WPAC: SHANSHAN - Post-Tropical

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WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SHANSHAN) WARNING NR 19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (SHANSHAN), LOCATED APPROXIMATELY 319 NM
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH IMPROVED EYEWALL
CONVECTION AND A 25NM ROUND EYE, WHICH PROVIDES GOOD CONFIDENCE IN
THE CURRENT POSITION. A 070346Z AMSR2 89GHZ IMAGE DEPICTS SPIRAL
BANDING WRAPPING TIGHTLY AROUND A COMPACT EYEWALL, APPROXIMATELY
70NM DIAMETER. ANIMATED WATER VAPOR IMAGERY REVEALS A DISTINCT
POLEWARD OUTFLOW CHANNEL ENHANCED BY A SHORTWAVE TROUGH POSITIONED
EAST OF HONSHU, WHICH HAS CLEARLY AIDED THE RECENT INTENSIFICATION
TREND. THIS SHORTWAVE TROUGH IS NOW PROPAGATING QUICKLY EASTWARD AND
IS CURRENTLY LOCATED NEAR 160E. DUE TO THE IMPROVED UPPER-LEVEL
OUTFLOW AND CONVECTIVE STRUCTURE, THE DVORAK INTENSITY ESTIMATES
FROM KNES AND PGTW JUMPED TO T5.0 (90 KNOTS), THEREFORE, THE CURRENT
INTENSITY IS ASSESSED AT 90 KNOTS. TY 17W IS TRACKING POLEWARD ALONG
THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL TRACK NORTHWESTWARD THROUGH TAU 24 AS IT
APPROACHES THE STR AXIS THEN A MORE NORTHWARD TRACK THROUGH TAU 36
AS THE SYSTEM BEGINS TO ROUND THE STR AXIS. NUMERICAL GUIDANCE IS IN
TIGHT AGREEMENT THROUGH THIS PHASE OF THE TRACK WITH A 55NM SPREAD
IN SOLUTIONS AT TAU 36 NEAR THE KANTO PLAIN. AFTER TAU 36, THERE IS
INCREASING UNCERTAINTY IN THE TIMING AND EXACT RECURVE TRACK WITH
HWRF AND GFS INDICATING A NORTHWARD TRACK OVER HONSHU THEN A SHARP
NORTHEASTWARD TURN SOUTH OF MISAWA AB. THE BULK OF THE GUIDANCE
INDICATES A SHARPER RECURVE WELL SOUTH OF MISAWA. THE JTWC FORECAST
FAVORS A SHARPER RECURVE AS THE SYSTEM ENCOUNTERS THE STRENGTHENING
WESTERLIES OVER NORTHERN HONSHU--EVEN GFS SHOWS WESTERLIES OVER
NORTHERN HONSHU AT 200MB, WHICH SHOULD DEFLECT THE SYSTEM EASTWARD.
BEYOND TAU 48, TY 17W WILL ACCELERATE NORTHEASTWARD AND QUICKLY
TRANSITION INTO AN EXTRA-TROPICAL CYCLONE BY TAU 72, AS IT
BECOMES EMBEDDED IN THE MIDLATITUDE WESTERLY FLOW. GRADUAL WEAKENING
IS EXPECTED THROUGH TAU 12 AS POLEWARD OUTFLOW WEAKENS. AFTER TAU
36, RAPID WEAKENING IS FORECAST AS SST AND VWS CONDITIONS BECOME
INCREASINGLY UNFAVORABLE. CONFIDENCE IN THE FORECAST TRACK REMAINS
LOW DUE TO HIGH UNCERTAINTY IN THE POINT OF RECURVATURE AND THE
FORWARD SPEED OF THE CYCLONE DURING EXTRA-TROPICAL TRANSITION.//
NNNN

