WPAC: KROSA - Post-Tropical

[1900hurricane]

It looked like it may have tried to develop two eyewalls, which does happen on occasion with these large monsoon trough systems. Recent passes have shown some improvements though with the outer appearing to become dominant.

[Tailspin]

Its a big system that may threaten JP upstream.

[dexterlabio]

I just feel like Krosa has better chance to flirt with Cat5 intensity than Lekima.

[Hayabusa]

TY 1910 (Krosa)
Issued at 09:45 UTC, 8 August 2019

<Analysis at 09 UTC, 8 August>
Scale Large
Intensity Very strong
Center position N22°05' (22.1°)
E140°35' (140.6°)
Direction and speed of movement Almost stationary
Central pressure 950 hPa
Maximum wind speed near center 45 m/s (85 kt)
Maximum wind gust speed 60 m/s (120 kt)
≥ 50 kt wind area ALL 170 km (90 NM)
≥ 30 kt wind area ALL 650 km (350 NM)

[euro6208]

WDPN33 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 167 NM SOUTH-
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTHEASTWARD AT 01 KNOT
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS THE SYSTEM HAS BECOME QUASI-STATIONARY (QS) AS IT RAPIDLY
INTENSIFIED (RI) AND MAINTAINED A 14-NM EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EYE FEATURE. THE INITIAL
INTENSITY OF 100KTS IS BASED ON THE DVORAK ESTIMATES OF T5.5/102KTS
FROM PGTW AND RJTD AND REFLECT THE RI. ENVIRONMENTAL ANALYSIS
INDICATES EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW (TEMPERED ONLY
BY SUBSIDENCE ALONG THE NORTHWEST SECTOR), LOW VERTICAL WIND SHEAR
(VWS) AND WARM SST (30C). TY 11W IS IN A COL BETWEEN A WEAKENED
SUBTROPICAL RIDGE (STR) TO THE EAST AND A BUILDING NEAR EQUATORIAL
RIDGE (NER) TO THE SOUTH.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. TY 11W WILL REMAIN QS IN THE COL UP TO TAU 12. AFTERWARD, THE
NER WILL SLOWLY STEER IT NORTHEASTWARD. AROUND TAU 36, THE STR WILL
REBUILD AND RESUME STEERING AND DRIVE THE SYSTEM NORTH-NORTHWESTWARD
TOWARD JAPAN. INCREASING VWS AND REDUCED POLEWARD OUTFLOW WILL
GRADUALLY WEAKEN THE SYSTEM DOWN TO 70KTS BY TAU 72. THE NUMERICAL
MODELS ARE IN OVERALL GOOD AGREEMENT; HOWEVER, GIVEN THE UNCERTAINTY
IN THE TRANSITION BETWEEN THE STEERING MECHANISMS, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
C. AFTER TAU 72, TY KROSA WILL CONTINUE TRACKING
NORTH-NORTHWESTWARD UNDER THE INFLUENCE OF THE STR. COOLING SSTS, IN
ADDITION TO THE INCREASING VWS, WILL CONTINUE TO ERODE THE SYSTEM
DOWN TO 65KTS BY TAU 120. THE NUMERICAL MODELS SPREAD OUT TO OVER
400 NM BY TAU 120, LENDING TO LOW CONFIDENCE IN THE EXTENDED PORTION
OF THE JTWC FORECAST TRACK.//
NNNN

[euro6208]

[euro6208]

JTWC have been really bad catching up. Sigh days of post recon...

CURRENT ESTIMATE
Date (mmddhhmm): 08080410
SATCON: MSLP = 939 hPa MSW = 112 knots
SATCON Member Consensus: 107.0 knots
Pressure -> Wind Using SATCON MSLP: 112 knots
Distance to Outer Closed Isobar Used is 215 nm
Eye Size Correction Used is 0.7 knots Source: IR

[1900hurricane]

It had better start moving some or upwelling might become an issue.

[euro6208]

Krosa must be jealous of Lekima. She is bigger but the less intense.

[euro6208]

