WPAC: DIANMU - Post-Tropical

[Hayabusa]

90W INVEST 210921 0000 13.0N 118.0E WPAC 15 0

[Hayabusa]

ABPW10 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND
/SOUTH PACIFIC OCEANS REISSUED/212100Z-220600ZSEP2021//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/211221ZSEP2021//
NARR/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(2) AN AREA OF CONVECTION (INVEST 90W) HAS PERSISTED NEAR
11.2N 116.4E, APPROXIMATELY 168 NM NORTHWEST OF PUERTO PRINCESA,
PHILIPPINES. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A
DEFINED LOW LEVEL CIRCULATION (LLC) OBSCURED BY FLARING CONVECTION
ALONG THE WESTERN SEMICIRCLE. A 1755Z AMSR2 89 GHZ IMAGE FURTHER
EMPHASIZES THE CONVECTION WITHIN THE WESTERN SEMICIRCLE.
ENVIRONMENTAL ANALYSIS REVEALS GOOD OUTFLOW ALOFT ACCOMPANIED BY LOW
(10-15 KT) VERTICAL WIND SHEAR (VWS) AND WARM (29-30C) SEA SURFACE
TEMPERATURES. GLOBAL MODELS ARE IN AGREEMENT THAT 90W WILL TRACK
NORTHWESTWARD TOWARDS THE INDOCHINESE PENINSULA AS IT STEADILY
INTENSIFIES WITH THE GFS ENSEMBLE INDICATING A HIGHER LEVEL OF
DEVELOPMENT IN THE SOUTH CHINA SEA. MAXIMUM SUSTAINED SURFACE WINDS
ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS
ESTIMATED TO BE NEAR 1010 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A
SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO
LOW.

[Hayabusa]

Now medium, can it reach warning though?

ABPW10 PGTW 220930
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND
/SOUTH PACIFIC OCEANS REISSUED/220930Z-230600ZSEP2021//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/211221ZSEP2021//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA):
A. TROPICAL CYCLONE SUMMARY: NONE.
B. TROPICAL DISTURBANCE SUMMARY:
(2) THE AREA OF CONVECTION (INVEST 90W) PREVIOUSLY LOCATED
NEAR 12.3N 115.6E IS NOW LOCATED NEAR 12.4N 114.4E, APPROXIMATELY
297 NM WEST-NORTHWEST OF PUERTO PRINCESA, PHILIPPINES. ANIMATED
MULTI SPECTRAL IMAGERY DEPICTS A BROAD CIRCULATION WHICH HAS STARTED
TO CONSOLIDATE WITH DEVELOPING CONVECTION AROUND THE ASSESSED LOW
LEVEL CIRCULATION CENTER (LLCC). A RECENT SCATTEROMETER PASS
INDICATED A DISCREET LLCC WITH 20 KNOT WINDS IN ALL QUADRANTS, AND
HIGHER WINDS IN A BAND TO THE SOUTH. RECENT TRENDS FROM A SHIP
TRANSITING JUST EAST OF THE LLCC INDICATES WINDS SHIFTING FROM WEST-
NORTHWEST TO EAST-NORTHEAST BETWEEN 15-20 KNOTS, AND A PRESSURE
READING OF 1004.2 MB, INDICATING A CLOSE PASSAGE TO THE CENTER AND A
LOWER PRESSURE THAN MODELS SUGGESTED. ENVIRONMENTAL ANALYSIS
INDICATES A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH STRONG
EQUATORWARD OUTFLOW ALOFT ACCOMPANIED BY LOW (5-10 KT) VERTICAL WIND
SHEAR (VWS) AND WARM (29-30C) SEA SURFACE TEMPERATURES (SST). GLOBAL
MODELS ARE STILL IN AGREEMENT THAT 90W WILL TRACK WEST-NORTHWESTWARD
TOWARDS VIETNAM AS IT STEADILY CONSOLIDATES. GFS, ECMWF AND NAVGEM
ALL AGREE ON THE SYSTEM CONSOLIDATING AND STRENGTHENING TO NEAR
TROPICAL DEPRESSION STRENGTH OVER THE NEXT 48 HOURS WITH THE GFS
ENSEMBLE INDICATING SLIGHTLY HIGHER LEVEL OF DEVELOPMENT IN THE
SOUTH CHINA SEA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT
15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR
1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

