WPAC: LAN - Post-Tropical

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 https://twitter.com/zoom_earth/status/1691425361962127360

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WDPN31 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR
034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 38.1N 135.4E
INITIAL INTENSITY: 45 KTS
GEOGRAPHIC REFERENCE: 266 NM NORTHWEST OF YOKOSUKA, JAPAN
MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 12 KTS
SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 07W (LAN) CONTINUES TO ACCELERATE TOWARDS THE
NORTHEAST FURTHER INTO THE SEA OF JAPAN. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED, BROAD LOW LEVEL
CIRCULATION CENTER (LLCC) WITH LOW LEVEL BANDING FEATURES
SURROUNDING THE MAJORITY OF THE LLCC, WITH A WEDGE OF DEEP
CONVECTION DEVELOPING IN THE NORTHWEST QUADRANT. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC
AND EXTRAPOLATION OF A 152135Z SSMIS 37GHZ MICROWAVE LOW EMISSIVITY
REGION (LER). ADDITIONALLY, A 152053Z RCM-1 SAR PASS REVEALED AN
IRREGULAR SHAPED CENTER WITH BANDS OF ELEVATED WINDS SURROUNDING
THE CORE. THE SAR ALSO REVEALED STRONG BANDS OF DOWNSLOPE AND
FUNNELED WINDS EMANATING FROM THE COASTAL VALLEYS NEAR JOETSU AND
EXTENDING ALL THE WAY INTO THE NORTHERN PERIPHERY OF THE CORE
CIRCULATION OF TS 07W. THE INITIAL INTENSITY OF 45 KNOTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAR DATA, WHICH NOTED
MAXIMUM WINDS BETWEEN 45-50 KNOTS IN ALL BUT THE SOUTHWEST
QUADRANT. THE ENVIRONMENT IS BECOMING INCREASINGLY HOSTILE, WITH
CIMSS ESTIMATED SHEAR UP TO 20 KNOTS AND EXPECTED TO CONTINUE
CLIMBING, OFFSETTING THE OTHERWISE VERY STRONG POLEWARD OUTFLOW.
SSTS REMAIN WARM, BUT THE SYSTEM IS RAPIDLY APPROACHING THE SHARP
SST GRADIENT WHERE TEMPERATURES WILL DROP BY SEVERAL DEGREES WITHIN
A VERY SHORT DISTANCE.

INITIAL WIND RADII BASIS: SAR DATA

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.5 - 35 KTS
RJTD: T2.0 - 30 KTS
RCTP: T2.5 - 35 KTS
KNES: T2.0 - 30 KTS
CIMSS SATCON: 40 KTS AT 152248Z
CIMSS ADT: 33 KTS AT 152330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 20-25 KTS
SST: 28-29 CELSIUS
OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: OVER THE PAST SIX HOURS, TS 07W LOOKS TO HAVE
TAKEN MORE NORTHEASTWARD TRACK THAN ANTICIPATED, TRACKING AT ABOUT
025 DEGREES AT 12 KNOTS. THUS THE TRACK FORECAST HAS SHIFTED A BIT
MORE TO THE EAST THAN THE PREVIOUS FORECAST, BUT OTHERWISE THE
OVERALL SCENARIO HAS NOT CHANGED APPRECIABLY. THE SYSTEM WILL
TRACK GENERALLY NORTHEASTWARD THROUGH THE FORECAST PERIOD BEFORE
CROSSING OVER SOUTHERN SAKHALIN ISLAND AND MOVING INTO THE SEA OF
OKHOTSK BY TAU 48. EVEN AS DVORAK-BASED INTENSITY ESTIMATES HAVE
FALLEN LIKE A ROCK DUE TO THE LACK OF CONVECTION, THE ACTUAL WIND
SPEEDS ASSOCIATED WITH THE CIRCULATION HAVE NOT DROPPED OFF
APPRECIABLY BASED ON THE SAR DATA. HENCE, WHILE THERE IS NO
POSSIBILITY OF INTENSIFICATION, THE SYSTEM WILL TAKE TIME TO SLOWLY
WIND DOWN THROUGH THE FORECAST PERIOD. BETWEEN TAU 18 AND TAU 24,
THE SYSTEM WILL BEGIN TO INTERACT WITH A MID-LATITUDE TROUGH AND
WEAK BAROCLINIC ZONE, MARKING THE START OF EXTRATROPICAL TRANSITION
(ETT). TRANSITION TO A GALE-FORCE EXTRATROPICAL LOW IS EXPECTED TO
BE COMPLETED NO LATER THAN TAU 48, AND POSSIBLY AS EARLY AS TAU 36.


MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN VERY TIGHT
AGREEMENT THROUGH THE FORECAST PERIOD, WITH MINIMAL CROSS OR
ALONG-TRACK SPREAD. THE JTWC FORECAST LIES ALONG THE INSIDE EDGE OF
THE GUIDANCE ENVELOPE IN LIGHT OF THE RECENT TRACK MOTION, BUT
OTHERWISE IS VERY CONSISTENT WITH THE MULTI-MODEL CONSENSUS.
INTENSITY GUIDANCE IN GOOD AGREEMENT ON A SLOW DECAY OF THE SYSTEM,
DOWN TO 35 KNOTS BY TAU 48 AND CONSISTENT WITH THE JTWC FORECAST.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
INTENSITY 0 - 72 HR: HIGH//

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WDPN31 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (LAN) WARNING NR
036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
INITIAL POSITION: 40.9N 136.5E
INITIAL INTENSITY: 35 KTS
GEOGRAPHIC REFERENCE: 216 NM WEST OF MISAWA, JAPAN
MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 15 KTS
SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH MINIMAL FLARING
CONVECTION BEING RAPIDLY EVACUATED POLEWARD. A 160859Z SSMIS 91GHZ
MICROWAVE IMAGE REVEALS A BROAD AND DEFORMED FULLY EXPOSED LLCC
WITH MINIMAL CONVECTIVE COVER. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON EIR AND SSMIS IMAGERY. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
AGENCY DVORAK INTENSITY ESTIMATES AND CIMSS DPRINT INDICATING 35
KTS WHILE CIMSS ADT IS SHOWING A LOWER ESTIMATE OF 29KTS.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T2.0 - 30 KTS
RCTP: T2.5 - 35 KTS
CIMSS ADT: 29 KTS AT 161140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
VWS: 25-30 KTS
SST: 26-27 CELSIUS
OUTFLOW: STRONG POLEWARD

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: TS 07W IS FORECAST TO MAINTAIN ITS GRADUAL
POLEWARD CURVE TOWARD THE SEA OF OKHOTSK THROUGHOUT THE FORECAST
PERIOD. OVER THE NEXT 12 HOURS, STRONG POLEWARD OUTFLOW ALOFT WILL
LARGELY NEGATE STEADILY MOUNTING VERTICAL WIND SHEAR (VWS),
RESULTING IN A VERY SLOW DECLINE OF INTENSITY DURING THAT TIME.
SHORTLY AFTER TAU 12, VWS TOGETHER WITH COOL DRY AIR ENTRAINING THE
SYSTEM WILL BEGIN TO DRIVE INTENSITY VALUES DOWN. AT THE SAME TIME,
THE SYSTEM WILL BEING TO INTERACT WITH A WEAK BAROCLINIC ZONE AS IT
PROCEEDS POLEWARD OF THE 44TH PARALLEL, THIS WILL INITIATE
EXTRA-TROPICAL TRANSITION (ETT). AS THE SYSTEM CONTINUES TO WEAKEN
AND INTEGRATE INTO THE MID-LATITUDE TROUGH, IT WILL CONTINUE
THROUGH ETT UNTIL ENTERING THE SEA OF OKHOTSK WHERE IT WILL
COMPLETE ETT NEAR TAU 36.

MODEL DISCUSSION: NUMERICAL MODELS AND RELIABLE MODEL INTENSITY
GUIDANCE ARE BOTH IN GOOD AGREEMENT AND DEVIATE VERY LITTLE FROM
THE MULTI-MODEL CONSENSUS. THE JTWC TRACK AND INTENSITY FORECASTS
ARE THEREFOR PLACED CLOSE TO THEIR RESPECTIVE CONSENSUS MODELS WITH
OVERALL HIGH CONFIDENCE.

FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
INTENSITY 0 - 72 HR: HIGH//
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