WPAC: YAGI - Post-Tropical

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WDPN32 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (YAGI) WARNING NR
15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (YAGI), LOCATED APPROXIMATELY 323 NM
SOUTHEAST OF KADENA AB, HAS TRACKED WEST-SOUTHWESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH
CONVECTION CONFINED TO THE SOUTHWEST QUADRANT. THE INITIAL POSITION
IS PLACED WITH GOOD CONFIDENCE BASED ON A 100600Z HIMAWARI VISIBLE
SATELLITE IMAGE WHICH SHOWS THE LLCC AND THE CONVECTION SHEARED TO
THE SOUTHWEST. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON A
100027Z METOP-B ASCAT IMAGE WHICH SHOWS A LARGE SWATH OF 35 KNOT
WINDS. THIS IS ALSO HEDGED BETWEEN DVORAK CURRENT INTENSITY (CI)
ESTIMATES OF T3.0 (45 KNOTS) FROM PGTW AND T2.0 (30 KNOTS) FROM RJTD.
UPPER LEVEL ANALYSIS SHOWS THAT TS 18W IS EXPERIENCING UNFAVORABLE
VERTICAL WIND SHEAR (25 TO 30 KNOTS). THIS IS OFFSET BY GOOD
EQUATORWARD OUTFLOW. HOWEVER, POLEWARD OUTFLOW REMAINS WEAK. SEA
SURFACE TEMPERATURES REMAIN FAVORABLE, NEAR 30 DEGREES CELSIUS. TS
18W IS QUASI-STATIONARY AS IT REMAINS BETWEEN A NEAR EQUATORIAL RIDGE
(NER) TO THE SOUTH AND A SUBTROPICAL RIDGE (STR) TO THE NORTHWEST AND
NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. THROUGH TAU 24, THE STR TO THE NORTHEAST WILL BECOME THE
DOMINANT STEERING FEATURE AS TS 18W SLOWLY TRACKS NORTHWESTWARD.
UNFAVORABLE VERTICAL WIND SHEAR WHICH IS OFFSET BY FAVORABLE OUTFLOW
AND WARM SEA SURFACE TEMPERATURES WILL ALLOW TS 18W TO GRADUALLY
INCREASE IN INTENSITY, REACHING A PEAK INTENSITY OF 45 KNOTS BY TAU
48. AFTER TAU 48, TS 18W WILL TRACK NORTH-NORTHWESTERLY AS THE STR TO
THE NORTHWEST WEAKENS. TS 18W WILL ALSO BEGIN TO ROUND THE WESTERN
EDGE OF THE STR LOCATED TO THE EAST. ALL DYNAMIC MODEL GUIDANCE
INDICATES A NORTHWESTWARD TRACK OVER THE NEXT 48 HOURS. HOWEVER,
THERE IS A 180NM SPREAD IN GUIDANCE BY TAU 48. THEREFORE, THERE IS
LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
C. BEYOND TAU 72, TS 18W WILL ROUND THE AXIS OF THE STR TO THE
EAST AND START TO TRACK TO THE NORTHEAST. INCREASING VERTICAL WIND
SHEAR AND COOLER SEA SURFACE TEMPERATURES WILL LEAD TO A SLOW
DECREASE IN INTENSITY. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT
DURING THIS PORTION OF THE FORECAST TRACK. THE MAJORITY OF THE MODEL
GUIDANCE INDICATES THE NORTHEASTWARD TURN WILL OCCUR AFTER TAU 72.
HOWEVER, AFUM, EGRR, AND CTCX INDICATE A TURN TO THE SOUTHWEST. THE
JTWC FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS WHICH
INDICATES THE NORTHEASTWARD TURN. THERE IS LOW CONFIDENCE IN THIS
PORTION OF THE JTWC FORECAST TRACK.//
NNNN

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TS 1814 (Yagi)
Issued at 09:50 UTC, 10 August 2018

<Analysis at 09 UTC, 10 August>
Scale -
Intensity -
Center position N22°55' (22.9°)
E132°00' (132.0°)
Direction and speed of movement Almost stationary
Central pressure 992 hPa
Maximum wind speed near center 18 m/s (35 kt)
Maximum wind gust speed 25 m/s (50 kt)
≥ 30 kt wind area SE 390 km (210 NM)
NW 220 km (120 NM)

