WPAC: SEPAT - Tropical Storm

[supercane4867]

21.5N 157.8E

[euro6208]

A CIRCULATION HAS PERSISTED NEAR 23.2N 158.5E,
APPROXIMATELY 500 NM WEST-NORTHWEST OF WAKE ISLAND. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS A NORTH-SOUTH ORIENTED,
HIGHLY ELONGATED, AND BROAD CIRCULATION WITH DEEP CONVECTION
DISPLACED ALONG THE EASTERN PERIPHERY. A 280420Z SSMI MICROWAVE
IMAGE SHOWS THE OVERALL BROAD AND PARTIALLY EXPOSED NATURE OF THE
SYSTEM AS DRY AIR IS BEGINNING TO WRAP IN FROM THE NORTHWEST. A
280128Z OSCAT PASS REVEALS RELATIVELY WEAK WINDS NEAR THE CENTER (10
TO 15 KNOTS), WHILE THERE ARE STRONGER (20 TO 25 KNOTS) GRADIENT
INDUCED WINDS ALONG THE EASTERN PERIPHERY IN THE CONVECTION. UPPER
LEVEL ANALYSIS REVEALS AN UPPER LEVEL LOW IS PERSISTING OVER THE
SYSTEM WHICH IS PRODUCING HIGH LEVELS OF VERTICAL WIND SHEAR (20 TO
30 KNOTS). BASED ON THIS DATA, THIS SYSTEM IS CLASSIFIED AS
SUBTROPICAL. MAXIMUM SUSTAINED SURFACE WINDS NEAR THE CENTER ARE
ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1006 MB. THE POTENTIAL FOR THIS SUBTROPICAL SYSTEM TO
DEVELOP INTO A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS
IS LOW.

this should be our 21st cyclone of the season but we don't see subtropical systems get classified in our region...

[Grifforzer]

Minami torishima

** WTPQ20 RJTD 290600 ***
RSMC TROPICAL CYCLONE ADVISORY
NAME TD
ANALYSIS
PSTN 290600UTC 26.0N 152.8E POOR
MOVE WNW 07KT
PRES 1002HPA
MXWD 030KT
GUST 045KT
FORECAST
24HF 300600UTC 26.0N 148.0E 120NM 70%
MOVE W 10KT
PRES 998HPA
MXWD 035KT
GUST 050KT =

[euro6208]

THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 23.2N
158.5E, IS NOW LOCATED NEAR 26.2N 152.3E, APPROXIMATELY 875 NM NORTH-
NORTHEAST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS
A HIGHLY ELONGATED AND BROAD CIRCULATION WITH DEEP CONVECTION
DISPLACED ALONG THE NORTHWESTERN PERIPHERY. UPPER LEVEL ANALYSIS
REVEALS A LOW TO THE SOUTH IS CREATING A MODERATE TO HIGH (20 TO 30
KNOTS) VWS ENVIRONMENT WITH AN IMPROVING POLEWARD OUTFLOW. TOTAL
PRECIPITABLE WATER IMAGERY SHOWS THE ELONGATED CIRCULATION HAS
BECOME LESS ORGANIZED OVER THE PAST 24 HOURS, WITH DRY AIR STARTING
TO ISOLATE THE SYSTEM FROM THE TROPICAL WARM MOISTURE. BASED ON THIS
DATA, THIS SYSTEM IS CLASSIFIED AS SUBTROPICAL. MAXIMUM SUSTAINED
SURFACE WINDS NEAR THE CENTER ARE ESTIMATED AT 15 TO 20 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 MB. THE
POTENTIAL FOR THIS SUBTROPICAL SYSTEM TO DEVELOP INTO A SIGNIFICANT
TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW.

[Alyono]

TCFA now in effect

[hurricanes1234]

Looks very much like a TD to me.

[euro6208]

Dvorak at 2.0 I expect JTWC to upgrade soon.