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WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SHANSHAN) WARNING NR 21//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (SHANSHAN), LOCATED APPROXIMATELY 212 NM
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD AT 08 KNOTS
OVER THE PAST SIX HOURS. ANIMATED EIR SATELLITE IMAGERY SHOWS THE
SYSTEM HAS MAINTAINED DEEP CENTRAL CONVECTION AND A WELL-DEFINED EYE,
ALBEIT MORE COMPACT AND CONSTRICTED TO 9 NM, RESPECTIVELY. THE
INITIAL POSITION IS BASED ON THE EYE FEATURE WITH HIGH CONFIDENCE.
THE INITIAL INTENSITY OF 85 KNOTS IS BASED ON AN OVERALL ASSESSMENT
OF AGENCY AND OBJECTIVE DVORAK ESTIMATES RANGING FROM T4.5 (77 KNOTS)
TO T5.0 (90 KNOTS) AND REFLECTS THE SUSTAINED EIR SIGNATURE. ANIMATED
WATER VAPOR IMAGERY REVEALS INCREASING PRESSURE OVER THE NORTHERN
PERIPHERY OF THE SYSTEM AND A WEAKENING POLEWARD OUTFLOW CHANNEL AS
THE SHORTWAVE TROUGH, PREVIOUSLY AIDING OUTFLOW, PROPAGATES QUICKLY
EASTWARD. TY 17W IS
TRACKING ALONG THE WESTERN PERIPHERY OF, AND ALMOST LINED UP WITH,
THE AXIS OF THE STR TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. THE 34-KNOT WIND RADII HAVE
BEEN ADJUSTED BASED ON A RECENT ASCAT IMAGE.
B. TY SHANSHAN WILL TRACK NORTHWESTWARD THROUGH TAU 18 AS IT
APPROACHES THE STR AXIS THEN A MORE NORTHWARD TO NORTHEASTWARD
TRAJECTORY AFTER TAU 24 AS THE SYSTEM ROUNDS THE STR. BEYOND TAU 36,
TY 17W WILL ACCELERATE NORTHEASTWARD AND QUICKLY TRANSITION INTO AN
EXTRA-TROPICAL CYCLONE BY TAU 72, AS IT BECOMES EMBEDDED IN THE
MIDLATITUDE WESTERLY FLOW. GRADUAL WEAKENING IS EXPECTED THROUGH TAU
36 AS POLEWARD OUTFLOW WEAKENS AND THE SYSTEM BEGINS TO INTERACT WITH
LAND. AFTER TAU 36, RAPID WEAKENING IS FORECAST AS SST AND VWS
CONDITIONS BECOME INCREASINGLY UNFAVORABLE. NUMERICAL MODEL GUIDANCE
HAS COME INTO TIGHTER AGREEMENT, THEREFORE, CONFIDENCE IN THE JTWC
FORECAST TRACK IS ASSESSED AT HIGH WITH THE JTWC FORECAST POSITIONED
CLOSE TO THE MULTI-MODEL CONSENSUS.//
NNNN

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TPPN11 PGTW 072140

A. TYPHOON 17W (SHANSHAN)

B. 07/2100Z

C. 32.89N

D. 142.20E

E. THREE/HMWRI8

F. T4.5/4.5/D0.5/24HRS STT: S0.0/03HRS

G. IR/EIR

H. REMARKS: 09A/PBO RAGGED EYE/ANMTN. OW EYE SURROUNDED BY DG
YIELDS AN E# AND DT (NO EYE ADJUSTMENT) OF 4.5. MET AND PT
AGREE.

I. ADDITIONAL POSITIONS: NONE


LOWE

TXPQ28 KNES 072108
TCSWNP

A. 17W (SHANSHAN)

B. 07/2030Z

C. 32.9N

D. 142.2E

E. ONE/HIMAWARI-8

F. T4.5/4.5/D0.5/24HRS

G. IR/EIR/SWIR

H. REMARKS...THIS INTENSITY ESTIMATE WAS DERIVED USING 4 KM IR
DATA. SYSTEM CHARACTERIZED BY AN OW EYE SURROUNDED BY MG AND EMBEDDED DG
FOR A DT=4.5 WITH NO EYE ADJUSTMENT. MET AND PT AGREE. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...FISHER