WDPN33 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 168 NM SOUTH OF
IWO TO, HAS TRACKED EASTWARD AT 01 KNOT (KT) OVER THE PAST SIX
HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON A
36 NM RAGGED EYE IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI).
ENHANCED INFRARED IMAGERY REVEALS AN AREA OF WARMER CLOUD TOP
TEMPERATURES OVER ABOUT 50 PERCENT OF THE EYEWALL. THE INITIAL
INTENSITY OF 90 KTS IS CONSISTENT WITH A T5.0 (90 KTS) PGTW DVORAK
FIX CURRENT INTENSITY ESTIMATE. THE ENVIRONMENT IS FAIRLY SUPPORTIVE
WITH EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW, MODERATE (10-20 KT)
VERTICAL WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURE BEING PARTIALLY OFFSET BY SUBSIDENCE ALONG THE NORTHERN
SECTOR DUE TO AN INDUCED UPPER-LEVEL TROUGH. TY 11W IS QUASI-
STATIONARY IN A COMPLEX STEERING ENVIRONMENT WITH A NEAR EQUATORIAL
RIDGE (NER) TO THE SOUTH AND A SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. IN THE NEXT 72 HOURS, PRIMARY STEERING FOR TY 11W WILL
GRADUALLY TRANSITION TO THE STR AND THE TRACK WILL SLOWLY SHIFT
NORTHWESTWARD TOWARD JAPAN, PASSING IWO TO AROUND TAU 36. SLIGHTLY
DIMINISHED OUTFLOW, WEAK ENVIRONMENTAL SUBSIDENCE, AND CONTINUED
MARGINAL VWS WILL MAKE THE ENVIRONMENT SOMEWHAT UNFAVORABLE AND
WEAKENING TO 70 KTS IS ANTICIPATED BY TAU 72. MODEL TRACK GUIDANCE
GENERALLY AGREES WITH THE JTWC FORECAST TRACK FORECAST FOR THIS
PORTION OF THE FORECAST. HOWEVER, GIVEN HIGH UNCERTAINTY WHENEVER
THERE IS A TRANSITION BETWEEN STEERING MECHANISMS, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.
C. AFTER TAU 72, TY 11W WILL CONTINUE TRACKING NORTHWESTWARD
UNDER THE INFLUENCE OF THE STR UNTIL TAU 96 WHEN IT SHIFTS
MORE NORTHWARD AS IT BEGINS TO ROUND THE STR AXIS. THE SLIGHT
INCREASE IN INTENSITY AT TAU 120, REFLECTS THE POSSIBILITY THAT
IMPROVED OUTFLOW COULD OCCUR AS TY 11W ROUNDS THE STR AXIS. IN THE
EXTENDED PERIOD, NAVGEM BECOMES AN OBVIOUS EASTERN OUTLIER AND THE
JTWC TRACK FORECAST IS PLACED JUST WEST OF THE CONSENSUS TRACK TO
OFFSET THE OUTLIER. BASED ON HIGH UNCERTAINTY IN THE NEAR TERM
FORECAST, CONFIDENCE IN THE JTWC TRACK FORECAST REMAINS LOW IN THE
EXTENDED PERIOD.//
NNNN

[1900hurricane]

Looks like upwelling is indeed taking a toll.

[Hayabusa]

TY 1910 (Krosa)
Issued at 18:50 UTC, 9 August 2019

<Analysis at 18 UTC, 9 August>
Scale Large
Intensity -
Center position N22°20' (22.3°)
E141°25' (141.4°)
Direction and speed of movement Almost stationary
Central pressure 970 hPa
Maximum wind speed near center 35 m/s (70 kt)
Maximum wind gust speed 50 m/s (100 kt)
≥ 50 kt wind area ALL 150 km (80 NM)
≥ 30 kt wind area S 650 km (350 NM)
N 560 km (300 NM)

[Highteeld]

Upwelling getting very noticable

[euro6208]

WDPN33 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (KROSA) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TYPHOON (TY) 11W (KROSA), LOCATED APPROXIMATELY 115 NM SOUTH OF
IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 05 KNOTS OVER THE PAST SIX
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS
CONVECTIVE BANDING WRAPPING INTO A DEFINED LOW-LEVEL CIRCULATION
CENTER (LLCC). HOWEVER, DEEP CONVECTION OVER THE CORE AND NORTHWEST
QUADRANT REMAINS COMPARATIVELY WEAK DUE TO THE PRESENCE OF CYCLONIC
FLOW AND CONVERGENCE ALOFT WHILE STRONG DIFFLUENCE OVER THE EASTERN
AND SOUTHERN FLANK CONTINUE TO FUEL DEEP CONVECTIVE BANDING. A 100520
SSMI 85GHZ IMAGE INDICATES TIGHTLY-CURVED BANDING WRAPPING INTO A
DEFINED, BROAD LLCC, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD
CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 65 KNOTS, HEDGED
SLIGHTLY BELOW DVORAK CURRENT INTENSITY ESTIMATES OF 4.5 (77 KNOTS)
BASED ON WARMING CLOUD TOPS ACROSS THE SOUTHERN PERIPHERY. WITH THE
EXCEPTION OF THE COMPLEX, MARGINALLY-FAVORABLE OUTFLOW, VERTICAL WIND
SHEAR AND SST VALUES REMAIN FAVORABLE. TY 11W IS LOCATED WITHIN A
WEAK STEERING ENVIRONMENT WITH A NORTH-SOUTH SUBTROPICAL RIDGE
POSITIONED TO THE EAST, A WEAK STR OVER WESTERN JAPAN AND A BREAK TO
THE NORTH. THEREFORE, TY 11W IS TRACKING SLOWLY POLEWARD (AND
ERRATICALLY).
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. IN THE NEXT 72 HOURS, THE PRIMARY STEERING FOR TY 11W WILL
GRADUALLY TRANSITION TO THE BUILDING STR TO THE NORTH OF TY 11W WITH
A NORTHWESTWARD TRACK TOWARD JAPAN, PASSING SOUTHWEST OF IWO TO
AROUND TAU 12. SLIGHTLY DIMINISHED OUTFLOW, WEAK SUBSIDENCE AND
POSSIBLE UPWELLING OF COOLER WATER WILL MAKE THE ENVIRONMENT SOMEWHAT
UNFAVORABLE THROUGH TAU 48 WITH GRADUAL WEAKENING TO ABOUT 60 KNOTS.
AFTER TAU 48, AS THE SYSTEM BEGINS TO ACCELERATE WEST-NORTHWESTWARD
TO NORTHWESTWARD OVER WARM SST, SLIGHT INTENSIFICATION IS EXPECTED.
C. AFTER TAU 72, TY 11W WILL BEGIN TO RECURVE POLEWARD ALONG THE
SOUTHWEST
PERIPHERY OF THE STR TO THE NORTH, WHICH IS EXPECTED TO WEAKEN AND
REORIENT WITH THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH. TY
11W SHOULD RE-INTENSIFY TO A PEAK INTENSITY OF 70 KNOTS AS POLEWARD
OUTFLOW IMPROVES UNTIL UPPER LEVEL CONVERGENCE AND LAND INTERACTION
GRADUALLY WEAKENS TY 11W. SST VALUES WILL REMAIN CONDUCIVE (28-29C)
DURING THIS EXTENDED PERIOD. NUMERICAL MODEL GUIDANCE DIVERGES
SLIGHTLY BUT REMAINS IN GOOD AGREEMENT WITH SOME UNCERTAINTY IN TRACK
SPEED AS TY 11W APPROACHES THE SOUTHERN COAST OF KYUSHU. BASED ON THE
ERRATIC SHORT-TERM MOTION AND UNCERTAINTY IN THE LATER TAUS, THERE IS
OVERALL MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.//
NNNN