[euro6208]

THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 26.2N
152.3E IS NOW LOCATED NEAR 26.0N 149.8E, APPROXIMATELY 465 NM EAST
OF IWO-TO, JAPAN. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS A
CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH PERSISTENT DEEP
CONVECTION OVER THE WESTERN SEMI-CIRCLE. A 291132Z AMSU IMAGE SHOWS
CONVECTIVE BANDING WRAPPING FROM THE NORTHEAST QUADRANT INTO THE
SOUTH QUADRANT OF A DEFINED CENTER. TOTAL PRECIPITABLE WATER (TPW)
IMAGERY INDICATES A MOISTENING PHASE WITH A NEAR-SYMMETRIC CORE OF
DEEP MOISTURE EVOLVING OVER THE PAST 12 HOURS. THE TPW IMAGERY ALONG
WITH RECENT AMSU CROSS-SECTIONS, WHICH SHOW A +1C WARM ANOMALY,
PROVIDE EVIDENCE THAT THE SYSTEM HAS TRANSITIONED FROM A SUBTROPICAL
(COLD-CORE) SYSTEM TO A WARM-CORE SYSTEM. A 291132Z ASCAT IMAGE
DEPICTS AN ELONGATED CIRCULATION WITH 25 TO 30 KNOT WINDS OVER THE
NORTHERN SEMI-CIRCLE AND 15 TO 20 KNOT WINDS OVER THE CORE BUT ALSO
SHOWS THAT THE RADIUS OF MAX WINDS HAS DECREASED TO ABOUT 60 TO 80
NM, WHICH IS MORE TYPICAL OF TROPICAL CYCLONES. UPPER-LEVEL ANALYSIS
INDICATES A MARGINALLY-FAVORABLE ENVIRONMENT WITH WEAK TO MODERATE
VERTICAL WIND SHEAR (10 TO 20 KNOTS) AND DIFFLUENT EASTERLY FLOW.
THE SYSTEM IS CURRENTLY LOCATED JUST NORTH OF A TUTT CELL BUT IS
EXPECTED TO TRACK WESTWARD INTO AN IMPROVING UPPER-LEVEL
ENVIRONMENT. THE SYSTEM IS CURRENTLY LOCATED OVER FAVORABLE SST (28
TO 29C). MAXIMUM SUSTAINED SURFACE WINDS NEAR THE CENTER ARE
ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED
TO BE NEAR 1004 MB. THE POTENTIAL FOR THIS SUBTROPICAL SYSTEM TO
DEVELOP INTO A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS
IS UPGRADED TO HIGH.

[Typhoon Hunter]

This is already a TD per JMA. I'm hoping it doesn't beat 95W to the name Sepat, it's a name fitting for a deep tropics long track monster not this higher latitude "looks to be short lived and weak" system. For those wondering why I respect the name Sepat, check out 2007's incarnation!

Edit it just got named Sepat...

[supercane4867]

** WTPQ20 RJTD 300000 ***
RSMC TROPICAL CYCLONE ADVISORY
NAME TS 1322 SEPAT (1322) UPGRADED FROM TD
ANALYSIS
PSTN 300000UTC 26.4N 147.0E FAIR
MOVE W 11KT
PRES 1000HPA
MXWD 035KT
GUST 050KT
30KT 150NM
FORECAST
24HF 010000UTC 28.9N 141.9E 75NM 70%
MOVE WNW 11KT
PRES 998HPA
MXWD 035KT
GUST 050KT
48HF 020000UTC 33.1N 141.5E 180NM 70%
MOVE N 11KT
PRES 998HPA
MXWD 035KT
GUST 050KT
72HF 030000UTC 40.0N 146.3E 250NM 70% EXTRATROPICAL LOW =

[hurricanes1234]

This is already a TD per JMA. I'm hoping it doesn't beat 95W to the name Sepat, it's a name fitting for a deep tropics long track monster not this higher latitude "looks to be short lived and weak" system. For those wondering why I respect the name Sepat, check out 2007's incarnation!

Edit it just got named Sepat...

