. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
280300Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 9.5N 107.5W.//
NNNN
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 94E)//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/270300ZAUG2026//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PHNC 270300)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
A 170 NM RADIUS OF 11.6N 134.4W WITHIN THE NEXT 12 TO 24 HOURS.
AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL
CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO
BE 18 TO 23 KNOTS. METSAT IMAGERY AT 270300Z INDICATES THAT A
CIRCULATION CENTER IS LOCATED NEAR 10.9N 135.0W. THE SYSTEM IS
MOVING NORTH-NORTHEASTWARD AT 03 KNOTS.
2. REMARKS: AN AREA OF CONVECTION (INVEST 94E) IS LOCATED NEAR 10.9N
135.0W, APPROXIMATELY 1269NM EAST-SOUTHEAST OF HILO. ENHANCED INFRARED
SATELLITE IMAGERY (EIR) DEPICTS A BROAD LOW-PRESSURE SYSTEM, WITH
WESTERLY WINDS FLOWING INTO THE SOUTHERN EDGE OF THE LOW-LEVEL
CIRCULATION CENTER (LLCC). IT HAS BEEN SLOWLY CONSOLIDATING OVER THE
LAST SEVERAL HOURS. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE
CONDITIONS FOR DEVELOPMENT WITH LOW VERTICAL WIND SHEAR (15 KNOTS OR
LESS), UPPER-LEVEL RADIAL OUTFLOW, AND WARM SEA SURFACE TEMPERATURES
(29-30 C). GLOBAL MODELS ARE IN GENERAL CONSENSUS THAT 94E WILL
CONTINUE TO TRACK ANOMALOUSLY EASTWARD, WHILE SLOWLY CONSOLIDATING AND
INTENSIFYING OVER THE NEXT 24 HOURS, BEFORE EVENTUALLY TURNING NORTH-
NORTHWESTWARD OVER THE NEXT 36-48 HOURS. MAXIMUM SUSTAINED SURFACE
WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE
POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE
WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
280300Z.
4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT
LOCATED NEAR 9.5N 107.5W.//
NNNN
GTH Outlook Discussion
Last Updated - 08/25/26
Valid - 09/02/26 - 09/15/26
The strong El Niño continues to be the major influence on anomalous rainfall and tropical cyclone (TC) development throughout the global tropics. Other sources of tropical variability are becoming more difficult to detect, since the El Niño footprint is becoming so dominant and drowning out subseasonal modes. The RMM index is rather weak, as the latest observations within the unit circle in phase 7. The very strong El Niño has been causing significant interference with any MJO activity, making for difficult interpretation of any signal in RMM space. Model guidance is also weak, with most models keeping the RMM index near or inside the unit circle throughout the forecast period, with a wide range of solutions regarding any propagation around the diagram. Despite poor signal from RMM-based observations and forecasts, MJO activity can still be noted based on upper level divergence. With such a strong El Nino, the main indication of the MJO is how it interferes with the near-stationary El Nino footprint. The ECMWF forecast best depicts this, placing the MJO initially in phase with El Nino during week-1, then shifting around to be anti-phased with El Nino by week-4.
It has been an active week for TCs with 6 separate systems forming, all over the Pacific Ocean. In the East Pacific, TC Iselle formed near 15N-114W on Aug 23, and TC Julio formed near 13N-121W on Aug 25. In the Central Pacific, TC Moke formed near 12N-143W on Aug 20. All three systems remain active, but none are expected to impact land in the near future. For the latest information on Iselle, Julio, or Moke, please refer to the National Hurricane Center (NHC). In the West Pacific, TC Saudel formed near 8N-155E on Aug 18, TC Narra formed near 20N-108E on Aug 20, and TC 19W formed near 21N-137E on Aug 22. As in the East Pacific, all three storms remain active. For the latest information on Saudel, Narra, or 19W please refer to the Joint Typhoon Warning Center (JTWC).
The East Pacific has been a major hotspot for TC activity, and model guidance indicates a continuation of this trend through at least week-2. Persistent enhanced shear near the Mexican coast is favored to keep any TC development further west than typical, putting Hawaii at continued risk for impacts from TCs moving through or originating in the Central Pacific. Based on model guidance, the best phasing of MJO with El Nino will occur late week-1 into week-2. Solutions from the ECMWF, GEFS, and Google AI models all indicate a surge of activity during this time period, with potential genesis points appearing across much of the western reaches of the East Pacific and into the Central Pacific. Given favorable conditions and strong support from model guidance, a >60% chance of TC genesis is indicated for the area roughly from 10-15N and 110-125W, with a 40-60% chance covering the same latitude range and extending westward to 145W, and a 20-40% chance extending further west to 170W. During week-3 model guidance becomes very noisy and difficult to interpret, while MJO phasing also becomes less favorable. Prevailing El Nino conditions remain favorable for TCs in the East Pacific though, so a 20-40% chance of TC genesis is indicated for much of the East Pacific basin. Model guidance portrays a similar, albeit noisier picture over the Western Pacific, with potential genesis points from the South China Sea eastward to 160E. A 40-60% chance of TC genesis is posted for the area roughly from 15-20N and 130-150E for week-2, with a 20-40% chance extending eastward to 160E and westward into the eastern South China Sea. As with the Eastern Pacific, guidance gets very noisy during week-3, but generally indicates modest potential for TC genesis, so a 20-40% chance remains posted for much of the Western Pacific during week-3.
