Invest 97W: Tropical Cyclone Formation Alert

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WESTERN NORTH PACIFIC

TS  NEOGURI(21W)
As of 12:00 UTC Oct 18, 2019:
Location: 20.4°N 129.2°E
Maximum Winds: 45 kt ( 85km/h)
Gusts: 55 kt ( 100km/h)
Minimum Central Pressure: 1001 mb
WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 21W (NEOGURI) WARNING
NR 009//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 21W (NEOGURI), LOCATED APPROXIMATELY 374 NM
SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 05 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY REVEALS AN APPROXIMATELY 100 NM WIDE CENTRAL DENSE OVERCAST,
SHEARED SLIGHTLY TO THE NORTHEAST WITH GOOD POLEWARD OUTFLOW. THERE
IS FAIR CONFIDENCE IN THE INITIAL POSITION BASED ON AN 181014Z SSMIS
91 GHZ MICROWAVE IMAGE THAT SHOWED BANDING FEATURES WRAPPING INTO
THE LOW LEVEL CIRCULATION CENTER FROM THE SOUTH. THE INITIAL
INTENSITY OF 45 KTS IS CONSISTENT WITH THE PGTW DVORAK CURRENT
INTENSITY ESTIMATE OF T3.0 (45 KTS). MODERATE (15-20 KT) VERTICAL
WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT FROM UPPER LEVEL SUBSIDENCE
TO THE WEST ARE OFFSETTING GOOD POLEWARD OUTFLOW, FAIR EQUATORWARD
OUTFLOW, AND WARM (27-28 CELSIUS) SEA SURFACE TEMPERATURE TO MAKE
THE ENVIRONMENT MARGINALLY FAVORABLE. TS 21W IS TRACKING SLOWLY
ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE; HOWEVER, THE EXTENDED
FORECAST ALONG TRACK SPEEDS WERE INCREASED.
   B. THROUGH TAU 24, TS 21W WILL CONTINUE TO TRACK ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR. AFTER TAU 24, THE SYSTEM WILL
BEGIN GRADUALLY TURNING POLEWARD AS IT ROUNDS THE STR AXIS. BY TAU
72, TS 21W WILL BE TRACKING NORTHEASTWARD. THE MARGINALLY FAVORABLE
ENVIRONMENT SHOULD ALLOW SLIGHT INTENSIFICATION THROUGH TAU 36. BY
TAU 36, HIGH VWS AND DRY AIR ENTRAINMENT SHOULD PREVENT FURTHER
INTENSIFICATION DESPITE ENHANCED POLEWARD OUTFLOW AS THE SYSTEM
ROUNDS THE STR AXIS. WITH THE EXCEPTION OF ECMWF AND THE ECMWF
ENSEMBLE MEAN, THE BULK OF THE GUIDANCE DEPICTS RECURVATURE SIMILAR
TO THE JTWC TRACK FORECAST. ALTHOUGH THE ECMWF CONTROL AND THE ECMWF
ENSEMBLE MEAN DO NOT DEPICT RECURVATURE, QUITE A FEW MEMBERS OF THE
ECMWF ENSEMBLE DO SHOW A TRACK SIMILAR TO THE JTWC TRACK FORECAST.
BASED ON HIGH UNCERTAINTY IN THE MODEL GUIDANCE, THERE IS LOW
CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.
   C. BEYOND TAU 72, TS 21W IS EXPECTED TO TRACK NORTHEASTWARD ALONG
THE NORTHWESTERN PERIPHERY OF THE STR. PRIOR TO TAU 120, TS 21W WILL
BEGIN TO INTERACT WITH THE MID-LATITUDE BAROCLINIC ZONE, INITIATING
EXTRATROPICAL TRANSITION (ETT). THE SLIGHT INCREASE IN INTENSITY AT
TAU 120 IS CONSISTENT WITH SEVERAL MODELS SHOWING SLIGHT
INTENSIFICATION AS ETT BEGINS.  THERE IS LOW CONFIDENCE IN THE
EXTENDED JTWC TRACK FORECAST DUE TO HIGH UNCERTAINTY, PARTICULARLY
IN ALONG TRACK SPEED, IN THE MODEL TRACKERS.//
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INVEST 97W
As of 18:00 UTC Oct 18, 2019:
Location: 9.7°N 158.2°E
Maximum Winds: 20 kt
Minimum Central Pressure: 1009 mb
WTPN21 PGTW 181530
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 97W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
160 NM EITHER SIDE OF A LINE FROM 9.0N 161.2E TO 11.9N 150.4E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 18 TO 23 KNOTS. METSAT
IMAGERY AT 181200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 9.2N 160.2E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 20
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED
NEAR 8.0N 163.8E, IS NOW LOCATED NEAR 9.2N 160.2E, APPROXIMATELY 950
NM EAST-SOUTHEAST OF ANDERSEN AFB, GUAM. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS A LARGE AREA OF FLARING CONVECTION
OBSCURING A CONSOLIDATING LOW LEVEL CIRCULATION. AN 181041Z ASCAT
PASS SHOWS A SWATH OF 20-25KT WINDS BELOW THE CONVECTION AND A WEAK
RETURN FLOW, CONSISTENT WITH THE FORMATIVE NATURE OF THE LOW LEVEL
ENVIRONMENT. ENVIRONMENTAL CONDITIONS ARE OVERALL FAVORABLE, WITH
LOW (5-10KT) VWS, GOOD DIVERGENCE ALOFT, AND 29-31C SSTS. GLOBAL
MODELS ARE IN BETTER AGREEMENT, WITH GFS AND ECMWF SHOWING
DEVELOPMENT IN THE NEAR TERM, AND NAVGEM AND UKMO HOLDING OFF ON
DEVELOPMENT UNTIL THE MID-LATE TAUS. TRACK SOLUTIONS ARE IN GOOD
AGREEMENT THROUGH TAU 72, ANTICIPATING A WEST-NORTHWESTWARD TRACK
TOWARDS GUAM/CNMI. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT
18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR
1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL
CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
191530Z.//
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