Oh no, I'm sorry, Typhoon Hunter, better luck next time when the name comes about again!

[euro6208]

WTPN31 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/291721ZSEP2013//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. TROPICAL DEPRESSION 21W (TWENTY-ONE) WARNING NR 001
02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
300000Z --- NEAR 26.6N 146.7E
MOVEMENT PAST SIX HOURS - 285 DEGREES AT 13 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: 26.6N 146.7E
---
FORECASTS:
12 HRS, VALID AT:
301200Z --- 27.4N 144.0E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 24 HR POSIT: 305 DEG/ 13 KTS
---
24 HRS, VALID AT:
010000Z --- 28.8N 141.6E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 330 DEG/ 11 KTS
---
36 HRS, VALID AT:
011200Z --- 30.7N 140.3E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 010 DEG/ 16 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
020000Z --- 33.8N 141.0E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
VECTOR TO 72 HR POSIT: 030 DEG/ 26 KTS
---
72 HRS, VALID AT:
030000Z --- 42.8N 147.7E
MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
300300Z POSITION NEAR 26.8N 146.0E.
TROPICAL DEPRESSION 21W (TWENTY-ONE), LOCATED APPROXIMATELY
634 NM SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED WEST-
NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. MAXIMUM
SIGNIFICANT WAVE HEIGHT AT 300000Z IS 10 FEET. NEXT WARNINGS
AT 300900Z, 301500Z, 302100Z AND 010300Z. THIS WARNING
SUPERSEDES AND CANCELS REF A, JOINT TYPHOON WRNCEN PEARL HARBOR
HI 291721Z SEP 13 TROPICAL CYCLONE FORMATION ALERT (WTPN22 PGTW
291730). REFER TO TYPHOON 20W (WUTIP) WARNINGS (WTPN32 PGTW)
FOR SIX-HOURLY UPDATES.//
NNNN

21st Tropical Cyclone of the season.

[euro6208]

Weakening...

Dvorak agencies are reporting numbers of 1.5 and 1.0 and has never went higher than 2.0...

Waste of a storm...

[supercane4867]

I'm very surprised at how pathetic it is right now

Even Jerry will likely go further than this

[euro6208]

WDPN31 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (SEPAT)
WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 21W (SEPAT), LOCATED APPROXIMATELY 485 NM
SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD
AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS A FULLY EXPOSED AND WELL DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH SHALLOW CONVECTION WRAPPING ALONG THE
WESTERN SEMI-CIRCLE. A 301112Z AMSU-B MICROWAVE IMAGE CONTINUES TO
DEPICT A WEAK CONVECTIVE ORGANIZATION DESPITE THE LLCC REMAINING
TIGHTLY WRAPPED. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION
AND RECENT MOTION BASED ON THE EXPOSED AND DEFINED NATURE OF THE
LLCC. THE INITIAL INTENSITY HAS BEEN HELD AT 30 KNOTS BASED UPON THE
TIGHT WRAPPING OF THE LLCC AND DVORAK CURRENT INTENSITY ESTIMATES OF
THE SAME VALUE FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A
POOR TO MARGINAL ENVIRONMENT AS AN UPPER-LEVEL LOW HAS MOVED OVER
THE SYSTEM WHICH IS PROVIDING MODERATE (10 TO 20 KNOTS) VERTICAL
WIND SHEAR (VWS) AND IS ADDITIONALLY HINDERING OUTFLOW. TD 21W IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
B. TD 21W IS FORECAST TO TRACK WEST-NORTHWESTWARD ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 24 AND THEN BEGIN TO
RE-CURVE POLEWARD EAST OF JAPAN. AFTER TAU 36, TD 21W IS FORECAST TO
ACCELERATE AHEAD OF A MIDLATITUDE SHORTWAVE TROUGH, WHICH IS
EXPECTED TO DEEPEN OVER JAPAN. TD 21W IS FORECAST TO REMAIN WITHIN A
MARGINAL ENVIRONMENT THROUGHOUT THE FORECAST WITH A SLIGHT INCREASE
AT TAU 24 AS POLEWARD OUTFLOW IMPROVES AND A PEAK INTENSITY OF 35
KNOTS IS EXPECTED. ADDITIONALLY, THERE IS A COOL POOL OF SEA SURFACE
TEMPERATURES LOCATED OVER AND TO THE NORTH OF IWO TO, WHICH SHOULD
ALSO IMPEDE DEVELOPMENT. TD 21W IS FORECAST TO BEGIN EXTRA-TROPICAL
TRANSITION (ETT) NEAR TAU 36 AS IT BEGINS TO INTERACT WITH THE
MIDLATITUDE WESTERLIES AHEAD OF THE DEEPENING TROUGH. COMPLETE
TRANSITION IS EXPECTED BY TAU 72 AS TD 21W BECOMES EMBEDDED WITHIN
THE MIDLATITUDE TROUGH. THE AVAILABLE DYNAMIC MODELS, AS WELL AS THE
ENSEMBLE MODELS ARE IN EXCELLENT AGREEMENT, THEREFORE, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY
FASTER AND TO THE RIGHT OF THE MULTI-MODEL CONSENSUS AFTER TAU 36.//
NNNN