[Hayabusa]

Straight to warning not surprising

21W TWENTYONE 210922 1200 12.8N 113.3E WPAC 25 1004

[Hayabusa]

WDPN32 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (TWENTYONE)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 12.8N 113.3E
INITIAL INTENSITY: 25 KTS
GEOGRAPHIC REFERENCE: 348 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
RAPIDLY CONSOLIDATING SYSTEM WITH FLARING DEEP CONVECTIVE BLOOMING
OVER THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC) OVER THE PAST
SIX HOURS. A 221121Z SSMIS 89GHZ MICROWAVE IMAGE SHOWED INTENSE
CONVECTIVE BANDS WRAPPING ALONG THE WESTERN PERIPHERY OF THE
DEFINED LLCC. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE AFOREMENTIONED MICROWAVE IMAGE AND A 221248Z ASCAT-B
SCATTEROMETER BULLSEYE. THE INITIAL INTENSITY IS ASSESSED WITH LOW
CONFIDENCE BASED ON THE T1.5 PGTW CURRENT INTENSITY ESTIMATE AND
THE RAPIDLY IMPROVED STRUCTURE. WHILE THE AFOREMENTIONED ASCAT-B
PASS ONLY SHOWED 20 KNOT WIND BARBS MOSTLY FAR TO THE NORTHEAST, AN
EARLIER SCATTEROMETER PASS INDICATED 25-30 KNOT WINDS SURROUNDING
THE LLCC. ADDITIONALLY, A SHIP OBSERVATION FROM 0800Z WITHIN 40 NM
OF THE ASSESSED CENTER AT THAT TIME INDICATED A PRESSURE OF 1004 MB
EQUATING TO 24-25 KNOTS USING THE WIND PRESSURE RELATIONSHIP.
SUBSEQUENT IMAGERY FROM THE 1400Z HOUR SHOWS WHAT COULD POTENTIALLY
BE THE INITIAL INDICATIONS OF AN EYE IN THE EIR, THOUGH WITHOUT
MICROWAVE IMAGERY IT IS HARD TO CONFIRM THIS AS A NASCENT EYE
FEATURE OR JUST AN AREA OF WARMER CLOUD TOPS. THE SYSTEM LIES IN A
FAVORABLE ENVIRONMENT CHARACTERIZED BY LOW VWS, WARM SSTS AND
MODERATE EQUATORWARD AND WEAK POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
VWS: 10-15 KTS
SST: 29-30 CELSIUS
OUTFLOW: MODERATE EQUATORWARD
OTHER FACTORS: LIMITED WEAK POLEWARD OUTFLOW.

ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: LOW
INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 21W IS FORECASTED TO TRACK STEADILY
WEST-NORTHWESTWARD THROUGH THE DURATION OF THE FORECAST PERIOD
ALONG THE SOUTHERN PERIPHERY OF THE LOW- TO MID-LEVEL STR CENTERED
TO THE NORTH. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG THE
CENTRAL VIETNAM COASTLINE AROUND TAU 24, TO THE SOUTH OF DA NANG.
CONDITIONS ARE GENERALLY FAVORABLE FOR INTENSIFICATION WITH THE
ONLY LIMITING FACTORS BEING THE MODEST, SINGLE-CHANNEL OUTFLOW AND
LIMITED TIME AVAILABLE PRIOR TO LANDFALL. TD 21W IS EXPECTED TO
INTENSIFY AT A CLIMATOLOGICAL RATE TO A PEAK OF 35 KNOTS AT OR JUST
PRIOR TO LANDFALL NEAR TAU 24. ONCE INLAND THE SYSTEM WILL RAPIDLY
DISSIPATE BY TAU 48 OVER EASTERN THAILAND DUE TO TERRAIN
INTERACTION.

