Tapah(18W) will begin extratropical transition in 48h over the cooler Sea of Japan

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WESTERN NORTH PACIFIC

TS TAPAH(18W)
As of 00:00 UTC Sep 21, 2019:
Location: 26.3°N 125.8°E
Maximum Winds: 55 kt ( 100km/h)
Gusts: 70 kt ( 130km/h)
Minimum Central Pressure: 974 mb
WDPN31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (TAPAH) WARNING NR
009//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 18W (TAPAH), LOCATED APPROXIMATELY 108 NM
WEST OF KADENA AB, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS (KTS)
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(AMSI) REVEALS CONVECTIVE BANDING, PRIMARILY ON THE EAST, WINDING
INTO A BROAD, PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER. THERE
IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE AMSI, RADAR
IMAGERY, AND SURROUNDING OBSERVATIONS. THE INITIAL INTENSITY OF 55
KTS IS ON THE HIGH SIDE OF DVORAK INTENSITY ESTIMATES RANGING FROM
T3.0-T3.5 (45-55 KTS) DUE TO OKINAWA OBSERVATIONS UP TO 55 KTS. THE
ENVIRONMENT, WITH MODERATE (10-15 KT) VERTICAL WIND SHEAR (VWS),
GOOD EQUATORWARD AND POLEWARD OUTFLOW, AND WARM (27-28 CELSIUS) SEA
SURFACE TEMPERATURE (SST), IS SUPPORTIVE OVERALL, HOWEVER, SOME DRY
AIR ENTRAINING INTO AND SUPPRESSING CONVECTION ON THE WESTERN HALF
OF THE SYSTEM IS EXPECTED TO LIMIT FURTHER INTENSIFICATION. TS 18W
IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. AROUND TAU 24, TS 18W WILL HAVE ROUNDED THE STR AXIS AND BEGIN
TURNING NORTHEASTWARD. THERE IS A BRIEF PERIOD WHERE THE ENVIRONMENT
IS MARGINALLY SUPPORTIVE BEFORE STRONG VWS, LAND INTERACTION, AND
COOL SST BEGIN TO CAUSE GRADUAL WEAKENING. BY TAU 48, TS 18W WILL
BECOME ENTRENCHED IN THE MID-LATITUDE BAROCLINIC ZONE AND BEGIN
EXTRATROPICAL TRANSITION (ETT). AFTER COMPLETING ETT (NO LATER THAN
TAU 72), A GALE-FORCE COLD CORE LOW WILL REMAIN. NUMERICAL GUIDANCE
IS IN STRONG AGREEMENT THROUGH TAU 36. AFTER TAU 36, CROSS-TRACK
AGREEMENT REMAINS GOOD BUT ALONG-TRACK DIFFERENCES CAUSE THE SPREAD
AMONG THE MODELS TO INCREASE. BASED ON STRONG AGREEMENT AND SHORT
DURATION OF FORECAST, THERE IS GOOD CONFIDENCE IN THE JTWC TRACK
FORECAST.//
NNNN
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INVEST 90W
As of 00:00 UTC Sep 21, 2019:
Location: 16.4°N 142.4°E
Maximum Winds: 15 kt
Minimum Central Pressure: 1007 mb
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NORTH INDIAN

INVEST 96A
As of 00:00 UTC Sep 21, 2019:
Location: 19.4°N 70.4°E
Maximum Winds: 20 kt
Minimum Central Pressure: 1002 mb