WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4N 133.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 743 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STILL
BROAD AND HOLLOWED-OUT VORTEX WITH A LARGE CENTRAL REGION OF LIGHT
WINDS AND FEW CLOUDS. THE VORTEX IS WAVENUMBER-3 STRUCTURED WITH
THREE MESOSCALE EDDIES ORBITING ABOUT A MUTUAL CENTROID. DEEP
CONVECTIVE COVERAGE REMAINS LARGELY CONFINED TO A STRONG BAND ALONG 
THE SOUTHERN SEMICIRCLE, AND IS HAVING DIFFICULTY SPREADING TO THE 
NORTHERN HALF OF THE CIRCULATION DUE TO APPROXIMATELY 15 KT OF 
NORTHEASTERLY SHEAR CAUSED BY AN UPPER-LEVEL RIDGE TO THE NORTH OVER 
THE RYUKYU ISLANDS. THERE IS ALSO A DRIER MID-LEVEL AIR MASS IN THE
NORTHEASTERN QUADRANT OBSERVED IN HIMAWARI-9 WATER VAPOR RGB
CAUSING FREQUENT EVAPORATION OF SPROUTING CONVECTIVE UPDRAFTS IN
THAT QUADRANT. UPPER-LEVEL OUTFLOW REMAINS RESTRICTED TO THE
EQUATORWARD DIRECTION. THE INITIAL INTENSITY IS HELD AT 40 KT BASED
ON A BLEND OF AGENCY DVORAK ESTIMATES AND OBJECTIVE SATELLITE 
IMAGERY-BASED INTENSITY ESTIMATES. NO NEW RELIABLE SCATTEROMETER OR 
OTHER SATELLITE-DERIVED WIND SPEED DATA WAS AVAILABLE FOR THIS CYCLE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER THE MARIANA
ISLANDS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 282230Z
   CIMSS ADT: 32 KTS AT 290030Z
   CIMSS AIDT: 34 KTS AT 290030Z
   CIMSS D-MINT: 39 KTS AT 282237Z
   CIMSS D-PRINT: 41 KTS AT 290030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 06W (JANGMI) CONTINUES TO TRACK
NORTHWESTWARD UNDER THE INFLUENCE OF A DEEP-LAYER ANTICYCLONE
CENTERED OVER THE MARIANA ISLANDS, WITH A RIDGE EXTENSION TO THE
NORTH OF THE STORM CONNECTING TO ANOTHER ANTICYCLONE OVER
SOUTHEASTERN CHINA. THIS GENERAL MOTION IS EXPECTED TO PERSIST FOR
ABOUT 48 HOURS AS THE SUBTROPICAL RIDGE SWELLS AND STRENGTHENS
SOUTHEAST OF JAPAN. THEREAFTER, JANGMI WILL ROUND THE WESTERN 
PERIPHERY OF THIS RIDGE, TURNING NORTHWARD INTO THE RYUKYU ISLANDS. 
THE JTWC FORECAST TRACK IS SIMILAR TO THE PREVIOUS WARNING, PASSING 
WITHIN ABOUT 30 NM WEST OF OKINAWA BETWEEN THE TAU 72 AND TAU 96 
FORECAST POINTS. BOTH PHYSICS-BASED AND AI-BASED MODEL GUIDANCE HAS 
GENERALLY SHIFTED WESTWARD OVER THE PAST 24 HOURS, WITH THE BULK OF 
RELIABLE MODELS NOW TAKING JANGMI SLIGHTLY WEST OF OKINAWA. THE 
EXCEPTIONS ARE THE AIFS AND EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE
MEAN, BOTH OF WHICH TRACK SLIGHTLY EAST OF OKINAWA AND FORM THE
EASTERNMOST EDGE OF THE GUIDANCE ENVELOPE. REGARDING THE SHORT-TERM
INTENSITY OUTLOOK, JANGMI IS LIKELY TO INTENSIFY ONLY GRADUALLY
OVER THE NEXT 24 HOURS DUE TO THE BROAD INNER CORE WIND FIELD AND
NORTHEASTERLY VERTICAL SHEAR, BUT WILL LIKELY STRENGTHEN MORE
QUICKLY DURING THE 24 TO 48 HOUR PERIOD AS THE INNER CORE CONTRACTS
SOMEWHAT AND VERTICAL SHEAR RELAXES. THE JTWC FORECAST BRINGS
JANGMI TO TYPHOON INTENSITY IN ABOUT 36 HOURS, AND A PEAK INTENSITY
OF 80 KT DURING THE 48 TO 72 HOUR PERIOD. THIS PEAK MAY BE SLIGHTLY
HIGHER BETWEEN THESE FORECAST POINTS, BUT IS EXPECTED TO BE CAPPED
BY A COMBINATION OF THE STORM'S BROAD CORE AND RAPIDLY DECLINING
OCEAN HEAT CONTENT VALUES AS 06W APPROACHES THE RYUKYU ISLANDS.
JANGMI IS EXPECTED TO BE ON A WEAKENING TREND AT THE TIME OF CLOSEST
APPROACH TO OKINAWA, BUT LIKELY STILL AT TYPHOON INTENSITY. AFTER
96 HOURS, A TURN NORTHEASTWARD INTO THE MID-LATITUDE WESTERLIES
WILL ENSUE, LIKELY CARRYING THE STORM CLOSE TO SOUTHERN KYUSHU AND
SOUTHERN HONSHU. WHILE IT IS TOO EARLY TO HAVE CONFIDENCE REGARDING
WHETHER 06W WILL MAKE LANDFALL IN MAINLAND JAPAN, CONSTRUCTIVE
PHASING WITH AN UPPER-LEVEL TROUGH OVER THE KOREAN PENINSULA IS
EXPECTED TO SUPPORT AN EXPANSIVE GALE TO STORM FORCE WIND FIELD
THAT MAY CAUSE IMPACTS EVEN IF THE STORM CENTER TRACKS OFFSHORE.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO A BLEND OF
TIGHTLY CLUSTERED PHYSICS-BASED AND AI-BASED GLOBAL MODELS. MODEL
SPREAD IS TIGHT THROUGH TAU 72, THEN GROWS SIGNIFICANTLY, ESPECIALLY 
IN THE ALONG-TRACK DIRECTION BY TAU 120. THERE IS THUS SOME TIMING 
UNCERTAINTY IN WHEN 06W WILL MAKE ITS CLOSEST APPROACH TO MAINLAND 
JAPAN. THE JTWC INTENSITY FORECAST IS CLOSE TO A MULTI-MODEL BLEND OF 
HAFS-A, HWRF, COAMPS-TC, AND THE EXPERIMENTAL GOOGLE DEEPMIND 
ENSEMBLE MEAN, STAYING BELOW SOME OF THE STRONGER RAPID 
INTENSIFICATION AIDS AND UNCOUPLED MODELS WHICH ARE NOT ACCOUNTING 
FOR THE STORM'S BROAD STRUCTURE AND POTENTIAL FOR DYNAMIC OCEAN 
COOLING AFTER 48 HOURS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
NNNN