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WDPN32 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (YAGI) WARNING NR
19//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (YAGI), LOCATED APPROXIMATELY 87 NM SOUTH-
SOUTHEAST OF KADENA AB, OKINAWA, HAS TRACKED WESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS A PARTIALLY-EXPOSED, LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH DEEP CONVECTION FLARING OVER THE WESTERN SEMICIRCLE DUE TO
MODERATE EASTERLY VERTICAL WIND SHEAR (VWS). ANIMATED RADAR IMAGERY
AND A 110553Z SSMI 85GHZ IMAGE SHOW SHALLOW BANDING WRAPPING INTO A
BROAD, DEFINED LLCC WITH FRAGMENTED DEEP CONVECTIVE BANDING OVER THE
WEST QUADRANT, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD
CONFIDENCE. TS 18W IS TRACKING ABOUT 60-70NM SOUTH OF OKINAWA AT
THIS TIME WITH KADENA AB REPORTING MAXIMUM SUSTAINED WINDS AT 26
KNOTS GUSTING TO 33 KNOTS. UPPER-LEVEL ANALYSIS INDICATES THE
MODERATE VWS IS OFFSET BY A POLEWARD OUTFLOW CHANNEL, WHICH IS
ENHANCED BY A WEAKENING UPPER LOW NORTH OF TAIWAN. ALONG-TRACK SSTS
REMAIN FAVORABLE AT 29-30 CELSIUS. THE SYSTEM IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF A DEEP-LAYERED STR TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS YAGI WILL TRACK WEST-NORTHWESTWARD TO NORTHWESTWARD UNDER
THE STR THROUGHOUT THE FORECAST. TS 18W WILL REMAIN UNDER MODERATE
UPPER-LEVEL EASTERLY TO SOUTHEASTERLY FLOW WITH DEGRADING POLEWARD
OUTFLOW AS THE UPPER LOW DISSIPATES, THEREFORE, THE SYSTEM IS
EXPECTED TO INTENSIFY ONLY SLIGHTLY TO 40 KNOTS BY TAU 24 BEFORE
MAKING LANDFALL AT TAU 30 ALONG THE EAST COAST OF CHINA. AFTER TAU
30, TS YAGI WILL CONTINUE TRACKING INLAND AND WILL DISSIPATE BY TAU
48 WELL INLAND. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT,
THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

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TPPN10 PGTW 110908

A. TROPICAL STORM 18W (YAGI)

B. 11/0840Z

C. 24.26N

D. 127.86E

E. FIVE/HMWRI8

F. T2.0/2.0/S0.0/24HRS STT: S0.0/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 49A/PBO PTLY XPSD LLCC/ANMTN. CNVCTN WRAPS .30 ON
LOG10 SPIRAL YIELDING A DT OF 2.0. PT AGREES WITH DT WHILE MET
YIELDS A 2.5. DBO DT.

I. ADDITIONAL POSITIONS:
11/0726Z 24.87N 127.92E SSMS


LEMBKE

TXPQ29 KNES 110907
TCSWNP

A. 18W (YAGI)

B. 11/0830Z

C. 24.4N

D. 127.4E

E. THREE/HIMAWARI-8

F. T2.0/2.0/S0.0/24HRS

G. IR/EIR/VIS/AMSR2

H. REMARKS...THIS INTENSITY ESTIMATE WAS DERIVED USING 4 KM IR
DATA. SYSTEM CENTER IS LOCATED UNDER AN IRREGULAR CDO WITH AN AVERAGE
DIAMETER OF 1.49 DEGREES. DT=2.0. MET AND PT AGREE. FT IS BASED ON DT.

