Krosa(11W) has been struggling

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WESTERN NORTH PACIFIC

TS KROSA(11W)
As of 00:00 UTC Aug 13, 2019:
Location: 27.4°N 135.2°E
Maximum Winds: 45 kt ( 85km/h)
Gusts: 55 kt (100km/h)
Minimum Central Pressure: 979 mb
WDPN33 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 444 NM
SOUTH-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI)
SATELLITE IMAGERY SHOWS A VERY EXPANSIVE SYSTEM WITH FRAGMENTED
CONVECTIVE BANDS SPIRALING IN FROM THE SOUTHWEST INTO A LARGE, RAGGED
AND FULLY EXPOSED LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION
IS PLACED WITH GOOD CONFIDENCE BASED ON THE CENTER OF THE LLC SEEN IN
A PARTIAL 130013Z METOP-B ASCAT PASS WHICH ALSO SHOWS A BROAD SWATH
OF 45 KNOT WIND BARBS IN THE NORTHEAST QUADRANT. THE INITIAL
INTENSITY OF 45 KNOTS IS SET FROM THE AFOREMENTIONED ASCAT PASS AND
IS ON THE LOW SIDE OF MULTI-AGENCY DVORAK CURRENT ESTIMATES RANGING
FROM T3.0-4.0 (45-65 KNOTS). THIS INTENSITY IS FURTHER SUPPORTED BY A
121146Z SATCON ESTIMATE OF 48 KNOTS. UPPER LEVEL ANALYSIS INDICATES A
MARGINAL ENVIRONMENT WITH A LOW DIRECTLY OVER THE LLC WHICH IS
INHIBITING CONVECTION. SEA SURFACE TEMPERATURE (SST) REMAINS
CONDUCIVE (29-30 DEGREES CELSIUS). THE CYCLONE IS TRACKING ALONG THE
SOUTHWESTERN 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 36 HOURS, TS 11W WILL CONTINUE ON ITS CURRENT
TRACK UNDER THE INFLUENCE OF THE PREVIOUSLY MENTIONED STR. NEAR TAU
36, IT WILL TURN POLEWARD AROUND THE STR AXIS, MAKING LANDFALL OVER
WESTERN SHIKOKU NEAR TAU 36. THE MARGINAL CONDITIONS WILL SUSTAIN THE
CURRENT INTENSITY UP TO TAU 12. AFTERWARD, INCREASING POLEWARD
OUTFLOW AHEAD OF A MID-LATITUDE TROUGH WILL PROMOTE A SLIGHT
INTENSIFICATION TO A PEAK OF 50 KNOTS BY TAU 24. LAND INTERACTION,
INCREASING VWS, AND COOLER SST (24-26 DEGREES CELSIUS) IN THE SEA OF
JAPAN (SOJ) WILL COMBINE TO GRADUALLY WEAKEN THE SYSTEM DOWN TO 40
KNOTS BY TAU 72 AS IT EXITS INTO THE SOJ. NUMERICAL MODELS ARE IN
GOOD AGREEMENT, WITH THE EXCEPTION OF NAVGEM, WHICH IS EXPECTING AN
EARLIER RECURVE, LENDING HIGH CONFIDENCE IN THIS PORTION OF THE JTWC
TRACK FORECAST.
   C. AFTER TAU 72, COOLER SST IN THE SOJ WILL COMBINE WITH INCREASED
SHEAR TO RAPIDLY WEAKEN THE SYSTEM DOWN TO 35 KNOTS BY TAU 96 AS IT
ACCELERATES INTO THE NORTHERN SOJ WEST OF HOKKAIDO. TS 11W WILL BEGIN
EXTRA-TROPICAL TRANSITION AS IT ENTERS THE BAROCLINIC ZONE, BECOMING
A COLD CORE LOW WITH AN EXPANSIVE WIND FIELD, BY TAU 96. WITH THE
EXCEPTION OF NAVGEM, NUMERICAL MODEL DIFFERENCE SPREADS OUT TO 250
NM, BY TAU 96. THERE IS OVERALL MODERATE CONFIDENCE IN THE JTWC
FORECAST TRACK FOR THIS PORTION OF THE FORECAST THAT IS LAID JUST TO
THE LEFT OF CONSENSUS TO OFFSET THE UNLIKELY NAVGEM/JGSM SOLUTION
THAT DRIVES THE VORTEX INTO THE STR.//
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