[euro6208]

WDPN31 PGTW 302100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (SEPAT)
WARNING NR 04//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 21W (SEPAT), LOCATED APPROXIMATELY 84 NM
NORTH OF CHICHI JIMA, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 15
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS A FULLY-EXPOSED AND WELL-DEFINED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH SHALLOW CONVECTION WRAPPING ALONG THE NORTHEAST
QUADRANT AND LONG STREAKS OF COLD AIR STRATOCUMULUS CLOUDS ADVECTING
IN FROM THE NORTHWEST. THESE FEATURES ARE CORROBORATED BY A 301758Z
SSMI/S MICROWAVE PASS. THERE IS HIGH CONFIDENCE IN THE INITIAL
POSITION IN VIEW OF THE ABOVE IMAGERY. THE INITIAL INTENSITY OF 30
KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES FROM ALL REPORTING
AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A POOR TO MARGINAL
ENVIRONMENT AS AN UPPER-LEVEL LOW OVER THE SYSTEM IS CAUSING
MODERATE (15 TO 20 KNOT) VERTICAL WIND SHEAR AND IS ALSO HINDERING
OUTFLOW. TD 21W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
B. TD 21W WILL BEGIN TO ROUND THE WESTERN EDGE OF THE STR AFTER
TAU 12 AND RECURVE NORTHEASTWARD. AFTER TAU 24, THE CYCLONE IS
FORECAST TO ACCELERATE AHEAD OF A MIDLATITUDE SHORTWAVE TROUGH,
WHICH IS EXPECTED TO DEEPEN OVER JAPAN. TD 21W IS FORECAST TO REMAIN
IN A MARGINAL ENVIRONMENT THROUGHOUT THE FORECAST WITH A SLIGHT
INCREASE AT TAU 24 AS POLEWARD OUTFLOW IMPROVES PEAKING THE
INTENSITY TO 35 KNOTS. ADDITIONALLY, SEA SURFACE TEMPERATURES ARE
EXPECTED TO GET COLDER AFTER TAU 06 WHICH WILL ALSO IMPEDE
DEVELOPMENT. TD 21W IS FORECAST TO BEGIN EXTRA-TROPICAL TRANSITION
(ETT) BEFORE TAU 36 AS IT BEGINS TO INTERACT WITH THE MIDLATITUDE
WESTERLIES AHEAD OF THE DEEPENING TROUGH. COMPLETE TRANSITION IS
EXPECTED BY TAU 48 AS THE SYSTEM BECOMES EMBEDDED IN THE COLD
BAROCLINIC AIR MASS. THE AVAILABLE DYNAMIC MODELS, AS WELL AS THE
ENSEMBLE MODELS ARE IN EXCELLENT AGREEMENT, LENDING HIGH CONFIDENCE
TO THE JTWC FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY FASTER AND
TO THE RIGHT OF THE MULTI-MODEL CONSENSUS. //
NNNN

