WDPN31 PGTW 070900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (YINXING) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 122.4E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 247 NM NORTH-NORTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 41 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 24W (YINXING) IS CURRENTLY MAKING LANDFALL ON THE
EXTREME NORTHEAST TIP OF LUZON, NEAR POZO ROBO BEACH AT THE 0600Z
HOUR. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A 20NM
WIDE EYE, WITH EMBEDDED MESOVORTICES RAPIDLY SPINNING AROUND THE
CENTER, ON THE INNER EDGE OF THE STRONG EYEWALL. AT 0000Z, THE EYE
WAS CLOUD-FILLED, WITH EYE TEMPERATURES NEARING ZERO CELSIUS. RAPID
WARMING DUE TO STRONG SUBSIDENCE IN THE EYE RESULTED IN A CLEARING
OF THE EYE AND EYE TEMPS INCREASING TO NEAR 19C BY ANALYSIS TIME.
DVORAK INTENSITY ESTIMATES CORRESPONDINGLY INCREASED, WITH MULTIPLE
AGENCIES INCREASING TO T7.0. A 070440Z NOAA-20 ATMS 88.2GHZ
MICROWAVE IMAGE SHOWED A WELL-DEFINED EYEWALL, CLOSED IN ALL BUT
THE WESTERN SIDE, WHERE IT WAS ALREADY BEGINNING TO INTERACT WITH
TERRAIN. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE 20NM EYE IN THE MSI. THE INITIAL INTENSITY IS ASSESSED
WITH MEDIUM CONFIDENCE, CONSISTENT WITH A MEAN OF THE SUBJECTIVE
AND OBJECTIVE INTENSITY ESTIMATES NOTED BELOW. THE ENVIRONMENT
REMAINS FAVORABLE, WITH THE EXCEPTION OF LAND INTERACTION, THE
EFFECTS OF WHICH WILL OVERWHELM THE OTHERWISE POSITIVE
ENVIRONMENTAL FACTORS IN THE NEAR-TERM.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH, EXTENDING FROM SOUTH OF HONG
KONG, OVER TAIWAN AND INTO THE WESTERN PACIFIC NORTH OF THE
NORTHERN MARIANAS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T6.5 - 127 KTS
   KNES: T7.0 - 140 KTS 
   DEMS: T6.5 - 127 KTS
   CIMSS SATCON: 119 KTS AT 070148Z
   CIMSS ADT: 127 KTS AT 070530Z
   CIMSS D-PRINT: 106 KTS AT 070630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: POLEWARD OUTFLOW CHANNEL.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TY 24W WILL TRACK WESTWARD ALONG THE NORTHERN
COAST OF LUZON FOR THE NEXT 12 HOURS. TRACK SPEEDS WILL SLOW DOWN,
AS ALREADY SEEN IN THE ANIMATED MSI, AS THE LOCALIZED EFFECTS OF
TERRAIN-INDUCED DRAG SLOW THE SYSTEM DOWN A BIT. BY TAU 12, THE
SYSTEM WILL BE REACHING THE NORTHWEST TIP OF LUZON AND MOVING BACK
INTO THE OPEN WATERS OF THE SOUTH CHINA SEA (SCS). TRACK SPEEDS
WILL INCREASE TO ABOUT 10 KNOTS AFTER THE SYSTEM MOVES AWAY FROM
LAND, AND THE STEERING GRADIENT ALONG THE SOUTHERN SIDE OF THE STR
TIGHTENS UP. BY TAU 48, A PASSING MID-LATITUDE TROF WILL PUSH IN
FROM THE WEST AND GENERATE A BREAK IN THE STEERING RIDGE NEAR HONG