Last Updated - 08/25/26
Valid - 09/02/26 - 09/15/26
The strong El Niño continues to be the major influence on anomalous rainfall and tropical cyclone (TC) development throughout the global tropics. Other sources of tropical variability are becoming more difficult to detect, since the El Niño footprint is becoming so dominant and drowning out subseasonal modes. The RMM index is rather weak, as the latest observations within the unit circle in phase 7. The very strong El Niño has been causing significant interference with any MJO activity, making for difficult interpretation of any signal in RMM space. Model guidance is also weak, with most models keeping the RMM index near or inside the unit circle throughout the forecast period, with a wide range of solutions regarding any propagation around the diagram. Despite poor signal from RMM-based observations and forecasts, MJO activity can still be noted based on upper level divergence. With such a strong El Nino, the main indication of the MJO is how it interferes with the near-stationary El Nino footprint. The ECMWF forecast best depicts this, placing the MJO initially in phase with El Nino during week-1, then shifting around to be anti-phased with El Nino by week-4.
It has been an active week for TCs with 6 separate systems forming, all over the Pacific Ocean. In the East Pacific, TC Iselle formed near 15N-114W on Aug 23, and TC Julio formed near 13N-121W on Aug 25. In the Central Pacific, TC Moke formed near 12N-143W on Aug 20. All three systems remain active, but none are expected to impact land in the near future. For the latest information on Iselle, Julio, or Moke, please refer to the National Hurricane Center (NHC). In the West Pacific, TC Saudel formed near 8N-155E on Aug 18, TC Narra formed near 20N-108E on Aug 20, and TC 19W formed near 21N-137E on Aug 22. As in the East Pacific, all three storms remain active. For the latest information on Saudel, Narra, or 19W please refer to the Joint Typhoon Warning Center (JTWC).
The East Pacific has been a major hotspot for TC activity, and model guidance indicates a continuation of this trend through at least week-2. Persistent enhanced shear near the Mexican coast is favored to keep any TC development further west than typical, putting Hawaii at continued risk for impacts from TCs moving through or originating in the Central Pacific. Based on model guidance, the best phasing of MJO with El Nino will occur late week-1 into week-2. Solutions from the ECMWF, GEFS, and Google AI models all indicate a surge of activity during this time period, with potential genesis points appearing across much of the western reaches of the East Pacific and into the Central Pacific. Given favorable conditions and strong support from model guidance, a >60% chance of TC genesis is indicated for the area roughly from 10-15N and 110-125W, with a 40-60% chance covering the same latitude range and extending westward to 145W, and a 20-40% chance extending further west to 170W. During week-3 model guidance becomes very noisy and difficult to interpret, while MJO phasing also becomes less favorable. Prevailing El Nino conditions remain favorable for TCs in the East Pacific though, so a 20-40% chance of TC genesis is indicated for much of the East Pacific basin. Model guidance portrays a similar, albeit noisier picture over the Western Pacific, with potential genesis points from the South China Sea eastward to 160E. A 40-60% chance of TC genesis is posted for the area roughly from 15-20N and 130-150E for week-2, with a 20-40% chance extending eastward to 160E and westward into the eastern South China Sea. As with the Eastern Pacific, guidance gets very noisy during week-3, but generally indicates modest potential for TC genesis, so a 20-40% chance remains posted for much of the Western Pacific during week-3.
The precipitation outlook for weeks 2 and 3 is based on potential TC activity, ENSO composites, and informed by GEFS, CFS, Canadian, and ECMWF ensemble mean solutions. Above-normal precipitation is noted in the southeast Pacific and into the coast of Chile, which may be problematic given very strong recent atmospheric river activity in the region. Above-normal temperatures are favored for much of the southern Contiguous U.S. and into Mexico during week-2. For hazardous weather conditions in your area during the coming two-week period, please refer to your local NWS office, the Medium Range Hazards Forecast produced by the Weather Prediction Center, and the CPC Week-2 Hazards Outlook. Forecasts made over Africa are made in coordination with the International Desk at CPC.