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WDPN31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SHANSHAN) WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 17W (SHANSHAN), LOCATED APPROXIMATELY 120 NM
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS A BROAD AREA OF CONVECTION WRAPPING INTO A POORLY DEFINED EYE
FEATURE ASSOCIATED WITH TY 17W. THE INITIAL POSITION IS BASED ON A
080626Z 37GHZ SSMIS MICROWAVE IMAGE WHICH SHOWS THE DEEPEST
CONVECTION IS LOCATED IN THE SOUTHERN SEMI-CIRCLE OF TY 17W. THE
INITIAL INTENSITY OF 80 KNOTS IS BASED ON DVORAK CURRENT INTENSITY
(CI) ESTIMATES OF T4.5 (77 KNOTS) FROM PGTW AND RJTD. ENVIRONMENTAL
ANALYSIS SHOWS TY 17W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR
(10 TO 15 KNOTS). TY 17W ALSO HAS STRONG OUTFLOW CHANNELS EXTENDING
TO THE SOUTHWEST AND NORTHEAST. SEA SURFACE TEMPERATURES REMAIN
FAVORABLE, BETWEEN 28 AND 29 DEGREES CELSIUS. TY 17W IS TRACKING
NORTHWESTWARD ALONG THE WESTERN EDGE OF THE SUBTROPICAL RIDGE (STR)
LOCATED TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY 17W WILL BEGIN TO TRACK NORTHWARD ALONG THE WESTERN EDGE OF
THE AFOREMENTIONED STR THROUGH TAU 12 AS IT GRADUALLY DECREASES IN
INTENSITY AND IT BEGINS TO TRACK OVER SLIGHTLY COOLER SEA SURFACE
TEMPERATURES. AFTER TAU 12, TY 17W WILL ROUND THE AXIS OF THE STR AND
BEGIN TO TRACK NORTH-NORTHEASTWARD. BY TAU 24, TY 17W WILL BEGIN TO
INTERACT WITH THE MID-LATITUDE WESTERLIES AND BEGIN TO RAPIDLY TRACK
NORTHEASTWARD. DURING THIS TIME TY 17W WILL TRACK OVER UNFAVORABLE
SEA SURFACE TEMPERATURES AND EXPERIENCE INCREASING VERTICAL WIND
SHEAR. TY 17W WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) BY TAU 48
AND COMPLETE ETT BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD
AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST
TRACK.//
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TPPN11 PGTW 080933

A. TYPHOON 17W (SHANSHAN)

B. 08/0900Z

C. 34.08N

D. 141.35E

E. THREE/HMWRI8

F. T4.0/4.5/W0.5/24HRS STT: W0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 11A/PBO RAGGED EYE/ANMTN. LLCC EMBEDDED IN MG
YIELDS A DT OF 4.0. MET YIELDS A 4.5 AND PT YIELDS A 4.0. DBO
DT.

I. ADDITIONAL POSITIONS: NONE


RICHARDSON

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Closing in.

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WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SHANSHAN) WARNING NR 25//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON 17W (SHANSHAN), LOCATED APPROXIMATELY 69 NM EAST OF
YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 08 KNOTS OVER THE PAST SIX
HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
DEEP CONVECTION TO THE EAST OF THE LOW LEVEL CIRCULATION CENTER WITH
BANDING WRAPPING AROUND, PRIMARILY FROM THE EAST. THE INITIAL
POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE ANIMATED EIR
SATELLITE IMAGERY, RADAR IMAGERY, AND RJTD RADAR FIXES. UPPER-LEVEL
ANALYSIS REVEALS MODERATE (10-15 KT) VERTICAL WIND SHEAR (VWS) AND
FAIR OUTFLOW. THE INITIAL INTENSITY IS ASSESSED AT 70 KNOTS, JUST
BELOW DVORAK CURRENT INTENSITY ESTIMATES OF 4.5 (77 KNOTS) FROM RJTD
AND PGTW. TY 17W IS TRACKING POLEWARD ALONG THE AXIS OF THE
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. AFTER TAU 12, TY 17W IS EXPECTED TO SHIFT TO AN EAST-
NORTHEASTWARD TRACK AND BEGIN EXTRATROPICAL TRANSITION (ETT) ONCE IT
FINISHES ROUNDING THE STR AXIS AND BEGINS TO ACCELERATE WITH THE
MIDLATITUDE WESTERLIES. THROUGHOUT THE FORECAST, TY 17W IS EXPECTED
TO WEAKEN RAPIDLY DUE TO INCREASING VWS AND DECREASING SST. TY 17W
WILL COMPLETE ETT BY TAU 48 AS IT GETS EMBEDDED IN THE STRONG
WESTERLY FLOW AND GAINS FRONTAL CHARACTERISTICS. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE
IN THE JTWC FORECAST TRACK.//
NNNN