[stormkite]

TROPICAL CYCLONE GUIDANCE FOR NORTH-WEST PACIFIC

GLOBAL MODEL DATA TIME 00UTC 01.10.2013


TROPICAL DEPRESSION SEPAT ANALYSED POSITION : 29.0N 141.5E

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
00UTC 01.10.2013 29.0N 141.5E WEAK
12UTC 01.10.2013 31.0N 140.7E MODERATE LITTLE CHANGE
00UTC 02.10.2013 33.4N 140.6E MODERATE LITTLE CHANGE
12UTC 02.10.2013 36.6N 142.2E MODERATE INTENSIFYING SLIGHTLY
:

[euro6208]

WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (SEPAT) WARNING NR
07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 21W (SEPAT), LOCATED APPROXIMATELY 264 NM SOUTH-
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
(EIR) SHOWS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC)
THAT IS STARTING TO SLIGHTLY ELONGATE WITH SHALLOW CONVECTION
WRAPPING ALONG THE NORTHERN SEMI-CIRCLE. THERE IS FAIR CONFIDENCE IN
THE INITIAL POSITION BASED ON THE PARTIALLY EXPOSED NATURE OF THE
LLCC SEEN IN THE EIR ANIMATION. THE INITIAL INTENSITY HAS BEEN HELD
AT 35 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF 35 KNOTS FROM
PGTW AND KNES. UPPER-LEVEL ANALYSIS INDICATES FAIR POLEWARD OUTFLOW
WHICH IS BEING OFFSET BY MODERATE TO HIGH (20-30 KNOTS) VERTICAL
WIND SHEAR (VWS) DUE TO A TROUGH THAT IS CURRENTLY OVER JAPAN. TS
21W IS BEGINNING TO TRACK POLEWARD ALONG THE WESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
B. TS 21W HAS STARTED TO RECURVE AS IT BEGINS TO CREST THE STR
AXIS. AFTER TAU 12, THE SYSTEM IS FORECAST TO BEGIN TO ACCELERATE
AHEAD OF THE DIGGING MIDLATITUDE SHORTWAVE TROUGH, WHICH IS EXPECTED
TO FURTHER DEEPEN OVER JAPAN. TS 21W IS FORECAST TO REMAIN IN A
MARGINAL ENVIRONMENT THROUGHOUT THE FORECAST AND WILL STRUGGLE TO
MAINTAIN TROPICAL STORM STRENGTH AS THE INCREASING POLEWARD OUTFLOW
CONTINUES TO BE OFFSET BY FURTHER INCREASING VWS. ADDITIONALLY,
ALONG-TRACK SEA SURFACE TEMPERATURES ARE EXPECTED TO DECREASE WHICH
WILL ALSO IMPEDE DEVELOPMENT. TS 21W IS FORECAST TO BEGIN EXTRA-
TROPICAL TRANSITION (ETT) BY TAU 24 AS IT BEGINS TO INTERACT WITH
THE MIDLATITUDE WESTERLIES AHEAD OF THE DEEPENING TROUGH. COMPLETE
TRANSITION IS EXPECTED BY TAU 36 AS THE SYSTEM BECOMES EMBEDDED IN
THE COLD BAROCLINIC AIR MASS. THE AVAILABLE DYNAMIC MODELS, AS WELL
AS THE ENSEMBLE MODELS ARE IN EXCELLENT AGREEMENT, LENDING TO HIGH
CONFIDENCE TO THE JTWC FORECAST TRACK, WHICH IS POSITIONED SLIGHTLY
FASTER AND TO THE RIGHT OF THE MULTI-MODEL CONSENSUS.//
NNNN

[euro6208]