[1900hurricane]

 https://twitter.com/WXappraiser/status/1160188404698451968

[1900hurricane]

With all the weakening from upwelling, the core has pretty much collapsed and RMW has greatly expanded. Looks like it's ~60 nm now based on ASCAT data.

[1900hurricane]

 https://twitter.com/TropicalTidbits/status/1160271578845929472

[euro6208]

WDPN33 PGTW 110900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 121 NM
SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTHWESTWARD AT 07 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
SHOWS VERY BROAD BANDS OF WEAK AND FRAGMENTED CONVECTION SPIRALING
AROUND A LARGE, RAGGED AND PARTLY EXPOSED LOW-LEVEL CIRCULATION (LLC)
WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE INITIAL
INTENSITY OF 50KTS IS AVERAGED FROM AGENCY DVORAK ESTIMATES RANGING
FROM T3.0/45KTS TO T4.0/65 KTS AND REFLECTS THE OVERALL WEAKENED
STATE. UPPER LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH A
LOW DIRECTLY OVER THE LLC THAT IS CAUSING SUBSIDENCE. HOWEVER, AROUND
THE LOW IS A BROAD ANTICYCLONIC OUTFLOW THAT IS PROVIDING VENTILATION
TO THE CONVECTIVE BANDS. ALONG-TRACK SST AT 30C REMAINS CONDUCIVE.
THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A BUILDING
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
B. OVER THE NEXT 72 HOURS, TS 11W WILL CONTINUE ON ITS CURRENT
TRACK UNDER THE STR. THE MARGINAL CONDITIONS WILL SUSTAIN THE CURRENT
INTENSITY AT BEST UP TO TAU 36. AFTERWARD, INCREASING POLEWARD
OUTFLOW AHEAD OF A MID-LATITUDE TROUGH WILL PROMOTE INTENSIFICATION
TO A PEAK OF 70 KNOTS BY TAU 72. NUMERICAL MODELS ARE IN GOOD
AGREEMENT, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK
FORECAST.
C. AFTER TAU 72, TS KROSA WILL CREST THE STR AXIS AND TURN
POLEWARD THEN ACCELERATE NORTHEASTWARD, MAKING LANDFALL OVER WESTERN
SHIKOKU JUST BEFORE TAU 96, THEN CROSS INTO THE SEA OF JAPAN (SOJ).
LAND INTERACTION, INCREASING VWS, AND COOLER SSTS IN THE SOJ WILL
COMBINE TO GRADUALLY WEAKEN THE SYSTEM DOWN TO 45 KNOTS AS IT
APPROACHES THE BAROCLINIC ZONE. NUMERICAL MODELS SPREAD OUT TO OVER
260 NM BY TAU 120 WITH NAVGEM AS THE SOLE RIGHT OUTLIER. THERE IS
OVERALL MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK THAT IS LAID
JUST TO THE LEFT OF CONSENSUS TO OFFSET THE UNLIKELY NAVGEM SOLUTION
THAT DRIVES THE VORTEX INTO THE STR.//
NNNN

[euro6208]

EURO and GFS has strengthening before another Japan landfall...

[Tailspin]

I just feel like Krosa has better chance to flirt with Cat5 intensity than Lekima.

I was thinking along those lines too. It just never made the grade. Under super-ty intensity in august is a fizzer.