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WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (SHANSHAN) WARNING
NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 17W (SHANSHAN), LOCATED APPROXIMATELY 120 NM
NORTH-NORTHEAST OF NARITA AIRPORT, HAS TRACKED NORTH-NORTHEASTWARD
AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS A COMPACT BUT WELL-ORGANIZED SYSTEM
WITH SPIRALING RAINBANDS WRAPPING INTO THE CENTER. THE INITIAL
POSITION IS PLACED WITH GOOD CONFIDENCE USING THE ANIMATED MSI AND
RJTD RADAR FIXES. UPPER-LEVEL ANALYSIS REVEALS MODERATE (10-15 KT)
VERTICAL WIND SHEAR (VWS) AND A SINGLE OUTFLOW CHANNEL. THE INITIAL
INTENSITY IS ASSESSED AT 55 KTS BASED ON THE PGTW DVORAK CURRENT
INTENSITY OF T3.5 (55 KTS), SLIGHTLY BELOW THE 090348Z SATCON
ESTIMATE OF 63 KTS. A 092343Z ASCAT PASS REVEALS A MORE COMPACT
SYSTEM THAN PREVIOUSLY ESTIMATED, AND WIND OBSERVATIONS FROM 35-45NM
AWAY ON HONSHU ARE UNDER 25 KTS. COOL SSTS BELOW 26 CELSIUS AND LAND
INTERACTION WITH JAPAN HAVE WEAKENED THE SYSTEM OVER THE PAST 6
HOURS. TS 17W HAS BEGUN TO MOVE TO THE NORTHEAST AND HAS ROUNDED THE
AXIS OF THE SUBTROPICAL RIDGE (STR) TO THE EAST-SOUTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. THE TRACK FOR TS 17W HAS BEGUN CURVING TO THE NORTHEAST. 17W
WILL SOON BE PICKED UP IN THE MIDLATITUDE WESTERLIES, ACCELERATE TO
THE NORTHEAST, AND BEGIN EXTRATROPICAL TRANSITION (ETT). BEFORE
COMPLETING ETT AROUND TAU 36, TS 17W IS FORECASTED TO WEAKEN RAPIDLY
DUE TO INCREASING VWS AND DECREASING SSTS. ITS WIND FIELD WILL
EXPAND AND BECOME ASYMMETRIC UNDER THE HIGH VWS. DYNAMIC MODEL
GUIDANCE IS IN EXCELLENT AGREEMENT, THEREFORE, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK.//
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WTPN31 PGTW 091500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
RMKS/
1. TROPICAL STORM 17W (SHANSHAN) WARNING NR 028
02 ACTIVE TROPICAL CYCLONES IN NORTHWESTPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
091200Z --- NEAR 37.8N 142.6E
MOVEMENT PAST SIX HOURS - 060 DEGREES AT 08 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
BECOMING EXTRATROPICAL
RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT
075 NM SOUTHEAST QUADRANT
050 NM SOUTHWEST QUADRANT
040 NM NORTHWEST QUADRANT
REPEAT POSIT: 37.8N 142.6E
---
FORECASTS:
12 HRS, VALID AT:
100000Z --- 39.6N 146.7E
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
RADIUS OF 034 KT WINDS - 025 NM NORTHEAST QUADRANT
130 NM SOUTHEAST QUADRANT
100 NM SOUTHWEST QUADRANT
000 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 075 DEG/ 27 KTS
---
24 HRS, VALID AT:
101200Z --- 41.0N 153.5E
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
EXTRATROPICAL
RADIUS OF 034 KT WINDS - 010 NM NORTHEAST QUADRANT
145 NM SOUTHEAST QUADRANT
155 NM SOUTHWEST QUADRANT
000 NM NORTHWEST QUADRANT
---
REMARKS:
091500Z POSITION NEAR 38.2N 143.6E.
TROPICAL STORM 17W (SHANSHAN), LOCATED APPROXIMATELY 164 NM
NORTHEAST OF NARITA AIRPORT, HAS TRACKED EAST-NORTHEASTWARD AT 08
KNOTS OVER THE PAST SIX HOURS.
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 091200Z
IS 22 FEET. REFER TO TROPICAL STORM 18W (YAGI) WARNINGS (WTPN32 PGTW)
FOR SIX-HOURLY UPDATES.//
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[doomhaMwx]

LOW
Issued at 07:05 UTC, 10 August 2018

<Analysis at 06 UTC, 10 August>
Scale -
Intensity -
LOW
Center position N41°00' (41.0°)
E151°00' (151.0°)
Direction and speed of movement ENE 55 km/h (30 kt)
Central pressure 992 hPa