WDPN31 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (SEPAT) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 21W (SEPAT), LOCATED APPROXIMATELY 178 NM SOUTH-
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 14 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
(EIR) SHOWS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC)
THAT HAS BEGUN TO ELONGATE AS IT MAINTAINED SHALLOW CONVECTION
WRAPPING ALONG THE NORTHERN SEMI-CIRCLE. THERE IS FAIR CONFIDENCE IN
THE INITIAL POSITION BASED ON THE PARTIALLY EXPOSED NATURE OF THE
LLCC. THE INITIAL INTENSITY OF AT 35 KNOTS BASED ON DVORAK INTENSITY
ESTIMATES FROM PGTW, RJTD AND KNES. UPPER-LEVEL ANALYSIS INDICATES
STRONG POLEWARD OUTFLOW WHICH IS BEING OFFSET BY HIGH (25-40 KNOTS)
VERTICAL WIND SHEAR (VWS). TS 21W IS BEGINNING TO TRACK POLEWARD
ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
B. TS 21W HAS STARTED TO RECURVE AS IT BEGINS TO CREST THE STR
AXIS. AFTER TAU 12, THE SYSTEM IS FORECAST TO BEGIN TO ACCELERATE
AHEAD OF THE DIGGING MIDLATITUDE SHORTWAVE TROUGH, WHICH IS EXPECTED
TO FURTHER DEEPEN OVER JAPAN. TS 21W IS FORECAST TO REMAIN IN A
MARGINAL ENVIRONMENT THROUGHOUT THE FORECAST AND WILL STRUGGLE TO
MAINTAIN TROPICAL STORM STRENGTH AS THE INCREASING POLEWARD OUTFLOW
CONTINUES TO BE OFFSET BY FURTHER INCREASING VWS. ADDITIONALLY,
ALONG-TRACK SEA SURFACE TEMPERATURES ARE DECREASING WHICH WILL ALSO
IMPEDE DEVELOPMENT. TS 21W HAS BEGUN EXTRA-TROPICAL TRANSITION (ETT)
AND COMPLETE TRANSITION IS EXPECTED BY TAU 12 AS THE SYSTEM BECOMES
EMBEDDED IN THE COLD BAROCLINIC AIR MASS. THE AVAILABLE DYNAMIC
MODELS, AS WELL AS THE ENSEMBLE MODELS ARE IN EXCELLENT AGREEMENT,
LENDING TO HIGH CONFIDENCE TO THE JTWC FORECAST TRACK, WHICH IS
POSITIONED SLIGHTLY FASTER AND TO THE RIGHT OF THE MULTI-MODEL
CONSENSUS. //
NNNN

[euro6208]

Final Warning.


WTPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL STORM 21W (SEPAT) WARNING NR 009
02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
020000Z --- NEAR 33.9N 141.7E
MOVEMENT PAST SIX HOURS - 015 DEGREES AT 13 KTS
POSITION ACCURATE TO WITHIN 030 NM
POSITION BASED ON CENTER LOCATED BY A COMBINATION OF
SATELLITE AND RADAR
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
REPEAT POSIT: 33.9N 141.7E
---
FORECASTS:
12 HRS, VALID AT:
021200Z --- 37.7N 143.7E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
VECTOR TO 24 HR POSIT: 030 DEG/ 33 KTS
---
24 HRS, VALID AT:
030000Z --- 43.2N 148.3E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
---
REMARKS:
020300Z POSITION NEAR 34.8N 142.2E.
TROPICAL STORM 21W (SEPAT), LOCATED APPROXIMATELY 130 NM
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD
AT 13 KNOTS OVER THE PAST SIX HOURS. TS 21W IS RAPIDLY ACCELERATING
INTO THE MID-LATITUDE WESTERLY FLOW PATTERN AND WILL COMPLETE
EXTRATROPICAL TRANSITION WITHIN THE NEXT 24 HOURS. THEREFORE, THIS
IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN
PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF
REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 020000Z IS 18 FEET.
REFER TO TROPICAL STORM 22W (FITOW) WARNINGS (WTPN33 PGTW) FOR SIX-
HOURLY UPDATES.//
NNNN