KONG. THE BREAK IN THE RIDGE IS NOT EXPECTED TO BE STRONG ENOUGH TO
PULL TY 24W UP TO THE NORTH MUCH, BUT IT WILL LEAD TO A WEAKENED
STEERING GRADIENT, AND TY 24W WILL START TO SLOW DOWN ONCE MORE BY
TAU 48, REACHING ITS SLOWEST SPEED OF ADVANCE BY TAU 72. TY 24W
LIKELY REACHED PEAK INTENSITY AS IT WAS MAKING LANDFALL BUT WILL
WEAKEN STEADILY AND RAPIDLY OVER THE NEXT 12 HOURS AS IT MOVES
WESTWARD AND STRADDLES THE NORTH COAST OF LUZON. THE FORECAST CALLS
FOR ABOUT 25 KNOTS OF WEAKENING, WITH THE SYSTEM MOVING INTO THE
SCS AS A 100 KNOT TYPHOON. SOME REINTENSIFICATION IS EXPECTED AFTER
TAU 24, BUT RELATIVELY COOL (27-28C) WATERS AND LIMITED OUTFLOW
ALOFT WILL KEEP A LID ON THE PACE OF INTENSIFICATION. BY TAU 48,
SOUTHERLY SHEAR WILL BEGIN TO PICK UP, USHERING IN A WEDGE OF DRY
MID-LEVEL AIR. BY TAU 72, SOUTHERLY SHEAR, ESPECIALLY IN THE
MID-LEVELS, ALONG WITH AN INFLUX OF VERY DRY AIR, IS EXPECTED TO
DECAPITATE THE VORTEX, MARKING THE ONSET OF RAPID WEAKENING. AS THE
VORTEX SHALLOWS, THE TRACK SHIFTS SHARPLY SOUTHWESTWARD AFTER TAU
72, TRACKING THE LOW TO MID-LEVEL FLOW PATTERN. THE SYSTEM WILL
CONTINUE TO WEAKEN, NEARING FULL DISSIPATION, THROUGH TAU 120, AS
IT CONTINUES TO TRACK TOWARDS THE COAST OF CENTRAL VIETNAM. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 72, WITH MINIMAL CROSS-TRACK SPREAD, AND MARGINAL
ALONG-TRACK SPREAD, AFTER TAU 48. THE GFS IS THE NORTHERNMOST
OUTLIER, TAKING THE SYSTEM ON A VERY SLOW TRACK TO THE NORTH, UP TO
ABOUT 20N BY TAU 72, WHILE THE REMAINDER OF THE CONSENSUS IS
TIGHTLY CLUSTERED AROUND THE JTWC FORECAST, THOUGH THE UKMET,
GALWEM AND UKMET ENSEMBLE DO PUSH THE SYSTEM FURTHER WEST DURING
THIS TIMEFRAME THAN THE REMAINDER OF THE CONSENSUS MEMBERS. AFTER
TAU 72, CROSS-TRACK UNCERTAINTY INCREASES, WITH A SPREAD OF 255NM
BETWEEN THE UKMET AND ITS ENSEMBLE MEAN, THOUGH ALL CONSENSUS
MEMBERS AGREE ON THE SHARP TURN SOUTHWARD AFTER TAU 72. THE JTWC
FORECAST LIES ON THE NORTHERN SIDE OF THE GUIDANCE PACKAGE TO TAU
72 THEN CLOSE TO THE CONSENSUS MEAN THEREAFTER. INTENSITY GUIDANCE
IS MIXED IN TERMS OF HOW MUCH WEAKENING WILL OCCUR OVER THE
NEAR-TERM, AND THUS THE SECOND PEAK IN THE SCS. THE HAFS-A IS ON
THE HIGH END, WITH ONLY 10KTS OF WEAKENING AND A PEAK NEAR 120
KNOTS AT TAU 48. THE GFS ON THE OTHER HAND WEAKENS THE SYSTEM TO
JUST 70 KNOTS AND SHOWS NO REINTENSIFICATION, AND THE HWRF IS NEAR
THE MIDDLE BETWEEN THOSE TWO OUTLIERS. THE JTWC FORECAST IS
SLIGHTLY LOWER THAN THE HWRF TO TAU 24, BUT THEN FOLLOWS IT THROUGH
THE REMAINDER OF THE FORECAST. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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