MODEL DISCUSSION: DUE TO THE RAPID DEVELOPMENT OF TD 21W, THERE IS
LITTLE AVAILABLE DETERMINISTIC TRACK GUIDANCE AVAILABLE, WITH THE
NAVGEM AND GFS THE ONLY AVAILABLE TRACKERS AT 1200Z. THESE TWO
MODELS ARE TIGHTLY GROUPED ON A NORTHWESTWARD TRACK, MAKING
LANDFALL BY TAU 24, HOWEVER THE NAVGEM INDICATES A LANDFALL ABOUT
75 NM FURTHER NORTH UP THE COAST THAN THE GFS. THE GFS ENSEMBLE AND
ECMWF ENSEMBLE MEMBERS ALSO AGREE ON A NORTHWESTWARD TRACK, BUT
SHOW A LANDFALL A BIT FURTHER NORTH, AT OR JUST SOUTH OF DA NANG.
IN LIGHT OF THE LACK OF DISCREET TRACK GUIDANCE, THERE IS ONLY
MEDIUM CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH CLOSELY TRACKS
THE GFS FORECAST. SIMILARLY, THERE IS LITTLE TO NO DISCREET
INTENSITY GUIDANCE FOR THIS FORECAST, AND THE INTENSITY FORECAST IS
THUS BASED SOLELY ON ENVIRONMENTAL ANALYSIS, GLOBAL MODEL FIELDS
AND ENSEMBLE ESTIMATES, AND THUS THERE IS LOW CONFIDENCE IN THE
JTWC INTENSITY FORECAST.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: MEDIUM
INTENSITY 0 - 72 HR: LOW//
NNNN

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[Sciencerocks]

[Hayabusa]

WTPQ50 RJTD 230000
RSMC TROPICAL CYCLONE ADVISORY
NAME TD
ANALYSIS
PSTN 230000UTC 13.5N 111.7E POOR
MOVE WNW 10KT
PRES 1002HPA
MXWD 030KT
GUST 045KT
FORECAST
24HF 240000UTC 16.1N 108.6E 80NM 70%
MOVE NW 11KT
PRES 1000HPA
MXWD 035KT
GUST 050KT
48HF 250000UTC 16.2N 104.2E 130NM 70% TROPICAL DEPRESSION =

[Hayabusa]

Would 21W snatch Dianmu?

TXPQ24 KNES 222358
TCSWNP

A. 21W (NONAME)

B. 22/2330Z

C. 13.5N

D. 111.1E

E. THREE/HIMAWARI-8

F. T2.0/2.0

G. IR/EIR/VIS/GMI

H. REMARKS...THIS INTENSITY ESTIMATE WAS DERIVED USING 4 KM IR
DATA. 4.5/10 BANDING AROUND THE LLCC YIELDS A DT OF 2.5. MET IS EQUAL
TO 1.5 AND PT IS EQUAL TO 2.0. FT IS BASED ON CONSTRAINTS AS THE FT IS
LIMITED TO A CHANGE OF +0.5 IN THE FIRST 24 HOURS.

I. ADDL POSITIONS

22/1745Z 13.0N 112.5E GMI


...TUGGLE

[Hayabusa]

WTPQ20 RJTD 230600
RSMC TROPICAL CYCLONE ADVISORY
NAME TS 2115 DIANMU (2115) UPGRADED FROM TD
ANALYSIS
PSTN 230600UTC 14.8N 110.6E FAIR
MOVE NW 14KT
PRES 1000HPA
MXWD 035KT
GUST 050KT
30KT 160NM NORTH 90NM SOUTH
FORECAST
24HF 240600UTC 16.3N 106.1E 50NM 70% TROPICAL DEPRESSION =

[Sciencerocks]