I. ADDL POSITIONS

11/0459Z 24.8N 128.3E AMSR2


...VELASCO

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WDPN32 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (YAGI) WARNING NR
22//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (YAGI), LOCATED APPROXIMATELY 160 NM EAST
OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MSI SHOWS THE SYSTEM HAS MAINTAINED ITS
OVERALL CONVECTIVE SIGNATURE OVER THE PAST SIX HOURS. A ROBUST
POLEWARD OUTFLOW INTO A TUTT CELL TO THE NORTHWEST IS PROVIDING
VENTILATION TO THE FLARING CENTRAL CONVECTION. THE INITIAL POSITION
IS BASED WITH HIGH CONFIDENCE ON A COMPOSITE RADAR LOOP FROM OKINAWA.
THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON THE DVORAK ESTIMATES OF
T2.5 FROM PGTW AND RJTD AND SUPPORTED BY NEARBY SURFACE OBSERVATIONS,
INCLUDING MIYAKO-JIMA TO THE SOUTHWEST AND KUME-JIMA TO THE
NORTHEAST. UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF
MODERATE VWS THAT IS OFFSET BY THE POLEWARD OUTFLOW INTO THE TUTT
CELL. ALONG-TRACK SSTS REMAIN FAVORABLE AT 29-30 CELSIUS. THE SYSTEM
IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYERED STR TO
THE NORTHEAST.
3. FORECAST REASONING.
A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY SINCE
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TS YAGI WILL CONTINUE ON A NORTHWESTWARD TRACK UNDER THE STR
THROUGHOUT THE FORECAST. THE MARGINALLY FAVORABLE CONDITIONS WILL
MAINTAIN ITS INTENSITY OVER THE NEXT 12 HOURS. AFTERWARD, IT WILL
GRADUALLY WEAKEN AS POLEWARD OUTFLOW DIMINISHES AND LAND INTERACTION
WITH CHINA BEGINS. TS 18W WILL MAKE LANDFALL NEAR WENZHOU, CHINA,
APPROXIMATELY 160 NM SOUTH OF SHANGHAI NEAR TAU 18 THEN TRACK FURTHER
INLAND INTO CHINA. LAND INTERACTION WILL PRIMARILY BE RESPONSIBLE FOR
ITS RAPID DECAY LEADING TO DISSIPATION BY TAU 36. NUMERICAL MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT; THEREFORE, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

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WDPN32 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (YAGI) WARNING NR
23//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 18W (YAGI), LOCATED APPROXIMATELY 149 NM
NORTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWESTWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS AN EXPOSED LOW-LEVEL CIRCULATION CENTER WITH DEEP CONVECTIVE
BANDING OVER THE WESTERN SEMICIRCLE, WHICH SUPPORTS THE INITIAL
POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT
35 KNOTS BASED ON DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS) FROM
ALL AGENCIES. UPPER-LEVEL ANALYSIS INDICATES LOW TO MODERATE
VERTICAL WIND SHEAR WITH GOOD POLEWARD OUTFLOW, ENHANCED BY A TUTT
CELL POSITIONED NORTHWEST OF TAIWAN. TS 18W IS TRACKING
NORTHWESTWARD ALONG THE SOUTHWEST PERIPHERY OF THE SUBTROPICAL
RIDGE (STR).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
B. TS 18W WILL TRACK NORTHWESTWARD UNDER THE STEERING INFLUENCE
OF THE STR THROUGH THE FORECAST PERIOD. TS YAGI SHOULD MAKE LANDFALL
NEAR TAU 12 AND DISSIPATE BY TAU 24 WHILE TRACKING INLAND. NUMERICAL
MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE
IN THE JTWC FORECAST TRACK.//
NNNN

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TPPN10 PGTW 120909

A. TROPICAL STORM 18W (YAGI)

B. 12/0850Z

C. 27.44N

D. 122.91E

E. FIVE/HMWRI8

F. T3.0/3.0/D1.0/24HRS STT: D0.5/03HRS

G. IR/EIR/VIS/MSI

H. REMARKS: 40A/PBO SBC/ANMTN. CNVCTN WRAPS .70 ON LOG10 SPIRAL
YIELDING A DT OF 3.0. MET AND PT AGREE. DBO DT.

I. ADDITIONAL POSITIONS: NONE


VEERKAMP

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TXPQ29 KNES 120957
TCSWNP

A. 18W (YAGI)

B. 12/0830Z

C. 27.4N

D. 122.8E

E. THREE/HIMAWARI-8

F. T3.0/3.0/D1.0/24HRS

G. IR/EIR/VIS

H. REMARKS...THIS INTENSITY ESTIMATE WAS DERIVED USING 4 KM IR DATA. THE
0911Z SSMIS SHOWS A TIGHT CURVED WRAP. CONVECTIVE BANDING MEASURING 0.6
YIELDS A DT OF 3.0. MET IS 2.5 AND PT IS 3.0. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...RAMIREZ

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[mrbagyo]

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Up to 45 knots!

18W YAGI 180812 1200 27.5N 122.5E WPAC 45 983

[doomhaMwx]